Isolation and Characterization of Pasteurella spps from Pneumonic Cases of Livestock in Three Regional States of Ethiopia: Evidence of Differences between Field and Vaccine Biotypes

Pneumonic pasteurellosis is the leading cause of recurrent morbidity and mortality in ruminant livestock in Ethiopia. Its control is mainly done using an annual vaccination with a monovalent whole broth culture of Pasteurella (P.) multocida. However, the multiplicity of the serotypes circulating in the field and the lack of cross-protective immunity hinder the effectiveness of the vaccination program warranting the development of a vaccine with better efficacy. To this effect, the identification, and characterization of the strains from different regions of the country is necessary. In this paper, Pasteurella organisms collected from camels, cattle, goats, and sheep with respiratory signs suggestive of pasteurellosis in the Afar, Tigray, and Benishangul Gumuz regional states were isolated, and characterized. From clinically pneumonic cases, 793 nasal swabs (286 goats, 276 sheep, 168 camels, and 63 cattle) were collected aseptically and cultured on Blood Agar. Bacteria pathogens were identified at the species level by biochemical tests. Culture positivity was 29.3% (243/793). The isolation frequencies of B. trehalosi, M. haemolytica, and P.multocida were 47.7% (116/243), 43.2% (105/243), and 9.1% (22/243), respectively. A higher isolation rate was observed in sheep (37.4%), and the lowest in cattle (6.2%). Mixed infection with B. trehalosi and M. haemolytica was observed in sheep, goats, and camels. Despite the higher frequencies of isolation of B. trehalosi and M. haemolytica from all host species, the vaccine currently being used in Ethiopia consists of only P. multocida biotypes A for sheep and goats and biotype B for cattle. Moreover, camels are not considered in the pasteurellosis vaccination program in the country. Therefore, the result of the study suggests the need to include B. trehalosi and M. haemolytica in the vaccine preparation as well as underlines the relevance of considering camels in the vaccination program.