Porcine reproductive and respiratory syndrome (PRRS) becomes increasingly difficult to prevent as the number and density of pigs increase. How can pig farms prevent and control PRRS economically based on the present situation?

The prevalent PRRS strains in China are complex and diverse, and the difficulty of prevention and control is increased, and the time required for stabilization is increased compared with the past. The industry should be especially vigilant against the spread of PRRS-1 virulent strains. For the vast majority of pig farms, maintaining PRRS positive stable field is a more rational choice.

The virus is complex and varied, with new strains emerging constantly, and even multiple strains can be detected simultaneously within a herd. Among the many strains, pig farmers should be particularly vigilant against the strong strain of PRRS (PRRS-1). Existing studies have shown that PRRS-1 strains can cause severe symptoms in sows, piglets, and fattening pigs. Pregnant sows usually give birth prematurely one week before the expected date of delivery, mainly giving birth to white fetuses. The mortality rate of nursery piglets can reach more than 50%. PRRS-1 strains can cause lung injury, interstitial lung, lymph node enlargement and hemorrhage, individual gastric mucosal hemorrhage, and cause chronic infections such as mycoplasma and vice pigs. However, the existing PRRS-2 vaccine has limited protection against this strain, and if the pig farms that have been immunized are unfortunately recruited, the loss is still very large.

PRRS prevention and control cannot but mention the number one killer of pig farms-pig blue ear disease. The control of blue ear disease in pigs is systematic. The production conditions of pig farms, virus virulence, and infection status of pigs are all important factors that affect the difficulty of prevention and control. Zhong Weijun pointed out that the average time (TTS -time to stability) from the outbreak of blue ear to the production of negative weaning pigs in pig farms is 41 weeks. The specific time required for different strains varies. The TTS of pig farms with blue ear disease in summer is longer than that of pig farms with blue ear disease in autumn and winter. The TTS of pig farms that have experienced blue ear outbreaks within one year is shorter than that of pig farms. This also means that if the pig farm has immune weak blue ear seedlings, even if re-infected with new strains, the recovery will be faster.

PRRS vaccine cannot be used for sick pigs. More attention should be paid to unsick pigs.

Different pig farms have different immune conditions and morbidity conditions. Therefore, prevention and control plans must be adapted to local conditions to help pig farms calculate their economic accounts. Zhong Weijun shared PRRS prevention and control strategies for pig farmers according to the following three common situations:

1. For pig farms that have not been immunized with blue ear vaccine, the virus is positive in the delivery room, nursery and fattening pigs. When the reproductive disorder of sows is serious and weaned piglets and fattening pigs are greatly affected, the priority can be given to "herd closure + virus exposure after vaccination of sows". "Sows are vaccinated with blue ear vaccine 4 times a year + piglets are vaccinated with blue ear vaccine once every 14-21 days.

2. There is no immune vaccine and the sow group is not stable pig farm, choose the whole group of sows inoculated with blue ear seedling cost-effective.

3. If the pig farms where sows have been immunized with blue ear vaccine are still troubled by PRRS, resulting in greater losses (high mortality rate of weaned pigs and growing and finishing pigs), it is cost-effective to choose group sealing or virus exposure.