[Clinical situation, diagnosis and prevention of a Streptococcus suis serotype 7 problem on a farm]

Abstract

In an Austrian piglet producing farm with 1500 sows a high incidence of meningitis, arthritis and sudden death was recorded in five to eight week old piglets. Overall losses were 1.8%. Streptococcus (S.) suis serotype 7 was detected with an intermediate to high specific bacterial load in all samples taken from brains and joints of 17 untreated piglets with typical clinical signs. All isolates showed an identical spectrum of virulence-associated genes (mrp+, epf-, ofs-, sly-) and expressed a relatively small variant of MRP (Muramidase-Released Protein) called MRPs. A bacterin was produced using four of the S. suis serotype 7 isolates. An untreated and non-vaccinated control group A with 957 piglets, a non-vaccinated but amoxicillin-treated group B with 1012 piglets and an untreated group C with 998 piglets, which was vaccinated twice in the first and third week of life, were compared. Later, an additional group D with 290 piglets was vaccinated twice in the fourth and sixth week of life. Amoxicillin treatment in group B resulted in the lowest mortality and morbidity rate. Furthermore, the incidence of lameness and losses were significantly lower in vaccinated pigs compared to the control group. In an ex vivo blood survival assay, a strong bactericidal effect of the post immune sera of group D animals was found. This is likely due to the presence of specific opsonizing antibodies against S. suis elicited through vaccination and associated with the protective efficacy of the vaccine.