Lung pathology and infectious agents in fatal feedlot pneumonias and relationship with mortality, disease onset, and treatments.

This study charted 237 fatal cases of bovine respiratory disease (BRD) observed from May 2002 to May 2003 in a single Oklahoma feed yard. Postmortem lung samples were used for agent identification and histopathology. Late in the study, 94 skin samples (ear notches) were tested for Bovine viral diarrhea virus (BVDV) by immunohistochemistry (IHC). Bovine respiratory disease morbidity was 14.7%, and the mortality rate of all causes was 1.3%, with more than half (53.8%) attributed to BRD (0.7% total of all causes). The agents isolated were the following: Mannheimia haemolytica (25.0%), Pasteurella multocida (24.5%), Histophilus somni (10.0%), Arcanobacterium pyogenes (35.0%), Salmonella spp. (0.5%), and Mycoplasma spp. (71.4%). Viruses recovered by cell culture were BVDV-1a noncytopathic (NCP; 2.7%), BVDV-1a cytopathic (CP) vaccine strain (1.8%), BVDV-1b NCP (2.7%), BVDV-2a NCP (3.2%), BVDV-2b CP (0.5%), and Bovine herpesvirus 1 (2.3%). Gel-based polymerase chain reaction (PCR) assays were 4.6% positive for Bovine respiratory syncytial virus and 10.8% positive for Bovine coronavirus. Bovine viral diarrhea virus IHC testing was positive in 5.3% of the animals. The mean values were determined for the treatment data: fatal disease onset (32.65 days), treatment interval (29.15 days), number of antibiotic treatments (2.65), number of different antibiotics (1.89), and day of death (61.81 days). Lesions included the following: 1) duration: acute (21%), subacute (15%), chronic (40.2%), healing (2.8%), normal (18.1%), and autolyzed (2.8%); 2) type of pneumonia: lobar bronchopneumonia (LBP; 27.1%), LBP with pleuritis (49.1%), interstitial pneumonia (5.1%), bronchointerstitial pneumonia (1.4%), septic (0.9%), embolic foci (0.5%), other (2.8%), normal (10.3%), and autolyzed (2.8%); and 3) bronchiolar lesions: bronchiolitis obliterans (39.7%), bronchiolar necrosis (26.6%), bronchiolitis obliterans/bronchiolar necrosis (1.4%), other bronchiolar lesions (6.5%), and bronchiolar lesion negative (25.7%). Statistically significant relationships were present among the agents, lesions, and the animal treatment, disease onset, and mortality data. Clinical illnesses observed in this study were lengthier than those reported 16-20 years ago, based on fatal disease onset, treatment interval, and day of death.

Surveillance of Staphylococcus aureus in veterinary teaching hospitals.

Staphylococcus aureus isolates (n = 70) from 65 patients (36 canine, 18 equine, 7 bovine, 2 avian, and 2 feline) at seven veterinary teaching hospitals in the United States were studied. The majority of patients (83%) with an S. aureus infection were canine and equine, but this may have reflected a sample bias based on clinic case loads and diagnostic lab submissions at the participating institutions. Fourteen percent of patients with an S. aureus infection were infected with a methicillin-resistant S. aureus (MRSA) isolate. Six of seven institutions had at least one MRSA infection during the study. Pulsed-field gel electrophoresis on 63 of the 70 isolates yielded 58 unique strains of S. aureus. None of the strain types of the MRSA isolates matched each other or the type of any other S. aureus isolate. The proportions of patients infected with an MRSA isolate were not significantly different between institutions or animal species (P > or = 0.222). Methicillin-resistant S. aureus isolates in this study seemed to be community acquired rather than hospital acquired.

Isolation and antimicrobial susceptibilities of bacterial pathogens from bovine pneumonia: 1994--2002.

Between 1994 and 2002, a total of 390 (46.3%) Mannheimia haemolytica, 292 (34.7%) Pasteurella multocida, and 160 (19.0%) Histophilus somni were isolated at the Oklahoma Animal Disease Diagnostic Laboratory from lungs from 6-18-month-old beef cattle with pneumonia. The ratio of M. haemolytica isolations to P. multocida isolations decreased from 3.1 in 1994 to 0.8 in 2000 while increasing to 1.5 in 2002. Mannheimia haemolytica isolations significantly (P < 0.05) decreased from 62.5% in 1994 to between 30.6% and 50.4% in 1998--2002. Pasteurella multocida isolations significantly (P < 0.05) increased from 20.0% in 1994 to between 28.6% and 47.4% in 1998--2002. Histophilus somni isolations were <19% except in 1998 (40.8%) and 1999 (23%). Antimicrobial susceptibilities for M. haemolytica significantly declined for erythromycin (P = 0.0001), florfenicol (P = 0.0004), spectinomycin (P = 0.0001), and tilmicosin (P = 0.03). For P. multocida, antimicrobial susceptibilities significantly declined for erythromycin (P = 0.0001), florfenicol (P = 0.004), spectinomycin (P = 0.03), sulfachloropyridizine (P = 0.028), tetracycline (P = 0.017), tilmicosin (P = 0.0001), and trimethoprim/sulfamethoxazole (P = 0.0003). Antimicrobial susceptibilities for H. somni were variable for spectinomycin and sulfachloropyridizine, whereas susceptibilities to other antibiotics remained consistently high.