Serum Vitamin D and Calcium Metabolism in Asian Elephants Serologically Reactive and Non-Reactive to TB
American Association of Zoo Veterinarians Conference 2011
Dalen W. Agnew1, DVM, PhD, DACVP; Susan Mikota2, DVM; Thomas Herdt1, DVM, PhD; Patricia Schenck1, DVM, PhD; Michelle Miller3, DVM, PhD3; Ishwari Dhakal4, PhD; Kamal P. Gairhe5, DVM, MVSc
1College of Veterinary Medicine, Michigan State University, Lansing, MI, USA; 2Elephant Care International, Hohenwald, TN, USA; 3Palm Beach Zoo, West Palm Beach, FL, USA; 4Institute of Agriculture and Animal Science Rampur, Tribhuvan University, Chitwan, Nepal; 5Chitwan National Park, Department of National Parks and Wildlife Conservation, Nepal
Tuberculosis is a serious re-emerging disease affecting humans and domestic and wild animals, particularly captive elephants. Vitamin D and calcium metabolism have recently gained prominence in the evaluation of human tuberculosis patients. Research has indicated that vitamin D plays a critical role in the production of cathelicidin, important in killing intracellular mycobacteria. Other studies support the conclusion that vitamin D is important in the treatment and prevention of tuberculosis and its deficiency is associated with higher rates of infection. In this study, serum was collected from 15 captive elephants in Nepal reactive on the Elephant TB Stat-Pak® and/or MAPIA tests (Chembio Diagnostics, Medford, NY) and from 15 age- and sex-matched non-reactive controls. Samples were analyzed via ICP-MS for phosphorus, chloride, magnesium, potassium, bicarbonate, cobalt, copper, iron, manganese, molybdenum, selenium, sodium, and zinc. Ionized calcium was measured using an ion-sensitive electrode. Calcidiol (25-hydroxyvitamin D3) and calcitriol (1,25-dihydroxyvitamin D3, the active form of vitamin D3) were measured by radioimmunoassay. Average calcidiol levels were 2.20 nmol/L (range 0–10). Average serum calcitriol was 28.52 pmol/L (range 13.9–53.7). Calcitriol was significantly different between reactive and non-reactive elephants (p=0.017) The average calcitriol was 31.5 pmol/L in TB non-reactive elephants and 25.6 pmol/L in TB-reactive elephants. Copper also differed significantly between TB non-reactive and TB-reactive elephants (p=0.004). Copper in TB non-reactive elephants was 1.00 and in TB-reactive elephants 1.13 µg/ml. Other values did not differ significantly between groups. These data indicate that variations in vitamin D metabolism are significantly associated with TB status.
The authors would like to acknowledge the AAZV Mazuri fund for financial support, the Department of National Parks and Wildlife Conservation in Nepal for collaboration, and Justin Zyskowski and Susan Beyerlein for their laboratory expertise.