Larval Midcycle Disease (MCD) of Freshwater Shrimp
Category 3 (Host Not in Canada)
Common, generally accepted names of the organism or disease agent
Larval midcycle disease, MCD-like disease syndromes.
Scientific name or taxonomic affiliation
Unknown, but Enterobacter aerogenes has been associated with the disease.
Hawaii, Mauritius, Thailand, Philippines, Malaysia and northern Australia.
Macrobrachium rosenbergii larval stages IVXI.
Impact on the host
High larval mortality during the second third of the larval cycle, reduced food consumption, bluish grey in colour, weak spiralling swimming behaviour, possible cannibalism. Atrophy of hepatopancreatic epithelium. Causes death.
Gross Observations: Greyish colour and possible epibiotic fouling, spiralling behaviour.
Histology: Hepatopancreas atrophy, coccobacilli within the digestive tract.
Methods of control
Brock (1988) recommend that infected stocks be destroyed followed by disinfection of contaminated or potentially contaminated areas and establishment of standard hatchery sanitation procedures (i.e., routine disinfection between larval rearing cycles, separation of rearing tanks, use of individual equipment for each larval rearing unit, etc.). At least one grower believes that MCD is caused by improper diet and/or starvation (for details contact Craig Upstrom, Aquaculture of Texas, Inc., 4141 Fort Worth Hwy., Weatherford, TX, USA, 76987-8610 (e-mail: email@example.com)). Accordingly, Tonguthai (1992) proposed that when MCD occurs, condition can be reversed by reducing stocking density, improving pond husbandry and sanitation, and providing adequate nutrition through good quality Artemia. Advanced epizootics are not treatable.
Akita, G., R. Nakamura, J. Brock, G. Miyamoto, M. Fujimoto, F. Oishi and D. Sumikawa. 1981. Epizootiologic study of midcycle disease of larval Macrobrachium rosenbergii. Journal of the World Mariculture Society 12: 223230.
Brock J.A. 1983. Diseases (infectious and noninfectious), metazoan parasites, predators and public health considerations in Macrobrachium culture and fisheries. In: J.P. McVey (ed.). Handbook of Mariculture, Vol.I. Crustacean Aquaculture. CRC Press Inc., Boca Raton, FL, p. 329-370.
Brock, J.A. 1988. Larval mid cycle disease of M. rosenbergii. In: C.J. Sindermann and D.V. Lightner (eds.). Disease Diagnosis and Control in North American Aquaculture. Developments in Aquaculture and Fisheries Science 17. Elsevier, Amsterdam, p. 137-139.
Tonguthai, K. 1992. Diseases of the freshwater prawn Macrobrachium rosenbergii in Thailand. In: M. Shariff, R.P. Subasinghe and J.R. Arthur (eds.). Diseases in Asian Aquaculture. I. Fish Health Section, Asian Fisheries Society. Manila, Philippines, p. 89-95.
Bower, S.M. (1998): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Larval Midcycle Disease (MCD) of Freshwater Shrimp.
Date last revised: July 1998
Comments to Susan Bower
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