Submitted to: American Association of Bovine Practitioners Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 9/25/2008
Publication Date: 9/25/2008
Citation: Fulton, R.W., Blood, K.S., Panciera, R.J., Payton, M., Ridpath, J.F., Saliki, J.T., Burge, L.J., Confer, A.W., Welsh, R.D., Johnson, B.J., Reck, A. 2008. Lung Pathology and Infectious Agents in Fatal Feedlot Pneumonias and Relationship with Animal and Treatment Information [abstract]. American Association of Bovine Practitioners. Available: http://aabp.org. Interpretive Summary:
Technical Abstract: Bovine respiratory diseases (BRD) occurring in the feedlot represent the major disease entity during the feeding period. Several bacteria, viruses, and Mycoplasma spp. are reported as causative agents. Feedlot BRD may occur at various times, although the early disease appearing after arrival and processing often receives the most attention. The diagnostician and clinician are faced with several clinical presentations and agents/ lesions in the fatal cases. The purpose of this study was to chart the fatal pneumonia cases over a one-year period in one Oklahoma feedyard, recording agent identification, observed pathology and animal treatment information. These cattle died either in the sick pen or suddenly in regular feeding pens without treatment. A clinical diagnosis of BRD was assigned to all cases charted. Samples of lung collected at necropsy (fresh and formalin fixed) were submitted for agent identification and histopathology. In the later stages of the study, skin samples were tested for BVDV by immunohistochemistry (IHC). Materials and Methods: There were 237 sets of lung samples submitted from May 2002-May 2003. There were 94 skin samples for BVDV IHC from these 237 animals that died with BRD. The BRD morbidity over this interval was 14.7%. The mortality rate was 0.7% for BRD out of 1.3% total for all causes. The feedyard provided information on the individual animals including: fatal disease onset (FDO) day first treated; treatment interval (TI), interval from first treatment day until day of death; treatment numbers (no. of treatments); number of treatments with different antibiotics; and day of death. Results: The agents isolated by bacterial culture and Mycoplasma culture were: M. haemolytica (25.0%), P. multocida (24.5%), H. somni (10.0%), A. pyogenes (35.0%), Salmonella spp. (0.5%), and Mycoplasma spp. (71.4%). Viruses recovered by cell culture were: BVDV1a NCP (2.7%); BVDV1aCP vaccine strain (1.8%); BVDV1b NCP (2.7%); BVDV2a NCP (3.2%); BVDV2a CP (0.5%); and BHV-1 (2.3%). Using a gel based PCR assay for BRSV and bovine coronavirus (BCV) there were 10.8% BCV positive and 4.6% BRSV positive. There were 5.3% positive by BVDV IHC. Means for treatment and animal data were : FDO, 32.65 days (D); TI, 29.15 D; no. treatments, 2.65; no. antibiotics, 1.89; and day of death, 61.81 D. Summary of lesions: (1) duration, acute (21%); subacute (15%);chronic(40.2%) healing (2.8%) ; normal (18.1%);(2) pneumonia, fibrinous pneumonia (27.1%); fibrinous pleuropneumonia 49.1%; interstitial pneumonia (5.1%); fibrinous interstitial pneumonia (1.4%); septic positive (0.9%) ; embolic foci (0.5%); and other (2.8%); and (3) bronchiolar lesions, bronchiolar obliterans (39.7%), bronchiolar necrosis (26.6%), bronchiolar obliterans/necrosis (1.4%), and other bronchiolar lesions (6.5%). There were statistical significant relationships among the agents, lesions, and the animal/treatment data. Significance: There were several agents isolated from fatal feedlot pneumonias. Based on FDO, treatment interval, and day of death, the clinical illnesses observed in this study were lengthier than those reported 16-18 years ago. Potentially the treatments currently in use impact the length of illness. There were differences in lesions that correlated with differences observed in animal and treatments. In addition isolation of different BVDV subtypes correlated with differences in lesions and agent identification. This study illustrates the usefulness of BVDV IHC in the identification of PI animals in feedlots and detection and control of lung pathogens.