| Porcine reproductive and respiratory syndrome (PRRS), commonly known as blue ear disease, is an infectious disease caused by PRRS virus (PRRSV). It is divided into European and North American types, which is currently one of the most important swine diseases in the pig industry. The annual loss of PRRS for the American pig industry is 664 million U.S. dollars (approximately 4 billion RMB). China's pig production is much larger than that of the United States, therefore, the loss caused by PRRS in China should be much greater than that of the America. The impact of the disease on the sow herd is mainly to reduce the farrowing rate, the number of litters and the number of weaned pigs per litter. Genotype of PRRSV in China is mainly the North American type. PRRS can cause reproductive disorders in the sows and respiratory problems in piglets and growing-finishing pigs. In 2006, a highly pathogenic PRRS caused by a mutant strain of PRRSV broke out in China, and the disease was widespread throughout the country and damaged China's pig industry severely. After the year of 2013, NADC-30-like strains began to gradually spread in China, and various recombinant strains continued to appear, as a result, the prevention and control of PRRS became more complicated. PRRSV is easy to mutate, the strain is diverse and the infection time is long, so the prevention and control is difficult. Pigs infected with PRRSV will cause immunosuppression and are prone to various mixed infections and secondary infections, which increase the difficulty of prevention and control. This article reviews the clinical symptoms, pathogen characteristics, etiology, transmission routes, diagnostic methods, as well as prevention and control measures of PRRS. As for the prevention and control of PRRS, pig farms need good biosecurity, scientific vaccination protocol and correct medication strategy. This article also discusses the effect of using Tilmicosin for control in pig farms with PRRS infection. |
