Light microscopical description is presented for a new myxozoan species, Henneguya ghaffari, which infects the Nile perch Lates niloticus (Linnaeus, 1758) in Lake Wadi El-Raiyan in Egypt. The spore is characterized by a triangular thickening at the base of the caudal processes. The relatively long caudal processes run adherent to each other for two-thirds of their length, then bifurcate to very fine processes. Prevalence of infection was 34.6'% and peaked during winter and early spring. The infection was concentrated along the intestinal tract, and in severe cases gills and gill rakers were also infected. Histology revealed that, in contrast to findings of previously published works on related species, intralamellar plasmodia did not develop inside the blood capillaries of the gills. Intestinal plasmodia were very pathogenic due to their large number and size. These plasmodia caused atrophy of the muscularis Idyclr, and replaced and distended the submucosal and mucosal layers. The validity of some Henneguya specles in Afr~ca is discussed.

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