Prevalence of Black Gill (Hyalophysa lynni) in White Shrimp Litopenaeus setiferus and Brown Shrimp Farfantepenaeus aztecus along the Texas Gulf Coast

Abstract

Shrimp black gill is an emerging disease caused by a parasitic ciliate, Hyalophysa lynni, that attacks gill tissue in white shrimp Litopenaeus setiferus and brown shrimp Farfantepenaeus aztecus and induces an immune response that produces melanized tissue in shrimp gills. This immune response causes necrosis and damage in shrimp gill tissue, which limits shrimp metabolic capability and can lead to high predation mortality among infected individuals. Shrimp black gill was first observed in the southeast Atlantic shrimp fishery in the United States, and this ciliate has been increasing in prevalence in shrimp populations of this region since 2000. The Gulf of Mexico, with its lucrative shrimp fishery and extended warmwater conditions during the year, is a potential region for H. lynni spread. White and brown shrimp were sampled from seven major bays along the Gulf coast of Texas from March to November 2019 and underwent PCR analysis to detect H. lynni presence in gill tissue. From March to November, 65% of the collected shrimp samples tested positive for H. lynni. Samples from all seven bays tested positive for H. lynni, with the upper-coast bays having a significantly higher disease prevalence than lower-coast bays. Both white and brown shrimp samples tested positive for H. lynni; however, white shrimp samples had a significantly higher disease prevalence. Overall, disease prevalence showed a temporal pattern of low prevalence in the spring, peaking during the late fall. Generalized additive mixed models detected a high water temperature and a salinity level of 30‰ or less as significant contributors to high disease prevalence. This study validates the commonality of H. lynni presence in the western Gulf of Mexico, serves as a baseline for future shrimp black gill sampling efforts in this region, and contributes to the understanding and management of potential disease threats to the Texas shrimp fishery.