Disease has become a major constraint to shrimp aquaculture in Latin America. Especially since the outbreak of white spot disease (caused by the white spot syndrome virus, WSSV), shrimp production has decreased significantly in many countries and farmers are facing serious difficulties in continuing production. The resulting economic losses and their impacts are now significantly affecting national economies and the livelihoods of poorer sectors. For example, the shrimp exports from Ecuador in December 1999 fell to below 1985 levels. Provision of assistance for combating this situation is considered highly appropriate and timely. Such assistance will help secure shrimp aquaculture development, national income through trade (both local and international), and livelihoods of farmers and other service providers.
When the patterns of spread of diseases and pathogens of shrimp are examined, especially those for viral pathogens, there is convincing evidence that most major disease outbreaks are associated with the movement of live shrimp (broodstock, nauplii and postlarvae (PL)). It is important to remain very cautious over the international or regional movement of live shrimp stocks bound for aquaculture. This precaution applies even to domesticated stocks and to a single shrimp species cultivated in different places. However, movements should be permitted when proper quarantine and screening procedures have been applied.
Our understanding of the avenues and options for controlling shrimp diseases, especially WSSV, has improved over the past few years, mainly through the experiences gained in Asia and in Latin America. The ultimate solution for combating shrimp disease problems is to culture certified, domesticated stocks that are free of specific pathogens on nutritious, dry feeds in biosecure ponds under conditions that are nonstressful to the shrimp. This should be the ultimate goal for the shrimp industry.
With respect to stress, while it is impossible to control weather, we do have the ability to control many important variables, such as pond carrying capacity, feed inputs and water exchange. At present, dry feeds appear to be adequate, although there is obviously still room for improvement in their quality. The biggest potentially controllable problems that farmers currently face are uncertainty regarding the quality of postlarvae used in culture, and the lack of biosecurity of the pond environment from the entry of pathogens and their carriers.
The simplest way to solve the postlarval quality problem is to change from the use of postlarvae derived from captured broodstock to those derived from domesticated stocks. However, this practice requires considerable research effort and field-testing, and is still in its infancy. At least we can try to ensure biosecurity in ponds through appropriate screening of postlarvae for important pathogens prior to stocking. The procedures for screening postlarvae for important pathogens (predominantly WSSV) are known; however, additional training, capacity building, and upgrading of hatcheries and diagnostic centres are necessary.
Currently, harmonized technical standards for the hatchery production of postlarvae are lacking. It is imperative that such technical standards be developed, standardized, validated, and agreed upon by the hatchery producers, both nationally and internationally.
In November 1999, an FAO Expert Workshop was held in Cebu, Philippines, where representatives from 14 shrimp-producing countries, including five Latin American countries, attended. The workshop discussed and agreed upon a number of strategies for controlling shrimp disease problems and made recommendations for future activities. These ideas were further discussed at the recent APEC/NACA/FAO/SEMARNAP Expert Workshop on Transboundary aquatic animal pathogen transfer and the development of harmonized standards on aquaculture health management, held in Puerto Vallarta, Jalisco, Mexico, 24-28 July 2000. A consensus was achieved that the strategies should be incorporated into a regional technical cooperation project aimed at assistance, and the member countries of FAO in which the proposed project would be implemented gave their consent for formulation of the project proposal.
Developing regional technical guidelines and standards on quarantine and health certification for safe transboundary movement of live aquatic animals (broodstock, nauplii and postlarvae of shrimp), and harmonizing them within the region was considered timely and appropriate. However, this will take some time to realize, and compliance will remain an issue until appropriate national capacities are developed. Nevertheless, FAO's experience in developing technical guidelines on health management for safe transboundary movement of aquatic animals in Asia can be duly utilized for the benefit of Latin America (see FAO/NACA 2000, 2001a). Capacity building among national institutions, involved staff and shrimp farmers is important. Farmers should be made aware of the options and opportunities available for controlling diseases, especially WSSV. Developing good farm and hatchery management practices and documenting them with adequate scientific evidence and field data are also appropriate and timely.
Considering the above points, it became clear that the most timely and effective means to assist the Americas to deal with the existing shrimp disease situation would be: i) developing interventions for improving postlarval quality, ii) building capacity among farmers and appropriate state agencies and iii) developing a comprehensive information network within the region. The Government of Ecuador made a formal request to FAO for technical assistance to combat serious shrimp disease problems in Ecuador. FAO, in consultation and agreement with the shrimp-producing countries in the Americas, decided to prepare a Regional Technical Cooperation Programme Project addressing the above issues.
The Project, which began in 2001, involved the participation of 14 countries: Belize, Brazil, Costa Rica, Colombia, Cuba, Ecuador, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Peru and Venezuela. Representatives of each country responded to a questionnaire on shrimp maturation and hatchery practices in their country. The questionnaire covered a number of aspects of production, concentrating on maturation and hatchery types, sizes, species, management, physical and chemical treatments and disinfection procedures used; health management; production and quality assessment methods; transportation methods; and problems encountered.
The technical guidance provided in this document was developed by the National Coordinators (NCs) and experts who participated in the project and is based on the information provided by the participating governments.