Abstract

Two hundred thousand prawns from northern Australia were examined grossly for microsporidiosis. Ameson sp. was found infecting Penaeus semisulcatus, P. merguiensis and P. esculentus at low prevalence levels (<0.1%) across northern Australia. Thelohania sp, infected P. latisulcatus, P. longistylus and P. semisulcatus on the Great Barrier Reef, again at low prevalence levels (<0.1%). Histological attempts to find subclinical infections were unsuccessful. Ameson sp. infected the striated muscle bundles throughout the body, whereas Thelohania sp. infected mainly connective tissue, most organs and peripheral muscle bundles. Microsporidiosis is of concern, because it has been diagnosed from all areas where brood-stock females are collected for use in mariculture.