Responsible Aquaculture Foundation

WSSV in Mozambique, Madagascar

Front-Madagascar2White spot syndrome (WSS), a highly contagious viral disease of shrimp, has heavily impacted global shrimp farming since 1992. Until 2011, Madagascar and Mozambique remained free of the disease.

The case study on WSS by the Responsible Aquaculture Foundation reported that in September 2011, Mozambique first experienced WSS at both a farm and hatchery. In 2012, the disease limited shrimp production to 41 metric tons, down from 667 metric tons before WSS struck. The disease was detected in Madagascar in 2012.

Two common practices greatly increased farms’ vulnerability to WSS: the use of unscreened wild broodstock in hatcheries and high rates of water exchange to maintain pond water quality. The lack of animal health policies and ongoing disease surveillance was another factor.

Recovery from the WSS crisis required several changes at farm level. Since the WSS virus was widely found in wild shrimp along the coast, the most important change was to stop using wild broodstock. The study team recommended a regional breeding center to produce specific pathogen-free broodstock genetically selected for resistance to WSS.

Another major change was to reduce water exchange. Although the most effective approach was to install aeration systems, that strategy was incompatible with standards for the organic shrimp typically raised in the countries. Improved biosecurity methods were recommended to reduce the horizontal transmission of WSS.

The study team also supported expansion of national regulatory frameworks to establish aquatic animal health policies and fund regulatory agencies, reference laboratories and disease surveillance. Collaboration between the producer associations and government ministries was also recommended.