Streptococcus suis infection is a well known pathogen on Ontario pig farms. Generally the disease is recognised as a sporadic outbreak of meningitis, but there are other manifestations such as heart disease, pneumonia or arthritis. It has long been known that Strep. suis can cause disease in humans, but the cases have been extremely rare. However, in China from mid-July to the end of August 2005, a major outbreak occurred with a total of 215 cases of human Strep. suis infections. All infections involved backyard farmers who were directly exposed during the slaughtering process of pigs that had died of unknown causes or that had been killed for food because they were ill. Sixty-one farmers (28 percent) had streptococcal toxic shock syndrome; 38 (62 per cent) died. The other illnesses reported were sepsis (24 per cent) and meningitis (48 per cent) or both.

One significant outcome of this catastrophic event is that the world medical community is now much more familiar with Strep. suis as a potential cause of human disease. For example, the first case of human Strep. suis meningitis in the United States was diagnosed only a few months after the China outbreak and more recently, two cases in Australia were reported. This disease has the potential to strongly and negatively impact consumer confidence.

Prevalence of Strep. suis in Ontario's Pigs

Recently, the authors conducted a study to determine the prevalence and to characterise the types Strep. suis present in Ontario pigs (MacInnes et al., 2008). Tonsillar and nasal swabs were collected from weanling pigs in 50 representative herds.

All but one herd tested positive. Of the 35 different serovars of Strep. suis characterised to date, serovar 2 is by far the most important pathogen in people. On almost half of the farms tested in our study had either serovar 2 Strep. suis or the closely related serovar 1/2.

One important implication of this finding is that Strep. suis is very common in the Ontario pig population and the zoonotic threat, Strep. suis serovar type 2 appears to be present in the Ontario pig population.

Pork producers need to be aware that a low but real risk may be present during manipulation of Strep. suis-diseased animals. These pigs may shed very high numbers of bacteria, and wearing gloves and/or washing hands with soap and water immediately after handling is prudent.

There is still a great deal that is unknown about how Strep. suis causes disease and why certain strains seem to be more dangerous than others. At present there are no effective means to eradicate the organism from pig herds and even control of disease outbreaks has proven difficult.

Reference

Further Reading

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You can view other papers presented at the Centralia Swine Research Update 2009 by clicking here.

Further Reading

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Find out more information on streptococcal infections by clicking here.