Four AHPND strains identified on Latin American shrimp farms

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Four AHPND strains identified on Latin American shrimp farms

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AHPND is a major global disease of farmed shrimp that seriously affects the industry in many countries in Asia and Latin America. Photo by Darryl Jory.

Acute hepatopancreatic necrosis disease (AHPND), also commonly known as Early Mortality Syndrome (EMS), is a serious, major global disease of farmed shrimp that causes hepatopancreas dysfunction and secondary Vibrio infections and can result in 100 percent mortality in the animals’ juvenile stages.

The disease started in China in 2010 and has currently spread to aquaculture facilities in Vietnam, Malaysia, Thailand, the Philippines, Mexico and much of Latin America. Losses from EMS have been estimated to exceed $1 billion per year.

The literature reports AHPND as caused by a unique strain of Vibrio parahaemolyticus, an ubiquitous bacterium that colonizes uneaten feed and organic sludge in culture pond bottoms, and also the chitinous shrimp molts and the animals’ stomach linings, and is transmitted horizontally from shrimp to shrimp and vertically from spawner to egg. Here we present the first report describing the pathogenicity of non-V. parahaemolyticus AHPND strains.

Bacterial isolation and AHPND identification

Four Vibrio strains (16-902/1, 16-903/1, 16-904/1 and 16-905/1) were isolated from either stomachs of diseased shrimp or sediment samples from AHPND-affected farms in Latin America during 2016. Bacterial identifications were carried out using 16S rRNA sequencing and Vibrio-specific PCR assays targeting hly gene. These bacteria were grown on TSB+ (Tryptic soy broth plus 2 percent NaCl) at 28-29 degrees-C with gentle shaking (100 rpm) and further tested for AHPND PCR assays with primers targeting pirABvp.

By the PCR assays, these 4 strains were identified to V. campbellii by 16S rRNA sequence analysis and hly gene PCR. These V. campbellii strains had both pirAvp and pirBvp genes (Table).

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