Identification of Myxozoa Parasite in the Connective Tissue of a Cascadura Fish (Hoplosternum Littorale) In Trinidad and Tobago

ABSTRACT

Background: Thirty cascadura (Hoplosternum littorale) fish from 5 different ponds were submitted alive to the Aquatic Animal Health Laboratory of the School of Veterinary Medicine, University of West Indies as part of monitoring and quarantine procedures of a commercial aquaculture farm. Cascadura fish are commercially important in Trinidad. Methodology: Water from the five different ponds was tested for quality. All fish were euthanized and necropsies were performed. Pooled samples from each pond were submitted for microbiology, parasitology, and histopathology. Results: All water samples had low alkalinity, low hardness, and low pH. In general, all ponds had evidence of low to moderate ecto- and endoparasitism. A section of connective tissue from the histopathologic samples of the pond with the lowest pH contained an area of hemorrhage and numerous poorly staining oval to tear-drop shaped organisms. These organisms stained brightly acid fast, and some included two polar capsules and a polar filament. No other signs of infection were noted in these fish. Conclusion: This is the first histopathologic description and report of myxozoan parasites in the cascadura in Trinidad. Myxozoa can be pathogenic, and should be included in the differential for causes of death in farmed cascadura, particularly when there is poor water quality which could affect the immune system of the fish.