Table 2 The 10 Golden Rules
Rule | Rationale | |
|---|---|---|
1 | Minimise cross-fostering and movement of piglets: cross-foster only surplus piglets | The immune system is immature in newborn piglets; immunity depends on passive immunisation transmitted via colostrum [37]. Piglets receive optimal protection from their own mothers so should only be moved if a sow cannot support her whole litter. Furthermore, moving piglets to other sows causes weight loss in both moved piglets and their new litter mates [38] |
2 | Avoid cross-fostering after 48 h | Maternal immune protection starts to decrease when piglets reach 3 days of age [37]. Cross-fostering before maternal protection decreases is strongly recommended |
3 | Avoid spreading disease when handling piglets by keeping piglets in pens | Urine, blood, faeces and semen are vehicles for PRRSV transmission; special attention should be paid to the use of equipment (e.g. needles and castration equipment) |
4 | Change needles between litters | PRRSV is easily transmitted among pigs by needles, so regular replacement of needles (at least between litters) is recommended. Diseased piglets should be treated after healthy piglets |
5 | Do not move diseased piglets | Diseased piglets often have compromised immunity and comorbidities that increase the likelihood that they are also carrying PRRSV. Their viral load is also likely to be higher, increasing the risk of spreading infection. Therefore diseased piglets should remain with the same sow to limit viral spread: if a piglet is too weak for this, it should be euthanised |
6 | Wean all piglets from each batch simultaneously, and ban weaned piglets from the farrowing rooms | Holding smaller piglets back in the farrowing rooms for quality before they are weaned can jeopardise PRRS control programmes [39]. Such piglets are more likely to be diseased, and to spread PRRSV to others |
7 | Maintain strict AIAO batch production at all times from weaning to finishing | After piglets are weaned, batch production should continue, and should be either by site, barn or room. If a batch is not completely removed before placement of new pigs, infection pressure rapidly increases. Do not share needles, equipment, personnel and protective equipment between batches (unless cleaned and disinfected) |
8 | Avoid contact between age groups | Risk of infection is increased 13-fold if contact is permitted between growing pigs of different ages during restocking of rooms [40]. Mixing PRRSV-positive pigs in one age group with PRRSV-negative, non-vaccinated pigs in other age groups greatly increases PRRSV shedding [41, 42] |
9 | Avoid contact between sows and piglets (<6 months of age) | Breeding herds and grower/finisher pigs should never be in contact (i.e. when moving pigs and sows around the farm) because cross-contamination between groups can occur |
10 | Introduce incoming and home-produced gilts via quarantine. Administer PRRSV MLV upon entry to quarantine areas | Natural immunisation of gilts should be avoided because it cannot be monitored or controlled. If natural immunisation occurred just before entering a breeding site, there would be a high risk of introducing wild-type PRRSV to the breeding herd. While in quarantine, gilts should be immunised twice with PRRS MLV (vaccinations should be administered 4 weeks apart) |