Metacercariae of Austrodiplostomum spp. (Digenea: Diplostomidae) infecting the eyes and brains of fish in Brazilian Amazon

Abstract

The aim of this paper was to report the occurrence of Austrodiplostomum spp. in the eyes and brain of Acaronia nassa, Caquetaia spectabilis, Satanoperca acuticeps, Curimatella sp. and Crenicichla marmorata in a lake of the Amazon River system in the state of Pará (Brazil). Of 49 fish examined, 10.2% were parasitized by Austrodiplostomum spp. metacercariae, and A. nassa was the host with higher number of metacercariae. In five examined fish species, a total of 51 metacercariae were collected, with 45 found in the eyes and 6 in the cranial vault. In the eyes, the metacercariae were free and active in the vitreous humor, but no opacification was observed. In the brain, the metacercariae were also free and active, and located mainly below the encephalon, on the cranial floor, at the height of the ophthalmic lobes and near the optic nerve. In laboratory observations, however, the infected fish did not exhibit any behavioral disorders, and this may be related to the low level of parasitism. This was the first report of this digenean for C. spectabilis, S. acuticeps, Curimatella sp., C. marmorata and A. nassa.

Molecular identification of Austrodiplostomum sp., an eye parasite among farmed tambaqui in Amazonia

“…However, metacercariae of this species may also occur in other organs, such as the brain and gills ( Brasil-Sato and Santos, 2005 ; Machado et al, 2005 ). The presence of metacercaria in the eyes of farmed fish can cause mild optical damage, or have more severe impacts such as cataracts, blood vessel obstruction, retinal detachment and blindness ( Monteiro et al, 2016 ; Lima et al, 2019 ).…”