Bovine Respiratory Disease (BRD)

- Field and laboratory diagnosis of BRD

A-Case definition for BRD by auscultation and ultrasonographic examination

·       Case status as a BRD positive calf is determined by thoracic ultrasound and auscultation interpreted in parallel (i.e., a positive diagnosis on at least one of the tests is sufficient to declare the calf as BRD positive).

·       Criteria for the diagnosis of BRD are

o   Detection of abnormal lung sounds

o   Ultrasonography: focal or extensive consolidation or abscesses of at least one lesion 2 cm width × 2 cm depth, or any amount of pleural effusion.

B-Sampling suggested for further investigation on etiology of BRD

·       Nasal swabs have been used to monitor potential pathogens in a group of cattle or as diagnostic procedures in early clinical respiratory disease.

·       Collection technique is very important when using nasal swabs and different types of swabs are necessary for bacterial cultures versus virus isolation.

·       Dry cotton swabs are adequate for bacterial cultures.

·       Such swabs need to be inserted well into the nasal cavity taking care not to contaminate the swab with the many non-pathogens in the nostrils.

·       The swab should then be placed in a prepared transport medium or at least saline or lactated ringers’ solution for transport to a laboratory.

·       The nasal swab can be used for culture and sensitivity test or bacterial identification. However, bacteria such as Pasteurella hemolytica and Pasteurella multocida may be normally inhabit the upper respiratory tract and they are different isolates after colonization at the lower respiratory tract causing the BRD. Therefore, bronchoalveolar lavage could be a more accurate sample.

C- Summary of confirmatory tests for BRD

1-To assess pulmonary lesions  and severity
Method	Aim
Physical examination by auscultation of thoracic cavity at the triangular area of lung	Valuable tools to diagnose the bronchopneumonia of calves to detect the abnormal lung sounds, the increased bronchial sounds or abnormal sound (crackles, wheezes, or absence of sound)
The chest ultrasonography	can demonstrate the comet tail consolidation occurs in the lung that could be unilateral or bilateral
2- For confirmation of etiology
Polymerase Chain Reaction (PCR) testing methods	can be used to quickly detect viral or bacterial BRD pathogens