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CONTRIBUTOR(S): James Breen, Alexander Corbishley,

Infectious bovine rhinotracheitis (IBR)

Infectious bovine rhinotracheitis (IBR)

Infectious Bovine Rhinotracheitis (IBR) is a highly infectious and contagious respiratory disease of cattle.

In IBR the nose can appear very reddened and ulcerated
©James Breen

What causes IBR in cattle?

IBR is caused by a virus called Bovine Herpes Virus-1. There are several strains of BHV-1 in Europe, North America and Africa. The BHV-1 virus that causes IBR is endemic (i.e. widely present) in the UK. IBR is not a notifiable disease in the UK.

BHV-1 was originally recognized as a venereal disease (i.e. one that is sexually transmitted) as infection with BHV-1 during mating can cause sores in the female reproductive tract (Infectious Pustular Vulvovaginitis or IPV) and sores around the penis of bulls (Infectious Pustular Balanopostitis or IPB).

The respiratory form of infection with BHV-1 emerged in North America during the 1950’s and outbreaks of severe respiratory disease in the UK during the 1970’s was thought to be caused by imported Holstein cattle from North America.

Other Bovine Herpes viruses exist and they cause other symptoms and diseases such as some teat lesions (BHV-2) and embryo losses (BHV-4).

How is IBR spread?

The main source of the BHV-1 virus are infected cattle, and often those farms that have a problem with IBR have brought it in by buying infected cattle that have recovered from disease (see ‘latency’ below).

Respiratory infections are spread by aerosols, with virus present in water droplets in the air.

Direct contact between animals (i.e. nose to nose contact) or a shared air space that allows a sustained period of aerosol infection pressure between groups is required to pass on infection from infected cattle to uninfected cattle.

There is usually around 10-20 days between infection and the appearance of symptoms in infected animals – this is the incubation period.

The genital form of IBR infection is spread during natural breeding between infected bulls or cows.

Once infected, cattle are effectively infected for life – this is a key feature of infection with herpes viruses like BHV-1 and is called latency. This latent infection occurs because the BHV-1 virus infects nerves, particularly some of the nerves of the head such as the trigeminal nerve.

During periods of stress such as transport, group changes, illness or calving, re-activation of infection and shedding of the BHV-1 virus can follow, meaning infected animals can pass on the infection once again.

For the respiratory disease form of IBR, cattle that are more than 6 months of age are most likely to be affected, but infection and clinical signs can be seen in younger animals.

Clinical signs of infection are often worse in growing cattle age groups, between 6 and 24 months old.

What are the symptoms of IBR?

Mild symptoms are characterized by conjunctivitis (inflammation around the eyes), and epiphora (increased production of tears). Affected cattle have an increased temperature, which can be very high (40°C/104°F), and also show nasal discharge and an increased effort when breathing. Sometimes, the nose can appear very reddened and ulcerated (see picture above).

Lactating dairy cows will show a marked drop in milk yield.

A typical presentation of acute IBR would be seen in growing cattle (e.g. groups of heifers) and would be characterized by a fever, conjunctivitis (red eye) and secondary infection, e.g. a purulent (white) nasal discharge.

Complications are seen with more peracute (sudden onset) or severe disease, characterized by a very high fever and even death in 24 hours, caused by a secondary bronchopneumonia and necrotising tracheitis (i.e. infection of the main airways). Mortality (deaths) can be as much as 10% of those affected in younger animals.

SUDDEN outbreaks of respiratory disease in susceptible cattle over a few weeks/months can also raise suspicion of IBR infection, particularly if animals have been recently moved onto a farm.

IBR infection should be confirmed by a veterinary surgeon.

It is a severe disease problem that requires urgent action and should be differentiated from other conditions such as malignant catarrhal fever. This usually only affects individual cattle within the herd. Signs may be similar to IBR, but affected cattle will typically have mouth lesions and severe eye lesions affecting both eyes (keratitis).

How is IBR infection confirmed by your veterinary surgeon?

Often, the history of new animals or groups being brought into the herd, particularly when cattle have not been vaccinated, is highly suspicious of IBR, and when combined with the clinical signs described is almost diagnostic in itself.

For individually affected cattle, the most useful method of confirming infection is to take nasal and conjunctival swabs and send these swabs away to confirm the presence of the BHV-1 virus using what is called a Polymerase Chain Reaction or PCR test. This is much more desirable than blood testing (below) as results are much more rapid, allowing decisions about control to be made much more quickly.

Blood samples can be collected from acutely affected cattle with high fever and submitted for antibody testing for BHV-1; the same cattle are then blood sampled again 3-4 weeks later when recovering (‘convalescent’) and antibodies to the BHV-1 virus tested. If IBR is the cause of the symptoms seen in the group, the antibody levels will be much higher in the ‘convalescent’ samples than the ‘acute’ samples (so-called ‘rising antibody titres’).

For dairy herds where adult cows are not vaccinated, the quickest method of confirming exposure and infection in the milking herd is to test the bulk milk for antibodies to the BHV-1 virus, although this doesn’t inform us which cows are infected, only that the level of antibody in the herd is likely to mean infection with the BHV-1 virus is active.

What are the options to control IBR?

There are several options for herds that may have been exposed to the BHV-1 virus and/or experienced symptoms of IBR:

  • Vaccinate in the face of an outbreak – common.
  • Vaccinate the herd routinely to control clinical signs, using conventional or marker vaccines and accepting that infection is present.
  • Attempt to eradication infection using a combination of management and vaccination, although this is very dependent on biosecurity.

Vaccination plays a key role in the control and eradication of IBR and there are several ‘conventional’ vaccines available, based on ‘live’ or ‘inactivated’ strains of the IBR virus.Importantly, vaccination does NOT protect cattle that are already infected and incubating the disease, but does tend to reduce the amount of shedding from infected cattle.Some IBR vaccines are ‘live’ (i.e. the vaccine contains live virus, which may cause a mild infection when used but immunity is quicker), others are ‘inactivated’ (i.e. the vaccine is based on dead BHV-1 virus, meaning reduced chance of side effects but immunity takes longer to be acquired and requires several doses of vaccine).

Effective immunity in the face of an outbreak or high challenge (e.g. in groups of young cattle) is achieved by using intranasal live vaccines with immunity demonstrated after several days, although a second dose may be required for full protection.

Immunity can also be provided by using inactivated strains of the virus, and these are often combined with other respiratory viruses to try and give some widespread protection in young cattle. When using inactivated vaccines, it is important to vaccinated cattle TWICE, usually 3-4 weeks apart, and well before expected management stressors such as movement or re-grouping. These vaccines can be used in very young cattle that are 3-4 weeks old but more doses of vaccine are required.

The so-called marker vaccines provide another option and are based on the ‘DIVA’ principle, or ‘Differentiating Infected and Vaccinated Animals’. The IBR marker vaccines use different strains of the BHV-1 virus that have been modified (‘gE deleted’) so cattle that are marker vaccinated can be identified from those cattle that have been naturally infected. Marker vaccines for IBR come in both live and inactivated forms, and your veterinary surgeon should be consulted when you are deciding and implementing a vaccination strategy.

Antibody positive bulls, whether through natural exposure or vaccination cannot go to stud.

Biosecurity is also extremely important when attempting to control IBR in dairy and beef herds, and is focussed on preventing contact with cattle that may be infected. Examples of important areas of control for IBR infection include fencing for cattle at pasture (double fencing at field boundaries to prevent nose to nose contact).

Buying in vaccinated animals is NOT sufficient protection. Animals should be blood tested, even if vaccinated. 

Any cattle that are bought onto the unit MUST be quarantined – ideally herds should be closed to all movements to successfully control IBR. Quarantine involves keeping suspect cattle away from the main herd in a separate air space for 28 days, and these cattle are blood tested on arrival and at 28 days to see if a rising antibody titer for IBR virus is present.

Is it possible to eradicate IBR from dairy and beef herds?

Yes! Many countries have successfully eradicated BHV-1 from their national herds, for example Sweden, Norway and Denmark.

Once eradication is achieved, herds can apply for special status and be accredited as free of IBR. Accreditation schemes for IBR are available, and are listed on the Cattle Health Certification Standards (CHeCS) Scheme, for example the Premium Cattle Health Scheme (SRUC). These schemes often require a period of testing to confirm disease is absent, using bulk milk screens if a dairy herd or blood sampling adult beef animals, as well as blood sampling youngstock under 12 months of age. Accreditation also requires biosecurity measures AND the use of marker vaccination. The benefits of accreditation include reduced disease, pedigree animals and the export trade.

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