Hurricane Mitch: Development of Immunological Tools to Assess the Health Status of Shrimp

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. of immunological tools to assess the health status of shrimp: USGS Open File Report 03-176, xx p. Background Hurricane Mitch introduced several stressors to both aquacultured and feral shrimp populations. These stressors included influxes of anthropogenic pollutants, water turbidity, rapid salinity changes, and dissolved oxygen disturbances. Stressors are known to increase the susceptibility of animals, including invertebrates (Lacoste and others, 2001), to infection. Since the late 1990s, the white spot syndrome virus (WSSV) is a primary pathogenic agent in White spot disease is pandemic and affects shrimp, crabs, crayfish, and other crustaceans. Although there are specific diagnostic assays for WSSV in infected tissues, no diagnostic assays that reflect of invertebrate health or immune status have been developed. Assessments of immune status would be especially useful in the face of stressors that compromise immununological health. Within stressed shrimp, as with other animals, viruses that are better able to infect would preferentially replicate, thereby enhancing virulence and increasing the number of strains infective to invertebrate populations. For humans, viral pathogens that evolve to be more adaptive to host immune defense systems are responsible for recurrent epidemics. Devastating disease outbreaks and mass mortalities result from infection by WSSV. Corresponding risk factors, as well as risk reduction factors, have been identified for culture situations (Corsin and others, 2001). Multivariate and univariate analyses of 158 risk factors for WSSV outbreaks in a rice-shrimp farming system showed higher incidence in ponds closer to the sea, in shrimp that were smaller than average size 1 month after stocking, and with the use of commercial feed. One important risk reduction factor was the presence of high numbers of shrimp with bacterial infections, which may recruit and stimulate hemocytes (blood cells) into immune defensive reactions. A second factor was the presence of dead post larvae at stocking, which may reflect those shrimp having succumbed to bacteria. The thrust of these findings is that immunological stimulation of shrimp populations exposed to bacteria enhanced overall survival. The question of interest then was what components mediated the enhanced survival. To determine the overall " immune " or health condition of humans and agriculturally important species, available bioindicators include changes in blood cell numbers, body temperature, and the presence of acute phase proteins in serum. However, techniques to determine immunity are …