Identifying risk factors associated with White Spot Disease outbreaks of shrimps in the Gulf of California (Mexico) through expert opinion and surveys

White spot disease is one of the most serious problems in the shrimp-farming industry in Mexico. An assessment of risk of an outbreak of the disease could be useful for farmers making decisions concerning early harvest to minimize economic losses. A group of researchers identified the most important risk factors, classified in four broad categories: management variables at the regional level, environmental variables at the regional level, management variables at the farm and population variables at the farm. For each variable, categories were defined and a risk score assigned. To validate these scores, a survey was carried out with 65 stakeholders. A semi-quantitative risk assessment model was proposed and implemented as a questionnaire containing 21 risk variables with weighted scores. The most important risk factors were the period of fallowing within farm's region and health quality of larvae. Also important were estimated level of viral load and virus detection in wild hosts in the surrounding area, pond water temperature, length of fallowing period of pond, vector control at water intake and stocking density. The overall estimated risk was calculated as the sum of all scores with a further adjustment, according to maximum and minimum total scores. Three risk levels for white spot disease outbreak at ponds are based on estimated risk: low (≤0.2), moderate (0.2–0.4) and high (≥0.4).