Jay F. Kirkpatrick

Immunocontraception of African elephants

Concerted efforts to nurture elephant populations have resulted in elephant overpopulation in several areas, which in turn has led to damaging levels of browsing. As an alternative to culling entire family groups in order to control this damage, we have developed an immunocontraceptive vaccine from pig zona pellucida which safely and successfully controls free-roaming African elephants.

The effect of immunocontraception on the behavior and reproduction of white-tailed deer

Behavioral and reproductive consequences of porcine zona pellucida (PZP) immunocontraception were examined in a herd of white-tailed deer (Odocoileus virginianus; n = 30) from September 1992 to September 1994. Does were captured from a wild population and placed within either of 2 large (32-ha total) wooded enclosures. Does were administered either: (1) a single injection containing PZP-emulsified in Freunds complete adjuvent (FCA) and microsphere-encapsulated PZP; (2) 2 injections of PZP-emulsified in FCA and Freunds incomplete adjuvant (FIA), 4 weeks apart; or (3) no treatment. Mature, spermic bucks (n = 5) were added to each pasture 4 weeks after the final PZP treatment, and reproductive behaviors and fawn production were observed for 2 years. Immunocontracepted females exhibited increased activity compared to non-treated females, presumably reflecting an increased number of estrus intervals. Similarly, enclosure bucks exhibited an extended breeding season compared to males in the surrounding wild population. The 2-injection PZP regimen provided effective contraception during both years of the study. The 1-injection PZP regime provided effective contraception only during the second year, following administration of a PZP booster. Histological evaluations of ovaries failed to reveal among-group differences in ovarian architecture. Contracepted-nonpregnant does gained significantly more weight than control females during the study.

Contraceptive Vaccines for Wildlife: A Review

Citation Kirkpatrick JF, Lyda RO, Frank KM. Contraceptive vaccines for wildlife: a review. Am J Reprod Immunol 2011; 66: 40–50

Remotely Delivered Immunocontraception in Captive White-Tailed Deer

We tested a new contraceptive method that offers a potential alternative to white-tailed deer (Odocoileus virginianus) population control where hunting is unfeasible. We report the first successful, remotely delivered immunocontraception in captive, unrestrained white-tailed deer using porcine zona pellucida (PZP) antigen. None of 7 PZP-vaccinated does produced fawns, whereas 6 to 7 control does did. No adverse effects of treatment were observed. These results encourage further investigation of immunocontraception in wild white-tailed deer populations

Pregnancy determination in uncaptured feral horses by means of fecal steroid conjugates

This study was carried out to develop an accurate, rapid and inexpensive method for diagnosing pregnancy in uncaptured feral horses by analysis of fecal steroid metabolites and to compare the accuracy of this method with diagnosis by urinary estrone conjugates (E(1)C). Paired urine and fecal samples were collected from 40 sexually mature feral mares during August and October. Urine samples were extracted directly from the soil and analyzed by enzymeimmunoassay (EIA) for E(1)C. Water extracts of fecal samples were assayed by EIA for E(1)C and nonspecific progesterone metabolites (iPdG). Urinary E(1)C, fecal E(1)C and fecal iPdG concentrations for seven mares which produced foals were 3.9 +/- 1.3 (SEM) mug/mg creatinine, 4.2 +/- 0.8 ng/g feces and 1.411 +/- 569.6 ng/g feces, respectively. Urinary E(1)C and fecal E(1)C and iPdG concentrations for the 33 mares which did not produce foals were 0.1 +/- 0.0 mug/mg creatinine and 0.5 +/- 0.1 and 32.8 +/- 4.5 ng/g feces, respectively. These differed (P < 0.01) from values in mares which produced foals.

Chemical Fertility Control and Wildlife Management

Chemical fertility control is a neglected yet potentially powerful wildlife management tool that represents an effective, inexpensive, and humane alternative to current control methods. A large number of new contraceptive agents, designed primarily for use in humans, can be administered remotely by injection to large mammals or orally to smaller animals. These compounds will not cause death, do not disturb social order, and can be manipulated to protect nontarget species.

Effectiveness, Reversibility, and Serum Antibody Titers Associated with Immunocontraception in Captive White-Tailed Deer

Because immunocontraception may have management application for white-tailed deer populations in parks and preserves where hunting is illegal or impractical, we examined physiological aspects of immunocontraception with porcine zonae pellucidae (PZP) in fertile white-tailed does (Odocoileus virginianus). In 4 experiments, we examined the effectiveness of 3- and 2-PZP injections for controlling fertility of does, as well as 2 protocols using 1 injection. We used sample sizes of 5, 8, 6, and 7 does for PZP treatment and 8, 6, 6, and 7 does for controls in the experiments. We administered a single PZP booster inoculation after 1 year to all does used in the 3-injection experiment. Each 1-injection vaccination consisted of 1 dose of PZP as in other protocols plus a second controlled-release dose of PZP delivered via an osmotic mini-pump implant or injected biodegradable polymer microspheres. We monitored fawn production for 1-3 years in all does and measured serum anti-PZP antibody titers at various times post treatment in 15 randomly selected PZP-treated does and in 2 control does. Except for 2 of 7 does given 1 injection containing microspheres, none of the PZP-treated does in any experiment produced fawns the first year after treatment. In 49 possible breeding periods among control does (placebo = 8, untreated = 41) the pooled incidence of fawn production was 93.8%. Fawn production among 8 monitored does (2- and 3-injection protocols) was 75% 2 years after treatment was discontinued, demonstrating reversibility of treatment. Serum anti-PZP antibody titers (17 does tested) were present only after PZP treatment, and highest titers occurred in does given 2 or 3 separate PZP injections. Regardless of protocol, PZP-treated does with >50% of maximal antibody titers at the onset of a breeding season did not produce fawns, whereas does with 50% of maximal after 32-40 weeks. Our data demonstrate in white-tailed does that PZP vaccination: (1) can produce contraception for at least 1 breeding season, (2) yields greater efficacy with multiple injections than with 1 injection, (3) is reversible within 2 years in 75% of does, (4) is associated with elevated anti-PZP antibody titers, and (5) can produce a sustained antibody response through at least 1 breeding season. The titer data suggest that PZP vaccine in white-tailed deer behaves in a manner physiologically similar to PZP vaccine effects reported in several other species. The fawn count data indicate that PZP vaccine has potential management application for white-tailed deer.

Contraceptive potential of the porcine zona pellucida vaccine in the African elephant (loxodonta africana)

Immunocontraception has been successful in controlling free-roaming equids; however, what is the potential for the immunocontraceptive control of the African elephant (Loxodonta africana)? The porcine zona pellucida (pZP) glycoproteins share antigenic domains with the African elephant zona pellucida (elZP) glycoproteins, and anti-zona pellucida serum antibodies have been successfully stimulated. To determine the cross-reactivity of the pZP and elZP, immunocytochemistry was evaluated by light and electron microscopy. Specifically, the binding of polyclonal antibodies against total heat-solubilized-porcine zona pellucida to fixed elephant ovary sections was evaluated. The elZP of primary, secondary and tertiary follicles was recognized by the rabbit-anti-pZP serum, but there was no apparent recognition of the primordial follicles. The ability of anti-pZP antibodies to recognize the elZP demonstrates that there is molecular homology between the pZP and elZP glycoproteins. This homology makes the African elephant a candidate for pZP immunocontraception. Three captive elephants were vaccinated with 400 micrograms pZP with a synthetic trehalose dicorynomycolate (S-TDCM) adjuvant. The elephants received 2 boosters of 600 micrograms pZP at 4 wk and 10 m.o. after the primary vaccination. The vaccinated female elephants developed significant (P < 0.05) titers to pZP over prevaccination levels. These levels persisted for 12 to 14 m.o. after the third vaccination. This preliminary evidence shows that the female elephant can develop significant serum antibody levels to pZP. These levels of antibodies are comparable to those required in horses for successful immunocontraception. Thus, porcine zona pellucida immunocontraception might be used to control elephant populations.

Immunocontraception in Wild Horses: One Inoculation Provides Two Years of Infertility

Abstract Previous studies reported one year of contraception associated with a 1-injection porcine zona pellucida (PZP) vaccine. We have subsequently determined contraceptive effectiveness of a presumptive 1-injection, 2-year-duration PZP vaccine in free-roaming wild horses (Equus caballus) in Nevada, USA. In January 2000, we captured, freeze-branded, treated, and subsequently released 96 adult females that received 1) a primary dose of vaccine emulsion consisting of aqueous PZP and Freunds Complete Adjuvant, and 2) booster doses of PZP and adjuvant in controlled-release polymer pellets. We determined PZP release characteristics of pellets in vitro, prior to field use. We determined reproductive success in treated and untreated females through October 2004 via measurement of estrone sulfate and progesterone metabolites in fresh feces collected from the ground and by twice-annual foal counts. Among treated females, annual reproductive success from 2001 though 2004 sequentially was 5.9%, 14.0%, 32.0%, and 47.5%. Untreated females showed average reproductive success of 53.8 ± 1.3% across this period. This study revealed that: 1) PZP acted as an effective contraceptive for 2 years posttreatment; 2) some residual contraceptive effect remained in year 3; and 3) fertility returned to control levels by year 4 posttreatment. It appears that controlled-release technology can replace both the second (1-month) and annual booster injection of PZP vaccine, thereby decreasing cost and increasing efficiency of use of this vaccine in wild horse management.

Achieving population goals in a long-lived wildlife species (Equus caballus) with contraception

The ultimate goal of any wildlife contraceptive effort is some alteration of the target population, either through a slowing of growth, or stabilisation or reduction of the population. Early population models suggested that short-term contraceptive agents applied to long-lived species would not achieve significant population changes. Native porcine zona pellucida antigen (PZP), a short-term contraceptive vaccine, was applied to a herd of wild horses inhabiting Assateague Island National Seashore, MD, USA, over a 13-year period, with an immediate goal of achieving zero population growth, a secondary goal of reducing the population from 175 to 150 and a tertiary goal of reaching 120 individuals, all without the physical removal of animals. Contraceptive efficacy ranged from 92 to 100% on an annual basis (96.28 ± 2.49%), and the percentage of adult females that was treated on any given year ranged from 42 to 76% (67.78 ± 18.21%). The goal of zero population growth was achieved in 2 years, an initial decline in the population became apparent in 8 years and by Year 11, the population declined to 135, a decrease of 22.8%. The lengthy period required for achieving a population decline was caused by increasing body condition scores, reduced mortality and significantly increased longevity among treated females.