Insights into Pasteurellaceae carriage dynamics in the nasal passages of healthy beef calves

Summary

This longitudinal study characterised the carriage dynamics of three bovine respiratory pathobionts in 60 healthy beef calves housed under experimental conditions. The three species exhibited markedly different carriage prevalences and persistence profiles: P. multocida showed high initial carriage (95%) and prolonged median duration (55.5 days), whilst H. somni was also prevalent (75%) but cleared more rapidly (14.8 days median). Higher density P. multocida carriage was associated with slower clearance, providing mechanistic insights into pathobiont colonisation that may inform understanding of respiratory disease risk in housed cattle.

UK applicability

The findings are directly relevant to United Kingdom beef production, as winter housing of calves is standard practice. Understanding pathobiont carriage dynamics in this setting may inform biosecurity protocols and housing management to reduce respiratory disease incidence, though the experimental farm conditions may not fully reflect variation in commercial UK operations.

Key measures

Carriage rates (percentage of animals positive) at housing and over time; bacterial density quantified by qPCR; median duration of carriage (days, with 95% confidence intervals); association between bacterial density and clearance rate

Outcomes reported

The study quantified carriage rates and density profiles of three bovine respiratory pathobionts (Histophilus somni, Mannheimia haemolytica, and Pasteurella multocida) in the nasal passages of healthy beef calves over a 75-day winter housing period. Colonisation duration and clearance patterns were modelled using interval-censored survival analysis to estimate median carriage times and identify factors associated with persistence.

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