# Unveiling the Role of Bovine Herpesvirus Type 4 (BHV-4) in Dairy Cow Reproductive Disorders: Insights From a Multifaceted Study in China

## TL;DR

This study explores how bovine herpesvirus type 4 (BHV-4) may be linked to reproductive issues in dairy cows in China.

## Contribution

The study provides new evidence that BHV-4 is significantly associated with reproductive disorders and may be vertically transmitted.

## Key findings

- BHV-4 antibody and nucleic acid positivity rates were 57.8% and 36.3%, respectively.
- BHV-4 DNA was elevated in reproductive tracts of cows and stillborn fetuses.
- Histopathological analysis showed mucosal damage in fetal vaginal and uterine tissues.

## Abstract

Bovine herpesvirus type-4 (BHV-4) belongs to the gamma-herpesvirus subfamily, and its association with reproductive disorders in dairy cows is controversial. In this study, 386 whole blood and reproductive swab samples from dairy cows across eight provinces in China were collected. BHV-4 antibody levels in the serum were determined via ELISA, while real-time fluorescent quantitative PCR (qPCR) was employed to detect the DNA of BHV-4, BHV-1, bovine viral diarrhea virus type-I (BVDV-1), and bovine viral diarrhea virus type-II (BVDV-2) in the samples. Additionally, the DNA content of BHV-4 in various tissues of cows and stillborn fetuses was assessed via qPCR. Breeding information for the participating cows was gathered through farmer interviews, and correlation analyses were conducted between the detection results and breeding information. The findings revealed a BHV-4 antibody positive rate of 57.8% and a nucleic acid positive rate of 36.3%. Chi-square analysis revealed a correlation between BHV-4 and BHV-1 infections. Among several pathogens associated with reproductive disorders, only BHV-4 was significantly correlated, whereas BHV-1, BVDV-1, and BVDV-2 were not correlated. Furthermore, the study revealed elevated BHV-4 DNA in the reproductive tracts of cows and stillborn fetuses. Histopathological sections revealed mucosal damage in the vaginal and uterine tissues of stillborn fetuses, a phenomenon not previously reported. In summary, our study provides novel insight into the correlation between BHV-4 and reproductive disorders and presents new evidence that supports the vertical transmission of BHV-4.