A Streptococcus suis (S.suis) serotype 7 infection in an Austrian piglet producing farm with
1500 sows is described. Cleaning and disinfection protocols were at high standard and a clear
separation between all age groups was guaranteed Newborn piglets were treated parenterally
with ceftiofuro n the 1" day of live and witha n1oxicilline for ten days in medicated food after
weaning, routinely. \Vhen symptoms reoccured, treatruent with amoxicillinew as continued.
In a first step the actual situation was described. Piglets of the control group (Group A,
n=979) were not treated with antibiotics while piglets of the treated group received
amoxicillin (Group B, n=l012). In the control group a higher number of pigs developed
meningitis (1.8%) and arthritis (3.3%) at five to eight weeks of age compared to the treated
group (meningitis 0.8%, arthritis1 .1%). Mortality rate was significantly higher in the control
group (1.8%) than in the treated group (0.8%). Additional symptoms typical for S.suis
infection as endocarditis, wasting, pneumonia or polyserositis were not seen on the farm.
Brain and joint samples of untreated, euthanized piglets out of the control group (n= 17) with
symptoms of meningitis and/or arthritisw ere examined bacteriologically. Twenty-five S.suis
isolates out of 18 piglets (medium to high-grade bacterial growth) were recovered, 17 of them
were serotyped by coagglutination technique resulting in serotype 7 in all samples. All
isolates were tested by multiplex-PCR using primer pairs specific for virulence-associated
genes mrp (muraminidase- released protein), ef (extracellular factor), ofs (serum opacity
factor) and sly (suilysin). All isolates were positive for mrp, but negative for epf, ofs and sly.
No other pathogens typical for causing meningitis or arthritis could be isolated from clinical
Five serotype 7 isolates were chosen for farm-specific vaccine production, which was
applicated to suckling piglets in the first and third week of life, but without a protective effect.
This case showed, that not only Ssuis serotype 2 (most common serotype in Austria), but also
serotype 7 can cause clinical disease in Austrian pig farms. A vaccination program must be
adjusted to specific farm conditions taking a potential interference with maternal antibodies
and the time-point of outbreak of clinical disease into account.