Clinic and Pathologic Characterization of the Lymphoblastic Leukemia in Culture's salmonids

Abstract

In order to determine the types of gross and microscopic lesions in Salmonid fish with Lymphoblastic Leukemia in the X Region, the location and degree of severity amongst the different kinds of Salmonids and the relationship with the presence of the microsporidium Nucleospora salmonis, were analysed in 113 O. kisutch, 100 S. salar, 89 O. mykiss and 13 O. tshawytscha. Furthermore, histologically positive samples to Lymphoblastic Leukemia, from kidney, spleen, liver, pancreas, piloric caeca, eye, ovary and heart samples were analysed.

The histological study showed 5.7% of positive cases in fishes with Lymphoblastic Leukemia, characterised by edged location, dark skin, and pale gills. In the atlantic salmon (S. salar), the bilateral exophthalmos and the presence of haemorrhages in the base of fins were more emphasised,. Internally, the fish showed rhinomegaly and pale liver. Rainbow trout (O. mykiss) showed 40.0% of splenomegaly and the atlantic salmon (S. salar) showed a 33.3% of abnormal coloration in muscle and piloric caeca.

The most affected organs with Lymphoblastic Leukemia in all the species under study were kidney, spleen and with kidney and spleen as the principal affected organs association.

Microscopically, all the kidneys showed lymphoblastic cells infiltration diagnosed in 62.5% of the analysed samples. The rainbow trout (O. mykiss) showed severe tubular necrotic alterations and in the atlantic salmon (S. salar), a marked inflammatory reaction was observed. Liver, spleen, pancreas, piloric caeca, eye, ovary and heart were also affected by lymphoblastic cell infiltration, with cellular and nuclear pleomorphism. On the other hand, Nucleospora salmonis was detected in renal and splenic tissue in the coho salmon (O. kisutch), and in the lymphoblastic cells of the atlantic salmon (S. salar).