Coxiella burnetii shedding during the postpartum period and the impact on reproductive disease burden: A cross-sectional investigation in a single Scottish dairy herd

Weller, Griffin McCleod (2024) Coxiella burnetii shedding during the postpartum period and the impact on reproductive disease burden: A cross-sectional investigation in a single Scottish dairy herd. MSc(R) thesis, University of Glasgow.

Abstract

Coxiella burnetii is a poorly understood pathogen with a wide geographical distribution across a plethora of host species. Impact on cattle reproductive health and herd fertility has been indicated internationally, but detailed investigations of the prevalence and impact on production in the UK are scarce. The gap in knowledge of the clinical impact C. burnetii infections has on dairy cattle is quite large with varied clinical impacts across herds, so a study elucidating the behaviour and effects of C. burnetii in British herds is required. The objectives of this study were to determine the within-herd prevalence of C. burnetii on a commercial dairy farm and assess the relationships between pathogen shedding and key performance indicators (KPI) and reproductive health. A 900-cow dairy farm in Scotland was recruited in this study following positive screening for C. burnetii by PCR and ELISA. Vaginal swabs were collected from postpartum cows during checks performed within seven days of parturition. DNA extracts were tested by qPCR for C. burnetii using an IS1111 assay. The estimated log(n genomes per reaction) was calculated for all samples. Mixed effect Gaussian generalized linear models with identity link function were used to identify variables associated with higher (or lower) concentrations of bacterial DNA. The relationships between cow production and clinical data and this outcome were assessed in uni- and multivariable models. A total of 324 swabs were collected between December 2022 and July 2023, of which 310 (95.7%) had detectable C. burnetii with Ct ≤ 40. Cows shedding higher loads of bacterial DNA were more likely to be primiparous and to have experienced one or more negative gestational/obstetric outcomes including abortion, stillbirth, premature delivery, prolonged gestation and/or dystocia. Bacterial load did not correlate significantly with the days postpartum on which individuals were sampled. These findings indicate C. burnetii infections have negative impact on the health status and fertility of herd members in the sample population. Further investigation should take place to assess ongoing herd-wide effects of C. burnetii infections to better inform possible treatment and prevention strategies.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Subjects: S Agriculture > SF Animal culture > SF600 Veterinary Medicine
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Supervisor's Name: Halliday, Dr. Jo, Allan, Dr. Kathryn, Vazquez, Mr. Richard and Viora, Dr. Lorenzo
• Date of Award: 2024
• Depositing User: Theses Team
• Unique ID: glathesis:2024-84659
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 06 Nov 2024 12:45
• Last Modified: 06 Nov 2024 12:47
• Thesis DOI: 10.5525/gla.thesis.84659
• URI: https://theses.gla.ac.uk/id/eprint/84659