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

Summary

This longitudinal study of 60 beef calves tracked nasal carriage of three bovine respiratory pathobionts over winter housing, using optimised qPCR to quantify bacterial density. The three species exhibited distinct epidemiological profiles: P. multocida showed high initial carriage (95%) with prolonged median persistence (55.5 days), whilst H. somni was carried by 75% of calves but cleared more rapidly (14.8 days median). Higher density P. multocida carriage was associated with slower bacterial clearance, suggesting inoculum load influences host-pathogen dynamics in clinically healthy animals.

UK applicability

The findings are directly applicable to UK beef cattle production systems, particularly indoor winter housing conditions common in temperate climates. Understanding pathobiont carriage dynamics in healthy animals may inform herd health management strategies and potential interventions to reduce disease risk during high-risk housing periods.

Key measures

Carriage rates (%), bacterial density quantification via qPCR, median duration of carriage (days with 95% confidence intervals), interval-censored exponential survival models, association between bacterial density and clearance rate (p-value)

Outcomes reported

The study quantified nasal carriage rates and bacterial density of three respiratory pathobionts (Pasteurella multocida, Histophilus somni, Mannheimia haemolytica) in healthy beef calves over a 75-day winter housing period using validated qPCR. It measured colonisation patterns, clearance dynamics, and associations between bacterial density and persistence of infection.

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