Shrimp acute hepatopancreatic necrosis disease strategy manual

Book excerpt: The contents of this Shrimp acute hepatopancreatic necrosis disease strategy manual provides information and guidance relevant to the development of policies to respond to outbreaks of acute hepatopancreatic necrosis disease (AHPND) in farmed marine shrimp. The etiologic agents for AHPND are virulent strains of bacteria belonging to the genus Vibrio parahaemolyticus and related species, which harbor specific toxin genes. While these bacterial species are part of the normal microflora of the marine environment, they may cause substantial mortalities in whiteleg shrimp (Penaeus vannamei) and giant tiger prawn (Penaeus monodon) cultured in countries in Asia and the Americas. These strains of these Vibrio bacteria secrete a PirABvp binary toxin resulting in sloughing of tubule epithelial cells and dysfunctions of the hepatopancreas in the acute form; mortality can reach 100 percent in affected ponds. Chronic presentation of this disease involves secondary bacterial infection of hepatopancreas and running mortality over the culture cycle. Acute or chronic presentation would greatly depend on the culture conditions. This disease can be considered a toxicosis rather than an infection. Economic losses due to this disease have amounted to over USD 7 billion annually. Further outbreaks of AHPND, particularly in areas that are currently free of the disease, would be expected to experience similar devastating effects on local shrimp producers and the surrounding communities; and thus, there is an urgent need to develop a contingency plan to control and eradicate this disease. This manual includes information on: 1) the nature of AHPND: a brief review of current knowledge in disease etiology, susceptible species and global distribution; 2) diagnosis of disease: a description of gross clinical signs and laboratory methods; 3) prevention and treatment: farm management, the use and development of antibiotics, bacteriophages, probiotics, disease-tolerant shrimp, shrimp immunity and vaccination; 4) epidemiology: AHPND’s geographic distribution, genotype, persistence in the environment, reservoir hosts, modes of transmission, risk factors, and economic impacts; 5) principles of control and eradication: methods for containment, mitigation and eradication of AHPND, and trade and industry considerations; and 6) policy development and implementation: AHPND-specific objectives, options and strategies for eradication and control, education, capacity building, funding, and compensation.