PASTEURELLA SPP IN SYMPATRIC BIGHORN AND DOMESTIC SHEEP

Domestic sheep were sighted at different times from 1991 to 1993 on fo ur Nevada (USA) ranges occupied by bighorn sheep. Nasal and pharyngeal swab samples were collected from both sheep species and cultured to d etermine if any strains of Pasteurella spp. were shared on range condi tions after contact of the two species. Pasteurella spp. were isolated from all 38 bighorn sheep and 16 of 17 domestic sheep included in thi s study. The isolates were characterized on the bases of species, biot ype, serotype, biogroup, and restriction enzyme analyses (REA) as well as ribotyping of bacterial DNA. A P. haemolytica biotype 3, biogroup 11 isolate from a domestic sheep had biochemical, REA, and ribotype pr ofiles which were identical to those of isolates from three bighorn sh eep on the same range. None of the other isolates were found to be com mon to the two sheep species. Disease was not detected in any of the b ighorn populations. However, bighorn sheep populations were extirpated on two ranges while increasing on the other two, including the range on which P. haemolytica biotype 3, biogroup 11 strain was isolated. De clining sheep numbers were not correlated with the presence of any one strain of Pasteurella spp from the sheep.