Effects of exposure to calves persistently infected with bovine viral diarrhea virus type 1b and subsequent infection with Mannheima haemolytica on clinical signs and immune variables: Model for bovine respiratory disease via viral and bacterial interaction1,2

Abstract

The objective was to determine effects of an intratracheal Mannheimia haemolytica challenge after 72-h exposure to bovine viral diarrhea virus type 1b (BVDV1b) persistently infected (PI) calves on serum antibody production, white blood cell count (WBC), cytokine concentrations, and blood gases in feedlot steers. Twenty-four steers (initial BW = 314 +/- 31 kg) were randomly allocated to 1 of 4 treatments (6 steers/treatment) arranged as a 2 x 2 factorial. Treatments were 1) steers not exposed to steers PI with BVDV nor challenged with M. haemolytica (control; CON); 2) steers exposed to 2 steers PI with BVDV for 72 h (BVD); 3) steers intratracheally challenged with M. haemolytica (MH); and 4) steers exposed to 2 steers PI with BVDV for 72 h and challenged with M. haemolytica (BVD+MH). There were 12 h between exposure to PI steers and challenge with M. haemolytica. Rectal temperature was increased (P < 0.001) for MH and BVD+MH during the initial 24 h after the M. haemolytica challenge. For MH and BVD+MH, total WBC count was increased (P < 0.01) at 36 h post M. haemolytica challenge compared with CON, whereas in BVD steers, WBC count was decreased (P < 0.01). Total lymphocyte count was increased (P = 0.004) during the initial 72 h post BVDV exposure for the BVD and BVD+MH groups compared with MH and CON, and this difference remained at 96 h post M. haemolytica challenge. An increased (P < 0.001) total neutrophil count was observed during the initial 36 h for the MH group and at 72 h for the BVD+MH challenge group. Interleukin 1beta, IL-6, and tumor necrosis factor alpha (TNFalpha) concentrations were greater (P <or= 0.04) in BVD steers than steers not exposed to BVDV, and interferon gamma, IL-1beta, and TNFalpha were greater (P <or= 0.02) in MH steers than in steers not challenged with M. haemolytica. There were BVD x MH interactions (P <or= 0.04) for plasma carbon dioxide, carbonic acid, and sodium bicarbonate concentrations. Challenge with M. haemolytica decreased carbon dioxide, carbonic acid, and sodium bicarbonate concentrations to a greater extent when steers were not exposed to PI steers compared with steers exposed to BVDV. We conclude that the challenge model was successful at inducing bovine respiratory disease (BRD) associated with BVDV and M. haemolytica. Understanding the physiological changes in morbid animals will lead to improved strategies for decreasing severity and economic losses associated with BRD.

GROWTH AND DEVELOPMENT SYMPOSIUM: Impacts of inflammation on cattle growth and carcass merit1,2

“…Horadagoda et al (1999) measured a-GP, Hp, and SAA in 81 cattle that were diagnosed with acute or chronic inflammation, each from a number of different causes, and concluded that SAA and Hp would be the most valuable for discrimination between acute and chronic inflammation. Research in this area relative to feedlot cattle has foeused on serum Hp and SAA concentrations (Wittum et al, 1996;Carter et al, 2002;Burciaga-Robles et al, 2010b). Serum Hp has been shown to increase in response to experimental infection with M haemolytica (Conner et al, 1989;Burciaga-Robles et al, 2010b) or BVDV (Gânheim et al, 2003).…”

A Systematic Review of Bovine Respiratory Disease Diagnosis Focused on Diagnostic Confirmation, Early Detection, and Prediction of Unfavorable Outcomes in Feedlot Cattle

“…45 Based on an infection trial, exposure to persistently infected steers with bovine viral diarrhea virus resulted in significantly less WBC and neutrophils, whereas inoculation with Mannheimia haemolytica resulted in greater WBC and neutrophils. 39 Lymphocyte count decreased with exposure to persistently infected animals and M haemolytica. 39 In another infection trial, 42 WBC and segmented neutrophils increased on day 1 after infection with M haemolytica, but decreased to baseline thereafter.…”

“…39 Lymphocyte count decreased with exposure to persistently infected animals and M haemolytica. 39 In another infection trial, 42 WBC and segmented neutrophils increased on day 1 after infection with M haemolytica, but decreased to baseline thereafter. Neutrophil/lymphocyte ratio and WBC were compared with a clinical illness score and rectal temperature in naturally occurring BRD outbreaks.…”

Failure of Respiratory Defenses in the Pathogenesis of Bacterial Pneumonia of Cattle

“…The evidence that BHV-1 and BVDV negatively affect humoral immune responses has been previously reviewed. 22,33,193 The bacterial pathogens causing BRD have several mechanisms to limit antibody-mediated immunity, although it should be emphasized that induction of humoral immunity does confer protection in challenge models of the disease. The capsule of M. haemolytica confers partial resistance to antibody, whereas an acapsular mutant had similar sensitivity to complement as the parent strain.…”