The endemic region and infection regimes of the White Spot Syndrome virus (WSSV) in shrimp farms in northwestern México

Shrimp farming with a value annually of US$711 million approximately, is one of the most important primary activities in Mexico. However, shrimp farming has had to face various problems that have limited their development, within which the mortality caused by the white spot syndrome virus (WSSV) is the most important. To have scientific elements to focus on preventive health management actions is necessary to know, among other factors, aspects of the epidemiologyof white spot disease (WSD). Therefore this study focused on delimiting the endemic region for WSD and its temporal regimes of infection and discusses possible risk factors related to outbreaks of the disease in shrimp farms of northwestern Mexico. We analyzed information from the databases of the State Committees of Aquaculture Health of Baja California Sur, Sonora, Sinaloa and Nayarit, as well as data of Integrated Program on Shrimp Aquaculture Health (PISA 2007-2008) and the Strategic Alliance Network Aquaculture Industry Innovation (AERI-2008). Data analysis showed that, for the shrimp production cycles of 2007-2008, white spot syndrome virus (WSSV) was endemic to the region of Tuxpan, Nayarit in the south and to Agiabampo, Sonora in the north. Spring outbreaks of WSD in the fishfarms had a spatiotemporal distribution, indicating three infections regimes: (1) March-April in the southern shrimpfarming region (Local Aquaculture Health Boards [LAHBs] of Mazatlan, El Rosario, Escuinapa, Tecuala, and Tuxpan); 2) April-May in the central region (LAHBs of Navolato Norte, Navolato Sur, and El dorado); and (3) May-June in the northern region (LAHBs of Agiabampo-Sonora, Ahome, Guasave Norte and Sur). The WSD were consistent between 2007 and 2008, with slight variations among some LAHBs, with respect to the onset or presence of spring WSD outbreaks. It shows the association of infection regimes throughout the region endemic with the location of Mazatlan,Pescadero and Farallon oceanographic basins according to the increasing differential temperature within them, which may be a determinant factor for the presence of WSD outbreaks.