[Respiratory enzootics in sheep caused by Pasteurella haemolytica]

Bacteriologically in 25 per cent of the materials taken from lambs, weaned lambs, and adult sheep Pasteurella haemolytica was invariably isolated. Serologic typing revealed that serotypes A2 and A6 were mostly widespread. The remaining serotypes proved to be encountered. Widely occurring were likewise the carriers of Pasteurella haemolytica both among the diseased animals and among the normal contacts--30 and 6 per cent, respectively. The serotype of the isolated strains (swab samples) was shown to be identical with the serotype of the strains isolated from pathologic materials on the same farm. This spoke of the symptomless existence of the infection in the flock and the important part played by such stress factors as movement, transportation, etc. in the outbreaks and the aggravation of the P. haemolytica infections. The isolated strains were apathogenic for albino mice and were sensitive in vitro penicillin, chloramphenicol, tetracycline, and streptomocin.