Bovine Respiratory Syndrome (BRD) Etiopathogenesis, Diagnosis and Control

Bovine respiratory disease (BRD) complex is a major disease, classically in the indoor calves and feedlot young cattle. The etiopathogenesis of BRD is multifactorial and complex. In this complex etiology an equivalent role plays both the infectious agents as well as the environmental factors which are called also as environmental stressors (inappropriate livestock management like mistakes in animal nutrition, transport, handling, veterinary interventions etc.) (tab. 1). The most significant pathogens which are involved in the etiopathogenesis of BRD, i.e. suitable species of viruses such as (bovine respiratory syncytial virus (BRSV), parainfluenza virus type 3 (PI3V), bovine herpes virus type 1 (BHV1), bovine viral diarrhea virus (BVDV), are usually associated with concurrent bacterial infections represented by: Mannheimia haemolytica, Pasteurella multocida, Histophilus somni and others (tab. 1) (Jared et al., 2010a, Kita et al., 1994, Klimentowski et al., 1995) and also mycoplasmal factors such as: Mycoplasma bovis, Mycoplasma bovirhinis, Mycoplasma dispar, Ureaplasma diversum and even Mycoplasma canis (Szymańska et al., 2010). Among bacteria M. haemolytica and P. multocida have been traditionally considered as the most common bacterial infectious factors in the BRD etiology (Fulton et al.; Reggiardo et al., 2005). On the other hand the one of the most often isolated mycoplasmal factors from BRD cases is Mycoplasma bovis. Its adaptative ability to a host organism increases owing to different versions of the same vsp gene family which encode particular adhesive factors of the mycoplasma, i.e. variable surface proteins (Vsps; Razin et al., 1998). The variability of vsp gene based on DNA transposition (Lysnyansky, 1996). Therefore the high Vsp variation determines the phenotypic variability of the antigen (Rosengarten et al., 1994) which further increases the virulence of the pathogen. M. bovis possess the ability to immunomodulate host defence against infection (Razin et al., 1998), for example inducing a synthesis of proinflammatory agents, i.e. TNF-α and nitric oxide (Jungi, et al., 1996) or stimulation of some acute phase protein production, such as haptoglobulin and serum amyloid A, which represent one of the most important components of acute phase response for cattle (Dudek, 2010). It is known that M. bovis acts as a stimulant on major subsets of T-lymphocytes (Vanden Bush, 2003). In contrast, some data show inhibitory properties of the pathogen which come down to its suppressive effect on lymphocytes (Vanden Bush & Rosenbusch, 2002; Thomas et al., 1990)