1998, Number 2
Vet Mex 1998; 29 (2)
Histopathological characterization of tilapia (Oreochromis sp) response to a mixed infection by myxosporean parasites. A natural case
Auró de OA, Ocampo CL
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ABSTRACTAn histopathological diagnosis of a myxed myxosporean infection on forty naturally infected tilapias (Oreochromis sp) was made. These animals presented small white nodules in the gills, darkening of the skin, exophthalmos and loss of apetite. The necropsy showed increased abdominal volume, congestion and thickening of the medial and posterior intestine. Eight of them had ascites. Multicellular trophozoite cysts were found in the intestinal mucosa and submucosa, pancreas, kidney, brain and gills. Those cysts on gills were smaller than the rest of the trophozoites. The only response to the infection was fibrosis around the multicellular trophozoites cysts. Giemsa stain showed the bipolar structure of the capsules. Due to size and shape of trophozoites it is suggested that the systemic infection could have been caused by Myxobolus sp and the gill one to Myxosoma sp or Henneguya sp. An antigenic study is necessary for the aetiological diagnosis, because there have been very few reports on these type of infections in tilapia.