Antibiotics in pig and chicken farm soils in Asia: Environmental impacts and perspectives.

Animal production in Asia is extensive with high demand for antibiotics use. Based on 31 studies in Asia, a wide range of sulfonamides and quinolone antibiotics are used in pig and chicken farms. Unmetabolized antibiotics excreted by animals enter the environment contributing to the global problem on antimicrobial resistance (AMR). This review highlights the direct entry of antibiotics in soil through animal excrements and indirect entry through manure and wastewater application in agricultural lands. Across 60 sites identified in the studies, manure (71.67 %) and pig farms (55.00 %) are the main sources of antibiotic contamination in amended soil. Tetracyclines were reported in high detection frequency (81.18 %) with an average log10 concentration of 1.50 μg/kg in soil. From the soil, antibiotics are transported to other environmental matrices such as plants and aquatic systems. Antibiotics that are important in human and animal healthcare found in concentrations exceeding the ecotoxic trigger value of 100 μg/kg may pose risks of AMR. The burden of AMR compromises the effectiveness of last-resort antibiotics which is particularly experienced in low- and middle-income countries in Asia. This is also driven by the misuse of antibiotics in animal farms aggravated by misconceptions, poor practices, and unrestricted access to antibiotics. There is urgent need for multisectoral and multidisciplinary approaches to mitigate the impacts of antibiotics use in animal production through increased AMR awareness and proper antibiotics use, harmonized surveillance and research, establishment of infection prevention mechanisms, and innovations in animal farming practices.