The comparative pathogenicity of strains of eight serovars and untypable strains of Mannheimia haemolytica in experimental pneumonia of sheep

Abstract

-The experimental induction of pneumonic pasteurellosis in groups of conventionally reared lambs by 8 serovars (A1, A2, A6, A7, A8, A9, T10, and A11) and untypable (UT) strains of Mannheimia haemolytica (Mh) were examined and compared. The groups of lambs were inoculated intratracheally with 1.4 × 10 8 ± 0.6 × 10 8 (mean ± SD) colony-forming units of the Mh serovars or UT isolates in the 6-hour log phase of growth. The variables measured as indicators of disease severity were clinical score, percentage lung consolidation and microbiological re-isolation. The clinical parameters for each group were computed daily for 6 days post infection and the lambs which died were necropsied while the remaining lambs were killed on day 7 pi and the extent of lung consolidation was measured. Clinically, the mean scores for the M. haemolytica serovars were A1 (6.1), A2 (18.8), A6 (0.5), A7 (17.4) and A9 (8.5). The mean percent lung lesion scores for M. haemolytica serovars were A1 (12.5), A2 (66.3), A6 (5.0), A7 (51.3), A9 (33.8) and A11 (2.5). The percent mean pneumonic lung lesions recorded for groups inoculated with A2, A7 and A9 were significantly (P < 0.05) higher than the extent of lung lesions in the other groups. A statistically significant correlation was observed between clinical scores and the severity of the lung lesions (r = 0.96, P < 0.01). High titres of M. haemolytica were recovered from lung lesions, with 10 to100 times the number of organisms inoculated being present in the lung lesions of lambs inoculated with serovars A2 and A7. These data indicate that although M. haemolytica serovars A1, A2, A6, A7, A9 and A11 are important primary lung pathogens of lambs, serovars A2, A7, and A9 are to be regarded as highly virulent strains that have a greater predilection than the other serovars for causing pneumonia in lambs.sheep / pneumonia / Mannheimia haemolytica / comparative / pathogenicity

Transmission of Mannheimia Haemolytica From Domestic Sheep (Ovis Aries) to Bighorn Sheep (Ovis Canadensis): Unequivocal Demonstration With Green Fluorescent Protein-Tagged Organisms

“…Pleuritis was noted as present or absent. Representative samples of pneumonic and normal lung tissue were prepared for both bacteriologic and histopathologic examination (Odugbo et al, 2004). Animals that showed severe signs of pneumonia were euthanized by intravenous administration of pentobarbital and then necropsied in the same manner as those found dead.…”

Intact signal peptide of CD18, the β-subunit of β 2 -integrins, renders ruminants susceptible to Mannheimia haemolytica leukotoxin

“…S3). Also, inhibition of Lkt-induced cytolysis of PMNs of goats, domestic sheep, wild sheep, deer, and bison by peptide P17 (amino acids [5][6][7][8][9][10][11][12][13][14][15][16][17] indicates that the CD18 domain formed by amino acids 5-17 represents the Lkt-binding site on CD18 of other ruminants as well.…”

“…haemolytica is the most important bacterial pathogen of respiratory disease in cattle and other domestic and wild ruminants (4)(5)(6)(7). This disease, commonly known as pneumonic pasteurellosis or shipping fever in cattle, has been estimated to cost Ͼ$1 billion to the cattle industry of the United States alone (8).…”

Ocorrência de pneumonia associada à infecção por Mannheimia haemolytica em ovinos de Minas Gerais

“…Destes, os sorotipos A1 e A2 são a causa primária de pneumonia em bovinos e ovinos, respectivamente. Apesar disso, um estudo realizado na Nigéria (Odugbo et al 2004) com a inoculação de uma ampla variedade de sorotipos de M. haemolytica em ovinos, associou virulência e sorotipos e concluiu que os sorotipos A2, A7 e A9 são altamente patogênicos para ovinos, pois causaram mortalidade, sinais clínicos graves ou elevado grau de lesão pulmonar. Nesse estudo, não foi possível a determinação do sorotipo dessa bactéria.…”