Coccidian infestation in cultured common pandora (Pagellus erythrinus)

Abstract

Coccidia is a spore-forming obligate intracellular protozoan parasite that causes disease in many fish species. This study aimed to diagnose a parasitic disease case that affected a common pandora (Pagellus erythrinus) with a high mortality rate. The samples prepared from the internal organs of the diseased fish and the gills and muscle tissues were examined parasitologically using histological methods, a light microscope, and Transmission Electron Microscopy (TEM). No parasites or parasitic formations were found in the wet mount preparations. The presence of parasitic spores (1-1,5 x 0.3-0.7 μm) was detected towards the intestinal tissue between the intestinal microvilli of fish in the electron microscopy study. On the other hand, histological examination showed that a cystic structure full of spores (sporocyst) 550-750 μm in size developed in the abdominal muscles of the infected fish. At the same time, there were no such structures in the intestines. As a result, since the parasite spores observed in the diseased fish are very small, they settle in the cell and pass through the intestines by forming cysts in the abdominal muscles. They were identified as Coccidian sp. because of their similar morphology to those of the parasites in the Coccidian group. Coccidian infestation was detected in this fish species for the first time in this study. However, detecting the spores' entrance through the fish's intestines in the early stage and observing a small number of sporocyst structures suggest that the disease is in the development stage.