Invited review: Lung ultrasonography-Improving our understanding and management of respiratory disease in young calves.

Abstract

Lung ultrasonography (LUS) has emerged as an on-farm tool that can rapidly characterize pulmonary abnormalities in young cattle. This tool is particularly useful for detecting the lung consolidation associated with bronchopneumonia following bacterial infection of the lower airway. The aim of this review is to discuss on-farm LUS techniques, the contributions of LUS to bovine respiratory disease research, and potential applications in cattle practice. Lung ultrasonography studies consistently demonstrate associations between lung consolidation and negative economic outcomes, including (among others): reduced growth, lower future carcass weights in veal calves, premature culling, and lower future milk production in dairy cattle. Within the context of subclinical pneumonia (presence of lung lesions in the absence of abnormal clinical signs), the dynamics of respiratory tract infections and the presence of specific risk factors could be better characterized. Given its higher diagnostic sensitivity (ranging from 66% to 94%) and specificity (from 66% to 100%) for detecting calves affected with lung disease, LUS is a better reference test for randomized clinical trials evaluating therapy and vaccine efficacy compared with clinical scoring. In the handful of vaccination studies available, LUS results were significantly different between experimental groups despite no effect on clinical scores, demonstrating the added value of using this ancillary test as an outcome. On-farm applications of LUS include pneumonia detection for the purposes of monitoring patterns of disease, evaluating of clinical detection accuracy, initiating treatment, evaluating treatment efficacy, cure definition or determining duration of treatment, conducting pre-purchase examinations, and making culling decisions. Two LUS scoring systems that are based on quantifying lung consolidation, and therefore are best for characterizing bronchopneumonia, are commonly in use. Currently, there is no LUS scoring system for quantifying the severity of diffuse airway injury from viral infections or interstitial disease in dairy or veal calves. There is a need for a core outcome set for studies on respiratory-focused research that include LUS parameters as case definitions or treatment responses, in addition to key performance indicators (production and health outcomes), in order to motivate the dairy, dairy beef, and veal calf industries toward more sustainable production. Fortunately, momentum for implementing on-farm LUS is growing, but more work needs to be done to increase producer awareness and expand veterinary, research, or technical training. Certificate programs to document well-trained and highly qualified-professionals may prove useful for promoting on-farm implementation.