A geriatric colony of Jamaican fruit bats (Artibeus jamaicensis) at Zoo Miami was found to have an increasing occurrence of proliferative boney lesions on long bones of the wings, legs, and mandibles, which frequently were associated with decreased ability to fly and weight loss and led to euthanasia in numerous cases. Gross and histologic examination of the bone lesions revealed changes consistent with previously reported and unpublished cases of skeletal fluorosis in bats (Trupkiewicz, J.G. and D.M. Ialeggio, pers. comm.).4 Laboratory measurements of fluoride content of the bones of grossly affected and unaffected bats revealed high levels consistent with fluoride toxicosis (1,649–2,338 ppm, wet-weight).4 These values were compared with bone fluoride measured in another species of fruit bat (Seba’s short-tailed fruit bat, Carollia perspicillata) that had been at Zoo Miami for less than 6 mo whose values appeared to fall within a more normal expected range (392 ppm, wet-weight). Contact with the Lubee Bat Conservancy and the Oakland Zoo revealed similar cases of elevated skeletal fluoride levels and osteoproliferative lesions in other species of fruit bats (Pteropus vampyrus, P. hypomelanus, P. rodricensis, P. poliocephalus, P. giganteus, as well as A. jamaicensis). The Pteropus spp. had hyperostotic nodules predominantly in thumbs and digits and around the gumlines, suggesting a difference in predilection for proliferative lesion sites in various bat species, or different stages of the disease process. Dietary, water, and some substrate (rockwork, soil, caging) sources for fluoride were investigated separately at each institution, using different laboratories and testing methods. No conclusive source for the elevated fluoride levels was discovered; however, it was determined that a specific powdered supplement, and calcium diphosphate added to some diets, may have been the greatest contributors to the overall fluoride load in these bats. A survey was circulated by the Lubee Bat Conservancy to all zoos holding bats in North America, and a few respondents confirmed that they also had seen clinical cases which were consistent with fluorosis. Fluoride requirements and toxic levels have not been established for most species other than humans and domestic cattle, but excessive levels can result in bone and joint pain, tooth and skeletal lesions, polydypsia, and decreased feed intake with condition loss.1,2,3,4,5,6 Bats may be very susceptible to unrecognized additive quantities of fluoride in multiple dietary and environmental sources. The producer of the powdered supplement has worked closely with a nutritionist and the Lubee Bat Conservancy to restrict fluoride levels in their diet since the discovery of these cases. A newly formulated supplement powder now contains fluoride levels of 4–5 ppm. Other possible sources of fluoride at each institution, including fluoridated water and various substrates, were evaluated and attempts made to eliminate or reduce the bats’ cumulative exposures.
The authors would like to thank Dr. John Trupkiewicz, Dr. Ellen Dierenfeld, and A.J .Higginbottom for their investigative support, and the following laboratories for analyses and interpretation assistance with fluoride levels in bat tissues and dietary items: Animal Health Diagnostic Center, Cornell University, New York State College of Veterinary Medicine, Ithaca, NY 14853; Eurofins Scientific, Des Moines, IA 50321, USA; Veterinary Diagnostic Laboratory, Iowa State University, Ames, IA 50011; California Animal Health and Food Safety Laboratory System, University of California – Davis, School of Veterinary Medicine, Davis, CA 95616, USA.
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2. Dempsey, J.L. 2004. Fruit bats: Nutrition and dietary husbandry. Nutrition Advisory Group Handbook. Fact Sheet 014. Available online: www.nagonline.net/Technical Papers/technical_papers.htm. Accessed: 20 Apr 2010. (VIN editor: link could not be accessed on 01/17/21 and was updated https://nagonline.net/wp-content/uploads/2014/01/NAG-FS014-FRUIT-BATS-AUG-2004.pdf)
3. Dhar, V., and M. Bhatnagar. 2009. Physiology and toxicity of fluoride. Indian J. Dent. Res. 20:350–355.
4. Duncan, M., G.J. Crawshaw, K.G. Mehren, K.P.H. Pritzker, M. Mendes, and D.A. Smith. 1996. Multicentric hyperostosis consistent with fluorosis in captive fruit bats (Pteropus giganteus, P. poliocephalus, and Rousettus aegyptiacus). J. Zoo Wildl. Med. 27:325–338.
5. Lloyd, C. and M. Stidworthy. 2009. Clinical fluorosis in captive gerenuk and bongo antelope. Wildl. Middle East. 4(2). Available online: www.wmenews.com. Accessed: 08 Jun 2010.
6. Suttie, J. 1980. Nutritional aspects of fluoride toxicosis. J. Anim. Sci. 51: 759–766.