Abstract

The Taura syndrome (TS) is one of the viral shrimp diseases that has most affected cultivation of the shrimp Litopenaeus vannamei in America. We analyzed the presence of TS, from its first detection in May 1995 in 75% of the shrimp farms of the Guasave district in Sinaloa State, Mexico, and its progressive spreading from the north toward the central and southern zones of the state, to the districts of Navolato and Elota. The main histopathological findings in shrimp tissues analyzed were necrotic areas in the cuticular epithelium, near the sites where there is melanization, and in various parts of the surface of the body, appendages, gills, hindgut, esophagus, and stomach. As revealed with hematoxylin and eosin-phloxine staining, the cuticular lesions were generally spherical and with cytoplasmic inclusion bodies. Some of the affected cellular nuclei of the tissues were pycnotic or karyorrhectic, giving a "buckshot" appearance to the lesions. During 1996, shrimp samples were collected from 33 shrimp farms in different areas of Sinaloa. The histopathological analysis revealed a 92% prevalence of TS in the central zone, 78% TS in the southern zone, and 73% TS in the northern zone. In 1997 histo-pathological analysis of shrimp samples collected in the same shrimp farms revealed a decrease in TS. In 1998, a significant reduction in the prevalence of TS was observed, with only 30% incidence of TS in the farms sampled. We concluded that the epidemic of TS in shrimp farms of Sinaloa reached a peak in 1996, followed by a steady decline that closely paralleled the switch by the industry from culturing TS virus (TSV)-susceptible L. vannamei to TSV-resistant L. stylirostris .