Respiratory Affections in Calves in Upper and Middle Egypt: Bacteriologic, Immunologic and Epidemiologic Studies

Bovine respiratory disease is considered one of the most common and serious problems affecting calves all over the world. The objectives of this study were to perform a bacteriologic, immunologic, and epidemiologic studies on calves suffering from respiratory manifestations (fever, rapid breathing and nasal discharges) in 5 Governorates in Upper and Middle Egypt (Giza, El-Fayoum, Beni-Suef, Assiut and Sohag) with special reference to P. multocida and M. haemolytica as important causes of BRD. Deep nasal swabs and blood samples were collected from 406 bovine calves showing respiratory manifestations. Bacteriologic examination was achieved for isolation of P. multocida, M. haemolytica and other bacteria. The overall prevalence of both P. multocida and M. haemolytica infections was 26.6% (18.2% for P. multocida and 8.4%for M. haemolytica). The highest prevalence was reported in EL-Fayoum Governorate, whereas the lowest prevalence was in Beni-Suef. P. multocida was isolated singly from 4.9% and mixed with other bacteria from 13.3% of the infected calves. On the other hand, M. haemolytica was isolated singly from 1.7% and mixed with other bacteria from 6.7% of the infected calves. Mixed infections of both P. multocida and M. haemolytica with S. aureus were the most prevalent (4% and 2.7%, respectively), followed by mixed infection with both S. aureus and Streptococcus spp. (3.2% and 2.5%, respectively) and finally mixed infection with Streptococcus spp. (2.2% and 1.2%, respectively). More over, 56.2% of the samples showed isolation of other bacteria and 17.2% revealed no bacterial isolates. The in in-vitro sensitivity testing of P. multocida and M. haemolytica isolates showed high susceptibility to fluoroquinolones and cephalosporins. On the contrary, high resistances were obtained against tetracyclines, penicillins and aminoglycosides. Immunologically, all respiratory-manifested calves showed a significant elevation of serum nitric oxide and interleukin-6 levels compared with normal control calves while elucidated significant reduction of lysozyme activity.