Changes in peripheral blood leucocyte counts and subpopulations after experimental infection with BVDV and/or Mannheimia haemolytica

Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Uppsala, Sweden
Journal of Veterinary Medicine Series B (Impact Factor: 1.57). 12/2005; 52(9):380-5. DOI: 10.1111/j.1439-0450.2005.00882.x
Source: PubMed

ABSTRACT Leucocyte counts and subpopulations were studied in peripheral blood from calves experimentally infected in the respiratory tract with either bovine virus diarrhoea virus (BVDV) or Mannheimia haemolytica (Mh), or with a combination of both agents (BVDV/Mh). A non-inoculated control group was included. Peripheral blood samples were obtained for total leucocyte counts, and for neutrophil, lymphocyte and monocyte counts. The numbers of blood lymphocytes expressing the surface antigens CD4, CD8, WC1, B and IL-2R were analysed using flow cytometry. The results showed that BVDV inoculation induced a significant decrease in total leucocyte counts and in neutrophil and lymphocyte numbers, while Mh inoculation induced significant increases in total leucocyte counts and neutrophils, while the lymphocyte count decreased. In the BVDV/Mh group, the total leucocyte count and the lymphocyte numbers decreased significantly. In this group, the lymphocyte numbers remained on a very low level throughout the rest of the study. The numbers of CD4+, CD8+ and WC1+ lymphocytes decreased significantly compared with before inoculations mainly in the BVDV and BVDV/Mh groups. The drops were most pronounced in the BVDV/Mh group. The numbers of B+ lymphocytes and IL-2R+ cells did not change significantly.

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    • "M. haemolytica is an opportunestic pathogen that inhabits the nasopharynx and tonsils of cattle and sheep (Radostits et al., 2006) and is capable of causing infection when the body's defense mechanisms are impaired (Haig, 2011). Environmental stress factors like inclement weather, shipment, weaning, overcrowding and complex interactions among several infectious agents can serve as cofactors for pathogenesis of pneumonic pasteurellosis (Kraabel and Miller, 1997; Ganheim et al., 2005). A major problem in the control of pneumonic pasteurellosis is the lack of vaccine which consistently induces protective immunity against M. haemolytica (Dyer, 1982). "
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