Persistent bovine viral diarrhea virus subgenotype 1d infection in dairy heifer calves born within 38 days interval

Abstract

Bovine viral diarrhea virus (BVDV) causes a significant economic impact on the beef and dairy industries worldwide. Fetal infection with a non-cytopathic strain may lead to the birth of persistently infected (PI) offspring, the main event in the epidemiological chain of BVDV infection. This report describes the birth of 10 PI dairy calves from Brazil and the infecting BVDV subgenotype. Serum and blood samples were collected from 10 cows and 10 calves; all 10 calves were previously deemed BVDV positive by the ear notch rapid test. Serum samples were used in the virus neutralization technique to detect anti-BVDV antibody. Blood samples were used to detect BVDV RNA using the reverse transcription polymerase chain reaction (RT-PCR) assay of the 5' UTR and Npro genes. All 10 cows were negative for BVDV RT-PCR, while all 10 calves were RT-PCR positive. Phylogenetic analyses were performed and the strain was classified as BVDV-1d. High titers of BVDV-specific antibodies in the serum of cows indicated recent circulation of BVDV in the dairy herd, whereas calves presented intermediate, low, or no anti-BVDV-1a antibody titers. The monitoring of circulating BVDV subgenotypes and the detection of PI animals is of great importance in disease control, and regular vaccination alone is insufficient to prevent BVDV infection.