Prevalence of respiratory disease in Irish preweaned dairy calves using hierarchical Bayesian latent class analysis

Abstract

IntroductionBovine respiratory disease (BRD) has a significant impact on the health and welfare of dairy calves. It can result in increased antimicrobial usage, decreased growth rate and reduced future productivity. There is no gold standard antemortem diagnostic test for BRD in calves and no estimates of the prevalence of respiratory disease in seasonal calving dairy herds.MethodsTo estimate BRD prevalence in seasonal calving dairy herds in Ireland, 40 dairy farms were recruited and each farm was visited once during one of two calving seasons (spring 2020 & spring 2021). At that visit the prevalence of BRD in 20 calves between 4 and 6 weeks of age was determined using thoracic ultrasound score (≥3) and the Wisconsin respiratory scoring system (≥5). Hierarchical Bayesian latent class analysis was used to estimate the calf-level true prevalence of BRD, and the within-herd prevalence distribution, accounting for the imperfect nature of both diagnostic tests.ResultsIn total, 787 calves were examined, of which 58 (7.4%) had BRD as defined by a Wisconsin respiratory score ≥5 only, 37 (4.7%) had BRD as defined by a thoracic ultrasound score of ≥3 only and 14 (1.8%) calves had BRD based on both thoracic ultrasound and clinical scoring. The primary model assumed both tests were independent and used informed priors for test characteristics. Using this model the true prevalence of BRD was estimated as 4%, 95% Bayesian credible interval (BCI) (1%, 8%). This prevalence estimate is lower or similar to those found in other dairy production systems. Median within herd prevalence varied from 0 to 22%. The prevalence estimate was not sensitive to whether the model was constructed with the tests considered conditionally dependent or independent. When the case definition for thoracic ultrasound was changed to a score ≥2, the prevalence estimate increased to 15% (95% BCI: 6%, 27%).DiscussionThe prevalence of calf respiratory disease, however defined, was low, but highly variable, in these seasonal calving dairy herds.

Invited review: Bovine neonatal morbidity and mortality—Causes, risk factors, incidences, sequelae and prevention

“…Thus the prevalence of respiratory disease is dependent upon the diagnostic modality. The calf and farm‐level prevalence of respiratory disease, as diagnosed by CRS, is approximately 5%–20% and 0%–30%, respectively (Donlon et al, 2023; Dubrovsky et al, 2019; Lago et al, 2006; Rhodes et al, 2021). The calf and farm‐level prevalence of respiratory disease, as diagnosed by TUS, is approximately 5%–15% and 0%–50%, respectively (Buczinski et al, 2018; Donlon et al, 2023; Rhodes et al, 2021; van Leenen et al, 2020).…”

“…The calf and farm‐level prevalence of respiratory disease, as diagnosed by CRS, is approximately 5%–20% and 0%–30%, respectively (Donlon et al, 2023; Dubrovsky et al, 2019; Lago et al, 2006; Rhodes et al, 2021). The calf and farm‐level prevalence of respiratory disease, as diagnosed by TUS, is approximately 5%–15% and 0%–50%, respectively (Buczinski et al, 2018; Donlon et al, 2023; Rhodes et al, 2021; van Leenen et al, 2020). The proportion of calves with CRD as diagnosed by both clinical scoring and TUS is usually lower than by either modality separately (Donlon et al, 2023).…”

“…The calf and farm‐level prevalence of respiratory disease, as diagnosed by TUS, is approximately 5%–15% and 0%–50%, respectively (Buczinski et al, 2018; Donlon et al, 2023; Rhodes et al, 2021; van Leenen et al, 2020). The proportion of calves with CRD as diagnosed by both clinical scoring and TUS is usually lower than by either modality separately (Donlon et al, 2023).…”