Bovine herpesvirus (BHV) is a significant viral disease impacting cattle globally. As a herpesvirus, it is characterized by its DNA-based genetic material and capacity to establish latent, or dormant, infections. This pathogen carries economic consequences for the cattle industry due to its effects on animal health and productivity.
Understanding Bovine Herpes Virus
Bovine Herpes Virus encompasses a group of related viruses, but Bovine Herpesvirus 1 (BHV-1) stands out as the most clinically impactful strain. BHV-1 is a double-stranded DNA virus. A defining characteristic of BHV-1 is its ability to establish a lifelong latent infection within the host, typically residing in sensory neurons.
This latency means the virus can remain hidden without causing active disease, but it can reactivate and shed infectious virus during periods of stress, such as calving, transport, or other infections. The reactivation of this latent virus is a primary mechanism for new outbreaks within a herd.
Impact on Cattle Health
BHV-1 infection in cattle manifests in several distinct clinical syndromes, with severity often influenced by the viral strain, the animal’s age, and the presence of other pathogens. The most common and economically significant manifestation is Infectious Bovine Rhinotracheitis (IBR), which primarily affects the upper respiratory tract. Cattle suffering from IBR typically exhibit fever, nasal discharge, coughing, and labored breathing. The muzzle may become inflamed and reddened, leading to the common name “red nose”.
BHV-1 is also responsible for genital diseases, including Infectious Pustular Vulvovaginitis (IPV) in cows and Infectious Balanoposthitis (IBP) in bulls. In affected females, IPV presents as inflammation, swelling, and the development of pustules, ulcers, and erosions on the vulva and vagina, often accompanied by discharge and painful urination. Bulls with IBP can experience swelling of the prepuce and similar lesions on the penis, sometimes leading to reduced libido.
Another serious consequence of BHV-1 infection is abortion in pregnant cattle, which commonly occurs during the second half of gestation. The virus can cross the placental barrier, leading to fetal infection and abortion. While less common, BHV-1 can also cause conjunctivitis, characterized by inflamed, watery eyes, and in young calves, it may lead to encephalitis, a neurological disease affecting the brain, or a generalized systemic disease with high mortality.
Transmission and Diagnosis
Bovine herpesvirus 1 spreads primarily through direct contact between infected and susceptible animals, often via nose-to-nose interaction. The virus is shed in nasal and ocular discharges, making aerosol transmission through coughing and sneezing a significant mode of spread. Contaminated equipment or reproductive fluids, such as semen used in artificial insemination, can also transmit the virus. Latent carrier animals, which may appear healthy, can shed the virus during periods of stress, initiating new infections within a herd.
Diagnosing BHV-1 infection often requires laboratory confirmation. Polymerase Chain Reaction (PCR) tests detect viral genetic material in samples like nasal swabs, tissue, or semen. Serological tests detect antibodies in the animal’s blood, indicating past exposure to the virus.
Prevention and Management Strategies
Preventing Bovine Herpesvirus 1 infection and managing its impact requires a multi-faceted approach. Vaccination plays a significant role in reducing the severity of clinical disease and minimizing viral shedding within a herd. Both modified-live virus (MLV) and killed virus (KV) vaccines are available. However, some MLV vaccines may not be recommended for use in pregnant animals, requiring careful consideration of product labels.
Implementing biosecurity measures is important to prevent the introduction and spread of BHV-1. This includes isolating new animals before integrating them into the main herd, maintaining hygiene protocols, and minimizing stress factors that can trigger viral reactivation in latent carriers. Preventing contact with potentially infected herds and regularly cleaning shared equipment can further reduce transmission risks. During an outbreak, isolating affected animals, consulting with a veterinarian, and potentially administering booster vaccinations to the rest of the herd are important steps to contain the spread. There is no specific antiviral treatment for BHV-1, making supportive care and prevention key in managing the disease.