Review of Histologic Lesions and Mortality in Rio Cauca Caecilians (Typhlonectes Natans) over a 22-Year Period

Rio Cauca caecilians (Typhlonectes natans) are a unique, fully aquatic species of amphibian from the order Gymnophiona. They are housed in several zoological institutions and aquaria with limited information available regarding health and disease. This retrospective study evaluates common pathologic findings and causes of mortality of Rio Cauca caecilians from three different institutions over a 22-y period. Comparisons to previous medical health surveys were conducted with evaluation according to age class and sex to determine whether the primary causes of mortality and common histologic findings have remained similar over time and between institutions. Between 1997 and 2019, the 62 mortalities included males (15/62; 24.2%), females (26/62; 41.9%), and undetermined sex (21/62; 33.9%). The majority of examined individuals were adult (38/62; 61.3%), followed by juveniles (13/62; 21.0%), neonates (9/62; 14.5%), and undetermined age class (2/62; 3.2%). Thirteen (21.0%) individuals were euthanatized. Adult females (16/62; 25.48%) represented the largest group. In adults, the most common lesion and contributor to death was renal disease (28/38; 73.7%) followed by skin disease (16/38; 42.1%), including oomycete dermatitis (8/38; 21.1%) from Saprolegnia sp. Other common findings included bacterial dermatitis, gastrointestinal nematodiasis, and adrenal hyperplasia. This retrospective study will provide a useful reference to help guide veterinary care, management decisions, and collection management planning for this caecilian species in managed care.