Bovine Herpesvirus 5 Encephalitis in Cows: Seizures and Brain Inflammation in Cattle
- See your vet immediately. Bovine herpesvirus 5 (BHV-5) is a neurologic herpesvirus of cattle that can cause severe meningoencephalitis, seizures, circling, blindness, and rapid decline.
- Young cattle are affected most often, but any susceptible animal can become ill. Signs may start after a short respiratory phase or appear mainly as sudden neurologic disease.
- There is no specific antiviral treatment routinely used in cattle. Care is supportive and may include anti-inflammatory medication, seizure control, fluids, nursing care, and herd-level biosecurity.
- Your vet will usually recommend ruling out rabies and other causes of encephalitis first because several cattle neurologic diseases can look similar and some have public health implications.
- Typical US cost range for exam, farm call, basic supportive treatment, and diagnostic sampling is about $250-$1,200 per animal. More intensive hospitalization, repeated visits, or necropsy/PCR testing can raise total costs to roughly $1,500-$3,500+.
What Is Bovine Herpesvirus 5 Encephalitis in Cows?
Bovine herpesvirus 5 encephalitis is a viral brain disease in cattle caused by bovine herpesvirus 5 (BHV-5), also called bovine alphaherpesvirus 5. It is closely related to bovine herpesvirus 1, the virus involved in infectious bovine rhinotracheitis, and older references may list BHV-5 as the encephalitic subtype of BHV-1. In affected cattle, the virus targets the central nervous system and causes inflammation of the brain and its coverings, called meningoencephalitis.
This condition is uncommon in many US herds, but when it occurs it is serious and can be fatal. Calves and young stock are reported most often, though older cattle can be affected too. Signs can include behavior changes, incoordination, head pressing, circling, blindness, paddling, and seizures. Some cattle decline over hours to a few days.
Because BHV-5 causes neurologic signs that overlap with rabies, listeriosis, polioencephalomalacia, lead toxicity, thromboembolic meningoencephalitis, and other brain diseases, it should never be assumed at home. Your vet may need to treat the case as both a medical emergency and a biosecurity concern until testing helps narrow the cause.
Symptoms of Bovine Herpesvirus 5 Encephalitis in Cows
- Depression or sudden behavior change
- Incoordination or staggering
- Circling or head pressing
- Blindness or reduced menace response
- Muscle tremors, paddling, or seizures
- Recumbency
- Fever or recent respiratory signs
- Excess salivation or difficulty swallowing
Any cow with seizures, circling, sudden blindness, severe incoordination, or recumbency needs urgent veterinary care. Keep people and other animals away until your vet advises otherwise, because rabies must stay on the differential list for cattle with acute neurologic signs. Avoid handling the mouth or saliva, move the animal only if it can be done safely, and call your vet right away for next steps.
What Causes Bovine Herpesvirus 5 Encephalitis in Cows?
BHV-5 is a contagious herpesvirus of cattle. Like other herpesviruses, it can establish latent infection, meaning an animal may carry the virus after exposure and later shed it again during stress or immune suppression. Transmission is thought to occur mainly through close contact with infected respiratory secretions, especially in groups of young cattle housed or transported together.
After infection, the virus can spread from the upper respiratory tract into nervous tissue. Not every exposed animal develops encephalitis, but when the virus reaches the brain it can cause severe inflammation and tissue damage. Young cattle appear to be at higher risk for clinical neurologic disease.
Herd stressors may increase spread or reactivation. These can include weaning, transport, commingling, crowding, weather swings, and other illness. Because BHV-5 is closely related to BHV-1, herd history around respiratory herpesvirus exposure and vaccination matters. Your vet may also consider whether new additions, recent movement, or gaps in biosecurity could have played a role.
How Is Bovine Herpesvirus 5 Encephalitis in Cows Diagnosed?
Diagnosis starts with a farm call exam and neurologic assessment. Your vet will look at age, herd history, vaccination history, recent stress events, fever, respiratory signs, and the pattern of neurologic changes. Because cattle with encephalitis can resemble rabies cases, your vet may recommend strict handling precautions and limited contact until the risk is better defined.
There is no single barn-side test that confirms BHV-5 in a live cow with certainty. Testing often focuses on ruling out other urgent causes and collecting samples for laboratory work. Depending on the case, your vet may submit blood, nasal swabs, cerebrospinal fluid, or other samples, but postmortem testing of brain tissue is often the most definitive route. PCR, virus detection methods, histopathology, and immunohistochemistry can help identify herpesviral encephalitis and distinguish BHV-5 from other causes.
Common differentials include rabies, listeriosis, polioencephalomalacia, lead poisoning, thromboembolic meningoencephalitis, salt toxicity, brain abscess, and other viral encephalitides. If a cow dies or is euthanized, a prompt necropsy coordinated through your vet and a veterinary diagnostic laboratory can be very valuable for the affected animal and for herd planning.
Treatment Options for Bovine Herpesvirus 5 Encephalitis in Cows
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Urgent farm call and physical or neurologic exam
- Isolation from the herd and reduced stimulation
- Basic anti-inflammatory treatment if your vet feels it is appropriate
- Supportive nursing care such as shade, bedding, easy access to water, and monitoring
- Discussion of humane euthanasia if seizures, recumbency, or severe brain signs are present
Recommended Standard Treatment
- Farm call, full exam, and neurologic assessment
- Supportive treatment directed by your vet, which may include anti-inflammatory medication, fluids, thiamine while differentials are being addressed, and seizure control when feasible
- Diagnostic sampling such as bloodwork and selected infectious disease testing
- Rabies precautions and differential diagnosis planning
- Necropsy and laboratory submission if the animal dies or is euthanized
Advanced / Critical Care
- Referral or intensive on-farm management for valuable breeding or show cattle
- Repeated veterinary reassessments and more aggressive fluid or seizure support
- Expanded laboratory workup and coordinated diagnostic lab submission
- Enhanced nursing care for recumbent cattle, including frequent repositioning and pressure sore prevention
- Detailed herd investigation, biosecurity review, and vaccination program discussion with your vet
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Bovine Herpesvirus 5 Encephalitis in Cows
Bring these questions to your vet appointment to get the most out of your visit.
- What diseases are highest on your differential list for these neurologic signs, and does rabies need to be ruled out first?
- Which immediate treatments make sense for this cow based on the severity of the neurologic signs?
- Is this animal safe to handle, move, or isolate, and what precautions should our family or staff take?
- What samples can we collect now, and would necropsy give us the best chance of a diagnosis if the cow dies?
- What is the realistic prognosis for recovery, return to function, and long-term herd value?
- Should we monitor or separate pen mates, calves, or recent arrivals for early signs?
- Does our herd vaccination program against BHV-1 need to be updated to improve cross-protection?
- What biosecurity changes would most reduce the risk of spread or future cases on this farm?
How to Prevent Bovine Herpesvirus 5 Encephalitis in Cows
Prevention focuses on herd biosecurity, stress reduction, and respiratory herpesvirus control. Because BHV-5 is closely related to BHV-1 and latent carrier animals can shed herpesvirus again, your vet may recommend a vaccination plan that includes IBR protection as part of the herd program. Available BHV-1 vaccines are used widely in cattle and are considered helpful for herd control, although they are not a labeled, BHV-5-specific cure or guarantee against neurologic disease.
Work with your vet on quarantine and introduction protocols for new cattle, especially young stock. Avoid unnecessary commingling, reduce crowding, and support calves through weaning, transport, and weather changes with good nutrition and low-stress handling. These steps matter because stress can increase herpesvirus shedding and disease spread.
If a neurologic case appears, isolate the animal and contact your vet right away. Prompt diagnosis helps protect people, guides decisions about rabies precautions, and may identify whether herd-level changes are needed. If BHV-5 is confirmed or strongly suspected, your vet may advise reviewing vaccine timing, movement practices, and how groups of susceptible young cattle are managed.