Has PRRS role in onset of new pig diseases?
By Marianne Curtis
THERE is disagreement between vets about whether or not PRRS has a role in the onset of new pig diseases PMWS and PDNS. Porcine circoviruses (PCV), although linked with the diseases may not be the cause, believes a Belgian vet.
Willem Neirynck, a vet at pig breeding company Seghers in Belgium, is not convinced that PCVs cause the new diseases. "A trial using blood samples from an Aujeskys disease testing programme showed that 80% of samples were positive for PCV II but PMWS was not present on these farms.
"Frequently, pigs with the disease are found to be infected with PRRS, and other viral infections such as parvo, PRCV and flu may also have a role. Avoid overcrowding and consider vaccinating against PRRS," advises Dr Neirynck.
But it is too early to give recommendations on vaccinating against PRRS, says vet Paul Thompson of the East Yorks-based Garth Vet Group. "Herds struggling to control PMWS and PDNS may try different approaches, however, it is too early to say what will succeed.
"It is also early days for the PRRS vaccine and so far uptake has been low, with cost being the main disincentive. While many UK units will vaccinate against enzootic pneumonia, they have learned to live with PRRS."
Oxon-based vet Richard Potter is also doubtful about a PRRS link. "Ive seen two large outbreaks of the disease in PRRS negative herds so I dont believe this virus is involved."
Attempts to treat or prevent PMWS and PDNS are generally disappointing, according to Dr Neirynck, however, his company is adopting a strategy to minimise risk from breeding stock.
"We are supplying PRRS-free and PCV II-free stock. However, on many farms these viruses will be circulating around the herd. Managing the introduction of virus-free gilts to these farms correctly is critical.
"Too often decisions about buying gilts are made at the last minute, meaning they dont have the recommended six to eight weeks quarantine on the farm in which to develop immunity."
Introducing gilts to the rest of the herd too early runs the risk that they become infected with the disease, causing a recirculation of bugs which put animals in the existing herd in danger, he warns.
Checking with breeding companies that they havent had any disease breakdowns at the end of the quarantine period is also good practice, adds Mr Thompson.
Another wise precaution is to keep birds away from units, he advises. "It is possible that birds such as starlings may carry circoviruses, so avoid food spillages and cover feed troughs.
are covered. A clean, tidy farm is less attractive to birds."
• PRRS link?
• Isolate new breeding stock.
• Keep birds out.