Incidental transmural granulomatous enteritis caused by Molineus torulosus in a capuchin monkey (Sapajus nigritus) under human care: pathological and morphometric findings.

Primates of the genus Sapajus are widely distributed throughout Brazil, with several species currently listed as endangered by the IUCN. Identifying diseases that affect these populations is critical, particularly parasitic infections, which can debilitate hosts and predispose them to secondary pathogens. Molineus torulosus is a trichostrongylid nematode known to cause significant gastrointestinal injury in neotropical primates. This report describes the pathological and morphometric findings of an incidental case of M. torulosus parasitism in a captive female capuchin monkey (Sapajus nigritus) referred to the postmortem examination. The animal was admitted to the Center for Medicine and Research of Wild Animals, presenting perforating skin lesions and progressive spastic paralysis, under clinical suspicion of tetanus. Following the animal's death three days post-admission, gross examination revealed poor body condition and ulcerative skin lesions. The primary gross finding consisted of multiple whitish, firm, transmural nodules in the duodenum and jejunum. Histopathological evaluation of these nodules revealed multifocal, moderate, lymphohistiocytic and granulomatous enteritis associated with intralesional nematodes and eggs; meanwhile, the central nervous system showed no lesions, supporting the clinical suspicion of tetanus. Parasitological examination confirmed the agent as M. torulosus. This case highlights the severe pathological impact of this parasite and emphasizes the importance of diagnostic surveillance and health monitoring in wild animals under human care to expand the limited literature on parasitic diseases in Neotropical primates.