[A case of human infection with Clinostomum sp]

Morphological and Molecular Characterization of Clinostomum detruncatum (Trematoda: Clinostomidae) Metacercariae Infecting Synbranchus marmoratus

A complete morphological description, supported by molecular data, of Clinostomum detruncatum metacercariae is reported in this study. The metacercariae were found infecting Synbranchus marmoratus from the Paraná River, municipality of Guaíra, Paraná State, Brazil. The taenioidean uterus is the main morphological characteristic of this species. Both neighbor-joining (NJ) and maximum likelihood (ML) trees showed 2 clear separate clusters grouping together the species from the Palearctic region (Clinostomum complanatum, Clinostomum cutaneum, Clinostomum phalacrocoracis, Clinostomum philippinense) and those from the Nearctic/Neotropical regions (Clinostomum marginatum, Clinostomum tataxumui, C. detruncatum, Clinostomum sp. 7). The latter clade is divided into 2 subclades grouping species from North America and Mexico (C. marginatum and C. tataxumui), and those from Brazil (C. detruncatum and Clinostomum sp. 7).

The protective capacity of UV-exposed Clinostomum complanatum metacercariae against challenge infections in Ardeola ibis ibis

Exposure of encysted metacercariae of Clinostomum complanatum to UV light (254 nm) for 60 min reduced their development into adult worms in buff-backed herons (95.7% reduction in worm burden). Metacercariae that succeeded in developing into adult worms, showed low fecundity levels. Furthermore, 30% of eggs laid showed abnormal shape; however, all normal and abnormal eggs failed to hatch into miracidia. The effectiveness of UV-irradiated metacercariae as a vaccine was investigated. Compared to control unvaccinated herons, the vaccinated group showed a significantly high protection rate (73.8%) against challenge. In vitro, worm development after challenge showed decreased fecundity and increased egg abnormalities, where only 1.5% of all eggs produced hatched into miracidia. A passive haemagglutination test revealed increased antibody titres against soluble adult worm antigen in both vaccinated and vaccinated-challenged birds. It was concluded that vaccination of herons using encysted metacercariae UV-irradiated for 60 min can protect them against challenge infection.