Haplorchis pumilio (Trematoda: Heterophyidae) as a new fish-borne zoonotic agent transmitted by Melanoides tuberculata (Mollusca: Thiaridae) in Brazil: A morphological and molecular study.

The fishborne zoonotic trematode Haplorchis pumilio (Looss, 1896) is here reported for the first time in Brazil based on morphological, experimental and molecular studies. Pleurolophocercous cercariae emerged from the invasive snail Melanoides tuberculata collected in the municipality of Ceará-Mirim, state of Rio Grande do Norte, Northeast region of Brazil, in November 2018, were used for experimental infection of guppies, Poecilia reticulata. Metacercariae were extracted from the caudal musculature of these fishes and were used to infect mice. Adult parasites recovered in the small intestine of the mice were morphologically identified as H. pumilio. Molecular sequences were obtained for the Brazilian and Peruvian isolates of H. pumilio, and were compared with data available in GenBank. Analyses of fragments of the nuclear genes 28S (1219 bp) and ITS-2 (290 bp) revealed 98.48-100% similarity between the South American and Asian isolates of H. pumilio. Moreover, new sequences of the mitochondrial gene cox-1 obtained for the Brazilian (797 bp) and Peruvian (646 pb) isolates were 100% similar to a Mexican isolate of this species and 97.54% similar to an isolate from Thailand. This finding reveals the potential for occurrence of human haplorchiasis in Brazil, especially because of the increasing popularity of raw fish dishes in the country.