Use of a GnRH vaccine, GonaCon, for prevention and treatment of adrenocortical disease (ACD) in domestic ferrets.

Adrenocortical disease (ACD) is a common problem in surgically sterilized, middle-aged to old ferrets (Mustela putorius furo). The adrenal tissues of these ferrets develop hyperplasia, adenomas, or adenocarcinomas, which produce steroid hormones including estradiol, 17-hydroxyprogesterone, and androstenedione. Major clinical signs attributable to overproduction of these hormones are alopecia (hair loss) in both sexes and a swollen vulva in females. Pruritus, muscle atrophy, hind limb weakness, and sexual activity or aggression are also observed in both sexes. Males can develop prostatic cysts, prostatitis, and urethral obstruction. ACD is thought to be linked to continuous and increased LH secretion, due to lack of gonadal hormone feedback in neutered ferrets. This continuous elevated LH acts on adrenal cortex LH receptors, resulting in adrenal hyperplasia or adrenal tumor. This study investigated whether the immunocontraceptive vaccine GonaCon, a GnRH vaccine developed to reduce the fertility of wildlife species and the spread of disease, could prevent or delay onset of ACD and treat alopecia in ferrets with existing ACD. Results showed that GonaCon provided relief from ACD by causing production of antibodies to GnRH, probably suppressing production and/or release of LH. Treatment caused many ACD symptoms to disappear, allowing the ferrets to return to a normal life. The study also found that the probability of developing ACD was significantly reduced in ferrets treated with GonaCon when young (1-3 years old) compared to untreated control animals. GonaCon caused injection site reaction in some animals when administered as an intramuscular injection but caused few side effects when administered subcutaneously. Both intramuscular and subcutaneous vaccination resulted in similar levels of GnRH antibody titers. Subcutaneous vaccination with GonaCon is thus recommended to prevent the onset of ACD and as a possible treatment for ACD-signs in domestic ferrets.

Graphically characterizing the movement of a rabid striped skunk epizootic across the landscape in northwestern Wyoming.

A striped skunk (Mephitis mephitis) rabies epizootic in northwestern Wyoming was studied from the Index Case in 1988 to the last case in 1993, and possibly is the first rabies epizootic in a previously rabies-free zone monitored from beginning to end. The 843 km(2) study area comprised skunk habitat along 90 km of Shoshone River's floodplain from Bighorn Lake upstream to Cody. Of 1,015 skunks tested, 215 were rabies-positive. Integrating spatial and temporal data from positive cases, we analyzed the epizootic's movements and dynamics at 6-month intervals using multivariate movement maps, a new multivariate descriptive methodology presented here to demonstrate the epizootic's directional flow, while illustrating areas with higher case densities (i.e., wave crests). This approach should help epidemiologists and public health officials to better understand future rabies epizootics.

State-level approaches to managing the use of contraceptives in wildlife in the United States.

Several fertility control agents have recently been registered with the U.S. Environmental Protection Agency for management of wildlife or other free-ranging animals. The registration of GonaCon Immunocontraceptive Vaccine for use in white-tailed deer (Odocoileus virginianus) and OvoControl for use in Canada geese (Branta canadensis) and pigeons (Columba livia) has caused state wildlife and land management agencies to review their regulatory authority over the use of contraceptives in wildlife. As a result, many states are taking steps to ensure legislation or policies are current with emerging technologies. This article examines the various approaches states are taking to regulate the use of contraceptives. Regardless of the final regulatory approach, biological, social, economic, and political implications must all be discussed as this new tool is introduced into the field of ona wildlife management. Thoughtful consideration of all aspects of wildlife contraceptive use will lead to the development of sound, best management practices for current and future products.

Twenty years of immunocontraceptive research: lessons learned.

The National Wildlife Research Center (NWRC) began immunocontraception vaccine research by testing porcine zona pellucida (PZP) on white-tailed deer (Odocoileus virginianus). Early PZP research demonstrated that PZP induced infertility; however, increased length of the rut was observed in PZP-treated deer. An alternative vaccine using a keyhole limpet hemocyanin-gonadotropin-releasing hormone (KLH-GnRH) conjugate formulated with modified Freund's adjuvant was developed at NWRC. Suppression of GnRH has reduced reproduction in both sexes but is most effective in females. This vaccine was effective in preventing contraception in female deer for several years after a prime and boost. Due to adverse side effects of Freund's adjuvant, NWRC developed a new adjuvant called AdjuVac, a mineral oil/surfactant adjuvant with the addition of Mycobacterium avium as an immunostimulant. The price of KLH prompted a search for a more economical hemocyanin carrier protein for the GnRH peptide. Blue protein, derived from the mollusk Concholepas concholepas, proved to be a successful option. Formulation improvements resulted in a vaccine that can be effective as a single injection for multiple years, now called GonaCon. GonaCon is registered with the Environmental Protection Agency (EPA) for use in white-tailed deer in urban/suburban areas and for wild horses (Equus caballus) and burros (Equus asinus). Future GonaCon applications may include reducing reproduction to manage populations of other wildlife species, such as prairie dogs (Cynomys ludovicianus) in urban areas and suppressing reproduction to reduce the spread of venereal diseases such as brucellosis. Research is being conducted to develop a GnRH vaccine used in combination with the rabies vaccine to control population growth in free-roaming dogs, with the secondary effect of managing the spread of rabies. The EPA would regulate all these uses. Research is also ongoing on a GnRH vaccine to delay the onset of adrenocortical disease in pet ferrets (Mustela putorius), a use regulated by the United States Department of Agriculture.

The use of contraception as a disease management tool in wildlife.

Contraception offers potential as a tool for managing certain diseases in wildlife, most notably venereally transmitted diseases or diseases transmitted at parturition. Brucellosis is an excellent example of an infectious disease present in wild populations that could potentially be managed through immunocontraception. Previous studies in bison (Bison bison) suggest that a single injection of GonaCon (National Wildlife Research Center, U.S. Department of Agriculture/Animal and Plant Health Inspection Service/Wildlife Services, Fort Collins, Colorado 80521, USA) results in 3 or more yr of infertility. Ongoing studies will determine if the use of GonaCon in bison decreases shedding of Brucella abortus from infected animals and will better define the duration of infertility following a single injection

Feeding of grey squirrels (Sciurus carolinensis) with the contraceptive agent DiazaCon™: effect on cholesterol, hematology, and blood chemistry.

Grey squirrels (Sciurus carolinensis) are an invasive species in Britain and Italy. They have replaced native red squirrels (Sciurus vulgaris) throughout most of Britain, and cause damage to trees. Currently, lethal control is used to manage grey squirrel populations in Britain, but nonlethal methods might be more acceptable to the public. One such method is contraception with 20,25-diazacholesterol dihydrochloride (DiazaCon™). DiazaCon™ inhibits the conversion of desmosterol to cholesterol, resulting in increasing desmosterol concentrations and decreasing cholesterol concentrations. Because cholesterol is needed for the synthesis of steroid reproductive hormones, such as progesterone and testosterone, inhibition of cholesterol synthesis indirectly inhibits reproduction. Desmosterol is used as a marker of efficacy in laboratory studies with species that do not reproduce readily in captivity. Grey squirrels were gavaged with a DiazaCon™ solution for 2 days, and then fed DiazaCon™-coated peanuts for an additional 8 days at target doses of 50 and 100 mg DiazaCon™ per kg body weight. There was a significant difference in cholesterol concentrations in the treatment groups compared to the control group. Cholesterol was reduced by ≥ 40% for 2 months in both treatment groups. There were no differences among groups with respect to blood chemistry and hematology parameters, and mean values are reported. The mean overall dose of DiazaCon™ received was 29.0 ± 1.6 and 55.3 ± 4.3 mg/kg in the low (50 mg/kg) and high dose (100 mg/kg) groups, respectively. DiazaCon™ might provide an effective, acceptable alternative to lethal control.

Long-term fertility control in female cats with GonaCon™, a GnRH immunocontraceptive.

The uncontrolled reproduction of free-roaming feral cats contributes to overpopulation and associated concerns regarding their welfare and impact on public health and the environment. Nonsurgical fertility control that could be administered to feral cats in the field would be a powerful tool for cat population control. The objective was to test the efficacy and duration of activity of a single-dose GnRH immunocontraceptive vaccine (GonaCon™) on the fertility of adult female laboratory cats. Vaccinated cats (n = 15) received a single injection of vaccine containing a GnRH-KLH conjugate (200 µg) emulsified in a mycobacterial and oil adjuvant on study Day 0. Sham-treated cats (n = 5) received a single injection containing all vaccine components except the GnRH-KLH conjugate. A breeding trial started on study Day 120. Vaccinated cats had a longer time to conception (median 39.7 mo) compared to sham-treated cats (4.4 mo; P < 0.001). A total of 93% of vaccinated cats remained infertile for the first year following vaccination, whereas 73, 53, and 40% were infertile for 2, 3, and 4 y, respectively. At study termination (5 y after a single GnRH vaccine was administered), four cats (27%) remained infertile. The GnRH antibody titers declined more rapidly in short-term responding cats with < 2 y of infertility (n = 4), compared to long-term responding cats that experienced fertility control for >2 y (n = 11) (P < 0.05). Non-painful but persistent late-onset granulomatous injection site masses appeared 2 y after initial vaccination in five cats. We concluded that GnRH immunocontraception is an ideal candidate for further development for feral cat control.

Review of issues concerning the use of reproductive inhibitors, with particular emphasis on resolving human-wildlife conflicts in North America.

This manuscript provides an overview of past wildlife contraception efforts and discusses the current state of research. Two fertility control agents, an avian reproductive inhibitor containing the active ingredient nicarbazin and an immunocontraceptive vaccine, have received regulatory approval with the Environmental Protection Agency and are commercially available in the USA. OvoControl G Contraceptive Bait for Canada Geese and Ovo Control for pigeons are delivered as oral baits. An injectable immunocontraceptive vaccine (GonaCon Immunocontraceptive Vaccine) was registered with the Environmental Protection Agency for use in female white-tailed deer in September 2009. An injectable product (GonaCon Immunocontraceptive Vaccine) is registered for use in female white-tailed deer. Both products are labeled for use in urban/suburban areas where these species are overabundant. Several other compounds are currently being tested for use in wildlife in the USA, Europe, Australia and New Zealand that could have promise in the future. The development and use of reproductive inhibitors for resolving human-wildlife conflicts will depend on a number of factors, including meeting the requirements of regulatory agencies for use in the environment and on the biological and economical feasibility of their use. Use will also be dependent on health and safety issues and on public acceptance of the techniques.

The single-shot GnRH immunocontraceptive vaccine (GonaCon) in white-tailed deer: comparison of several GnRH preparations.

PROBLEM: An effective, single-injection, multi-year, GnRH contraceptive agent is needed to control reproduction in overabundant white-tailed deer populations. METHOD OF STUDY: Two GnRH conjugates, GonaCon (GnRH-KLH) and GonaCon-B (GnRH-blue protein), were prepared in emulsion form as one-injection and two-injection immunocontraceptive vaccine formulations. In addition, the GnRH-KLH protein conjugate was lyophilized and suspended in AdjuVac adjuvant to produce a fifth vaccine formulation. Each formulation was administered to a group of five captive adult female white-tailed deer. Reproductive performance of treated female deer was monitored for 5 years to determine the comparative efficacy of the various treatments. RESULTS: The longevity of the contraceptive response (2-5 years) was strongly influenced by the design of the conjugate antigen, the adjuvant used, and the delivery form of the vaccine. CONCLUSION: One-injection and two-injection formulations of GonaCon and GonaCon-B produced multi-year contraception in adult female white-tailed deer. GonaCon-B provided a longer lasting contraceptive effect.

GnRH immunocontraception of male cats.

The development of nonsurgical contraceptives for cats may facilitate population control of the species. The purpose of this study was to investigate the utility of GnRH for immunocontraception of male cats. Male cats (n=12) were divided into groups of three and were immunized once with 0 (sham), 50, 200, or 400 microg synthetic GnRH coupled to keyhole limpet hemocyanin and combined with a mycobacterial adjuvant to enhance immunogenicity. GnRH antibody titer, serum testosterone concentration, and scrotal size were determined monthly. At 6 months, semen was collected by electroejaculation and testes were examined histologically. GnRH antibodies were detected in all cats receiving GnRH vaccine by 1 month post-treatment and persisted throughout the study. No dose effect of GnRH was observed; titers were not different among cats treated with 50, 200, or 400 microg GnRH (P=0.5). Six of nine treated cats were classified as responders based on high GnRH antibody titers (>32,000). By 3 months post-treatment, responder cats had undetectable testosterone concentrations and testicular atrophy. Nonresponder cats had GnRH titers of 4000-32,000 and testosterone concentrations intermediate between responder and sham-treated cats. At 6 months, total sperm counts were similar for sham-treated cats (3.1+/-1.8 x 10(6) sperm) and nonresponder cats (3.4+/-1.6 x 10(6) sperm; P=0.7). Only one of the six responder cats produced sperm, none of which were motile. Combined testicular weights of responder cats (1.3+/-0.1 g) were lower than sham-treated controls (5.3+/-1.3 g; P=0.02) and nonresponder cats (2.9+/-0.3 g; P=0.02). Histologic evaluation of the testes revealed that in responder cats, the interstitial cells that were present were pale and shrunken compared to the plump, polyhedral eosinophilic cells in sham-treated cats. GnRH responder cats had marked tubular atrophy with vacuolated Sertoli cells and a paucity of germ cells. Single-dose GnRH treatment resulted in testosterone concentrations and semen quality consistent with immunocastration in a majority of cats treated.

Quantification of plasma and egg 4,4'-dinitrocarbanilide (DNC) residues for the efficient development of a nicarbazin-based contraceptive for pest waterfowl.

Urbanization and associated landscaping has increased the abundance of year-round habitat for waterfowl, resulting in vegetation damage, loss of recreational activities, air transportation mishaps and health hazards. As part of a research program to develop socially acceptable techniques for management of pest bird populations, we are evaluating nicarbazin as a contraceptive in pest and surrogate avian species. As reproductive studies with Canada Geese (Branta canadensis) are tedious due to the difficulty of conducting controlled field studies and/or breeding geese in captivity, we evaluated the effects of oral nicarbazin administration on the production and hatchability of chicken eggs. Blood plasma and egg DNC concentrations were correlated to contraceptive efficacy. Subsequent studies are being conducted with geese to determine the diet nicarbazin concentration required to produce the desired blood and plasma DNC concentrations. This approach permits the expeditious evaluation of formulations and dosing regimes by simply monitoring blood DNC concentrations in target species.