Bacterial agents in the etiology of respiratory disease in dairy calves

Abstract

Respiratory diseases in cattle are triggered by the interaction between environmental factors, host susceptibility and the presence of viral or bacterial agents. This study aimed to identify bacteria involved in the etiology of respiratory diseases in dairy calves in Maranhão. A total of 550 calves distributed among 29 herds in 11 municipalities were evaluated. Forty-five nasal secretion samples were collected from animals with clinical signs suggestive of respiratory disease and inoculated onto blood agar, chocolate agar and MacConkey agar plates. Gram staining, biochemical tests and antibiogram were performed on the isolated colonies. The frequency of positive herds was 44.82% (n=13) and that of municipalities was 63.63% (n=7). Of the 45 samples, 37 showed growth, representing 82% positivity. The following bacterial species were identified: Mannheimia haemolytica in nine samples (24.32%); Pasteurella multocida in seven (18.91%); Moraxella bovis in eight (21.62%); Staphylococcus spp. in four (10.8%); Yersinia spp. and Corynebacterium spp. in two (5.40%) samples, for each species; Histophilus somni, Actinobacillus pleuropneumoniae, Pseudomonas aeruginosa, Streptococcus spp. and Arcanobacterium spp. in one sample (2.70%), for each species. In the antibiogram, 27% of the isolates showed resistance to penicillin and 100% were sensitive to amoxicillin+clavulanic acid, amoxicillin, erythromycin, ceftiofur and tetracycline. Thus, it is concluded that the identified bacterial species have zoonotic importance and have a resistance profile against several antimicrobials. It is recommended to perform an antibiogram and use amoxicillin+clavulanic acid, amoxicillin, erythromycin, ceftiofur and tetracycline as an alternative treatment for these diseases.