Abstract
Simple Summary Respiratory infection is one of the most common problems facing the livestock industry in Egypt, and results in substantial economic losses. Several bacterial pathogens are implicated in respiratory infections in young calves. In our study, Mycoplasma bovis, Mycoplasma bovigenitalium, Pasteurella multocida, and Staphylococcus aureus were the most common bacterial pathogens isolated from calves suffering from respiratory manifestations in Menoufiya Governorate, Egypt. However, the results revealed a low prevalence of these pathogens compared to other studies carried out in Egypt. This may be due to the low number of samples or application of vaccination programs in the study area. Mixed infection is the main perceived criteria in this study. The genetic characterization of these pathogens revealed the high identity and similarities within several global and local linages, proposing the probability of disseminating these bacterial pathogens through several routes during animal contact and movements and animal trading between different geographic locations around the world. Bovine respiratory disease (BRD) is a complex syndrome associated with high mortality in young calves and causes severe economic losses in the cattle industry worldwide. The current study investigated the prevalence and molecular characterization of common bacterial pathogens associated with respiratory symptoms in young calves from Sadat City, one of the largest industrial cities in Menoufiya Governorate, Egypt. In between December 2020 and March 2021, 200 mixed-breed young calves of 6-12 months were examined clinically. Of them, sixty (30%) calves showed signs of respiratory manifestations, such as coughing, serous to mucopurulent nasal discharges, fever, and abnormal lung sound. Deep nasal (Nasopharyngeal) swabs were collected from the affected calves for bacteriological investigation. Phenotypic characterization and identification revealed Mycoplasma bovis, Mycoplasma bovigenitalium, Pasteurella multocida, and Staphylococcus aureus in 8.33%, 5%, 5%, and 5% of the tested samples, respectively. The PCR technique using species-specific primer sets successfully amplified the target bacterial DNA in all culture-positive samples, confirming the identity of the isolated bacterial species. Partial gene sequencing of 16S rRNA gene of M. bovigenitalium, P. multocida, and S. aureus, and mb-mp 81 gene of M. bovis revealed high nucleotide similarity and genetic relationship with respective bacterial species reported from Egypt and around the world, suggesting transmission of these bacterial species between animal host species and localities. Our study highlights the four important bacterial strains associated with respiratory disorders in calves and suggests the possible spread of these bacterial pathogens across animal species and different geographic locations. Further studies using WGS and a large number of isolates are required to investigate the realistic lineage of Egyptian isolates and globally.