Pathogenesis of Primary Respiratory Disease Induced by Isolates from a New Genetic Cluster of Bovine Viral Diarrhea Virus Type I

Abstract

The pathogenesis of infection induced by cytopathogenic isolates from the newly identified genetic cluster Id of bovine viral diarrhea virus (BVDV) type I was studied in two experimental infections of previously seronegative, immunocompetent calves. Experiment 1 focused on the evaluation of clinical patterns, viremia, and serological responses. All infected calves in this experiment developed respiratory symptoms and seroconverted to BVDV positivity. Contact calves also contracted a respiratory tract infection following exposure to infected animals. Viremia was demonstrated between postinfection days 2 and 17, and the virus was detected in organ specimens of all but one each of the infected and contact calves. In experiment 2, the distribution of BVDV in various tissues of calves euthanized at defined days postinfection was studied. In two of these calves recurrent shedding of BVDV in nasal secretions was shown. BVDV was detected in various tissues of all infected calves throughout the experiment and also following seroconversion and the clearance of BVDV from the circulatory system. Despite the widespread distribution of the virus in various organs, significant tissue damage was found mainly in respiratory tract and lymphoid tissues. These experiments revealed that viruses from cluster Id of BVDV are able to induce primary respiratory disease in previously seronegative, immunocompetent calves. Contact transmission and virus recurrence, contrary to observations from acute experimental infections with noncytopathogenic BVDV, are likely to reflect differences in biological features of these cytopathogenic isolates. Virus shedding and its presence in tissues following peripheral clearance and in the presence of antibodies may have implications in the diagnosis, pathogenesis, and epidemiology of BVDV-induced syndromes in cattle.

Genetic characterization of Brazilian bovine viral diarrhea virus isolates by partial nucleotide sequencing of the 5'-UTR region

“…Factors associated with host, the environment and agent can influence the clinical outcome of BVDV (Baker 1995, Hamers et al 2001) and despite Jones et al (2004) and Baule et al (2001) related to subgenotypes BVDV-1b and BVDV-1d with respiratory disease, a correlation between BVDV genotypes and subgenotypes and clinical signs has not yet been evidenced (Ripath et al 1994, Lettelie et al 1999, Fulton et al 2005.…”

Mycoplasma bovis and bacterial pathogens in the bovine respiratory tract

“…The cause is multifactorial and disease appears to result from the interaction of infectious microorganisms and such predisposing factors as host defence, environment and stress (Hartel et al, 2004). Viral pathogens usually play a role and may cause primary respiratory disease and mild respiratory disorder in calves (Baule et al, 2001;Callan and Garry, 2002). Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Arcanobacterium pyogenes, or the Mollicutes Mycoplasma dispar and Mycoplasma bovis are usually associated with concurrent virus infection (Arcangioli et al, 2008).…”

Manejo do complexo respiratório bovino em confinamento: Revisão

“…O efeito imunossupressor da BVD aguda parece ser mediado por hiperplasia inicial dos órgãos linfoides dentro de dez dias após a infecção, seguido por depleção linfoide (Baule et al, 2001). Além disso, a BVD prejudica a produção de anticorpos humorais, deprime a quimiotaxia de monócitos e prejudica o sistema mieloperoxidase antibacteriana em leucócitos polimorfonucleares (Roth et al, 1981).…”

“…Além disso, a BVD prejudica a produção de anticorpos humorais, deprime a quimiotaxia de monócitos e prejudica o sistema mieloperoxidase antibacteriana em leucócitos polimorfonucleares (Roth et al, 1981). Presumivelmente, esses mecanismos favorecem a colonização dos pulmões por outros agentes patogênicos, que podem exacerbar a doença pulmonar que eles geram (Baule et al, 2001). O vírus da BVD também tem efeitos citopáticos diretos, que podem resultam em inflamação aguda catarral na cavidade nasal e traqueia e pneumonia intersticial focal intralobular, podendo este agente ser primário ou favorecer e agravar pneumonias causadas por outros agentes.…”

“…O vírus da BVD também tem efeitos citopáticos diretos, que podem resultam em inflamação aguda catarral na cavidade nasal e traqueia e pneumonia intersticial focal intralobular, podendo este agente ser primário ou favorecer e agravar pneumonias causadas por outros agentes. (Baule et al, 2001).…”