A 40-Year Retrospective Analysis of Mannheimia haemolytica, Pasteurella multocida and Bibersteinia trehalosi Cases from South Africa: Insights into Distribution and Serotype Diversity

Respiratory diseases caused by Mannheimia haemolytica, Pasteurella multocida and Bibersteinia trehalosi cause substantial economic losses in livestock.This study investigated the long-term epidemiological trends of Pasteurellaceae based on diagnostic laboratory reports submitted to the Agricultural Research Council-Onderstepoort Veterinary Research diagnostic laboratory in South Africa between 1969 and 2018.The study aimed to characterize the temporal distribution of Pasteurellaceae species from 1969 to 2018 and describe long-term patterns in species diversity and dominance.A total of 2,317 bacterial laboratory reports were retrospectively analyzed.M. haemolytica was the predominant species (57.0%), followed by P. multocida (27.1%) and B. trehalosi (13.3%).Most laboratory reports originated from sheep and cattle, which together accounted for more than two-thirds of submissions.Host-specific analyses demonstrated marked differences in bacterial distribution, with M. haemolytica predominating in ruminants, whereas P. multocida was more frequently recorded among pigs, companion animals and laboratory animals.Although temporal variation was statistically significant, year of isolation was not independently associated with bacterial species after multivariable analysis.Serotyping revealed considerable diversity, with M. haemolytica serotypes A1, A2, A6, A7 and A9 predominating, while serogroup A was the most common among typed P. multocida.This study provides one of the longest retrospective assessments of Pasteurellaceae in South Africa, demonstrating persistent host-associated patterns, geographic variation and considerable recorded serotype diversity over four decades.These findings support continued host-focused surveillance, improved serotyping and molecular characterization, and demonstrate the value of historical diagnostic records as a baseline for future surveillance.