Pathologic and Parasitologic Findings of Free-Ranging Yacare Caiman (Caiman yacare) in the Brazilian Pantanal.

Abstract

Periods of drought have been observed in the Brazilian Pantanal for several decades, typically occurring from May to November. These droughts impact the conservation of thousands of species, including the yacare caiman (Caiman yacare). This study aimed to describe the pathologic and parasitologic findings from postmortem examinations of free-ranging yacare caimans to provide insights regarding the influence of extreme drought on the health of this species. In total, 13 caimans were necropsied, representing deaths during a period of extreme drought (October 2021, 12 individuals) and a period of typical rainfall (October 2022, 1 individual). The main lesions identified in the respiratory tract included pulmonary granulomas (10/13, 77%), tracheal granulomas (8/13, 61.6%), tracheal pentastomids (5/13, 38.5%), and pulmonary pentastomids (3/13, 23.1%). The main lesions identified in the gastrointestinal tract included lesions caused by helminthiasis (Nematoda and Acanthocephala: 10/13, 77%), granulomas (5/13, 38.5%,), and intestinal hemorrhage (2/13, 15.4%). Other findings included myocardial granulomas, bacterial endocarditis, and unidentified helminths within renal tubules. Five helminth species were morphologically identified: the intestinal acanthocephalan Polyacanthorhynchus rhopalorhynchus, the respiratory pentastomids Alofia platycephala and Leiperia gracilis, the gastric nematode Ortleppascaris alata, and the intestinal nematode Micropleura vazi. The increased number of reported deaths and the consistent identification of parasite-associated lesions in the necropsied caimans from 2021 suggests an association between extreme drought, parasite infections, and the health status of yacare caiman.