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New Pig Disease Poses A Puzzle

“These pigs look very similar to pigs that simply starve to death.”

– JOHN HARDING, U OF S

Scientists at the University of Saskatchewan have discovered a new and baffling swine ailment in which newly weaned pigs fail to eat and starve to death.

Postweaning Wasting/ Catabolic Syndrome (PWCS), can cause death losses of up to 10 per cent in piglets.

Only a handful of cases have been detected so far in Saskatchewan, plus a few suspected cases in Manitoba and Alberta.

But the industry has been aware of PWCS, its unknown cause and the mystery surrounding it since 2008.

“I really am puzzled by this one,” said Dr. John Harding, an associate professor with the Western College of Veterinary Medicine at the University of Saskatchewan in Saskatoon.

Harding’s colleague Yanyun Huang gave a presentation on PWCS at the recent Manitoba Swine Seminar in Winnipeg.

SIMILAR BUT DIFFERENT

At first glance, PWCS appears to be like Postweaning Multisystemic Wasting Syndrome (PMWS), a pig disease caused by porcine circovirus Type 2 (PCV2). PMWS was first detected by University of Saskatchewan researchers in 1994 and is now known worldwide.

But although it exhibits similar clinical signs (e. g., wasting), PWCS is not PMWS, Harding asserted.

For one thing, PMWS occurs at the late nursery stage or, more commonly, the grower-finisher stage. PWCS usually affects pigs at a younger stage – one to three weeks after weaning.

Also, PMWS causes extensive and easily visible damage to internal organs. The organs of PWCS pigs show three characteristic lesions, of which only one – severe atrophy of the thymus gland – is readily obvious. The other two are detectable only by microscope.

Finally, there’s no evidence in PWCS pigs of circovirus, the agent in PMWS. These are normal pigs weaned after a few weeks who just do not feed, said Harding.

“This is not caused by circovirus because we’ve looked hard for it,” he said. “These pigs look very similar to pigs that simply starve to death.”

FIRST NOTED

Researchers stumbled across PWCS in 2008 after a local Saskatchewan veterinarian reported that wasting continued in piglets even after they were vaccinated for circovirus. Mortality rates fluctuated monthly but sometimes reached 10 per cent in peak months.

Harding said researchers are now trying to reproduce the disease, if indeed that’s what it is. The process involves taking piglets immediately after

birth before they can suckle colostrum, removing them to a clean environment and feeding them bovine colostrum, which contains antibodies not related to swine diseases.

When piglets are one to two weeks old, they are exposed to tissues from PWCS pigs to see if it can be reproduced in them.

If it can, that means PWCS is an infective disease which can be subjected to molecular studies to see what viruses or bacteria are involved, said Harding.

Harding isn’t yet convinced PWCS is infective. He speculates it could be a behavioural disorder caused by an immaturity of the brain.

Dr. Mike Sheridan, a Steinbach swine veterinarian, said PMWS made producers highly sensitive to different, abnormal symptoms in their herds. For that reason, producers will watch animals carefully for any early signs of PWCS.

Sheridan emphasized PWCS appears rare, little is known about it and so there’s no reason to panic.

But it is weird, he acknowledged.

“We don’t know if this is serious but it is different.” [email protected]

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