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Infectious bovine rhinotracheitis
Infectious bovine rhinotracheitis, known by the acronym IBR, is a contagious viral disease of cattle. It is caused by a herpesvirus which mainly attacks the upper respiratory tract: nose, throat, trachea. Its particularity lies in the herpe...
What is it?
Infectious bovine rhinotracheitis, known by the acronym IBR, is a contagious viral disease of cattle. It is caused by a herpesvirus which mainly attacks the upper respiratory tract: nose, throat, trachea.
Its particularity lies in the herpesvirus family: once an animal is infected, the virus no longer leaves its body. It goes to sleep in the nerves and can wake up months or years later, during stress. The animal then excretes the virus again and contaminates its peers, often without appearing sick.
A herd can therefore remain infected for a long time from a single apparently healthy animal purchased. This is what makes this disease difficult to eliminate and explains the importance of purchasing controls.
Key point
Disease regulated in many countries, including Tunisia, where it is monitored and affects animal movements. Any respiratory episode affecting several cattle, and any abortion, must be reported to the veterinarian and the veterinary services.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Respiratory form, the most common: marked fever, discharge from the nose initially clear then thick, cough, rapid and noisy breathing.
The eyes are often red and watery, without affecting vision.
The animal eats less, stays behind, and milk production drops significantly in a few days in dairy cows.
The mucous membrane of the nose is very red, which has earned the disease the nickname “red nose”.
Genital form: redness and small lesions of the vulva in females, with discharge, or from the sheath in bulls. It can exist alone, without respiratory signs.
Abortions, generally in the second half of gestation, sometimes several weeks after the episode of illness.
In young, unprotected calves, a serious generalized form is possible.
Many infected animals show no signs: they are silent carriers and still contribute to contamination.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The disease is caused by bovine herpesvirus type 1.
This virus multiplies in the mucous membrane of the nose, throat and trachea, which it weakens. This attack opens the way to respiratory bacteria already present in the animal, which explains the bronchopneumonia which often follows.
After the acute phase, the virus takes refuge in the nerve ganglia and remains there for life. Significant stress — transport, calving, mixing of batches, high heat, other illness — can reactivate it.
Purchase of animals whose health status is not known, or absence of quarantine on arrival.
Mixture of animals from different origins: markets, gatherings, pensions, common pastures.
Overcrowded or poorly ventilated buildings, where heavy air promotes contagion.
Any period of stress: transport, weaning, calving, change of diet, extreme heat.
Use of seed whose origin is not controlled.
Transmission
By direct contact between animals and by secretions from the nose and eyes.
By fine droplets projected when coughing, over short distances inside a building.
By the genital route: natural protrusion, or semen from an infected bull.
By soiled equipment, feeders, drinkers, clothing and hands of workers.
The introduction of a carrier animal, even without any signs, is by far the primary cause of entry of the virus into an unaffected herd.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Respiratory signs are not enough to confirm IBR: several viruses and bacteria give a similar picture. Only the laboratory decides.
The veterinarian examines the affected animals, takes the temperature, listens to the lungs and assesses the extent of the attack in the lot.
He takes swabs from the nose or eyes in the acute phase to look for the virus, and blood samples to measure antibodies.
Antibody testing can be carried out on tank milk in dairy farming: it is a simple way to monitor the herd as a whole.
Certain so-called “marked” vaccines make it possible to distinguish a vaccinated animal from a truly infected animal: this distinction is essential for managing a sanitation plan, and it is the veterinarian who chooses the strategy.
Treatment
No medication destroys the virus. We treat the animal and prevent complications.
Sick animals are isolated from the rest of the herd, kept quiet, in a well-ventilated room without drafts, with clean water at all times and palatable food.
The veterinarian can prescribe an anti-inflammatory to reduce the fever and provide relief to the animal.
An antibiotic is justified not against the virus, but against the bacteria which take advantage of the damaged mucous membrane to cause pneumonia. The choice, route and duration are solely a matter for veterinary prescription.
Never use a leftover prescription or a product intended for another animal: you risk masking the signs, delaying the diagnosis and promoting resistance to antibiotics.
Monitor the resumption of drinking and eating: these are the best indicators of progress.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Checking any animal before entering the herd and isolating it while the veterinarian validates its status: this is the most effective measure.
Avoid contact between herds: double fences or sufficient distance from neighboring pastures.
Only use semen from controlled centers.
Clean and disinfect buildings, equipment and transport vehicles; bring boots and clothing dedicated to breeding.
Reduce avoidable stress and not overload buildings.
Participate in regular screening of the herd, on blood or tank milk, to identify an entry of the virus before it spreads.
Vaccination
Vaccines exist, in live attenuated or inactivated form, by injection or by nasal route depending on the product.
Vaccination greatly reduces clinical signs and the quantity of virus excreted by infected animals: it protects the herd and limits its spread.
It does not eliminate the virus already installed in a carrier animal: a vaccinated bovine can remain a carrier for life.
Marked vaccines allow the real infection to continue to be detected despite vaccination, which is essential in a sanitation plan.
The choice of vaccine, the age of the first injection and the frequency of boosters depend on the status of the herd and the objective pursued: they are defined by the veterinarian.
Possible complications
Bacterial bronchopneumonia, which significantly worsens the picture and can lead to the death of young animals.
Sometimes lasting drop in milk production, even after apparent recovery.
Abortions and reproductive delays in the weeks following the episode.
Temporary drop in fertility in the affected bull in its genital form.
Long-term installation of the virus in the herd, with recurrences during each period of stress.
When to see a veterinarian
Several animals present at the same time with fever, runny nose and cough.
An animal breathes with difficulty, its head is tense, or blows at rest.
Milk production drops suddenly in several cows.
Abortions occur in the herd: notify the veterinarian immediately, an official investigation into the causes must be initiated.
You have just introduced animals and the first signs appear in the days that follow.
An affected calf stops drinking or quickly weakens: it is an emergency.
Prognosis
In adult cattle in good condition, respiratory signs most often resolve within one to two weeks and mortality remains low.
The prognosis worsens when bacterial pneumonia sets in, in young calves and in farms where environmental conditions are poor.
The heaviest consequences are economic and lasting: lost milk, stunted growth, abortions, and above all restrictions on the sale of animals until the herd is cleaned up.
Frequently asked questions
Can a cured cow still contaminate others?
Yes. The virus remains dormant in its body throughout its life and can wake up during stress, such as calving or transport. The animal then sheds virus again, often without appearing ill.
Can I consume milk from a cow with IBR?
This virus does not infect humans. On the other hand, a sick cow often receives treatments which require a waiting period before her milk is usable: scrupulously respect the veterinarian's instructions.
Is vaccination enough to rid my herd of the virus?
No. It limits the signs and contagion, which is already a lot, but it does not eliminate the virus in animals already carrying it. Sanitation involves screening, purchasing control and a strategy decided with the veterinarian.
How to avoid bringing in disease when buying a cow?
Ask for the health status of the original herd, have the animal checked, and keep it isolated from the rest of the herd until the veterinarian validates its entry. An uncontrolled purchase is the most common gateway.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
ANSES — Agence nationale de sécurité sanitaire (France)
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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