About this Research Topic
Bovine respiratory disease (BRD) is one of the major causes of loss for the cattle industry worldwide, especially in young and feedlot animals. Morbidity and mortality vary enormously depending on the management, applied prophylaxis measures, and involved pathogens, with higher percentages when both viral and bacteria are simultaneously involved. However, predisposing factors play a decisive role in the development of the disease: weaning, long-distance transport, stocking density, and commingling with animals from other sources are considered major risk factors favoring the proliferation of saprophytic and pathogenic microorganisms resulting in respiratory syndromes and pneumonia.
The main viruses associated with respiratory diseases are Bovine herpesvirus 1 (BoHV-1), Bovine viral diarrhoea virus (BVDV), Bovine respiratory coronavirus (BCoV), Bovine respiratory syncytial virus (BRSV), Bovine parainfluenza virus (BPiV) and Bovine adenovirus (BAdV), while among bacteria, Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis are generally the most identified pathogens often associated with an increased incidence of respiratory distress. As is well known, viral infection interferes with the mucociliary clearance of the respiratory tract and dysregulates the tracheal antimicrobial peptides of the innate respiratory defenses of the host. However, recent studies speculate that the role of viral infections as the starting point for BRD on which secondary opportunistic bacteria enter was a simplistic view of the pathogenesis of the disease; meanwhile, the primary role of some pathogens rarely detected in the past and generally considered of minor importance was identified to elicit the disease. The potential pathogenetic role for these minor pathogens and the high frequency with which co-infections occur make BRD a complex disease difficult to control. Mass administration of long-acting antibiotics and vaccine prophylaxis against BoHV-1, BRSV, BPiV, M. haemolytica and H. somni are highly effective in counteracting infections after feedlot placement through both reductions of pathogen colonization and weakening of disease evolution. Therefore, despite increasing use of prophylaxis and treatment measures, feedlot placement remains a high-risk period for calves to develop respiratory disorders, also considering that infection spread is favored by viral shedding which is greatest even before animals become symptomatic. Consequently, the most important aspect for BRD control to restrain the development of the syndrome remains the proper management of cattle.
Minimizing the risk and, consequently, the incidence of BRD is crucial to improve cattle productivity, health and welfare. To better clarify the pathogenetic mechanisms involved in BRD development, experimental prospective and retrospective studies, as well as critical reviews, are welcome in this issue. A multidisciplinary approach is required in line with the multifactorial etiology of the syndrome. Scientific aspects related to the management of transport and breeding, as well as immunopathological and aetiological implications, epidemiology, risk factors, new technologies for the diagnosis and prophylaxis measures to counteract the infection will be the primary aims of this Research Topic.
Keywords: Bovine, respiratory diseases, welfare, management, prophylaxis
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