IBR affects both adult and youngstock on dairy and beef farms. The symptoms can vary and it’s tricky, but achievable, to get to grips with, as Ben Pedley, from the Willows Vet Group, Cheshire explains.
Infectious Bovine Rhinotracheitis (IBR) is caused by a virus; one of the Herpes family of viruses. This group includes the virus which causes cold sores in humans. This virus lies dormant until the person affected is under "stress" and then the virus starts to multiply, causing disease.
People are carriers for life. IBR is similar to this in that once exposed to the virus, cattle are carriers for life. Stress factors such as calving, housing, change of holding, change of social groups and extreme weather changes can all cause disease in the affected animal, and for that animal to start shedding the virus in large quantities.
Cattle, when shedding the virus, pass it to other cattle via infected discharge from the nose and lungs. However, the virus can survive in the environment for a couple of hours so it could be spread on stockman’s clothing or buckets. Feed infected stock last to minimise transmission to healthy stock.
Symptoms
Although the signs of IBR seem to differ year to year the following are some of the symptoms you may spot:
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Raised body temperature, up to 106F (41C).
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Decreased appetite.
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Decreased yield.
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Increased breathing rate.
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Nasal discharge (can be clear or "snotty").
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Discharge from the eyes (like tears coming down the face).
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Redness around the edge of the eyeball (where it’s usually white).
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Abortion.
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Infertility and early embryonic death.
Swabs taken from the nose or eye when discharge is clear can confirm diagnosis.
Diagnosis
Diagnosis by your vet will often be from clinical signs and the recent history of the affected animals. However, signs can vary from a full blown case with most of the above symptoms, to milder forms where most of the herd is affected to varying degrees.
Diagnosis may be confirmed from swabs taken from the nose or eyes, preferably while the discharge is clear before it becomes "pussy". While still clear, more virus is being produced which makes diagnosis more accurate.
Blood sampling can be used, although until the launch of the new "marker" vaccines, interpreting the results from cows that may have been vaccinated in previous years was difficult.
Response to vaccination sometimes confirms the diagnosis. Within a few days a whole herd can be eating more and milk yields can go up. Diagnosis may be confirmed by post mortem.
Bulk milk samples can help monitor the level of IBR in the herd, as long as you have not vaccinated in the previous few years, or you have not purchased previously vaccinated stock. It is always good practice, and not expensive, to monitor the level of IBR (and other diseases too) via bulk milk as this gives a basic level of the disease status of your herd.
Economic impact
The cost of this disease is potentially huge, given the varying symptoms and degree of disease. Profitability will be lost, from decreased milk yield in the dairy herd to reduced growth rates in the beef herd and dairy replacements. In the worst case scenario, animals will die from IBR.
It is more common though that any loss of animals comes about from forced culling. In other words, the animal is treated, but never fully recovers and ends up being culled. As the economic impact of the disease can be so damaging to herd profits, vaccination is a must. The cost of one replacement heifer is equivalent to 700 doses of vaccine.
Given the varying symptoms and degree of disease, IBR can be incredibly economically challenging for beef and dairy herds.
Treatment
As IBR is a virus, we can’t kill it directly with drugs, so treatment consists of the following:
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Isolation rom the rest of the herd.
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Supportive therapy (eg, fluids, anti-inflammatory drugs).
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Antibiotics (to treat/prevent secondary bacterial infections).
Vaccination
Vaccination can be used in the face of a disease outbreak, administered intra-nasally. This intra-nasal vaccine produces anti-bodies in the upper airways and helps the animal kill the virus.
Of the IBR vaccines available in the UK, there are live and dead (sometimes called inactivated) ones. An intuitive view would be that live are better than dead vaccines, but for IBR it isn’t that straightforward. For protecting IBR-naive animals, it is the case that a live vaccine is the preferred option.
In practice, this applies mainly to heifer calves getting their first course of protection. In animals already carrying the IBR virus, it has been shown that an inactivated IBR marker vaccine is more efficient at reducing viral shedding than a live one. The choice of vaccine type should be made in conjunction with your vet, who can advise on, and devise a suitable protocol.
Vaccination helps dampen the virus down, even in carrier cows.
Bought in stock should be vaccinated, preferably before arrival. If this is not possible, then vaccination upon arrival and isolation from the rest of the herd for two weeks is advisable. Don’t forget bought in breeding bulls as these can carry the virus and cause disease in your cows. IBR will also have an effect on bull fertility.
Most IBR vaccines in the UK are now licensed for six months protection, so a booster every six months is required. This can be timed to be given before the greatest risk period to give maximum effect, such as before housing and turnout.
Accreditation
Accredited status as a disease-free herd in the UK is rare and not yet required. Screening of bulls before going into AI studs is about all the compulsory screening there is. However, in Europe several countries are now disease free or in the process of reaching this stage.
It involves blood sampling, removal of virus antibody positive animals and sometimes vaccination with marker vaccines. These vaccines produce antibodies that on blood samples show up as being produced by the vaccine, and not the actual virus. This disease free accreditation may well come to the UK one day, hence the use of marker vaccines here.