Abstract
Crocodilians are reported to have a low susceptibility to the toxic effects of lead.1,2 Cumulative effects of iatrogenic lead toxicity were observed in a group of Nile crocodiles at a private collection following the prolonged intermittent feeding of bird carcasses contaminated with ammunition pellets. Antemortem lesions included extensive tooth loss, anorexia, weakness, lethargy, limb paresis and deep skin ulceration. Hematological and chemistry changes included chronic nonregenerative anemia and elevations of aspartate aminotransferase (AST) and creatine kinase (CK). Mean blood lead concentrations in the group were 3.86 ppm. The group was treated using D-penicillamine administered orally at doses and frequencies calculated based upon the principles of allometric scaling.3 After three weeks of treatment, blood lead concentrations within the group had dropped significantly (mean±SD; p<0.03). Despite therapy, all animals died. Lead ammunition pellets at varying stages of degradation were present in the stomachs of two animals at necropsy. Dominant histopathological findings included moderate to severe demyelination of the brain stem, renal tubular necrosis, and hyaline necrosis of skeletal muscle suggestive of secondary myopathy. Contrary to anecdotal evidence, Nile crocodiles appear susceptible to fatal lead poisoning after cumulative exposure to high levels of this heavy metal.
Literature Cited
1. Cook RA, Behler J, Brazaitis P. A survey of blood lead levels in crocodilians. In: Proc International Assoc Aquat Anim Med; 1988:146–147.
2. Hammerton KM, Jayasinghe N, Jeffree RA, Lim RA. Experimental study of blood lead kinetics in estuarine crocodiles (Crocodylus porosus) exposed to ingested lead shot. Arch Environ Contam Toxicol. 2003;45:390–398.
3. Mayer J, Kaufman G, Pokras M. Allometric scaling. In: Mader DR, ed. Reptile Medicine and Surgery. 2nd ed. St. Louis, MO: Saunders Elsevier:419–427.