Comparative evaluation of ultrasonography and lung function testing with the clinical signs and pathology of calves inoculated experimentally with Pasteurella muftocida

Abstract

Seventeen calves were inoculated intratracheally with Pasteurella multocida 0 on three consecutive days with 10 ml of an inoculum containing 10(9) colony forming units/ml per day per calf. Before the first inoculation and 24 hours after the third, each calf was examined non-invasively by means of a clinical examination, chest ultrasonography, and impulse oscillometry to measure the impedance of the respiratory system. The inoculation of P multocida caused fever and a significant increase in respiratory rate and a decrease in tidal volume. There were also significant changes in the ultrasonographic results and in the impedance of the respiratory system. The percentage of the total surface area of the lungs showing pathological changes when the calves were euthanased 48 hours after the third inoculation ranged from 0.4 to 39 per cent. There were statistically significant correlations between the ultrasound scores and the pathological findings and between the ultrasound scores and the respiratory rate and tidal volume. The changes in the impedance of the respiratory system were not correlated with either the ultrasonographic or the pathological findings.

Comparison of Thoracic Auscultation, Clinical Score, and Ultrasonography as Indicators of Bovine Respiratory Disease in Preweaned Dairy Calves

“…Previous experimental studies using Pasteurella multocida‐ induced pneumonia have shown that the evolution of clinical signs, spirometric signs and ultrasonographic lesions are not closely correlated 18. Severely damaged lungs can be observed with minimal impact on breathing dynamics or spirometric values, and on the other hand, calves with severe respiratory signs may have minimal lung lesions on ultrasonography 18. It was not the aim of this study to directly compare the diagnostic accuracy of the CRSC to assess BRD in dairy calves given that the score and ultrasonography (which was used as a comparator in this study) do not focus on the same stage of the disease.…”

“…The complementary nature of these 2 tools is evident. Previous experimental studies using Pasteurella multocida‐ induced pneumonia have shown that the evolution of clinical signs, spirometric signs and ultrasonographic lesions are not closely correlated 18. Severely damaged lungs can be observed with minimal impact on breathing dynamics or spirometric values, and on the other hand, calves with severe respiratory signs may have minimal lung lesions on ultrasonography 18.…”

“…Thoracic ultrasonography was used in this study in order to assess lesions secondary to lung infection. It has been proven to be a reliable tool to assess lung consolidation as well as the extent of lesions in calves15, 16, 18 and can be done easily in a field setting 419 However, it is important to remember that consolidated lung is not systematically associated with lung infection.…”

“…The sensitivity and specificity of clinical inspection (Se = 61.8%; 97.5% PI, 55.7–68.4%; Sp = 62.8%; 97.5% PI, 60.0–65.7%) were lower than for lung lesions at harvest (Se = 77.4%; 97.5% PI, 66.2–87.3%; Sp = 89.7%; 97.5% PI, 86.0–93.8%). Adding ultrasonography to the clinical examination of calves potentially should increase the sensitivity of lung lesion detection and may help to more accurately detect BRD because it is a good estimate of the extent of lung lesions 14, 18. Furthermore, this method avoids delaying results to the end of the feeding period for beef calves or to necropsy.…”

“…Thoracic ultrasonography is correlated with both radiographic15, 16 and macroscopic findings 14, 16, 18. It can be done quickly calf‐side, and therefore has the potential to be used by bovine practitioners and researchers in a field setting.…”