Broad strategy shows progress on major pig disease

Although a major pig virus continues to threaten the livelihood of Canadian pork producers, front line researchers in the global pork industry say progress is being made in the fight. Porcine circovirus associated disease (PCVAD) has produced severe losses for pork producers worldwide but poses no threat to humans.

Robert Desrosiers, a technical service veterinarian with Boehringer Ingelheim, gave a "state of the union" on what causes the disease, its clinical signs, lesions or physical changes, transmission means and control options. He also discussed some of the questions that remain unanswered. He was one of five speakers from around the world to tackle the subject at a half-day session of the Banff Pork Seminar, January 16-19, 2007.

"The symptoms and lesions are fairly well characterized and new, effective vaccines are now available to pork producers," says Desrosiers. "We are also finding that certain genetic lines, or genetic combinations, such as a specific boar line with a specific sow line, are producing pigs that are more resistant to the disease than others. Management practices that appear to reduce the severity of problems have been identified, but very few appear to give consistent results."

Pigs can become infected with the causal organism, porcine circovirus type 2 (PCV2), in a number of ways, says Desrosiers. These include direct contact with infected animals or infected premises, contact at short distances of one to two metres, transmission from the dam to its foetuses in the uterus, and potentially through infected semen, although the latter is not fully proven at this time.

It was discovered in Western Canada in the early '90s and has subsequently resulted in severe losses for pork producers throughout the world. More recently, Quebec and Ontario herds have been hit particularly hard with the condition.

Although researchers have identified lesions that strongly suggest PCVAD infection, such as enlarged lymph nodes and white spots on kidneys, no specific lesion appears to be present in all cases.

"However, in many cases where several pigs are autopsied, it is possible to have a good idea as to whether or not PCVAD is involved. Ultimately the lab is needed for a full proof confirmation," says Desrosiers.

Vaccines available today have been shown to be effective in the control of the disease, and in many situations a complete elimination of problems was observed. This appears to be particularly true for piglet vaccines. Good results have also been observed with a vaccine used in gilts and sows, but the results may not be as consistent, says Desrosiers.

"While it is clear that genetics can have an impact, the data is not all going in the same direction, so care should be taken before making radical changes to a pork production program. In my opinion, however, genetics, with vaccines, is one of the control options which offer the most possibilities."

Held since 1972 in Banff, Alberta, the Banff Pork Seminar is coordinated by the Department of Agricultural, Food and Nutritional Sciences, University of Alberta, in cooperation with Alberta Pork, Alberta Agriculture and Food and other pork industry representatives from across Canada. Program and proceedings of the 2007 Banff Pork Seminar are available on the Seminar Web site, www.banffpork.ca.

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