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. The present paper is a description by light and electronic microscopy of Henneguya ghaffari found in Chad and Senegal.Materials and methods. Eighty-six specimens of Nile perch Lates niloticus were caught in Chari and Logone rivers near N'Djaména (Chad) and in the Senegal River near Djoudj Parc (Senegal) and dissected for parasite research. A myxosporean, Henneguya ghaffari, was found in the gills and intestine of some of the fish.For light microscopy studies, fresh plasmodia were used for measuring the size of living spores, and 37 measurements were made. For histological studies, fish tissues were fixed in Carnoy's solution and embedded in paraffin. Sections (5 to 7 µm) were stained with hematoxylin-eosin.For ultrastructural studies, fresh cysts were fixed at 4°C with 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.2) for 24 h, then post-fixed at 4°C with 1% osmium tetroxide in the same buffer for 1 h. After dehydration through a gradual ethanol and propylene oxide series, the cysts were embedded in Spurr resin. Ultrathin sections were made and stained with uranyl acetate and lead citrate, and examined under a Jeol 100 CXII electron microscope. Semithin sections were stained with Toluidine blue and examined under a light microscope.For scanning electron microscopy (SEM), spores were smeared on circular cover glasses, lightly airdried and fixed in 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.2) at 4°C for 12 h. After washing in the buffer, and critical point drying, the smears were covered with metallic gold and paladium and observed with a Jeol 35CF SEM.Results. Location of the parasite in the host: The plasmodia were found in the intestine and in the middle and at the base of the gill filaments (Fig. 1) ABSTRACT: Henneguya ghaffari Ali, 1999, described for the first time in Egypt, has been found on gills and intestine of Nile perch Lates niloticus L. from Chad and Senegal (Africa). It formed plasmodia which induced lesions of infected tissues. In fresh state, the spore body was ovoid and its size was 11.07 ± 0.7 (range 11 to 13) × 7.7 ± 0.4 (range 7 to 8) µm. The length of the caudal appendages was 44.2 ± 1.7 (42 to 48) µm. The polar capsules were pyriform, of equal size, with the polar filament showing 4 coils, and measuring 3.17 ± 0.1 (range 3 to 4) × 2.2 ± 0.1 (range 1 to 2) µm. The total length of the spore was 55.73 ± 1.7 (range 53 to 61) µm. At ultrastructural level, our results confirm that in Henneguya species, the sporoplasm is binucleate and the pansporaoblast is disporous.KEY WORDS: Myxosporea · Henneguya ghaffari · Ultrastructure · Fish · Chad · SenegalResale or republication not permitted without written consent of the publisher