Host-Parasite Interaction Between the Nematoda Procamallanus (Spirocamallanus) paraensis and Fish Hoplias malabaricus From the Natural Environment in the Brazilian Amazon.

Histopathological studies of parasitic infections in fish from the natural environment of Brazilian Amazon, are quite scarce. In this study, we investigated the histopathological changes of the proximal intestine of specimens of the Amazonian fish Hoplias malabaricus infected by the hematophagous nematode Procamallanus (Spirocamallanus) paraensis. The prevalence of the infection was 60%, with an average abundance of 1.46 and an average intensity of 2.43 parasites/fish. No significant difference was observed in the prevalence of infection and fish size or sex, but larger fish showed greater infection intensity, which was also significantly higher in male hosts. Histological sections of the proximal intestine showed reduction and loss of the epithelial lining, exposure of the lamina propria where the nematode interacts with the intestine wall, through the insertion of the buccal capsule and fish cellular debris in the intestinal lumen. In addition, areas with bleeding and inflammatory infiltrate were observed, but no changes or presence of parasite structures were observed in the other tunics of the intestinal wall.