A MULTIMODAL CLINICAL AND DIAGNOSTIC APPROACH TO BOVINE RESPIRATORY DISEASE COMPLEX (BRDC) IN DAIRY CALVES
Tesi di Dottorato
Data di Pubblicazione:
2023
Citazione:
A MULTIMODAL CLINICAL AND DIAGNOSTIC APPROACH TO BOVINE RESPIRATORY DISEASE COMPLEX (BRDC) IN DAIRY CALVES / V. Ferrulli ; tutor: D. Pravettoni ; phd coordinator: F. Ceciliani. Dipartimento di Medicina Veterinaria e Scienze Animali, 2023 Sep 12. 35. ciclo, Anno Accademico 2022.
Abstract:
Calf bronchopneumonia (BP), or Bovine Respiratory Disease Complex (BRDC), to date is still difficult to diagnose due to the multifactorial nature of its etiopathogenesis and aspecificity of clinical symptomatology.
In this research project, four studies were conducted to investigate various aspects of BRDC, the objectives were:
1) To study the prevalence of BRDC-related pathogens in the territory of northern Italy;
2) To develop an accurate ultrasound diagnosis method that can be used under field conditions;
3) To standardize lung auscultation in order to increase its diagnostic accuracy;
4) To analyze hemogas-analytical and metabolic changes during BRDC by correlating them with clinical and ultrasonographic diagnosis.
For this purpose, pre-weaning Italian Friesian calves from herds in northern Italy were included, and observations were performed under field conditions.
In our first study, an epidemiological investigation of pathogens in the lower airways of calves that showed respiratory symptoms for less than three days and had not received antibiotic treatment in the previous two weeks was conducted. Ten farms in northern Italy were included, and trans-tracheal washes (TTW) were performed on 6 calves from each farm. Culture and molecular tests were performed on the samples, the results were analyzed obtaining the total and farm prevalence, and the prevalence of coinfections were evaluated. Pasteurella multocida and Mannheimia haemolytica were found in 37% and 12% of the samples, respectively, with a prevalence of 70% and 40% of the farms examined. The presence of Mycoplasma bovis was detected in 20% of the farms with a prevalence of 13% of the tested population. The viral pathogens detected were Bovine Coronavirus and Bovine Respiratory Syncytial Virus in 15% and 7% of cases, respectively. Only coinfections determined by two pathogens were evidenced: for P. multocida in 36% of the isolations, M. haemolytica (86%), M. bovis (50%), BCoV (56%), BRSV and others in 100% of the isolations. We observed that the prevalence of Mycoplasma bovis, although low in the population, reaches very high values at the farm level. In our population, the etiological agents with higher occurrence were Pasteurella multocida and BCoV. In order to reinforce the prudent use of antimicrobials, diagnoses should also be investigated from the etiological aspect so as to set up treatment choices in the most effective way.
In the second study, the accuracy of a rapid ultrasound technique: Focused Lung Ultrasound (FLUS) was evaluated by comparing it with systematic Thoracic Ultrasonography (TUS) nowadays considered an imperfect gold standard for the diagnosis of BRDC-associated lung lesions. For this study 135 animals were subjected to both ultrasound investigations, and the McNemar test was used to evaluate statistical differences and agreement was assessed by weighted Kappa. A total of 76 calves out of 135 had a TUS score ≥ 2 (focal lung lesion > 1 cm) and were therefore considered to be affected by BRDC. The FLUS had sensitivity of 81.6% (95% CI = 71.0-89.5%), specificity = 100% (95% CI = 93.9-100%), positive predictive value of 100%, negative predictive value of 96.6% (95% CI = 94.7-97.9%) and accuracy of 97% (95% CI = 92.6-99.2%). McNemar's test showed a difference of 10.3% between FLUS and TUS. The agreement between TUS and FLUS was substantial (weighted kappa test 0.78). This study shows that the focused method could be used as an additional tool for evaluating consolidation, especially when examining a large number of postweaned dairy calves.
In our third study, we investigated the accuracy of lung auscultation. This method suffers from non-unique definition of lung sounds, resulting in poor/moderate accuracy. To evaluate if standardizat
Tipologia IRIS:
Tesi di dottorato
Keywords:
BRDC; calves; pneumonia; thoracic ultrasound; transtracheal wash; bacteriology; virology; lung auscultation; arterial blood gas analysis
Elenco autori:
V. Ferrulli
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