An outbreak of myxozoan parasites in farmed freshwater fish Colossoma macropomum (Cuvier, 1818) (Characidae, Serrasalminae) in the Amazon region, Brazil

•Out of the 60 specimens of tambaquis analyzed, 83.3% (50/60) were parasitized in different organs for Myxobolus, Ellipsomyxa, Henneguya and Thelohanellus.•This is the first report of occurrences of the genera Ellipsomyxa and Thelohanellus for this species.•This report suggests that the mortality among C. macropomum specimens was caused by the outbreak of myxosporidians.