Bovine herpesvirus 1 (BOHV-1) is a virus that causes Infectious Bovine Rhinotracheitis (IBR), infectious pustular vulvovaginitis, temporary infertility, embryonic death and abortions in cattle. The virus affects herds around the globe, causing significant economic losses. As is the case for other herpes viruses, BoHV-1 has the ability to establish a latent infection, meaning that animals are carriers for life and can infect other animals after viral reactivation.
Stress or other factors that cause a weakened immune system in the affected animal lead to reactivation of BoHV-1 and viral shedding. The implication of shedding is that viral transmission to other animals in the herd occurs, making the disease challenging to control.
BoHV-1 causes abortion, however the way the organism reaches the uterus from the respiratory system or post activation sites is still poorly understood. A recent study conducted in the Federal University of Vicosa, Brazil, investigated the presence of BoHV-1 in reproductive organs of naturally infected cows. Blood and genital organ samples from 75 cows that did not receive a vaccine against BoHV-1 were collected after slaughter and used in this study.
In this research, serum antibodies against BoHV-1 were found in 54.7% of the analyzed samples and it was detected in the uterus of all seropositive cows. In addition, the oviducts were positive in 73.2 % of the samples and the ovaries contained virus in 58.5% of the seropositive cows. Correlation between antibody titer and detection of the virus in reproductive tissues or number of infected structures per cow, was not found. For the 34 seronegative cows, the virus was not present in the reproductive organs.
The fact that the reproductive structures tested were positive for BoHV-1 in all or some seropositive cows, likely suggests that these organs could be a target for active viral replication and a likely source of viral dissemination to the embryo and fetus leading to embryonic death or abortion. The uterus was positive for BoHV-1 in all of the seropositive cows. It is probable that the uterus would be a principal organ for viral replication, and that from there the virus infects the placenta leading to fetal death.
Another possible route of genital organ infection is via the BoHV-1 adherence to the oocyte zona pellucida or even associated with the spermatozoa. The virus can be transferred from the uterus to the zona pellucida of embryos in the early stages of development, thus representing another possible cause of abortion.
Vanessa Lopes Dias Queiroz-Castro, Eduardo Paulino da Costa , Saullo Vinicius Pereira Alves, Jose Domingos Guimaraes , Virgínia Teles Dohanik, Marcus Rebouças Santos, Luiz Fernando Lino de Souza, Caroline Gomides Ribeiro, Rebeca Toledo Caldas, Abelardo Silva-Júnior. 2019. Detection of bovine herpesvirus 1 in genital organs of naturally infected cows. Theriogenology, 130, 125-129.
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