A retrospective study of neuroschistosomiasis in aquatic birds.

Schistosomatidae is a family of trematodes that generally have an indirect life cycle, with snails as intermediate hosts in avian schistosomiasis and aquatic birds as definitive hosts. Although multiple studies report avian schistosomes, there are only a few reports describing gross and histological lesions of neuroschistosomiasis in aquatic birds. Herein, a retrospective study including 12 aquatic birds with neuroschistosomiasis was conducted to further characterize the clinical, gross, and histologic findings and to identify the trematodes. The median age of birds was 12 years, and schistosomes were observed in the brain, with or without granulomatous inflammation. Neuroschistosomiasis was likely related to death in 5 out of 12 birds. Twelve formalin-fixed paraffin-embedded (FFPE) samples containing brain, 1 FFPE sample containing intestine, and 1 fresh brain sample were used for polymerase chain reaction (PCR) and sequencing to identify the schistosomes. Dendritobilharzia pulverulenta was identified from 3 out of 13 FFPE samples and 1 fresh brain sample. Neuroschistosomiasis presumptively associated with Dendritobilharzia sp. infection has been reported in swans and geese; however, the identification was based on the clinical signs, lesions, location within the hosts, and the morphology of adult worms without molecular analysis. To the authors' knowledge, the histologic description and molecular identification of schistosomes that cause neuroschistosomiasis in multiple aquatic bird species other than swans and geese have not been reported.