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INFECTIOUS BOVINE RHINOTRACHEITIS (IBR) SUMMARY
IBR is caused by a herpes virus that results in acute upper respitory tract disease among all ages of cattle. This can lead to fatal pneumonia. The severity of the respiratory disease in part is dependant upon the strain of virus but also upon management factors. The respiratory form of the disease is most commonly seen when store cattle are housed in the autumn i.e. when stresses animals from different backgrounds mix together. Some strains of the virus can also cause abortion and reduced fertility or a drop in milk yield in adult cattle or pustular inflammation of the vagina/prepuce. Infected animals usually shed the virus in secretions from the respiratory tract and eyes but IBR virus can also be spread via genital tract secretions including semen.
Following infection most animals develop an effective immune response, but because IBR is a herpes virus infected animals remain carriers for life and can shed virus later during periods of stress. Movement of animals is a major stress and carrier cattle become the source of infection when introduced into a new herd. Although vaccines are an effective means of control they cannot prevent infected animals from shedding virus when stressed. Marker vaccines are available that allow a blood test to differentiate antibodies due to natural infection from those induced by vaccination. These marker vaccines can be used in this health scheme when eradicating IBR from an infected herd. At present they should not be used in cattle intended for export.
This disease can have very serious effects upon herd productivity and it is likely that virulent strains will reappear in the future. However in recent years several countries have eradicated IBR and currently its main significance is as a potential barrier to trade to other European regions. Future access to these markets will be dependent upon freedom from IBR.
Exclusion or eradication of IBR virus from the herd is therefore a good option given the potential losses associated with herd infection. This is especially true fro herds planning to export cattle in the future. There is potential for savings to many farm businesses through the reduction in losses due to pneumonia and improved calf health and a reduction in abortion/reproductive losses.
IBR Screening and Eradication Programme
Initial Herd Screen
In herds where the IBR status is uncertain, limited blood sampling or bulk
milk antibody testing can be carried out as an aid in deciding whether
to progress with eradication of the disease. Once you have decided to eradicate
the disease, all animals of 12 months of age or older must be sampled.
Animals that test positive are reactors and should be removed. If there
are too many reactors to remove in one go we will advise on the appropriate
strategy to follow. It is likely to involve the use of marker vaccine.
Once reactors are removed a second herd test is carried out between 3 and
12 months later. This is repeated until a clear test is achieved.
IBR Accreditation Programme
To show freedom from disease all that is required are two clear tests of
all animals of 12 months of age or over. The second herd test can follow
as soon as 4 weeks up to 12 months after the first clear test.
One accredited you must test a statistically based sample of animals 12 months of age or older from each management group each year. This would usually mean a sample from the cow herd and samples from the followers. All breeding bulls, all animals that are not home bred and have come from a herd that is non-accredited for IBR and those from herds using marker vaccine must be tested each year.
IBR Biosecurity Measures
Added animals must be quarantined and tested before entry to the herd in
accordance with CHeCS rules. Ideally the animals should also be tested
on the farm of origin because if positive it saves considerable time and
expense.