Eastern Canada Hit Hard

CANADA - Between the fall of 2004 and the spring of 2005, finishing units in Quebec were hit hard by disease characterized by wasting, anemic pigs showing respiratory distress, diarrhea, ulcers and dermatitis nephropathy syndrome between 13-18 weeks of age.

17 August 2006

3 minute read

North America

Due to its sudden and acute appearance, many practitioners first thought these cases were an emergence of atypical, very virulent strains of PRRS, according to a paper presented by Dr. Laura Batista, University of Montreal, at the recent American Association of Swine Practitioners annual meeting.

Since the clinical presentation of these new outbreaks presented characteristics not seen before in PRRS outbreaks, serum samples, organs, live pigs and carcasses were submitted to the faculty of veterinary medicine and provincial diagnostic laboratories. Most of the cases were diagnosed as postweaning multisystemic wasting syndrome (PMWS). Several were complicated with different concurrent pathogens such as PRRSV, swine influenza virus, M. hyopneumoniae, S. suis and H. parasuis.

Before the fall of 2004, PMWS had been a disease of nursery pigs and not of grower and/or finisher animals as it is today, says Batista. Presently, PMWS is one of the major disease concerns to Quebec's pork industry and is becoming significant in Ontario, Manitoba and Saskatchewan.

To date, observational data shows that:
Typical clinical presentation is between 4-8 weeks after placement in the finisher.
It is more acute and common in site production than farrow-to-finish operations.
It is more acute and common in multi-source than in mono-source operations.
Morbidity and mortality are always higher in PRRS-positive vs. PRRS-negative systems.
Morbidity ranges between 30-50% of the affected groups.
Mortality ranges between 7-30% of the group with extreme reports of 50%.

The Quebec veterinary researcher believes that PMWS is not an emerging disease, but rather changes in the virus genome are responsible for the epizootic episodes of PCV2-related diseases. Even though there are many reports of the stability of PCV2, Batista feels the virus has changed and that there are more virulent strains than others. Research to prove this hypothesis, she adds, is developing in several parts of the world.

Immuno-stimulation due to certain oil adjuvants is another plausible explanation for the presentation of PMWS, notes Batista. And even though there are many questions related to genetic resistance, changing genetics might be a possible option to reduce the presentation of PMWS.