White tail disease (WTD) of Macrobrachium rosenbergii in India
Posted on 19/11/2003
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As aquaculture expands and intensifies, more and more new diseases will emerge. Until recently, freshwater prawn, Macrobrachium rosenbergii was regarded as disease resistant. The recent report of white tail disease (WTD) in freshwater prawn hatcheries and farms has sent shock waves through the prawn aquaculture industry in India. Information presented during the recently held “Freshwater Prawn 2003 International Symposium??? in Cochin, India, is summarized here.
In India, the disease has been described and studied by Hameed (2003), Salin and Nair (2003) and Vijayan et al (2003). In hatcheries, the clinical signs include lethargy, anorexia and opaqueness of the abdominal muscle in post larvae (PL). The opaqueness gradually extends on both sides and leads to degeneration of telson and uropods, in severe cases. Within 2-3 days, 100% mortality is observed in hatcheries. A whitish appearance of the tail is the main clinical sign, and has given rise to the name white tail disease.
The disease has been experimentally transmitted in PL and adults (Hameed 2003). In PL, the clinical signs and mortality reproduced were similar to natural infections. However, in experimentally infected adults, the cephalothorasic region was massively swollen with two fluid filled sac-like structures on either side of the hepatopancreas. Interestingly, similar clinical signs, referred to as branchiostegite blister disease (BBD) accompanied by mortalities, have been reported from adults in grow out farms (Salin and Nair, 2003).
Two viruses, Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV) have been found to be associated with WTD (Bonami and Widada, 2003). Genome based detection methods for MrNV and XSV have been developed (Widada and Bonami, 2003). As there are no treatments to viral pathogens, hatcheries and farms should adopt better management practices to minimize the spread and impact of WTD. Creating awareness about the emerging disease is the first step towards its control. The groups working on this emerging disease can be contacted at the addresses below.Send information about emerging diseases in aquaculture to the attention of CV Mohan, Aquatic animal health specialist, NACA, Bangkok
Drs Bonami and Widada
CC 080, Universite Montpellier II
Place Eugene Bataillon
34095 Montpellier Codex 05
Dr Sahul Hameed
Department of Zoology
C Abdul Hakeem College
Tamil Nadu, India
Dr CM Nair
College of Fisheries
Kerala Agricultural University
Dr KK Vijayan
75 Santhome High Road
Bonami JR and Widada FS (2003) Characterisation of 2 virues (MrNV and XSV), pathogenic agents of the white tail disease (WTD) of the giant freshwater prawn Macrobrachium rosenbergii. In Freshwater Prawns 2003, International Symposium, Cochin , 20-23 August 2003.
Sahul Hameed AS (2003) Studies on white tail disease of Macrobrachium rosenbergii. In Freshwater Prawns 2003, International Symposium, Cochin , 20-23 August 2003.
Salin KR and Nair CM (2003) Emerging diseases of giant freshwater prawn in India- a potential threat to sustainability. In Freshwater Prawns 2003, International Symposium, Cochin , 20-23 August 2003.
Vijayan KK, Raj VS, Alavandi SV, Sekhar VT, Vaseeharan B and Santiago TC (2003) Need of novel diagnostics in the health management of Macrobrachium rosenbergii, with special reference to an emerging epizootic in India, the white muscle syndrome (WMS). In Freshwater Prawns 2003, International Symposium, Cochin , 20-23 August 2003
Widada JS and Bonami JR (2003) Genome based detection methods of MrNV and XSV, pathogenic agents of the white tail disease (WTD) in Macrobrachium rosenbergii: possible use in the study of viral association and the evaluation of disease severity. In Freshwater Prawns 2003, International Symposium, Cochin , 20-23 August 2003.