RESEARCH

TOO MANY DEER can contribute to animal-vehicle collisions, spread tick-borne diseases, decimate ornamental plants, and cause extensive damage to agricultural crops.

• 41 free-ranging fallow deer (Dama dama) were vaccinated with a single injection of SpayVac, and none of them became pregnant for 3 years following treatment compared to 97% of untreated deer found pregnant each year. 
• 38 free-ranging white-tailed deer (Odocoileus virginianus) were given a single injection of SpayVac, and none of them became pregnant during the first 2 years after vaccination compared to 78% of untreated deer that became pregnant each year.9,10
• 5 captive white-tailed deer (Odocoileus virginianus) were given a single injection of SpayVac, and none of them became pregnant during the next 3 years of the study compared to 100% of the control deer.12
• A recent study completed in wild, free-roaming red deer (Cervus elaphus) in Germany demonstrated that SpayVac® successfully reduced fertility to 11% for at least one year, compared to a fertility rate of 86% in control animals (results are being published).
  
   

TOO MANY HORSES can compact soils, increase erosion, decrease plant cover, compete with native animals over resources, and be associated with loss of biodiversity.

In the U.S., the Bureau of Land Management (BLM) manages free-roaming equids by removing animals from the range and occasionally applying fertility control measures.  The majority of horses (Equus caballus) that are removed are sent to long-term holding facilities. The BLM off-range population currently includes nearly 62,000 horses and burros and cost $108.5 million USD in FY2023 to maintain. On-range equid numbers were estimated in March 2023 to be approximately 82,883 (68,928 horses and 13,955 burros), which is three times more than the mandated appropriate management level. These populations can grow at a rate of 20%+ annually!

• 12 captive mares were given a single injection of SpayVac, which dropped pregnancy rates to 0, 17, 17 and 17% for 1 to 4 years post-treatment, respectively, compared to 75, 75, 88 and 100% for untreated mares.6
   
• 14 captive mares were given a single injection of SpayVac, and 3-4 months post-vaccination, 93% of the mares stopped cycling compared to control mares that continued to cycle. This study was also designed as a safety trial and demonstrated no adverse health effects to any treated mares.5
   
• 30 feral mares maintained in holding facilities were given a single injection of SpayVac, and fertility rates in the treated group dropped to 13, 47, and 43% compared to 100, 98 and 100% in controls for 1 to 3 years post-vaccination, respectively.4

Several other trials with SpayVac in horses are ongoing and will help us determine the best injection site, ideal antigen dose, and test efficacy in feral, free-ranging populations.

 

TOO MANY ELEPHANTS living near people can destroy crops, raid food stores, damage infrastructure, and cause injury and loss of human life.

• 6 captive African elephants (Loxodonta africana) were vaccinated with SpayVac-pZP and antibody titers remained elevated for over 7 years post-vaccination. 13

A trial with Asian elephants (Elephas maximus) will soon get underway to test contraceptive efficacy of a single SpayVac-pZP vaccination in both captive and free-ranging animals.

TOO MANY SEALS can negatively impact the dynamics of marine fish populations.

• 101 wild grey seals (Halichoerus grypus) were vaccinated with a single injection of SpayVac-pZP shortly after pupping, which resulted in a 80-85% decrease in fertility for over 10 years. 2,17,18

FARMED FISH (Oncorhynchus mykiss) that escape and breed with their wild counterparts may produce offspring that are less suited to surviving in the wild, and as females mature, they put the majority of their energy into egg production.

• 50 fish have been vaccinated with SpayVac-pZP and 50 fish have been vaccinated with SpayVac-GnRH to see if immunization can prevent sexual maturation.  Results are pending.

SEVERAL TRIALS WITH SPAYVAC IN WILD HORSES ARE ONGOING OR PLANNED. 

• With funding and support from the US Department of the Interior's Bureau of Land Management, a 5-year trial with 55 captive mares was initiated in 2023 to determine if injection site results in a difference in immune response and subsequent contraceptive efficacy after vaccination with SpayVac-pZP. Deepening our understanding of how SpayVac initiates an immune response and affects reproduction in mares will help us optimize administration and ultimately lead to a reliable fertility control option that can be broadly applied by managers of feral horse populations.
• A 5-year study with 100 free-ranging horses in Romania was initiated in 2023 to test differences in contraceptive efficacy based on injection site location; and a second study will be started in 2024 with another 100 free-ranging mares to test differences in contraceptive efficacy based on pZP quantity. SpayVac for horses is currently made with 400 µg pZP per dose, but earlier trials demonstrated efficacy with just 200 µg pZP per dose. If less pZP can be used in SpayVac formulations, unit costs can be lowered, because isolating pZP is a labor-intensive process. Both of these studies are being funded by a global animal welfare organization.

Macaques can spread diseases to humans, steal belongings, and damage property, agriculture, and native vegetation. Macaques are considered to be an invasive species in some parts of the world, including Florida and South Carolina.

• 50 female macaques (Macaca mulatta) in a semi-free-ranging environment were vaccinated with a single injection of SpayVac-pZP, and results for the first year were promising with 37% of the females giving birth compared to 79% of control animals (p<0.01). The study is ongoing, and results are expected to be published upon completion.

As free-ranging Asian elephant (Elephas maximus) populations become increasingly confined to smaller ranges, concerns grow about human-elephant conflict and its negative impact on flora and fauna.  A trial with Asian elephants in Thailand is now underway to test contraceptive efficacy with a single SpayVac-pZP vaccination in both captive and free-ranging animals.

Overviews

1. Fertility control options for management of free-roaming horse populations. Bechert U, Turner Jr, J, Baker D, Eckery D, Bruemmer J, Lyman C, Prado T, King S, Fraker M. 2022. Human-Wildlife Interactions 16(2):1-38.

2. Twenty years of SpayVac® research: Potential for regulating feral horse and burro populations in the U.S. Bechert U, Fraker M. 2018. Human Wildlife Interactions 12(1):117-130.

Feral Horses

3. IgG4/7 responses correlate with contraception in mares vaccinated with SpayVac. Bechert U, Rohde J, Freer H, Wagner B. 2018. Theriogenology 121:168-174.

4. Efficacy of SpayVac® as a contraceptive in feral horses. Roelle JE, Germaine SS, Kane AJ, Cade BS. 2017. Wildlife Society Bulletin 41(1):107-115.

5. Effects of two porcine zona pellucida immunocontraceptive vaccines on ovarian activity in horses. Bechert U, Bartell J, Kutzler M, Menino Jr, A, Bildfell R, Anderson M, Fraker M. 2013.  Journal of Wildlife Management 77(7):1386-1400. 

6. Four-year contraception rates of mares treated with single-injections porcine zona pellucida and GnRH vaccines and intrauterine devices. Killian G, Thain D, Diehl N, Rhyan J, Miller L. 2008.  Wildlife Research 35(6):531-539.

7. Achieving population goals in a long-lived wildlife species (Equus caballus) with contraception. Kirkpatrick JF, Turner A. 2008. Wildlife Research 35:513-519.

8. Immunocontraception and increased longevity in equids. Kirkpatrick FJ, Turner A. 2007. Zoo Biology 26(4):237-44.

Deer

9. Effectiveness of SpayVac® for reducing white-tailed deer fertility. Locke SL, Cook MW, Harveson LA, Davis DS, Lopez RR, Silvy NJ, Fraker MA. 2007.  Journal of Wildlife Diseases 43(4):726-730.

10. Effects of SpayVac® on urban female white-tailed deer movements. Hernandez S, Locke SL, Cook MW, Harveson LA, Davis DS, Lopez RR, Silvy NJ, Fraker MA. 2006.  Wildlife Society Bulletin 34(5):1430-1434.

11. Long-lasting, single-dose immunocontraception of feral fallow deer in British Columbia. Fraker MA, Brown RG, Gaunt GE, Kerr JA, Pohajdak B. 2002. Journal of Wildlife Management 66(4):1141-1147.

12. Factors contributing to the success of a single-shot, multiyear pZP immunocontraceptive vaccine for white-tailed deer. Miller LA, Fagerstone KA, Wagner DC, Killian GJ. 2009. Human-Wildlife Conflicts 3(1):103-115.

Elephants

13. The response of African elephants to a single-dose of SpayVac®, a pZP contraceptive vaccine, over a 7-year period. Bechert U, Fraker M. 2016. Pachyderm 57:97-108.

14. Implementing immunocontraception in free-ranging African elephants at Makalali Conservancy. Delsink A, van Altena J, Grobler D, Bertschinger H, Kirkpatrick J, Slotow R. 2007. Journal of South African Veterinary Association 78:25–30.

15. How immunocontraception can contribute to elephant management in small, enclosed reserves: Munyawana population as a case study. Druce H, Mackey R, Slotow R. 2011. PLoS ONE 6:e27952.

16. Contraceptive potential of the porcine zona pellucida vaccine in the African elephant (Loxodonta africana). Fayrer-Hosken R, Bertschinger H, Kirkpatrick J, Grobler D, Lamberski N, Honneyman G, Ulrich R. 1999. Theriogenology 52:835–846.

Seals

17. Evidence for a long-lasting single administration vaccine in wild grey seals. Brown RG, Bowen WD, Eddington JD, Kimmins WC, Mezei M, Parson JL, Pohajdak B. 1997. Journal of Reproductive Immunology 35(1):43–51.

18. Temporal trends in antibody production in captive grey, harp and hooded seals to a single administration of immunocontraceptive vaccine. Brown RG, Bowen WD, Eddington JD, Kimmins WC, Mezei M, Parsons JL, Pohajdak B. 1997. Journal of Reproductive Immunology 35(1):53–64