Retrospective study of the relative frequency of cattle respiratory disease pathogens in clinical laboratory samples submitted by UK veterinary practices.

BACKGROUND: The objective of this study was to explore the relative frequency and seasonality of bovine respiratory pathogens in the UK, based on clinical case submission for laboratory PCR testing. METHODS: This study used retrospective data generated by a central Scotland laboratory using 407 clinical (pooled) samples collected by 95 veterinary practices located throughout the UK between November 2020 and September 2022. Statistical analyses were performed using descriptive spatial analysis (choropleth maps), chi-squared analysis, Poisson and logistic regression modelling. RESULTS: The majority (77.6%) of the samples had more than one species of bacteria identified, and 17.7% had multiple viruses identified. In comparison with the colder months of autumn and winter (September to February), the warmer months (March to August) were significantly associated with lower odds of respiratory disease caused by certain pathogens. Poisson models showed small but significant univariable associations between total viruses (coefficient = ‒0.01, standard error [SE] = 0.004, 95% confidence interval [CI] = ‒0.02 to ‒0.003) and total pathogens (coefficient = ‒0.005, SE = 0.002, 95% CI = ‒0.008 to 0.002) and increasing weekly age. LIMITATIONS: This is an inherently biased population because it only comprises clinical samples submitted to a single UK laboratory, and the data were analysed retrospectively. CONCLUSIONS: A large majority of clinical bovine respiratory disease (BRD) samples were multipathogenic, and pathogens such as bovine coronavirus (which has generally not been considered a significant contributing pathogen in the BRD complex in the UK) were prevalent.

Mannheimia haemolytica serovars associated with respiratory disease in cattle in Great Britain.

BACKGROUND: Mannheimia haemolytica is commonly associated with respiratory disease in cattle worldwide as a cause of fibrinous pneumonia, bronchopneumonia and pleuritis. M. haemolytica is further subdivided into 12 serovars, however not all are considered to be pathogenic in cattle. The study aim was to determine the most common serovars of M. haemolytica associated with respiratory disease in cattle in Great Britain, which is currently unknown and could be useful information for clinicians when considering preventative strategies. RESULTS: One hundred four M. haemolytica isolates isolated from bovine clinical pathology and post-mortem samples from pneumonia cases between 2016 and 2018 were tested using a multiplex PCR assay to identify M. haemolytica serovars A1, A2 and A6. 46 isolates (44.2%) typed as M. haemolytica serovar A1, 31 (29.8%) as M. haemolytica serovar A2 and 18 isolates (17.3%) as M. haemolytica serovar A6. Nine isolates (8.7%) were not A1, A2 or A6 so were considered to belong to other serovars or were not typable. CONCLUSION: This study highlights the importance of M. haemolytica serovars other than A1 which may be responsible for respiratory disease in cattle and could help guide the veterinarian when making choices on preventative vaccination programmes.

Use of thoracic ultrasound on Scottish dairy cattle farms to support the diagnosis and treatment of bovine respiratory disease in calves.

BACKGROUND: Bovine respiratory disease (BRD) is common in cattle youngstock on UK dairy farms. The current diagnostic methods lack sensitivity and specificity. Thoracic ultrasound (TUS) is a relatively new BRD diagnostic tool with increased accuracy. METHOD: Data were collected from TUS examinations of 347 calves on Scottish dairy farms and compared to farmer BRD treatment rates. A calf health scoring tool was used to collect information on youngstock health and management on these farms. RESULTS: Of 347 ultrasonographic examinations, 53 (15.3%) were classified as abnormal and 294 (84.7%) as normal. Of the 53 calves classified as abnormal, only 13 (24.5%) were treated by the farmer; however, of the 294 classified as normal, 22 (7.5%) were treated. CONCLUSION: The results indicated farmers were misdiagnosing BRD in youngstock. Use of TUS on UK farms may improve diagnostic rates and accuracy, reduce the unnecessary use of antimicrobials and demonstrate the value of preventive healthcare programmes.