Shrimp Health Management Extension Manual - Library - Network of ...

Shrimps with loose shell syndromeHistological section showing the chronicinflammatory lesions in hepatopancreasindicative of bacterial infectionDuring the risk factor study conducted in 365 ponds (184 ponds in Nellore and 181 ponds inWest Godavari) in 2001, the dominant shrimp disease problem in both the districts was WSD.Eighty percent of the ponds affected by disease outbreaks were affected by WSD. Therefore,this manual mainly addresses management of WSD. However, the managementrecommendations and principles detailed in the manual are also relevant to reducing risks ofmost Penaeus monodon disease outbreaks, and improving shrimp farm production.2.2. Shrimp disease risk factorsIn aquaculture systems, a risk factor is a crop-related factor, which simply increases or decreasesthe probability of occurrence of an adverse event happening during a specified time period.For example, WSD is an adverse event during the shrimp cropping period. If a high prevalenceof WSSV in seed batches stocked in ponds increases the probability of occurrence of WSDthen the high prevalence of WSSV in seed batches is called a risk factor to WSD. Epidemiologyinvestigates the statistical and biological significance of the relationship between the adverseevent and the hypothesised risk factor to determine whether the hypothesised risk factor is arisk factor or not. The risk factor study of the MPEDA/NACA Technical Assistance consideredshrimp disease outbreak and poor production as adverse crop events for the epidemiologicalanalyses.The results from the risk factor study of shrimp farms in Nellore and West Godavari districtsclearly show that there are a number of significant risk factors that influence shrimp diseaseoutbreaks and shrimp yields at pond level, many of which can be managed by the individualfarmers.4