Five grey-headed flying fox (Pteropus poliocephalus) housed in a large mixed-species exhibit at the National Aquarium in Baltimore developed skeletal fluorosis based on exam findings and diagnostic testing. Initial clinical signs were firm multifocal swellings of digits and long bones and decreased mobility. Radiographs showed significant periosteal proliferation of digits and long bones suspicious of chronic fluorosis as seen at other institutions (Ialeggio D, personal communication).1 Bloodwork revealed elevated alkaline phosphatase and hypocalcemia. There was a moderate negative correlation between alkaline phosphatase and calcium values at initial presentation (r=−0.402). Analyses of the animals’ diet (as fed with supplements), water, and juice showed low fluoride concentrations (1.77 ppm, 0.86 ppm, and 0.86 ppm respectively). Salt precipitate that collected on the bat roosting wire had very high fluoride concentrations (1065 ppm). Salts formed from the exhibit misting system which sprayed municipal water just above the roosting wire. The salts were consumed by the bats. There was an inverse relationship between animal weight and severity of bone and blood chemistry changes. The animals improved with medical management off exhibit. Bloodwork values were normalizing, and bone lesions remained stable to improved several months after cessation of exposure to the exhibit salts. A sixth individual housed off exhibit with no exposure to the salts, maintained on the same diet as the exhibit animals, had no bone changes/lesions and normal blood chemistries. Annual bloodwork review showed abnormalities developed prior to the bone changes and may allow for early detection of cases.
1. Duncan M, Crawshaw GJ, Mehren KG, Pritzker KPH, Mendes M, Smith DA. Multicentric hyperostosis consistent with fluorosis in captive fruit bats (Pteropus giganteus, P. poliocephalus, and Rousettus aegyptiacus). J Zoo Wildl Med. 1996;27(3):325–338.