This study investigated Perkinsus spp. infecting Crassostrea rhizophorae from the Jaguaribe River estuary, Ceará, Brazil. Fragments of gills and rectum of the oysters (n=150) were incubated in Ray's fluid thioglycollate medium (RFTM). Genus Perkinsus-specific PerkITS85/750 PCR assays were performed and their amplicons were sequenced by the Sanger method. The RFTM assays confirmed Perkinsus spp. The sequencing of the amplified fragments from the rDNA internal transcribed spacers (ITS) of Perkinsus spp. confirmed Perkinsus chesapeaki. Neighbor-Joining analyzes place P. chesapeaki identified in this study in a well-supported clade with other isolates of the same species. This is the first record of P. chesapeaki infecting C. rhizophorae in South America.

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This work investigated the occurrence of Perkinsus sp. in clam Anomalocardia brasiliana, oyster Crassostrea sp. and mussel Mytella falcata from the Jaguaribe River estuary, northeastern Brazil. The collection of clam (N = 300), oysters (N = 300) and mussels (N = 300) were carried out in the estuary of the Jaguaribe River, Ceará, in March and April (rainy season) and October (dry season) in 2017. The mollusks were measured in their major axis, open, and had their tissues submitted to tissue incubation techniques in Ray's fluid thioglycollate medium (RFTM), histology, real-time polymerase chain reaction (qPCR), PCR and sequencing. The RFTM assays showed Perkinsus sp. infecting the three mollusks investigated. The prevalence of infected clams was 1.33% in both sampling periods, oysters ranged from 2.66 (rainy season) to 8% (dry period), and mussels from 0% (dry period) to 51.33% (rainy season). The intensity of infection was very light to light in clams, very soft to severe in oysters and very soft to moderate in mussels. Histological analyses showed cells of Perkinsus sp. infecting the gills and connective tissue around the digestive gland of some individuals. The qPCR generated amplicons in all positive samples in RFTM, confirming the presence of Perkinsus sp., while the sequencing evidenced high similarity (99%) with the species P. beihaiensis. In conclusion, the results obtained contribute to increasing knowledge about the occurrence of Perkinsus sp. in bivalve mollusks from northeastern Brazil.

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