Protozoan Infestation - Crustacean Diseases Caused By Parasites

Protozoan Infestation

CAUSATIVE AGENTS:

Vorticella (10-150 µm) (Fig. 5-18a), Zoothamnium (50-250 µm) (Fig. 5-18b), Epistylis (160 µm) (Fig. 5-18c), Acineta (35-55 µm) (Fig. 5-18d), Ephelota (250 µm) (Fig. 5-18e)

SPECIES AFFECTED:

Shrimps, crabs

GROSS SIGNS:

Heavily infested shrimp have fuzzy mat on gills and body surface.

EFFECTS ON HOST:

The parasites may cause respiratory and locomotory difficulties when present in large numbers. Heavy infestation may result in mortalities, par-ticularly at low oxygen levels.

DIAGNOSIS:

Microscopic examination of wet mounts of shell and gill scrapings.

PREVENTION AND CONTROL:

•               Removal of organic detritus

•               Rigid sanitary control of rearing water

•               For adult shrimps, 50-100 ppm formalin, 30 min (for Zoothamnium) or 30 ppm formalin (for Epistylis)