Fatal toxoplasmosis in free-ranging Colombian night monkeys (Aotus lemurinus) from a peri-urban area of Cali, southwestern Colombia.

Toxoplasma gondii is a globally distributed protozoan parasite capable of causing severe disease in highly susceptible hosts, including Neotropical non-human primates. We report two cases of fatal toxoplasmosis in free-ranging Colombian night monkeys (Aotus lemurinus) from a peri-urban area of Cali, southwestern Colombia. An adult male carrying an infant and an adult pregnant female were found moribund or dead and submitted for necropsy and histopathological evaluation. Both individuals exhibited severe multisystemic lesions characterized by necrosis and abundant intralesional tachyzoites consistent with T. gondii. In the pregnant female, the diagnosis was further confirmed by real-time PCR performed on whole blood. These cases represent the first report of fatal toxoplasmosis in free-ranging Aotus spp. The findings highlight the susceptibility of night monkeys to T. gondii and underscore the growing risk of toxoplasmosis for wildlife inhabiting urban and peri-urban environments.