Management measures to control diseases reported by tilapia (Oreochromis spp.) and whiteleg shrimp (Litopenaeus vannamei) farmers in Guangdong, China

Culture of tilapia (Oreochromis spp.) and whiteleg shrimp (Litopenaeus vannamei) has intensified during the last decade in China with increased production, meanwhile it has also brought some problems, including diseases, increased use of antimicrobials and other chemicals for disease control and pond water quality management.

This study investigated the knowledge, practices and challenges of tilapia and whiteleg shrimp farmers when preventing and controlling diseases through the use of antimicrobials and other compounds in Guangdong province, which is the most important shrimp and tilapia production area in China. Tilapia farmers (25) mainly reported streptococcosis (9) and exophthalmia disease (9) which often was treated with sulfadiazine, florfenicol and vitamins or rhubarb (Rheum rhabarbarum) extract, although farmers thought the effectiveness of antimicrobial treatment has decreased in recent years. Shrimp farms (30) mainly experienced outbreaks of red body disease (19) and white spot syndrome (5), both viral diseases, and so-called "secret death disease" (5) which farmers controlled by application of a variety of disinfectants, probiotics and vitamins. Most of the farmers reported they did not use antimicrobials to treat shrimp disease. All farmers applied disinfectants and probiotics to control pond water quality although the efficacy of such use was not known. Farmers prepared their own medicated feed through mixing antimicrobial water-based solutions into the feed pellets with bare hands with small and medium scale farmers having little awareness of associated occupational health hazards. This practice together with inferior drug quality will lead farmers to administer sub-therapeutic antimicrobial concentrations with the subsequent risks of treatment failure and resistance development. Farmers stated lower costs and stricter regulation on antimicrobial usage as reasons for the popularity of probiotics. Farmers also reported the use of herbal extracts for disease control and water quality improvements, partly because of the low number of reported negative side effects and no antimicrobial residue problems. Local chemical supply shops, with representatives often visiting the farms, were important sources of information that farmers used when diagnosing and treating diseases. Farmers also relied on their own experience and current practices of chemical use do not seem cost-effective. Thus, government, academia, and the private sector should cooperate, e.g. in private-public partnerships, to improve advisory services and offer training to farmers, in particular on prudent and efficient use of antimicrobials and other compounds. Approval procedures and legislation of products used in aquaculture should be strengthened and enforced ensuring farmers' access to quality and efficient agents for disease control.