Lung ultrasonography and clinical follow-up evaluations in fattening bulls affected by Bovine Respiratory Disease (BRD) during restocking period and after Tulathromycin and Ketoprofen treatment

Objectives: The bovine respiratory disease (BRD) is a syndrome which reduces animal well-being and increase economic losses. The clinical observations of systemic and respiratory signs are used for diagnosis. Treatment is generally based on antibiotics such as the macrolides class. The ultrasonography is a diagnostic method for an early diagnosis, useful to evaluate the treatment efficacy and clinical follow-up. The aim of this study was to evaluate animals’ response to tulathromycin and ketoprofen treatment over 21 days using thoracic ultrasonography (TUS) as a screening diagnostic tool during restocking period in the farm. Materials and methods: Animal care and procedures were in accordance with the European Directive 2010/63/EU and the national law D.L. 2014/26. Sixty Limousine fattening bulls of a single stock were enrolled with a weight and age of 364.5±6.42 Kg and 10.23±1.37 months, respectively. Animals were evaluated the day of restocking (T0): the clinical examination assessed the sensory status, cough, nasal and ocular discharges, and rectal temperature assessment in order to calculate the respiratory score (RS). After clinical examination, a TUS evaluation of six lung’s areas (cranial 4th – 3rd intercostal space (ICS), middle 6th – 5th ICS, and caudal 10th – 7th ICS area of right and left lungs) was performed. Two groups were determinated based on ultrasonographic score (US): group C (control group) with 29 animals and US<3; group D (disease group) with 31 animals and US≥3. In the same day, the group D received a deep nasal swab for bacteriological examination and a single injection of tulathromycin and ketoprofen (2,5 mg/kg + 3 mg/kg, Draxxin plus). The group D was revaluated by clinical examination and TUS after 1.5 (T1), 3 (T2), 7 (T3), 14 (T4), and 21 (T5) days; whereas the group C was only revaluated at T5. The TUS images were used for a post-sampling quantitative assessment of hepatization and fluid alveolograms areas at each lung’s area investigated. Total area of hepatization and fluid alveolograms were then calculated. The statistical differences between groups were assessed in accordance with data distribution by Wilcoxon test (US, RS, nasal and ocular discharges, lesion score) or t-test (rectal temperature, hepatization and fluid alveolograms’ areas), whereas the Kruskal-Wallis test was used to evaluate differences over time. The differences in the total area of hepatization and fluid alveolograms were assessed in both cases by mixed models. A p-value≤0.05 was accepted. Results: No animal enrolled in group C showed a RS or US indicative of BRD during the study. The group D showed a greater US, RS, nasal and ocular discharges, and rectal temperature compared to group C at T0, whereas only RS was different at T5. Regarding lung’ lesions, the most affected lung areas were the cranial and middle lungs in both sides with greater areas of hepatization and fluid alveolograms. The total area of hepatization was 11.29±0.70 cm2 in group D, while the total area of fluid alveolograms was 1.98±0.35 cm2. No differences were found between groups in lung’ lesions at T5 and only 4 animals showed fluid alveolograms. Despite the total area of hepatization was not different between groups, it was still present at T5 in group D (5.16±0.69 cm2). However, the treatment was effective in reducing the US and rectal temperature from T1, and RS from T3. The lung’ lesions of the single areas improved between T2 and T4, whereas the total area of hepatization improved from T1 and total area of fluid alveolograms from T2. Conclusions: The TUS is a useful diagnostic tool to screen the respiratory diseases in farm identifying ill animals, allowing a correct management and therapy. Furthermore, TUS was a sensitive tool to monitor treatment effectiveness and the healing time after tulathromycin and ketoprofen treatment.