Diagnostic Molecular Investigation of White Spot Syndrome Virus Finds No Infection in Wild White Shrimp and Brown Shrimp along the Texas Gulf Coast.

White spot syndrome virus (WSSV) is a virulent disease that disrupts shrimp farm operations throughout the world. While the United States has had only limited outbreaks of WSSV within the past several decades, it is important to ensure that this disease does not infect wild penaeid shrimp populations. In Texas, there is a potential for WSSV to spread to wild penaeid populations in the Gulf of Mexico via infected imported nonnative bait shrimp, imported broodstock, or wild crustacean hosts. Due to these potential threats, the Texas Parks and Wildlife Coastal Fisheries Division monitored WSSV in wild brown shrimp Farfantepenaeus aztecus and white shrimp Litopenaeus setiferus from seven major bay systems along the Texas coast during 2019. While no positive samples were detected from the collected shrimp, a power analysis illustrated a potential for low-level WSSV prevalence within Texas shrimp populations that would not be detectable by this monitoring survey. Overall, WSSV does not appear to be a major threat in the Texas region of the Gulf of Mexico, but continual observation and monitoring of wild penaeid shrimp is necessary to protect this resource from future WSSV outbreaks.

First report of acute hepatopancreatic necrosis disease (AHPND) occurring in the USA.

In June 2017, mass mortalities were reported at whiteleg shrimp Penaeus vannamei farms in Texas, USA. PCR testing for OIE-listed and non-listed pathogens detected the pirA and pirB toxin genes associated with acute hepatopancreatic necrosis disease (AHPND). DNA sequence analyses of cloned pirA and pirB genes showed them to be identical to those detected in other AHPND-causing Vibrio sp. Amplicons generated using PCR tests targeted to the toxR gene showed the Pir toxin genes to be associated with a V. parahaemolyticus type more similar to a genotype found in Mexico compared to that found in Asia. Histology detected masses of bacteria and hemocytic infiltrations as well as extensive necrosis and sloughing of epithelial cells in hepatopancreatic tubules pathognomonic of AHPND. The data support AHPND as the cause of the mortalities. Given that US companies produce shrimp broodstock for farms in Asia and Latin America, the further spread of AHPND in the USA needs to be prevented to avoid serious economic consequences to these industries.