RESUMO
The thermodimorphic fungus Paracoccidioides brasiliensis is the etiological agent of paracoccidioidomycosis (PCM), a deep mycosis endemic in Latin American countries that affects mainly male rural workers. Infection by P. brasiliensis has also been reported in several species of terrestrial animals; however, the capacity of the fungus to infect aquatic organisms is poorly known. The aim of this study was to detect P. brasiliensis in a fish species, Nile tilapia (Oreochromis niloticus), the most farmed and widely distributed fish in endemic areas for human PCM in Brazil. As a first step, the humoral immune response against the fungus was evaluated in an experimental group of three fish immunized with inactivated P. brasiliensis yeast cells. For the seroepidemiological study, serum samples of Nile tilapia raised in cages (n = 109) and in ponds (n = 105), collected from a fish slaughterhouse, were analyzed for P. brasiliensis antibodies by ELISA using gp43 as antigen. All the inoculated fish produced antibodies against the fungus. The seropositivity observed in fish raised in cages and ponds was 17.4 and 5.7%, respectively. Due to the higher seropositivity observed in caged fish, 100 tissue samples (encephalon, liver, and kidney), from another group of tilapia raised in cages, were analyzed by polymerase chain reaction (PCR; Pb-ITSR and Pb-ITSE). Three tissue samples (liver n = 1, kidney n = 1, and enchepahlon n = 1) from three different fish resulted positive to PCR. This is the first report to show serological and molecular evidence of P. brasiliensis infection in a fish species.