‘WILD HORSE FOUNDATION’ ™
A Former BLM Director thought it was important to have this sent back out.
HSUS, Humane Society of the Untied States uses WILD HORSES AS TEST RATS for there experimental guinea pigs for the drug PZP.!
The very people who want to stop the monkeys testing, rat testing and all other animal experimental testing USES WILD HORSES FOR THERE FINANCIAL GAIN.
MAYBE SOME WILL FIND THIS REPORT INTERESTING……. I Like page 29 and 30 and who said the tail doesn’t wag the dog… I find it better informative that the Pryor Mountains wild horses were rushed to be removed as they were part of this experiment so that the long term effect could not be seen. No where does this talk about the long term effects as we have seen it with wild horses here at the WHF….
Immunocontraceptive Reproductive Control
Utilizing Porcine Zona Pellucida (PZP)
in Federal Wild Horse Populations
(First Edition) (NOTICE THERE HAS BEEN UP DATES TO THIS)
(© 2006 by Drs. Jay F. Kirkpatrick and Patricia M. Fazio. All rights reserved.)1
Ω
Contributors
~
Jay F. Kirkpatrick, Ph.D., Allen T. Rutberg, Ph.D.,
and Linda Coates-Markle
Compiler and Editor
~
Patricia M. Fazio, Ph.D.
July 2006
1 This document is the sole intellectual property of Drs. Jay F. Kirkpatrick and Patricia M. Fazio.
As such, altering of content in any manner is strictly prohibited. However, material may be
printed and distributed freely in hardcopy form or shared as a PDF file, electronically. Please
Note: This file may not be placed on any organizational or individual Website.
2
Contributors
Jay F. Kirkpatrick, Ph.D. is Director of The Science and Conservation
Center, Billings, Montana and holds a Ph.D. in reproductive physiology
from the New York State College of Veterinary Medicine at Cornell
University, Ithaca, New York.
Allen T. Rutberg, Ph.D. is a Research Assistant Professor, Center for
Animals and Public Policy, Cummings School of Veterinary Medicine at
Tufts University, North Grafton, Massachusetts; and Consultant and Senior
Research Scientist for The Humane Society of the United States. Dr.
Rutberg holds a Ph.D. in zoology from the University of Washington (1984)
and an A.B. in biological anthropology from Harvard College (1976).
Linda Coates-Markle is the Montana/Dakotas Wild Horse and Burro
Specialist and the Wild Horse and Burro National Research Coordinator,
Bureau of Land Management, Billings Field Office, Billings, Montana.
Wildlife Forever Website, “Wildlife Fertility Control,”
http://www.pzpinfo.org/liu.html (Permission for use granted by Priscilla
Cohn, Ph.D.)
Compiler and Editor
Patricia M. Fazio, Ph.D. is Statewide Coordinator, Wyoming Animal
Network, Cody, and an environmental writer/editor. Dr. Fazio holds a B.S.
in animal husbandry/biology from Cornell University (1964); an M.S. in
environmental history from the University of Wyoming, Laramie (1982);
and a Ph.D. in environmental history from Texas A&M University, College
Station (1995). Her dissertation was an establishment history of the Pryor
Mountain Wild Horse Range (1968) in Montana/Wyoming.
Acknowledgements
The editor wishes to express heartfelt appreciation to Dr. Jay F. Kirkpatrick,
Dr. Allen T. Rutberg, and Linda Coates-Markle for providing answers to
complex scientific questions in a professional, obliging manner. The
following Website was also a valuable information resource: Wildlife
Forever, “Wildlife Fertility Control,” http://www.pzpinfo.org/liu.html .
3
Table of Contents
page(s)
Contributors 2
Editor and Compiler 2
Acknowledgements 2
Table of Contents 3-5
Memorandum of Understanding (HSUS and BLM) 6
INTRODUCTION 7
THE PZP VACCINE
- What is porcine zona pellucida (PZP), and how does it work to
block pregnancy? 8
- How is it made, and who manufactures it? 9
- How is the PZP vaccine obtained? 9
- Are any pigs killed, expressly to produce the vaccine? 10
- Is this drug FDA approved and patented? If so, who is making
all the profit from its use? 10, 11
- What groups are on the PZP Contraceptive Research Team? 11, 12
- Who Funds PZP Contraceptive Research and Applications? 12, 13
- Who controls vaccine use in wild horse populations? 13
- Does an agency have to do an environmental assessment (EA) or an
environmental impact statement (EIS) prior to using PZP on a wild horse
herd? 14
- What wild horse populations, within the United States, are presently
being managed with PZP? 14-16
- What herds do you propose to treat with contraceptives in the near
future? Why did you choose these particular herds? Who decides?
What are your long-term goals? 16
4
DELIVERY, APPLICATION, AND BIOLOGICAL EFFECTS OF PZP
- How is the vaccine delivered? 16, 17
- Isn’t darting mares painful and potentially harmful or even lethal? Will it
result in mares being shot in critical anatomical areas – abdomen or chest,
causing inhumane deaths? 17, 18
- Will PZP harm mares or foals, physiologically? Have any negative
pharmacological side effects been observed? Are any benefits derived from
its use? 18, 19
- Does PZP application create late foaling in treated populations? 19, 20
- For how many years is a mare generally treated with PZP? 20
- How do you determine which mares within a herd will be treated? 21
- How effective is PZP? Won’t some mares still become pregnant after
treatment? 21
- Why can’t you block pregnancy with just one inoculation instead of the
two shots you use now? 21-23
- What do you mean by a one-year, two-year, or three-year vaccine?23, 24
- How can you tell if a wild mare is pregnant, so you don’t treat her with
PZP? 24
- Is the drug residual in urine or feces or in the dead carcasses of treated
mares, where PZP could get into the food chain or cause adverse effects to
wildlife, or even contaminate water? 24
- What about compensatory reproduction in PZP-treated herds? 25
BEHAVIORAL EFFECTS OF PZP
- Is wild horse behavior affected by PZP use? Are there any effects on
motivation or drive, general contentedness, and the emotional stability of
mares treated with PZP? Is band social stability affected negatively? Has
any aberrational behavior been seen in PZP-treated mares, band stallions, or
bands where mares have been treated with a contraceptive? What behavioral
studies have been conducted on wild horses, both in eastern and western
wild horse herds? Do you plan additional behavioral studies? 25, 26
5
- Won’t mares just keep coming back into estrus (heat) if they don’t get
pregnant? Won’t prolonged estrus cycling make stallions “edgy” and
aggressive, creating continuous “unrest?” In the chaos, won’t foals be
harmed or even killed? 26, 27
- I “live” with wild horses and feel that some of your behavioral studies
(measuring PZP effects) are wrong or incomplete. 28
- I wish the BLM had used a bit of (its research) money or allocated new
money to do a study regarding the effects of PZP on the social structure and
health of wild horses in the west. 28
- Isn’t the use of PZP “against nature?” Why can’t you just leave these
animals alone? 28
OPPOSITION TO PZP
- Why are some wild horse advocacy groups so vehemently opposed to
PZP? It seems like the perfect solution. 29, 30
- Aren’t you trying to bring wild horses to extinction (using PZP)? 30
REFERENCES 30-37
Җ
6
MEMORANDUM OF UNDERSTANDING
between the Humane Society of the United States
and the Bureau of Land Management
After a workshop held in Santa Fe, NM, November 29 and 30, 2005 on wild
horse fertility control, the Humane Society of the United States and the
Bureau of Land Management have agreed to develop a Memorandum of
Understanding to co-operate on: –
1) The further development and wider use of contraception in wild horse
populations,
2) Resolve some of the uncertainties being faced in producing the vaccine
and ensuring a continuing supply of a safe and effective vaccine,
3) Assist in public outreach on the issues, and
4) Maintain healthy and viable herds in the existing BLM wild horse Herd
Management Areas.
“The BLM sees this as a way to reduce horse removals, to place fewer
horses in short- and long-term holding facilities, and to achieve budgetary
savings,” said Don Glenn, Acting Group Manager of the BLM Wild Horse
and Burro Program, Washington, DC.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Source: HSUS-BLM Press Release on Fertility Control, e-mail from Tom
Gorey WO/BLM/DOI, sent 11/30/2005 01:17 PM. Forwarded by Linda
Coates-Markle /MTSO/MT/BLM/DOI on 12/05/2005 10:55 AM.
7
Introduction
Two fundamental questions exist…
1) Does PZP harm wild horses?
2) Will its use eliminate entire herds?
The quick answers are that the Food and Drug Administration (FDA), The
Humane Society of the United States (HSUS), and animal care committees
all carefully review protocols for PZP use, and more than 19 years of data,
carried out under these set of rules, clearly show that wild horses are neither
injured by this drug, nor do aberrational behaviors occur as a consequence of
its application. Too, oversight by The Humane Society of the United States
assures that the vaccine is used only to slow reproduction and may not be
used for the extermination of entire herds. PZP is designed to bring about
short-term infertility and is reversible, if not used beyond five consecutive
years. It reduces the need for gathers and preserves the original gene pool in
each herd.
Expanding on these central points, the contributors and editor of material
presented within this document have aspired to answer, with scientific
objectivity, common questions and concerns raised by actual individuals and
groups about porcine zona pellucida (PZP) and to provide citations and
references that may be accessed through interlibrary loan, or other sources,
for further study. Updates and additional questions and answers (Q&A’s)
will be provided periodically, as research progresses or protocols change.
PZP use in wild horse herds has been studied extensively for nearly two
decades, with papers published in peer-reviewed scientific journals by
experienced reproductive physiologists, equine scientists, wildlife biologists,
geneticists, and animal behaviorists, providing a portrayal of safety, high
efficacy, and absence of long-term behavioral, physical, or physiological
effects from the vaccine. Those involved in the creation of this Q&A have
endeavored to produce a factual document of scientific merit, supported by
field data, with statistically adequate sample sizes. Data was collected by
trained, unbiased individuals, who adhere to established research
methodology within his or her respective field.
8
Questions & Answers
THE PZP VACCINE
- What is porcine zona pellucida (PZP), and how does it work to block
pregnancy?
- A non-cellular membrane known as the zona pellucida (ZP) surrounds all
mammalian eggs. The ZP consists of several glycoproteins (proteins with
some carbohydrate attached), one of which, ZP3, is thought to be the sperm
receptor (the molecule that permits attachment of the sperm to the egg
during the process of fertilization). The PZP vaccine is derived from pig
eggs. When this vaccine is injected into the muscle of the target female
animal, it stimulates her immune system to produce antibodies against the
vaccine. These antibodies also attach to the sperm receptors on the ZP of her
own eggs and distort their shape, thereby blocking fertilization. [see
Paterson and Aitkin 1990; Miller et al. 2001]
Thus far, PZP has been a promising form of contraception in wild horses and
other wildlife for the following reasons:
- Pregnancy is prevented approximately 90% of the time in treated animals;
- The vaccine can be delivered remotely by small darts;
- Contraceptive effects are reversible (up to five years in wild horses);
- PZP is effective across many species;
- No debilitating health side effects have been observed, even after
long-term use;
- No effects on social behaviors have been observed;
- The vaccine cannot pass through the food chain;
- It is safe to administer the vaccine to pregnant animals.
(Adapted from: “Wildlife Fertility Control,” Wildlife Forever Website,
http://www.pzpinfo.org/pzp.html, January 2006) and originally published in
Kirkpatrick and Turner 1991a.
9
- How is it made, and who manufactures it?
- The porcine zona pellucida (PZP) vaccine used on BLM, U.S. Forest
Service, and NPS wild horse mares is produced by The Science and
Conservation Center (SCC) in Billings, Montana. Each batch is subjected to
a qualitative and quantitative quality-control program and shipped under the
authorization of an Investigational New Animal Drug (INAD) exemption for
wild horses (FDA # 8857-G0002) issued to The Humane Society of the
United States (HSUS) by the Center for Veterinary Medicine of the Food
and Drug Administration. In collaboration with other investigators, The SCC
continues to conduct research with the contraceptive vaccine, focusing on
the ability to produce larger quantities, and increasing the efficacy of longterm
contraception through a single inoculation (see Turner et al. 2002).
- How is the PZP vaccine obtained?
- Once all necessary authorizations and approvals have been obtained for
use of the vaccine, it may be ordered from:
Kimberly M. Frank
The Science and Conservation Center (SCC)
2100 S. Shiloh Road
Billings, MT 59106
(406) 652-9719 (phone)
(406) 652-9281 (fax)
e-mail: zoolab@wtp.net
The vaccine is not commercially available and is provided at cost of
production, which currently runs about $21/dose. This is the price of the
standard, one-year, 100 microgram dose. The 2-3 year vaccine uses
considerably more than 100 micrograms, as well as more adjuvant, and
includes the added cost of pelleting. The 2-3 year PZP vaccine costs about
$200 per dose, plus the personnel costs of administration, which are minor,
if horses are being gathered anyway. Compared with the $1,100 – $1,600 it
takes to gather, remove, transport, hold, and adopt a horse (or care for it
indefinitely), PZP is a bargain.
10
- Are any pigs killed, expressly to produce the vaccine?
- Pig ovaries are obtained from a slaughterhouse in Iowa, as a by-product
of hogs already destined for slaughter. Therefore, no fewer hogs will be
killed if the PZP vaccine were no longer made. Major competitors for pig
ovaries include Chinese restaurants, and pharmaceutical companies, that use
ovarian endocrine components for research and production of products.
- Is this drug FDA approved and patented? If so, who is making all the
profit from its use?
- In FDA language, “approval” refers to approval for commercial
distribution and marketing, and PZP is not a commercial product. No
one is profiteering from PZP. The Humane Society of the United States
holds the Investigational New Animal Drug exemptions (INAD), which are
the oversight process by which FDA compiles data to examine vaccine
safety and effectiveness. Basic and applied research that generated most of
the knowledge about the vaccine was carried out with public funds (from the
National Science Foundation, National Institutes of Health, U.S. Department
of Agriculture, Bureau of Land Management, etc.). The research team
considers products developed with public monies to be in the domain of the
public, and therefore has no intention of commercialization. Therefore, it
will always be called “experimental,” despite the fact that PZP has been
studied and field-tested extensively, for safety and efficacy, and is currently
being used with more frequency on federal wild horse mares.
However, at the same time, use of public monies for research and
development does not legally prohibit the commercialization of a product.
Some researchers are, nonetheless, offended (due to a personal sense of
ethics) and will not move forward with commercialization of a product
developed with public funds. The rationale is that the public has already paid
for the product, and commercialization only allows private companies and
individuals to profit from sale without having contributed to the process of
research, development, and testing.
A possible exception to this rides on the back of the recently passed
Minor Use Drug Bill, promulgated into law by Congress in 2004. This bill
was aimed at drugs with limited use, for minor species, and for which there
11
are no financial incentives to develop the product as a commercial drug. This
might provide a means for “provisional approval,” but that remains
to be seen. Because of this, PZP cannot be used on wildlife without the
Investigational New Animal Drug exemption, or INAD. Once the INAD
from FDA (one for horses, one for deer and zoo animals) was obtained, it
was turned over to The HSUS, leaving that organization to deal with the
ethical issues. This means that each project – even at the management level –
must have a research question attached to it, and The HSUS must approve
the project. An added note is that the Investigational New Animal Drug
exemption (INAD) issued to HSUS by the FDA requires a sound safety base
before it is issued and would never have been issued were there a significant
(or even an insignificant) health or safety concern.
Therefore, neither HSUS nor The SCC make money from the vaccine. The
SCC provides PZP vaccine at cost of production. Coupled with the paperwork
required, The SCC actually loses money. That is why The SCC is a nonprofit.
Currently, The SCC’s annual budget is about $120,000, and PZP
income results in less than half of that, meaning that a great deal of vaccine is
donated.
The patent issue is a different question, not to be confused with the FDA
process. Merck patented PZP in the 1970s, but the patent lapsed, and it is
assumed that the technology is no longer patentable. Organon International, a
large drug company based in the Netherlands, holds the patent for PZP use in
humans, but that application may never take place, as scientists have not yet
been able to make an effective synthetic form. Also, the variability in time for
infertility reversal is significant and could potentially result in litigation.
- What groups are on the PZP Contraceptive Research Team?
- Today, the team consists of The Science and Conservation Center,
Billings; Medical College of Ohio, Toledo; University of California-Davis;
Tufts University, Medford, Massachusetts; The Humane Society of the
United States, Gaithersburg, Maryland and Washington, DC; and the
University of Iowa, Iowa City. Many other individuals contribute to the
effort in one form or another. Governmental agencies that can be considered
team members include the National Park Service and the Bureau of Land
Management.
12
The entire PZP contraceptive effort involves many people, several
institutions, and numerous funding agencies. This team works together,
bringing many disparate disciplines and talents in concert to solve the
problems at hand.
- Who Funds PZP Contraceptive Research and Applications?
- Funding for application of the vaccine to wildlife has been provided by
many individual communities, agencies, and organizations, including but not
limited to:
- The Humane Society of the United States
- Elinor Patterson Baker Trust
- Geraldine R. Dodge Foundation
- Bernice Barbour Foundation
- Leuthold Family Foundation
- Panaphil Foundation
- Delta-Sonics
- PNC, Inc.
- U.S. Navy
- National Park Service
- Bureau of Land Management
- Rachel Carson National Estuarine Reserve
- U.S. Department of Commerce
- National Institutes of Health
- Fire Island Community Association
- 112 different zoos in North America, Europe, New Zealand and
Australia
- South African National Parks Board
13
- U.S. Fish and Wildlife Service – African elephant conservation fund
- Fripp Island (SC) Property Owners Association
- Morris County (NJ) Parks Commission
- Franklin County/Columbus (OH) Metro Parks
- and several anonymous donors.
This list is not all-inclusive but provides a picture of the breadth of support
for this approach to wildlife management.
- Who controls vaccine use in wild horse populations?
- The Bureau of Land Management cannot use the vaccine without the
assent of HSUS, which monitors management plans and the INAD. In fact,
the BLM approached the FDA and tried to circumvent HSUS control over
vaccine use but was turned down by the FDA. Therefore, oversight and
approval by HSUS still exists. BLM will not have control of the PZP
vaccine in the foreseeable future. Every µg of vaccine that is produced can
only be used in projects where HSUS has reviewed and approved a wild
horse herd management plan.
All projects in which the vaccine crosses state lines must be on record with
the FDA. As explained previously, the authority to carry out these projects is
issued by two separate Investigational New Animal Drug documents
(INADs) issued by the FDA to HSUS. As each new project is identified,
HSUS reviews the need for the project in the context of scientific, ethical,
and moral issues and, if approved, issues permission to proceed. Notification
of each project is accomplished by means of a form, filed with the FDA by
The Science and Conservation Center, which specifies how much vaccine is
being shipped and what species are to be treated. The INAD also requires
that data from each project be gathered in a systematic way and filed, and be
made available to the FDA when the need arises. These files are maintained
at The Science and Conservation Center. Additionally, the legal managers of
the horses (NPS or BLM) or the Animal Care Committee of each zoo must
also provide permission to treat animals. This regulatory process is similar
for any wildlife species not classified as a food animal by the FDA or as a
game animal by a state fish and wildlife agency.
14
- Does an agency have to do an environmental assessment (EA) or an
environmental impact statement (EIS) prior to using PZP on a wild
horse herd?
- Yes. Environmental Assessments are mandatory. One difference between
agencies is that the NPS does a single management EA, that is in force for
years, while the BLM does one annually for every application in each herd
management area.
- What wild horse populations, within the United States, are presently
being managed with PZP?
- The vaccine has been used successfully to manage the wild horse
population of Assateague Island National Seashore (ASIS), in
Maryland/Virginia, under the sponsorship and authority of the National Park
Service (NPS). The population has been treated for more than 17 years,
without health problems, and the population has decreased by 10%, since
management-level application began in 1995. Wild horses are also being
treated on Cape Lookout National Seashore (Shackleford Banks), North
Carolina, for the NPS; on Carrot Island, North Carolina; on the Rachel
Carson National Estuarine Reserve, North Carolina; and on many areas of
Nevada, for the Bureau of Land Management (BLM). Other treated herds
include Return To Freedom (American Wild Horse Sanctuary), California;
Pryor Mountain Wild Horse Range (Montana/Wyoming); Little Book Cliffs
National Wild Horse Range, Colorado; McCullough Peaks Horse
Management Area, Wyoming; and Little Cumberland Island (Georgia). In
Nevada and Wyoming, at least 12 different wild horse herds are being
treated “experimentally,” to evaluate population effects. For Nevada
references, see (1) Turner et al. 2001; (2) Turner et al. 1997; (3) Kirkpatrick
et al. 1997; (4) Kirkpatrick et al. 1997.
In the case of the four barrier island herds, the Pryor Mountain Wild Horse
Range, Little Book Cliffs, and Return To Freedom, horses are treated
remotely, with dart guns. In Nevada, they are treated in conjunction with
gathers, as most of these HMA’s are too large, and the horses too wild, to
dart them.
15
In addition to controlling the horse population on Assateague Island,
treatment has extended the lives and improved the health condition of older
mares, by removing the stresses of pregnancy and lactation [see Kirkpatrick
1995; Kirkpatrick and Turner 2002; 2003; Kirkpatrick et al. 1990, 1991,
1992, 1995a, 1996a,b, 1997; Liu et al. 1989; Turner and Kirkpatrick 2002;
Turner et al. 1996a]. Horses on Assateague are doing well. About 155 total
animals roamed the area in 2005 (10% less than the starting number of 173
in 1995), and their body conditions have improved significantly since 1990
[Turner and Kirkpatrick 2002]. Mortality has almost disappeared, and the
horses are generating new age classes (large numbers between 20-25 years
of age, and a growing population between 25-30).
Thus, at the management level, horses are being treated with PZP for the
NPS, Rachel Carson National Estuarine Reserve, the BLM, and two private
groups. In addition, new forms of the vaccine are being tested for the BLM
in western horses, but not on a management level.
The following HMAs are sites for treatment with long-acting PZP:
Onaqui Mountain, UT – 56 mares
Sand Springs, OR – 31 mares
Fox-Hog, NV – 28 mares
Green Mountain, WY – 38 mares
Monte Cristo, NV – 53 mares
Blue Wing, NV – 136 mares
Antelope Hills, WY – 28 mares
Black Rock East, NV – 19 mares
Black Rock West, NV – 19 mares
Warm Springs, NV – 27 mares
Antelope Complex, NV – 29 mares
Calico, NV – 92 mares
Groshuite, NV – 44 mares
Granite Range, NV – 79 mares
Nellis Air Force Base Bombing Range, NV (Nevada Wild Horse Range) –
358 mares
McCullough Peaks, WY – 34 mares
Additionally, another form of the long-acting PZP is being tested in
captive mares at Canon City, CO; a reduced dose of PZP is being tested
16
in captive mares at Canon City, CO; and a lyophilized form of the vaccine is
being tested in domestic mares in Clark, WY and Billings, MT.
- What herds do you propose to treat with contraceptives in the near
future? Why did you choose these particular herds? Who decides?
What are your long-term goals?
- While the PZP vaccine is currently being used on at least 20 horse
management areas for the National Park Service or the Bureau of Land
Management, its use is appropriate for all free-ranging wild horse herds.
Application to particular herds is at the invitation of the managing agency.
The long-term goal is to reduce or eliminate the need for gathers and
removals.
DELIVERY, APPLICATION, AND BIOLOGICAL EFFECTS OF PZP
- How is the vaccine delivered?
- The PZP vaccine must be injected into the muscle of the target animal.
This can be done by hand if the animal is restrained, or by dart, for remote
delivery. There are many commercial dart systems available but the thick
viscosity of the vaccine requires a large needle and a quick injection. Thus
far, Pneu-Dart(r) systems (Williamsport, Pennsylvania) seem to work the
best. The Pneu-Dart(r) 1.0 cc barbless darts can be fired from Pneu-Dart(r)
capture guns or from several other commercial dart guns [Pax-Arms(r) or
Dan-Inject(r), for instance]. The darts are disposable, and after hitting the
animal in the rump or hip (the only acceptable location for darting), they
inject by means of a small powder charge, and then pop out. Because of their
bright colors, the darts are usually retrieved in the field. Darts that have not
been discharged cannot be discharged by stepping on them or by any other
kind of casual contact. Over a six-year period on Fire Island National
Seashore, and with more than 1,000 dartings of deer, only two darts have not
been recovered.
Normally, each animal is darted twice the first year, with the first injection
being given up to a year before a booster, just preceding the breeding season
(March for wild horses or September for deer). Thereafter, a single annual
booster inoculation will maintain contraception. The second inoculation of
the first year requires that…you are able to recognize the individual animals;
17
or you do the first inoculation with a special “marker dart,” which leaves a
dye mark on the animal at the same time it injects the vaccine; or
selected mares are treated to allow for both genetic diversity within a
specific herd and for the promotion of health and improved body condition
of an individual animal (through temporary infertility).
An alternative strategy is to give only a single inoculation the first year,
from which there will be little contraception, and then a single annual
inoculation thereafter, from which there will be significant contraception
(see McShea et al. 1997; Turner and Kirkpatrick 2002.)
New approaches using small non-toxic, biodegradable lactide-glycolide
pellets, that result in several years of contraception after a single application,
are being tested. [Turner et al. 2002].
(From: http://www.pzpinfo.org/pzp.html)
- Isn’t darting mares painful and potentially harmful or even lethal?
Will it result in mares being shot in critical anatomical areas – abdomen
or chest, causing inhumane deaths?
- As long as only 1.0 cc Pneu-Darts are used, there is almost no risk of
injury to the animal. These are very small, light darts. Over a 19-year period,
no horse has ever been injured on Assateague Island, the Shackleford Banks,
Carrot Island, the Pryor Mountains, or the Little Book Cliffs (translating to
well over 1,000 dartings, over the course of 19 years).
On the Pryors, PZP remote-darting operations typically take place in late
summer/early fall, and any wild mares receiving the vaccine are
individually-identified and tracked regularly with data non-intrusively
gathered on behavior, estrus, fertility, reproduction, survival, and any health
concerns. The field studies are conducted by seasonal and term USGSBiological
Resources Division and BLM biological technicians under the
18
supervision of BRD research biologists and the BLM Wild Horse and Burro
Specialist.
Injection site reactions tabulated for all PZP treated mares show currently
that of 38 total treated mares, 55% exhibit no reaction to darting, 6% have
some level of swelling around the injection site, 22% have a small nodule
about the size of a marble, and no animals currently have abscesses. Only
one mare of 38 has ended up with a medium-level swelling, about one year
after treatment. Only one mare had a nodule that was accompanied by a
small abscess with drainage. The abscess healed within two weeks. These
swellings and nodules are most notable post-injection but typically disappear
over time. Ultimately these nodules are very difficult to discern amongst
other natural scars within the coats of these wild mares. Furthermore, there is
no indication that the presence of these nodules has compromised the quality
of life for these horses. Field technicians have never recorded the mares
showing any indication that these nodules are causing any level of
discomfort during daily activities and/or interfering with reproductive
activities.
- Will PZP harm mares or foals, physiologically? Have any negative
pharmacological side effects been observed? Are any benefits derived
from its use?
- Safety data has been accumulated over 19 years. It essentially says there
are no short- or long-term health problems of any kind, and that the vaccine
is reversible, unless the mare is treated for more than five consecutive years
(in which case you probably didn’t want her to reproduce again anyway).
The data make clear that pregnancies in progress are not affected in any way
by the vaccine, nor is the health or fertility of the foals compromised, once
they are born. Treating mares carrying female fetuses does not affect the
fertility of the offspring.
In fact, as mentioned previously, mares on Assateague Island are living
longer than ever, and their mortality has decreased, they are achieving new
age classes never before seen on the island, and all this happened because
their body condition scores have increased steadily since 1989, when PZP
application started. Historically, a mare never survived to 20 years of age,
but now a significant percentage has passed twenty and about 29 animals
19
(20% of the herd) are between 25 and 30 years old. Removal of the stresses
of pregnancy and lactation gives them an immense health advantage.
Foal mortality has dropped significantly. This is probably because their
mothers, when they finally do become pregnant, after several years of
contraception and then withdrawal of PZP treatments, are much healthier.
All of this data (derived not from casual observation) is published.
The other victory for horses is that every mare prevented from being
removed, by virtue of contraception, is a mare that will only be delaying her
reproduction rather than being eliminated permanently from the range. This
preserves herd genetics, while gathers and adoption do not. [Kirkpatrick and
Turner 2002; Turner and Kirkpatrick 2002, 2003; Willis et al. (1994).]
- Does PZP application create late foaling in treated populations?
- No. Available data from 19 years of application to wild horses contradicts
this claim [see Kirkpatrick and Turner 2003]. From 1990 to present,
Assateague Island has records for 178 horses whose month of birth is known
(and in some cases, day of birth known). An examination of the published
data, from 1984, of Ron Keiper (retired Distinguished Professor of Biology
at Pennsylvania State University and currently Chairman of the Department
of Biology at Valencia Community College, Orlando, Florida) in which he
looked at eight years of birth dates for the same herd, which at that time was
much smaller than we have today (considerably less than 100 horses versus
155) indicates that approximately 85% of the foals were born in April, May
and June. Among the 178 horses with known birth dates, 95 were born to
mothers who were never treated with PZP, with 70 born in April, May and
June (73.6%), and 25 born outside this window. Another 83 foals were
born to mares that had at some point been treated with PZP before their
pregnancies, and 65 were born in April, May or June (78.3%), with 18
outside this window. Thus, with a database of 178 horses over an elevenyear
period, there is no evidence of late foals being born among treated
mothers.
20
That corroborates published work (Kirkpatrick and Turner 1983), where it
was demonstrated that Pryor Mountain wild horses did not extend their
season of ovulation even when placed on high planes of nutrition. Mares do
not extend their breeding season if they do not get pregnant.
One interesting issue is that the percent of untreated mares born on
Assateague Island in the April, May and June window has decreased from
85% down to 74% since 1984. This suggests that as herd size increases,
variability in birth dates also increases, but this may simply be a function of
larger numbers (in this case a 100% increase in herd size). There is also a
moderate pattern among some mares (the N9BF line in particular) with
regard to producing foals outside this window. This genetic line was
consistently producing foals in March. If that observation is correct (This is
only an untested observation.), then it corroborates Eric Palmer’s theory that
seasonal ovulatory patterns in mares are genetically controlled. In any case,
these data, at least, demonstrate that contraception with PZP does not cause
early or late births. Once again the Assateague Island (ASIS) horses and the
19-year treatment history produced a wealth of information. [Kirkpatrick
and Turner 2003]
In the Pryor Mountain Wild Horse Range, the normal foaling period has
been well documented (EA #BLM MT010 FY05 -16, figure 10) to primarily
take place in May and June, with limited foaling known to happen outside
this window, from February to September. Thus, later foaling dates are not
considered abnormal. In fact, during September 2005, one mare that was
never treated with PZP was known to be pregnant and had yet to foal on the
Pryors that season, at the time of observation.
- For how many years is a mare generally treated with PZP?
- This depends on the management plan of the agency, for a particular
herd. Perhaps the most effective plan is the one used on Assateague Island,
where all two-year-old mares are put on treatment, and then boosted at three
and four years of age. After this, they are removed from treatment until they
foal, which might occur anywhere from one to five years later. Mares that
have already made their genetic contribution to the herd, in the context of
the management plan are treated until extinction.
21
- How do you determine which mares within a herd will be treated?
- The question of which mares to treat with vaccine is an important one,
and the answer is embodied in the management plan. The approach used on
Assateague Island has proven very effective and safe, i.e., two, three and
four year olds are all treated and then withdrawn from treatment until they
produce a foal. Older mares with good genetic representation in the herd are
treated to extinction. Dr. E. Gus Cothran, an equine geneticist from the
University of Kentucky, monitors the plan on Cape Lookout.
Immunocontraceptive control is more logical (genetically) than removing
animals before they have had a chance to reproduce. Genetic representation
is the key element within the management plan.
The most important consideration is to ensure that all genetics are
represented, whether or not they reflect “wildness” or band stability,
phenotype, or whatever social hierarchy exists. The bottom line is that wild
horses are native North American wildlife, and humans should not be
selecting for anything other than complete genetic representation.
- How effective is PZP? Won’t some mares still become pregnant after
treatment?
- PZP treatment in wild horses is about 90+% effective [Turner and
Kirkpatrick 2002]. The failure of some horses to respond to the vaccine
results from an immune system that either doesn’t “recognize” the vaccine’s
antigen, or from a compromised immune system. This is true for human
vaccines as well. Regardless, 90% efficacy is enough to manage wild horse
populations effectively. In other species, efficacy varies in a species-specific
manner [Frank et al. 2005].
- Why can’t you block pregnancy with just one inoculation instead of
the two shots you use now?
- The issue of the “one-shot” is complicated. Currently there are tests with
two forms of a one-shot vaccine. Despite that, this matter clouds the real
issue of putting the vaccine to work NOW.
22
The initial “primer” dose of PZP causes the immune system to “recognize”
and type the antigen, not so much for immediate long-term response, but to
prepare the animal’s immune system for future exposures to the vaccine.
Thus, a booster inoculation is required the first year, and an annual booster
thereafter [Liu et al. 1989].
There is a second reason for the need for booster inoculations. Many human
and veterinary vaccines use attenuated (weakened) or killed viruses as the
vaccine, and these are powerful stimulators of the immune system. Often a
single inoculation lasts for years. The PZP, however, is a relatively small
protein that is not especially immunogenic. It is also very close in structure
to the native PZP on the target animals’ own ova; thus, the target animal has
difficulty in “recognizing” the PZP as foreign to the body. This, in turn,
means that multiple inoculations must be given, and with a more
immunogenic compound, known as an adjuvant [Lyda et al. 2005].
The subject of the one-shot also clouds the bigger topic of management
because it only provides an advantage in the first year. After that, the horses
are “one-shot” animals anyway. In 1994, almost every mare on Assateague
Island was treated with a single shot. That shot was not meant to cause
contraception but to set the herd up as a “one-shot” herd in preparation for
management a year later. It was done this way because the National Park
Service had to do an environmental assessment (EA) before they were
allowed to manage with contraception. Then in 1995, the whole herd was
managed with only a single shot per animal. The concept is fairly simple,
and a “one-shot” vaccine only aids in the first year. Of course, a single
inoculation that lasts multiple years would have more utility. [Turner et al.
2002].
The present advice given to the BLM is plain. Not a single mare that is
gathered, for any purpose, and returned to the range should get back there
without an inoculation. That makes them “one-shot” animals, and the
expense of developing “one-shot” vaccines becomes moot. Once they have
had that first shot, they can be treated anytime with a single shot.
23
A One-Inoculation Vaccine
Because of the need to inoculate animals twice the first year, and the
difficulty of doing this with wild species, research is proceeding toward a
“one-inoculation” vaccine. Such a vaccine would permit a single darting to
cause one or more years of contraception. The approach under study
incorporates the PZP into a non-toxic, biodegradable material, which can be
formed into small pellets. The pellets can be designed to release the vaccine
at predetermined times after injection (at one and three months, currently),
much the same way time-release cold pills work. Initial trials were
encouraging, and continued trials are underway (see Eldridge et al, 1989;
Turner et al, 2002).
(From: http://www.pzpinfo.org/future-pzp.html#one)
- What do you mean by a one-year, two-year, or three-year vaccine?
Response to the PZP antigen is variable among individual mares. Some
mares appear to be naturally poor responders to the vaccine and probably
never develop sufficient antibody titer levels to confer infertility (hence the
90% efficacy of the vaccine). Research with the Pryor Mountain wild horse
herd indicates that immune response in mares may be correlated with age
and fitness. One six-year-old mare, contracepted due to poor physical
condition in September 2003, responded poorly to the vaccine, conceived in
2004, and foaled in 2005. Similarly, two 16-year-old mares last boostered in
2003, also produced foals in 2005. Conversely, younger mares in good
condition may have a stronger than expected antibody titer response
resulting in a longer period of infertility. This appears to be the case with the
first young mares treated with PZP on the Pryor Mountain Wild Horse
Range (PMWHR).
Immunocontraception is not an exact science. The vaccines are designed to
offer an effective time period based on the average response for many
numbers of animals. As the treated number of animals increases, then the
known response time for a specific formulation of PZP and adjuvant
(carrying-agent) becomes better known. There are many variables to
consider, the largest factors being animal condition and related immune
response. Young PMWHR mares were healthy when injected (though a
small sample size), and it would appear the resulting immune response (to a
90% effective one-year agent) has resulted in 2 years of efficacy. Older
24
Pryor mares are relatively worn-out, and immune response appears limited.
As such, the vaccine was not effective in a couple of mares. This is also true
with a younger mare that was treated due her poor condition, but she still
produced a foal.
Perhaps animal condition on Assateague Island (ASIS) is such that one year
of efficacy is all that results with the same formulation of PZP and adjuvant
that has been used on the Pryors. These are questions that still need to be
dealt with, which is why the need exists for continued research. These
questions are addressed in individual-based study herds within the WH&B
Fertility Control Field Trial program. This is one of the reasons why the
efforts on the Pryors have been critical to knowledge of this vaccine for use
on western herds.
- How can you tell if a wild mare is pregnant, so you don’t treat her
with PZP?
- In some cases, a fecal or urine sample is collected off the ground, or from
yellow snow following urination. Reproductive steroid hormone metabolites
are measured that tell us, with almost 100% accuracy, which mares are
pregnant and which are not. A pregnancy can be diagnosed from 40 days
post-conception until the day of parturition, and the animal does not have to
be touched. That said, there is no danger to either the mother or the in utero
foal, if the mare is treated with PZP during pregnancy [Kirkpatrick and
Turner 2003].
- Is the drug residual in urine or feces or in the dead carcasses of
treated mares, where PZP could get into the food chain or cause adverse
effects to wildlife, or even contaminate water?
- Because PZP is primarily protein, it is readily destroyed in digestion,
reduced to amino acids, and therefore cannot pass through the food chain
intact and with biological activity [Oser 1965].
25
- What about compensatory reproduction in PZP-treated herds?
Thus far, after 20 years of PZP treatment, there is no evidence for
compensatory reproduction in a PZP-treated wild horse herd. This might be
an issue if a herd is treated for long periods of time and then all treatment
withdrawn, but that flies in the face of an effective management plan
[Kirkpatrick and Turner 1991b].
BEHAVIORAL EFFECTS OF PZP
- Is wild horse behavior affected by PZP use? Are there any effects on
motivation or drive, general contentedness, and the emotional stability
of mares treated with PZP? Is band social stability affected negatively?
Has any aberrational behavior been seen in PZP-treated mares, band
stallions, or bands where mares have been treated with a contraceptive?
What behavioral studies have been conducted on wild horses, both in
eastern and western wild horse herds? Do you plan additional
behavioral studies?
- After 19 years of treating the ASIS mares, there is still no evidence of
altering behaviors. The baseline behaviors of eastern wild horses were the
same as western horses. In order to understand this, a great deal of
information must be read, which examines wild horse behavior from a
variety of sites around the world. A huge body of literature exists on this
subject, and a few of the more salient publications include: Berger 1977;
Feist and McCullough 1976; Keiper 1976, 1986; Klingel 1975; McCort
1984; Rubnestein 1981; Rutberg 1990; Rutberg and Greenberg 1990; Salter
and Hudson 1982. An independent investigator from the National Zoological
Park has confirmed earlier results that show no behavioral changes [Powell
2000]. Thirty-years of observing wild horses in North America and
Australia and New Zealand have revealed no difference in fundamental
behavioral structures. On the other hand, the affects of gathers on social
behaviors are obvious [Ashley and Holcombe 2001; Hansen and Mosley
2000].
A good start on this subject can be obtained by reading Powell [1999],
which reports on a study done by researchers from the National Zoological
Park/Smithsonian. They found no behavioral effects, at that time, after
almost eight (8) years of PZP treatment. The same results were reported in
26
several of the Assateague Island papers, including (1) Kirkpatrick 1995, and
(2) Kirkpatrick et al. 1995. Also, other studies [Fayrer-Hosken et al. 2000;
Delsink et al. 2002] showed a lack of behavioral effects of this same vaccine
on free-roaming African elephants, which have an even more complex social
order than wild horses.
One critic of PZP claims, “The horses [on Assateague Island] seem more
listless than western wild horses…” However, this could only be determined
by time budget studies, and, in fact, no evidence for this has been found
(referenced above). Casual observation of wild horses proves nothing. For
example, casual observation has reported that Pryor horses travel less than
ASIS horses, but that has no scientific significance. If one understands the
biology of PZP, one would never suggest there is a “psychological” impact
of the vaccine.
The research has already shown that band structures do not change and
neither do hierarchies. The only major change in hierarchies that occurs is
when mares get pregnant, and then they drop down the ladder even more.
Most wild horse behavioral researchers still don’t know how to measure
hierarchy rank.
- Won’t mares just keep coming back into estrus (heat) if they don’t
get pregnant? Won’t prolonged estrus cycling make stallions “edgy”
and aggressive, creating continuous “unrest?” In the chaos, won’t foals
be harmed or even killed?
- At the heart of this issue is the subjective nature of casual observation.
Science is based on data, not informal surveillance. Systematically collected
data, reviewed by other scientists, accepted as legitimate, treated
appropriately statistically, and published in a recognized journal is the only
acceptable means for arriving at generalizable, accurate behavioral
information. A good start for understanding the rudiments of behavioral
research in social animals can be found in Craig [1986].
In 1983, it was shown [Kirkpatrick and Turner 1983; 1986 a,b] that wild
horses do not have the same ovulatory patterns as domestic horses, and that
wild horses have well-defined breeding seasons (usually from about late
March until July, but this will vary somewhat from herd to herd). Wild
mares do not extend their breeding season if they do not become pregnant.
27
Keiper and Houpt [1984] also showed this for Assateague horses. This
DOES happen, however, in deer [McShea et al. 1997] but not with wild
horses. In 27 years of data collection on Assateague Island, only a single
documented incident of a stallion killing another stallion, because of
fighting, has been observed. This occurred in the middle of breeding season
(late May).
The PZP vaccine does not prevent ovulation. Wild horses do not come into
estrus every month, whether or not they have been treated with a
contraceptive. They have a breeding season that barely makes it from April
through July. Many wild mares have but a single estrous cycle and some
have none in a given year, but they are highly seasonal and do not ovulate
year-round, or even half the year.
The implication of the question is that by treating wild horse mares with
PZP, they will continue to cycle throughout the year, and that this will cause
stallion “unrest,” aggression, and potential injury. By contrast, documented
evidence shows that mares will NOT continue to cycle if they do not
conceive, at least beyond the normal 3-4 month breeding season.
If critics were correct, and PZP did cause “unrest” and continuous cycling,
which, in turn, led to worked-up stallions and foals dying as a result of this
behavioral turmoil, then any area using PZP would have greater foal
mortality. However, after 11 years of management-level treatment on ASIS,
foal mortality has decreased. That is a data-driven fact.
Granted… wild horse behaviors are subtle, and individual horses will show a
wide range of variability in behavioral patterns. It takes a great deal of
observational experience to pick them up. We do know that traditional time
budget issues, as well as hierarchies and band fidelity, are not affected by
PZP application. We also know that aggressiveness and aberrational
behaviors are not caused by PZP use. Perhaps, however, there may be a
subtle change in daily routine. However, the larger question is, even if subtle
alterations in behavior may occur, this is still far better than the alternative
of wild horses being rounded up, bands broken apart, and all of the other
negatives that go with traditional management. These issues need to be put
into the perspective of risk-benefit by PZP opponents.
28
- I “live” with wild horses and feel that some of your behavioral
studies (measuring PZP effects) are wrong or incomplete.
- Living with wild horses and seeing them every day is one thing, but while
of interest, this doesn’t necessarily hold noteworthy meaning, unless a
parameter for study is identified, a hypothesis established, and a means of
testing that hypothesis is conducted. Additionally, this still does not indicate
a significant behavioral or other casually observed pattern for an individual
animal or for a band or herd unless the data is analyzed properly.
- I wish the BLM had used a bit of its research money or allocated new
money to do a study regarding the effects of PZP on the social structure
and health of wild horses in the west.
- The effects of PZP on social structure and herd health are currently being
studied on the Pryor Mountain Wild Horse Range and Little Book Cliffs
herds, and, thus far – after three years of treatment – no behavioral changes
have been noted, nor have any behavioral changes been noted on wild horses
at Return To Freedom (American Wild Horse Sanctuary) in California,
where animals are observed daily.
- Isn’t the use of PZP “against nature?” Why can’t you just leave these
animals alone?
- Except in a small number of wild horse herds (such as in the Montgomery
Pass herd [Turner et al. 1992], Bordo Atravasado in New Mexico, and a few
others), mountain lions cannot predictably predate a sufficient number of
wild horses to keep herd levels at population numbers in balance with the
carrying capacity of their ecosystem. The potential for both wolf and grizzly
bear predation of wild horses is in question, as well, especially if grizzlies
and wolves are delisted from the Endangered Species Act, making grizzlies,
wolves, and mountain lions all open to hunting pressures. Where lions,
wolves, and grizzlies exist naturally in sufficient numbers to influence horse
numbers, that phenomenon will be encouraged and accepted.
29
OPPOSITION TO PZP
- Why are some wild horse advocacy groups so vehemently opposed to
PZP? It seems like the perfect solution.
- Opposition to the contraception arises because wild horse advocates do
not trust the BLM with the PZP vaccine, despite assurances that the agency
cannot use it without approval from The Humane Society of the United
States (HSUS). BLM has inflamed the issue by asking FDA for their own
INAD, so they could bypass The HSUS. FDA told the BLM that no more
“use” INADs would be issued; so, currently, the agency has no choice but to
work with HSUS, unless they are willing to change horses in the middle of
the race. The HSUS will permit the use of PZP to manage, even reduce, but
not to eliminate wild horses.
This has now led the BLM to seek as many other forms of wild horse
contraception as possible, from other groups, but it will take significant time
to match the safety data studies that have been generated on PZP over many
years.
All wild horse advocates want horses to have a better life, but if this entails a
choice between having 130 healthy horses versus 200 living on the
nutritional edge (in the event of a drought or a severe winter), some would
choose the 130 healthy-horse option, out of (what they see as) concern for
the well being of the horses. The irony is that those who seek to control wild
horse populations through immunocontraceptive measures often spar with
other horse advocates who (in the opinion of PZP supporters) object to what
pro-PZP factions perceive as the humane treatment of wild horses. The anti-
PZP community, who often question factual information and historic
success, distrust the morals of those who strongly profess they care (about
the well being of the herds). Pro-PZP individuals and groups believe, with
conviction, that the primary motivation behind wild horse contraception is
keeping healthy wild horses in the wild, on the land forever, in as natural a
state as possible, with minimal interference from humans.
Many of these opponents dislike PZP because they fear it will reduce the
herd to lower numbers than they want. That has been the major contention
with most gathers. After 19 years of contraception on ASIS, and 11 at the
management level, contraception has only been able to reduce that herd
30
from 173 to 155. Zero population growth was achieved, and, to date, there
has been no need for gathers, but reduction has been slow. So, there is little
danger of massive reductions happening anywhere. Even the event of a
catastrophic winter has less danger inherent than most advocates might
think. The Pryor Mountain herd in Montana/Wyoming went from about 140
horses to 70 in a tragic winter die-off of 1977-1978, but the population had
recovered within three years. The only thing that would have changed, had
there been 200 animals instead of 140 is that more animals would have had
less to eat, and therefore more would have died. The severity of the winter
determined that 70 horses would survive, and not the starting population
number.
- Aren’t you trying to bring wild horses to extinction (using PZP)?
- A. The concerns of some anti-PZP wild horse groups over BLM use of the
vaccine are justifiable, and the BLM’s proposal to use PZP to cause an
Oregon herd to approach extinction, and other proposals that have surfaced
to use PZP to manipulate herd composition, prove this. These apprehensions
are legitimate and acknowledged by PZP researchers. However, Assateague
Island data have proven the safety and efficacy of the vaccine, and it is
obvious that the BLM is not going to be able to treat 30,000 wild horses to
extinction with contraception, especially with continued involvement from
The HSUS. Vigilance is important in the continued utilization of the PZP
vaccine and in monitoring questionable research studies by state and federal
agencies not sanctioned by The HSUS or the BLM, some involving the use
of contraceptives that may potentially cause complete sterilization or
deleterious effects in mares. Despite the utter rejection of scientific data as a
legitimate form of persuasion by some anti-PZP individuals and groups,
their hearts are in the right place. They are not the natural enemies of those
promoting PZP as a humane management tool. Affable cooperation is
needed to resolve issues of wild horse over-population, when and where it
legitimately exists, once other means of population reduction have failed or
are found to be undesirable.
31
*****************************************************
REFERENCES
References below are a sampling of the only known published reports, to
date, on the subject of PZP use in wild or domestic horses, or in zebras, wild
burros or Przewalski’s (Mongolian) horses. However, additional peerreviewed
papers, not listed below, have been published on these topics.
Those selected were chosen to support material included in answers to the
questions above.
Φ
Ashley, M.C., and D.W. Holcombe (2001). Effects of stress induced by gathers and
removals on reproductive success of feral horses. Wildlife Society Bulletin 29:248-
254.
Berger, J. (1977). Organization and dominance in feral horses in the Grand Canyon.
Behavioral Ecology and Sociobiology. 2:131-146.
Cameron, E.Z., W.L. Linklater, E.O. Minot, and K.J. Stafford (2001). Population
dynamics 1994-1998, and management of Kaimanawa wild horses. Science for
Conservation Bulletin 171, Department of Conservation, Wellington, New Zealand.
This is a second report almost identical to the one above, i.e., no effectiveness but no
deleterious affects either.
Craig, J.V. (1986). Measuring social behavior: Social dominance. Journal of Animal
Behavior 62:1120-1129.
Delsink, A.K., J.J. Van Altena, J.F. Kirkpatrick, D. Grobler, and R.A. Fayer-
Hosken (2002). Field applications of immunocontraception in African elephants
(Loxodonta africana) Reproduction (Supplement 60):117-124.
Dunbar, B. S., N. J. Waldrip and J. Hendrick (1980). Isolation, physiochemical
properties and macromolecular composition of zona pellucida from porcine oocytes.
Biochem. 19:356-365. Describes the process for isolating and purifying the porcine zona
glycoproteins.
Eldridge, J. H., R.M. Gilly, J.K. Stass, Z. Moldozeanu, J.K. Muelbroek, and T.R.
Tice (1989). Biodegradable microcapsules: Vaccine delivery systems for oral
immunization. Current Topics in Microbiology and Immunology 146:59-66.
Describes the fundamental technology used for developing a one-shot, multi-year
vaccine.
32
Feist, J.D., and D.R. McCullough (1976). Behavioral patterns and communication in
feral horses. Z. Tierpsychol. 41:337-371.
Frank, K.M., and J.F. Kirkpatrick (2002). Porcine zona pellucida
immunocontraception in captive exotic species: Species differences, adjuvant
protocols and technical errors. Proc. Amer. Assoc. Zoo Veterinarians, October
2002, Milwaukee, WI, pp. 221-223. This reports on the effectiveness and safety of PZP
in 29 zebras and is about the same as in horses except for the need to give the booster
inoculation sooner. No deleterious effects of any kind were found.
Frank, K.M., R.O. Lyda, and J.F. Kirkpatrick (2005). Immunocontraception of
captive exotic species. IV. Species differences in response to the porcine zona
pellucida vaccine and the timing of booster inoculations. Zoo Biology 24:349-358.
Frisbie, K.M., and J.F. Kirkpatrick (1998). Immunocontraception of captive exotic
species: A new approach to population management. Animal Keeper’s Forum
25:346-351. This is the first report on the use of PZP in zebras. About the only
difference from horses is the need to apply booster inoculations at 9 months rather than a
year.
Hansen, K.V., and J.C. Mosley (2000). Effects of roundups on behavior and
reproduction of feral horses. Journal of Range Management 53:479-482.
Kaul, R., A. Afzalpurkar, and S.K. Guipta (1996). Strategies for designing an
immunocontraceptive vaccine based on zona pellucida synthetic peptides and
recombinant antigens. Journal of Reproductive Fertility (Supplement 50):127-134.
This paper also describes the properties and efficacy of the zona vaccine.
Keiper, R.R., and K. Houpt (1984). Reproduction in feral horses: An eight-year
study. American Journal of Veterinary Research 45:991-995.
Keiper R.R. (1976). Social organization of feral ponies. Proc. Pennsylvania Acad.
Sci. 50:69-70.
Keiper R.R. (1986). Social behavior. Veterinary Clinics of North America. 2:465-
484.
Kirkpatrick, J.F. (1995). Management of Wild Horses by Fertility Control: The
Assateague Experience. National Park Service Scientific Monograph, National Park
Service, Denver, CO. (60 pp.). This scientific monograph describes the early
experiments on Assateague Island that led to the successful application of PZP to wild
horses.
33
Kirkpatrick, J.F. (1996). Some recent developments in immunocontraception. In:
Living with Wildlife, A. Rowen, and J.C. Weers (eds.). Tuft’s Center for Animal and
Public Policy, North Grafton, MA, pp. 87-98. This is a general review of PZP
immunocontraception through the mid-1990s.
Kirkpatrick, J.F. (2005). The wild horse fertility control program. In: Wildlife
Contraception. A.T. Rutberg (ed.) Humane Society Press, Washington, DC., pp. 63-
76.
Kirkpatrick, J.F., and J.W. Turner, Jr. (1983). Seasonal patterns of LH, progestins
and estrogens in feral mares. Journal of Equine Veterinary Science 3:113-118.
Kirkpatrick, J.F., and J.W. Turner, Jr. (1986a). Hormones and reproduction in
feral horses. Journal of Equine Veterinary Science 6:250-258.
Kirkpatrick J.F., and J.W. Turner, Jr. (1986b). Comparative reproductive biology
of feral horses. Journal of Equine Veterinary Science 6:224-230.
Kirkpatrick, J.F., and J.W. Turner, Jr. (1985). Chemical fertility control and
wildlife management. BioScience 35:485-491. This paper is the earliest review of the
topic of wildlife contraception, using all methods and all species.
Kirkpatrick, J.F., and J.W. Turner, Jr. (1991a). Reversible fertility control in
nondomestic animals. J. Zoo Wildlife Medicine 22: 392-408. An updated version of
the BioScience paper above.
Kirkpatrick, J.F., and J.W. Turner. Jr. (1991b). Compensatory reproduction in
feral horses. J. Wildlife Management 55(4): 649-652.
Kirkpatrick, J.F., and K.M. Frank (2005). Fertility control in free-ranging wildlife.
In: Contraception in Captive and Free-Ranging Wildlife. Asa C. and I. Porton
(eds.), John Hopkins Press, Baltimore, MD, pp. 195-221.
Kirkpatrick J.F., and J.W. Turner, Jr. (1991). Reversible fertility control in nondomestic
animals. J. Zoo Wildlife Medicine 22:392-408.
Kirkpatrick, J.F., and J.W. Turner, Jr. (2002). Reversibility of action and safety
during pregnancy of immunization against porcine zona pellucida in wild mares.
Reproduction (Supplement 60): 197-202. This paper reported on 12 years of research
and 7 of management with regard to safety in pregnant mares, the lack of injection site
reactions, reversibility (which was almost total after 5 consecutive years of treatment but
not after 7 consecutive years of treatment).
34
Kirkpatrick, J.F., and J.W. Turner, Jr. (2003). Absence of effects from
immunocontraception on seasonal birth patterns and foal survival among barrier
island horses. Journal of Applied Animal Welfare Science 6: 301-308. As the title
implies, this paper showed that treated mares taken off contraception do not produce
subsequent foals out of season, and that survival of foals born to previously treated
mares is actually better than that of foals born to untreated mares.
Kirkpatrick, J.F., I.K.M. Liu, and J.W. Turner, Jr. (1990). Remotely-delivered
immunocontraception in feral horses. Wildlife Society Bulletin 18:326-330. This
records the first use in wild horses and showed (1) high efficacy; (2) no effect on
pregnant mares; (3) no short-term effects on behavior; (4) ability to deliver PZP
remotely; and (5) no short-term debilitating effects.
Kirkpatrick, J.F., I.K.M. Liu, J.W. Turner, Jr., and M. Bernoco (1991). Antigen
recognition in mares previously immunized with porcine zonae pellucidae. Journal
of Reproductive Fertility (Supplement 44):321-325. This was the second paper on
PZP use in wild horses and demonstrated (1) reversibility; (2) the ability to maintain
contraception with single annual treatments; (3) no affects on behavior; (4) no shortterm
affects on behavior.
Kirkpatrick, J.F., I.K.M. Liu, J.W. Turner, Jr., R. Naugle, and R. Keiper. (1992).
Long-term effects of porcine zonae pellucidae contraception on ovarian function in
feral mares. Journal of Reproductive Fertility 94:437-444. This paper reported on
four years of treatment and showed (1) no debilitating effects; (2) absence of injection
site reactions; (3) no changes in behavior; and (4) efficacy approaching 90%.
Kirkpatrick, J.F., R. Naugle, I.K.M. Liu, M. Bernoco, and J.W. Turner, Jr. (1995a).
Effects of seven consecutive years of porcine zona pellucida contraception on
ovarian function in feral mares. Biology of Reproduction, Monograph Series 1:
Equine Reproduction: 411-413. This showed essentially the same things as the paper
immediately above, but after 7 consecutive years. At this point, the PZP appeared to be
effective, causing no injection site reactions, was reversible, didn’t change social
behaviors, had no long-term (7-year) debilitating health effects, etc.
Kirkpatrick, J.F., W. Zimmermann, L. Kolter, I.K.M. Liu, and J.W. Turner, Jr.
(1995b). Immunocontraception of captive exotic species. I.: Przewalski’s horse and
Banteng. Zoo Biology 14: 403-413. This reports the use of PZP in Przewalski’s horses
in the Koln Zoo (Germany). It was effective, and there were no other problems.
Kirkpatrick, J.F., I.K.M. Liu, and J.W. Turner, Jr. (1996a). Contraception of wild
and feral equids. In: Contraception in Wildlife Management. T.J. Kreeger (ed).
U.S. Government Printing Office, Washington, DC. pp. 161-169. This paper was
given at the Third International Symposium on Wildlife fertility Control, in Denver, Co,
in 1993, and reports on all equid immunocontraception up to that point in time.
35
Kirkpatrick, J.F., J.W. Turner, Jr., I.K.M. Liu, R.A. Fayrer-Hosken (1996b).
Applications of pig zona pellucida immunocontraception to wildlife fertility control.
Journal of Reproductive Fertility (Supplement 51):183-189. The only new
information here was that the antibodies raised by PZP treatment did not cross-react
with any other somatic tissues in the horse, or even with basic reproductive hormones.
Translated, this meant the vaccine was even safer than thought.
Kirkpatrick, J. F., J.W. Turner, Jr., I.K.M. Liu, R.A. Fayrer-Hosken, and A.T.
Rutberg (1997). Case studies in wildlife immunocontraception: Wild and feral
equids and white-tailed deer. Reproduction, Fertility and Development 9:105-110.
Klingel, H. (1975). Social organization and reproduction in equids. Journal of
Reproductive Fertility (Supplement 23): 7-11.
Liu, I.K.M., and A. Shivers (1982). Antibodies to the zona pellucida in mares.
Journal of Reproductive Fertility (Supplement 32):309-313.
Liu, I.K.M., M. Bernoco, and M. Feldman (1989). Contraception in mares
heteroimmunized with porcine zonae pellucidae. Journal of Reproductive Fertility
89:19-29. This paper reports on the first application of the PZP vaccine to horses.
McCort, W.D. (1984). Behavior of feral horses and ponies. Journal of Animal
Science 58:493-499.
Lowell Miller et al. (2001). Characterization of equine zona pellucida
glycoproteins by polyacrylamise gel electrophoresis and immunological techniques.
Journal of Reproductive Fertility 96: 815-825. This was in vitro work that explained
the molecular structure of the equine zona pellucida and speculated on how fertilization
is blocked by PZP.
Oser, B.L. (1965). Chapter 24. Protein metabolism. In: Hawke’s Physiological
Chemistry, McGraw-Hill, NY, p. 810.
Paterson, M., and R. Aitkin (1990). Development of vaccines targeting the zona
pellucida. Current Opinion in Immunology 2:743-747. Reports on the actual
mechanisms behind PZP contraception.
Powell, D. (1999). Preliminary evaluation of porcine zona pellucida
immunocontraception for behavioral effects in feral horses. Journal of Applied
Animal Welfare Science 2:321-335. Working with the behaviorist from the National
Zoological Garden, Powell showed no behavioral effects after years of use.
Rubenstein, D.I. (1981). Behavioral ecology of island feral horses. Equine
Veterinary Journal 13:27-34.
36
Rutberg, A.T. (1990). Inter-group transfer in Assateague pony mares. Animal
Behaviour 40:945-952.
Rutberg, A.T., and S.A. Greenberg (1990). Dominance, aggression frequencies and
modes of aggressive competition in feral pony mares. Animal Behavior 40:322-3331.
Salter, R.E., and R.J. Hudson (1982). Social organization of feral horses in western
Canada. Applied Animal Ethology 8:207-223.
Seal, U.S. (1991). Fertility control as a tool for regulating captive and free-ranging
wildlife populations. J. Zoo Wildlife Medicine 22: 1-5. This paper is another review of
the broader subject of wildlife contraception.
Shivers, A., and I.K.M. Liu (1982). Inhibition of sperm binding to porcine ova by
antibodies to equine zona pellucida. Journal of Reproductive Fertility (Supplement
32):315-318. In this paper, we seen the first investigation of how antibodies against the
PZP might interfere with fertilization; the work was all in vitro.
Stafford, K.J., E.O. Minot, W.L. Linklater, E.Z. Cameron, and S.E. Todd (2001).
Use of an immunocontraceptive vaccine in feral
Kaimanawa mares. Conservation Advisory Science Notes 330, Department of
Conservation, Wellington, New Zealand. This paper reports on the failure of an
attempt to inhibit fertility in New Zealand wild mares. They used the wrong dose, the
wrong adjuvant, and the wrong delivery system; so it is not surprising that it didn’t work.
Other than that, there were no harmful effects.
Turner, Jr., J.W., and J.F. Kirkpatrick (2002). Effects of immunocontraception on
population, longevity and body condition in wild mares. Reproduction (Supplement
60):187-195. This paper reported on 12 years of research and seven of management of
wild horses with PZP. It showed that (1) a significant population effect can be achieved;
(2) that horses thus treated achieved better body condition and lived significantly longer
than before treatment and still no behavioral effects had occurred.
Turner, Jr., J.W., M.L.Wolfe, and J.F. Kirkpatrick (1992). Seasonal mountain lion
predation on a free-roaming feral horse population. Canadian Journal of Zoology
70:929-934.
Turner, Jr., J.W., I.K.M. Liu, A.T. Rutberg, and J.F. Kirkpatrick (1996a).
Immunocontraception limits foal production in free-roaming feral horses in
Nevada. Journal of Wildlife Management 61:873-880. This report examines the largescale
application of PZP to western wild horses. It is significant because it presents
solid data for lack of injection site reactions.
37
Turner, Jr., J.W., I.K.M. Liu, J.F. Kirkpatrick (1996b). Remotely-delivered
immunocontraception in free-roaming feral burros. Journal of Reproductive
Fertility 107:31-35. This reports the first use of PZP in burros, and other than efficacy
and reversibility, no other data were collected. It was a short-term study, but there were
no negative facets to the work, physically orbehaviorally.
Turner, Jr., J.W. et al (1997). Immunocontraception limits foal production in freeroaming
feral horses. Journal of Wildlife Management 61:873-880. This is the first
report of large-scale use of PZP (in more than 100 animals at a time) in Nevada horses.
Other than the efficacy of nearly 90%, the primary noteworthy data included the
complete absence of any injection site reactions. In this case, the animals were
inoculated and kept in corrals for three weeks and examined daily for problems. There
were none.
Turner, Jr., J.W. et al (2001). Immunocontraception in feral horses: A
singleinoculation vaccine providing one-year of infertility. Journal of Wildlife
Management 65:235-241. This paper showed that the effectiveness of aprototype oneshot
form of the vaccine was as good as the standard two-shot treatment. More than 200
horses were treated, and none showed any deleterious effects.
Turner, Jr., J.W., I.K.M. Liu, D.R. Flanagan, K.S. Bynum, and A.T. Rutberg
(2002). Porcine zona pellucida (PZP) immunocontraception of wild horses in
Nevada: A 10-year study. Reproduction (Supplement 60):177-186. As the title
indicates, this is a summary of ten years of research with PZP, in several forms and with
several adjuvants. The paper reports on effectiveness and showed no deleterious effects
of any kind.
Lyda, R.O., R. Hall, and J.F. Kirkpatrick (2005). A comparison of Freund’s
Complete and Freund’s Modified adjuvants used with a contraceptive vaccine in
wild horses. Journal of Zoo Wildlife Medicine 36:(in press).
Willis, P., G. L. Heusner, R.J. Warren, D. Kessler, and R.A. Fayrer-Hosken (1994).
Equine immunocontraception using porcine zona pellucida: A new method for
remote delivery and characterization of the immune response. Journal of Equine
Veterinary Science 14:364-370. This reports on a study with domestic horses at the
University of Georgia. Aside from efficacy, there were no abscesses, no cross reactivity
with somatic tissues, and no clinical problems. This study was carried out in a
veterinary school.
copied in its entirety from the publication. WHF claims no responsibility of the report.
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