Histopathological Studies on Wild Broodstock of White Shrimp Penaeus vannamei in the Platanitos Area, Adjacent to San Blas, Nayarit, Mexico

Abstract

AbstractIn Mexico, the capture of wild broodstock of Penaeus vannamei or P. stylirostris for hatchery production of postlarvae is a common practice. During September 1995 and March‐April 1996, high mortalities were observed in the wild broodstock captured in the Platanitos area, on the coast of San Blas, Nayarit, Mexico. As a result of these mortalities, many hatcheries closed down their facilities. Because early histological analysis had shown that some of these animals were infected with different pathological agents, such as bacteria and viruses, the present study was carried out to determine the prevalence and severity grade of infectious diseases affecting these shrimp. During March 1996, a total of 28 female and 28 male shrimp were randomly selected from a recently captured stock of 600 breeders of P. vannamei. A second sampling (28 females and 28 males) was performed from a stock of 800 breeders captured in April 1996. On this occasion, the shrimp were sampled after 10 d of acclimation in a hatchery. The animals selected for examination were those with necrosis in the cuticule, red coloration in the telson and uropods, soft cuticle, empty gut, and erratic swimming. All of the specimens were subjected to histological analysis and dot blot hybridization with a gene probe specific for Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV). The results showed that both stocks were infected with at least three different viruses (Infectious Hypodermal and Hematopoitetic Virus, Taura Syndrome Virus and Hepatopancreatic Parvo‐Like Virus), gram‐negative bacteria and other parasites such as gregarines. It is likely that the high mortalities observed are due to the recent introduction of TSV in the wild population of P. vannamei.