Abstract
The results of experimental study of three noncytopathic and two cytopathic bovine viral diarrhea virus (BVDV) strains isolated from cattle in the Siberian region and belonging to the type 1 (subtypes 1a, 1b, and 1d) have been presented. All investigated strains caused the development of infectious process in the seronegative 4–6-month-old calves after aerosol challenge with the dose of 6 log10 TCID50. The greatest virulence had noncytopathic strain and cytopathic strain related to the subtypes 1d and 1b, respectively. All strains in infected calves caused some signs of moderate acute respiratory disease and diarrhea: depression 3–5 days postinfection (p.i.), refusal to food, severe hyperthermia to 41.9°С, serous exudate discharges from the nasal cavity and eyes, transient diarrhea with blood, leukopenia (up to 2700 cells/mm3), and macroscopic changes in the respiratory organs and intestine. The infected animals recovered from 12 to 15 days p.i. and in 90% cases formed humoral immune response 25 days p.i. (antibody titers to BVDV: 1 : 4–1 : 16). Our results confirmed the presence of virulent BVDV1 strains and showed the need for researches on the molecular epidemiology of the disease, development of more effective diagnostic systems, and optimization of control programs with use of vaccines.
Highlights
The Russian livestock industry, notably the dairy cattle industry, is currently facing serious changes
After 5–7 days of virus cultivation at 37∘C we registered the presence of cytopathic effect in the wells of the cell culture infected with cytopathic strains and the presence of BVDV1 genetic material by polymerase chain reaction (PCR) in the wells of the cell culture infected with noncytopathic strains, expressing the titer values in TCID50/0.1 cm3
This paper presents the results relating to the study of the virulent properties of five BVDV1 strains, first isolated and typed in Siberia region
Summary
The Russian livestock industry, notably the dairy cattle industry, is currently facing serious changes. Extensive movement of animals from multiple sources, the hallmark of large livestock importation programs such as this, bears the risk of the high probability for introduction of transmissible infectious diseases including bovine viral diarrhea virus (BVDV) infections, causing diseases in infected cattle that are economically important. Adult cattle seropositivity, indicating an early-borne infection, varies from 75 to 95% in six regions of Siberia (Glotov, unpublished data). In this situation, information on the circulation of the pathogen among susceptible animals is needed. Information on the circulation of the pathogen among susceptible animals is needed This data may serve as a foundation for designing and evaluating diagnostic tools and for choosing more effective vaccines; it may potentially be a contributing factor in controlling BVDV infection. There are no data on genotyping BVDV and the study of virulent properties of this virus in the naturally susceptible animals in the available Russian literature
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