GnRH Vaccine Reaction in Large Flying Foxes (Pteropus vampyrus)
2018 Joint EAZWV/AAZV/Leibniz-IZW Conference
Natalie D. Mylniczenko1, MS, DVM, DACZM; Daniel V. Fredholm1, MS, DVM, DACZM; Geoffrey W. Pye1, BVSc, MSc, DACZM; Hani D. Freeman1, PhD; Catharine J. Wheaton1, PhD; Natalie Hall1, DVM, DACZM
1Disney’s Animals, Science, and Environment, Bay Lake, FL, USA


Free-ranging large flying fox (Pteropus vampyrus) colonies are normally harems with one male to multiple females. All-male colonies are common in the population under managed care with adverse interactions occurring between males due to significant sexual conflict; resulting in trauma. These behaviors correlate with seasonal variations in hormones (i.e., testosterone, cortisol).2 Thus, hormone suppression was expected to decrease agonistic behaviors4 and improve welfare. One ml of GnRH vaccinea was administered subcutaneously to 12 male bats in an effort to suppress seasonal hormonal change. Eleven bats received the injection in the interscapular region and all developed vaccine reactions with one or more clinical presentations that included localized irritation, swelling, and pruritus that progressed to skin ulceration and necrosis with sloughing, and facial edema. One individual received the injection in the leg and did not develop any reaction. The nature of this species to behaviorally focus on areas of irritation escalated the extent of the wounds, with some cases requiring intense medical, surgical, and behavioral intervention. While this vaccine has been used widely in many species with few adverse effects,3 large flying foxes appear to be particularly sensitive. Proposed contributing factors include: injection site location, severe inflammatory reaction associated with stimulation of the volatile compounds made by shoulder scent glands7, stimulation of the androgen sensitive sebaceous glands,1,5 focal interaction with innate bacteria in the skin,6 and a complex sensitivity/hyper-response to the adjuvant. Ongoing data collection suggests successful hormonal suppressive effects, therefore the administration of this GnRH vaccine in large flying foxes warrants further investigation.

a. Improvest: gonadotropin releasing factor analog-diphtheria toxoid conjugate


Special thanks to the animal husbandry and animal health teams at Disney’s Animal Kingdom for managing these cases, and to Dr. Carlos Rodriguez, Dipl ACVP for pathology interpretation associated with the cases. Thanks to S. M. Nederveld and J.P. Crane, Zoetis, Kalamazoo, MI.

Literature Cited

1.  Dapson RW, Studier EH, Buckingham MJ, Studier AL. Histochemistry of odoriferous secretions from integumentary glands in three species of bats. J Mammal. 1977;58:531–535.

2.  Freeman HD, Wood M, Schook MW, Leighty KA, Lavin SR, Wiebe S, Blowers T, Daneault R, Mylniczenko ND, Wheaton CJ. Seasonality of agonistic behavior and non-invasively measured hormones in an ex situ all-male colony of large flying foxes (Pteropus vampyrus). Zoo Biol, In press.

3.  Garside D, Gebril A, Alsaadi M, Ferro VA. Fertility control in wildlife: review of current status, including novel and future technologies. In: Holt WV, Brown JL, Comizzoli P (eds.). Reproductive Sciences in Animal Conservation. New York (NY): Springer; 2014. p. 467–488.

4.  Karaconji B, Lloyd B, Campbell N, Meaney D, Ahern T. Effect of an anti‐ gonadotropin‐releasing factor vaccine on sexual and aggressive behaviour in male pigs during the finishing period under Australian field conditions. Aust Vet J. 2015;93:121–123.

5.  Scully WM, Fenton MB, Saleuddin AS. A histological examination of the holding sacs and glandular scent organs of some bat species (Emballonuridae, Hipposideridae, Phyllostomidae, Vespertilionidae, and Molossidae). Canadian J Zool. 2000;78:613–623.

6.  Voigt CC, Caspers B, Speck S. Bats, bacteria, and bat smell: sex-specific diversity of microbes in a sexually selected scent organ. J Mammal. 2005;86:745–749.

7.  Wood WF, Walsh A, Seyjagat J, Weldon PJ. Volatile compounds in shoulder gland secretions of male flying foxes, genus Pteropus (Pteropodidae, Chiroptera). Z Naturforschung C. 2005;60:779–784.


Speaker Information
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Daniel V. Fredholm, MS, DVM, DACZM
Disney’s Animals, Science, and Environment
Bay Lake, FL, USA

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