Protozoan diseases

Protozoa are unicellular organisms infecting the shrimps. They become lethal only when their number is beyond certain limits. Microsporidia, Haplospridia and Gregarina are some of the disease causing protozoa and the type of diseases caused by them are briefly described here.

Cotton shrimp disease:
This is also known as milky disease of shrimps. It is caused by protozoa belonging to Microsporidian group. Almost all the culturable species of shrimps are affected by these protozoa. The muscles of the infected shrimps become milky due to the abundant network of the mycelia. The fungus produces spores which are transmitted to other shrimps. So far no satisfactory treatment is evolved. However use of 0.0075 mg of malachite green per litre of water in static condition of the Post Larvae and addition of commercial bleaching powder to the culture system are found to be helpful.

Ciliate infestation:
These fungi as the name indicates belong to ciliates. They are: Zoothamnium, Epistylis and Vorticella. Besides these ciliates suctoreans like Ephelota gemmipara and Acineta also invade all the stages of shrimps causing respiratory and locomotive difficulties. The ciliate infection can be noticed by the fuzzy mat growth on the shell. Ciliate infection can be prevented by avoiding heavy silt, high nutrient supply, turbidity and low oxygen content in the water.

Gregarine disease:
Gregarines are parasites commonly found in the digestive tract of shrimps. They interfere with digestion and absorption of nutrients. causing mortality. Better water conditions prevent the disease to some extent.