Infectious Bovine Rhinotracheitis (IBR) is a hidden disease in many beef and dairy herds, but one that can prove costly. Because many of the symptoms of IBR infection are not specific to IBR, herds can be unknowingly infected, and suffering both production losses, and risk of clinical disease in naïve animals.
WHAT IS IBR?
IBR is the common name given to disease caused by a highly contagious virus called Bovine Herpes Virus 1 (BoHV-1). BoHV-1 affects cattle of all ages and can cause a variety of clinical signs.
BoHV-1 is endemic in the UK with infection present in 96% of dairy herds1 and 73% of beef suckler herds1. Following infection in a naïve animal (one not previously exposed to the virus) the virus becomes latent (dormant), so even though the animal can recover from the infection, it becomes a lifelong carrier of the virus. Subsequent stress can result in the virus re-activating, and the animal starting to shed virus, which can go on to infect other animals in the herd. This is how, even in closed herds, the virus can remain within the herd and continue to cause problems.
BoHv-1 most commonly causes upper respiratory tract disease in both young and adult stock, with animals developing a fever and conjunctival (eye) and nasal discharges. In adult breeding stock it can also cause abortions.
Animals which are chronically (latently) infected, i.e. those which are carrying the virus, have been shown to yield less milk, and they may relapse during times of stress and start shedding the virus, risking disease in other animals within the herd. Stressful events can include for example changes to housing, diet, pregnancy or illness.
IDENTIFYING IBR IN A HERD
In a dairy herd testing a bulk milk sample for IBR antibodies is a useful way of determining a herd’s IBR status.
Blood testing for antibodies is used in beef herds to confirm IBR status, and blood testing in dairy herds will confirm the infection status of individual animals.
HOW IS IT SPREAD?
Latently infected animals can start shedding the virus during periods of stress. Infection can be spread either directly through nose to nose contact, through the air over short distances, through contact with contaminated equipment or clothes or through infected semen.
In dairy herds heifers are often exposed to the virus for the first time when they calve down and enter the milking herd, so this represents a key risk period.
WHY DO YOU NEED TO CONTROL IBR?
With Brexit on the horizon and volatile market conditions it is important farmers are maximising profits from their farm. Controlling diseases like IBR helps avoid unpredictable disease outbreaks, and helps maximise production.
Although latently infected animals may not always show symptoms and can appear healthy within a herd, the underlying cost of IBR can be significant.
One study2 found that uninfected cows yielded an extra 250.9 litres/lactation compared to infected cows. Another study3 showed an even greater impact with uninfected cows producing an extra 2.6kg/day, equating to 793 litres / 305 day lactation. This represents a margin over purchased feed4 gain of up to £174/cow for uninfected vs infected animals.
The impact of clinical disease in naïve animals is more obvious, with costs arising from treatment, dramatic loss of production whilst the animal is sick, and possible deaths.
The Responsible Use of Medicines Alliance (RUMA) Targets Taskforce has also set targets for livestock farmers to reduce antibiotic use. Using vaccines to control disease in both adult and youngstock plays a key role in both keeping animals healthy and reducing antibiotic use.
Deciding which vaccine programme to introduce will depend on which pathogens you need to protect your calves against, length of protection required and how quickly you need the protection to take effect.
There are a number of vaccines available which can be used to control infection. These can be conventional or marker vaccines, and live or inactivated. Choice depends on the particular farm situation, age of animals and disease threat.
In the next blog post we will explore the different vaccine options and how they can help in the control of IBR.