Multisystemic and cerebral infection associated with Halicephalobus gingivalis in Brazilian Criollo horses

Abstract Halicephalosis is a rare cosmopolitan disease affecting equids, cattle, and humans, manifesting as meningoencephalitis. This study reports the detection of Halicephalobus gingivalis infection in two adult horses with neurological clinical signs in Rio Grande do Sul state, in the Southern Brazil. It underscores the pathological main findings and phylogenetic analyses. In both cases, the horses exhibited severe neurological manifestations and were euthanized due to poor prognosis. Pathological findings revealed gross brain lesions, in addition, alterations in the kidneys and lymph nodes. Histopathological examinations revealed granulomatous encephalitis, nephritis, and lymphadenitis, lesions that have been reported in human and animal infections. Molecular analyses by 28 S rRNA gene confirmed H. gingivalis infection and identified a genetic correlation of the isolates with Lineage 3 of the nematode, which is associated with infections in horses worldwide. This report represents the first phylogenetic description of H. gingivalis in Brazil and emphasizes the zoonotic significance of this parasite, particularly in occupational settings.