Streptococcus suis: an update

摘要

Streptococcus suis is one of the most important swine pathogen in modern swine production (Higgins and Gottschalk, 1998a). There are presently 35 capsular types or serotypes described (Gottschalk et al. 1989, Gottschalk et al., 1991; Higgins et al., 1995). S. suis has been reported in all countries where swine industry is important and for more than a decade, infections associated with this microorganism have been in emergence due to modem and intensive swine operations. In diseased pigs, capsular type 2 predominates in most countries (Reams et al., 1996; Higgins and Gottschalk, 1998b). Meningitis is the most striking feature and the one on which a presumptive diagnosis is usually based. Early nervous signs include ataxia and adoption of unusual postures, which soon progress to inability to stand, paddling, opisthotonos, convulsions, and nystagmus. The eyes are often stating, with reddening of mucous membranes. Septicemia, arthritis, and pneumonia are less remarkable manifestations of the disease and a tentative diagnosis is difficult to make on the same basis. Amongst other manifestations of S. suis infections, there are sudden death, endocarditis, rhinitis, abortions, and vaginitis. The implication of S. suis as a primary cause of pneumonia is controversial. Most S. suis isolated from diseased pigs belong to a limited number of capsular types often comprised between 1 and 8. However, some strains belonging to less common capsular types have been associated with severe cases of infection. S. suis capsular type 9 was associated with outbreaks of septicemia, meningitis, and pneumonia in weaned pigs. In the U.K., the isolation of capsular type 14 in several farms with clinicopathological findings similar to those associated with serotype 2, has also been reported.