Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/1999
Publication Date: N/A
Citation: Interpretive Summary: Bovine viral diarrhea virus (BVDV) infections cause substantial economic losses to cattle producers worldwide. Recently, a new type of BVDV has been identified in North America. This new type of BVDV is known as genotype 2 BVDV, or BVDV type 2. Some BVDV type 2 isolates cause a very severe disease called hemorrhagic syndrome. Others are able to infect animals that have been vaccinated with standard BVDV vaccines. Because BVDV type 2 was first found in North America, some researchers wondered if BVDV type 2 only occurred in North America and not in the rest of the world. This report is important because it identifies BVDV type 2 isolates from Brazil. Other recent reports have identified BVDV type 2 isolates from Europe. These findings suggest that BVDV type 2 viruses are found worldwide.
Technical Abstract: Nucleotide sequencing and phylogenetic analysis of Brazilian bovine viral diarrhea virus (BVDV) field isolates identified 4 viruses belonging to the genotype 2. Comparison of 5' UTR sequences from these isolates to those of North American BVDV type 2 revealed genomic variations that correlated with the geographic origins of the isolates. Two of the Brazilian type 2 viruses were isolated from clinical cases of gastroenteric/respiratory disease and 2 were isolated from healthy bovine fetuses. The clinical cases affected young animals (8 and 18-mo-old) and were characterized by diarrhea, respiratory signs, extensive oral and digestive tract erosions, conjunctival and vulvar congestion, occasional digestive bleeding and vulvar and heart petechial hemorrhage. Antigenic analysis of these isolates with a panel of 10 monoclonal antibodies revealed marked antigenic differences in the major envelope glycoprotein, gp53/E2, compared to standard laboratory and vaccine BVDV strains. In addition, virus-specific antisera raised to Brazilian BVDV type 2 viruses displayed very low serological cross-reactivity with standard BVDV type 1 strains. Differences up to 64-fold in cross-neutralization titers were observed between BVDV type 1 and Brazilian BVDV type 2 isolates. The identification of BVDV type 2 among Brazilian cattle may have important implications for epidemiological studies, diagnostic and immunization strategies. Furthermore, the low neutralizing activity of BVDV type 1 antisera against the recently identified Brazilian BVDV type 2 isolates raises the question about the degree of protection conferred by BVDV vaccines, most of them based on a single type 1 strain.