First report of microsporidiosis in fairy shrimp Branchinella thailandensis (Sanoamuang, Saengphan and Murugan, 2002)

The diagnosis of microsporidia infestation in the muscle of the fairy shrimp (Branchinella thailandensis [Sanoamuang, L., Saengphan, N., Murugan, G., 2002. First record of the family Thamnocephalidae, (Crustacea, Anostraca) from Southeast Asia and description of a new species of Branchinella. Hydrobiologia 486, 63–69.]) culture was examined by optical microscopy and transmission electron microscopy. The clinical sign of microsporidiosis in fairy shrimp was white tubular masses in the muscle tissue. There was no apparent host encapsulation or xenoma formation within the muscle fibers. Spores of this parasite were uninucleate. The length of the spores was about 2.829–3.269 (3.086) µm and the width was about 1.686–2.857 (1.850) µm. The polar filament had 12–13 coils, arranged in a single row at the posterior end of the spore. Based on the gross pathology, morphology, histopathology and ultrastructure of the spore, we suggest that this parasite is a species of Pleistophora sp. Although this disease was not acute, the fairy shrimp showed continuous mortality. Secondary bacterial infections occurred frequently in infected fairy shrimp. Fairy shrimp died within one to five days of contracting a bacterial infection. Finally, microsporidiosis affected the productivity of the fairy shrimp culture. Prophylaxis was performed by treating underground water that might be contaminated with this microspore before use in culture.