Ultrasonographic diagnosis of clinical and subclinical bovine respiratory disease in Holstein calves

Abstract

Background and aim: Bovine respiratory disease (BRD) is the main cause of death in calves, and early BRD diagnosis saves lives. This study aimed to diagnose clinical and subclinical BRD in calves by assessing some biochemical alterations and ultrasonography (USG).

Materials and methods: Fifty-four Holstein dairy calves in Al-Sharqiyah Province, Egypt, were used in the study. They were divided into three groups. The first control group consisted of 10 clinically healthy calves. The second group consisted of 34 calves suffering from clinical lower respiratory tract disorders. The third group consisted of 10 subclinical BRD-affected calves. Ultrasonographic examinations of chest and thoracic ultrasound scoring were performed once per 2 weeks for each calf. Blood samples were collected for serum separation to measure albumin (ALB), total protein (TP), ALB, globulin, and haptoglobin (HP).

Results: The USG revealed small consolidation areas within an aerated lung lobe, a hypoechoic parenchyma of the entire distal lung lobe, and a hypoechoic-circumscribed structure surrounded by an echogenic wall appeared within the lung tissue in calves that suffered from lobular pneumonia, lobar pneumonia, and lung abscess, respectively. However, subclinical cases showed a small consolidation area in the cranial aspects of the right cranial lung lobe. The ultrasound lung score (ULS) was greater in clinical than in subclinical cases. The BRD-affected calves recorded significant increases in serum TP, globulin, and HP. Meanwhile, serum ALB decreased significantly.

Conclusion: Thoracic ultrasound had a reliable tool in the BRD diagnosis, especially in the early prediction of subclinical cases in newborn calves. In addition, the ULS appeared to be a better classifier than the clinical respiratory score (CRS) for BRD diagnosis. On the other side, it was found that regression models were very useful in assessing the prediction of biochemical blood parameters based on the ULS and CRS in diseased cases.

Keywords: bovine respiratory disease; calves; haptoglobin; thoracic ultrasound.

Figure-1

Thoracic ultrasonographic image of control calves. (a) Ultrasonographic of cranial aspect of cranial lobe of the right lung with reverberation artifact and thoracic blood vessels (artery and vein) linear probe is placed on 2–3 intercostal space (ICS). (b) Ultrasonographic of caudal aspect of cranial lobe of the right lung with reverberation artifact (dorsally) and heart (ventrally), linear probe was placed on 3–4 ICS. (c) Ultrasonographic of caudal lobe of the right lung with hepatic parenchyma appeared as hypoechoic structure with an echoic blood vessel (ventrally) and lung appeared with normal reverberation artifact (dorsally), the line of separation (yellow arrow) represents diaphragm, linear probe was placed on 6–10 ICS. (d) Ultrasonographic of middle lobe of the right lung with reverberation artifact and costochondral junction, linear probe is placed on 5–6 ICS. Ds=Dorsal, Vt=Ventral, RA=Reverberation artifact (white arrow), TW=Thoracic wall, TB=Thoracic blood vessels, yellow arrow=Diaphragm, H=Heart, and P=Pleural line.

Figure-2

Thoracic ultrasonographic image of clinical bovine respiratory disease calves affected by lobular pneumonia. Examination of lung showed multiple areas of consolidation (1.5 × 1.6 cm) in ventral of caudal aspect of cranial lobe of the right lung linear probe placed on 3–4 intercostal space with reverberation artifact. Ds=Dorsal, Vt=Ventral, PL=Pleural line, RA=Reverberation artifact, and C=Consolidation.

Figure-3

Thoracic ultrasonographic image of clinical bovine respiratory disease calves affected by lobar pneumonia. Examination of lung revealed hyperechoic structure (lung consolidation) of all cranial lobe of the left lung, linear probe placed on 2–5 intercostal space. Ds=Dorsal, Vt=Ventral, and LC=Consolidation.

Figure-4

Thoracic ultrasound of clinical bovine respiratory disease calves affected by lung abscess. Examination of lung showed hypoechoic circumscribed structure surrounded by echogenic wall appeared within lung tissues. Right lobe; multiple small-sized abscess in cranial lobe of the left lung sized 1 × 2 cm, linear probe placed on 2–3 intercostal space (ICS). Left lobe; single large abscess in cranial lobe of the right lung sized 3 × 4 cm, linear probe placed on 1–4 ICS. Ds=Dorsal, Vt=Ventral, LA=Lung abscess, and TW=Thoracic wall.

Figure-5

Thoracic ultrasound of subclinical bovine respiratory disease-affected calves. Examination of cranial aspect of cranial lung lobe of the right lung revealed of small area of consolidation (0.5 cm), linear probe placed on 1–2 intercostal space. PL=Pleural line, RA=Reverberation artifact, and C=Consolidation.

Figure-6

Receiver operating characteristic curve for clinical respiratory signs.

Figure-7

Receiver operating characteristic curve for ultrasound lung score.

Figure-8

Receiver operating characteristic curve comparison for both ultrasound lung score and clinical respiratory signs.

Figure-9

A good model has a value above 0.5. A value < 0.5 indicates that the model is no better than random prediction.