STREPTOCOCCUS-EQUI SUBSP ZOOEPIDEMICUS AS THE CAUSE OF MASS MORTALITY AMONG LABORATORY MICE

The report describes an epizootic caused by Streptococcus e qui subsp. zooepidemicus among laboratory mice. The disease developed in a group of newly purchased 600 white mice of strain Swiss and spread also to the same mice of the laboratory flock. Death occurred in two waves (each lasting only a few days) during which 11.7 % of the newly purchased mice and 40 (circa 4 %) mice of the original laboratory flock died. The only clinical sign deserving mention was occasional oedema in the head region (inflammation of submandibular lymph nodes). Post-mortem examination revealed tumor lienis, larger or smaller in size, in all the cases. Cultivation from the internal parenchymas yielded streptococcal colonies in growth phases M and D. This dissociation was reversible; it was present up to 25th passage on blood agar after which phase D gradually disappeared. The epizootic was liquidated by two courses of five day's experimental treatment, apart, with a penicillin-streptomycin mixture added to the drinking water.