IBR is a disease that is often mentioned in passing but not often in much detail, here is a short piece to lift the lid on IBR.
Infectious bovine rhinotracheitis (IBR) is a viral infection that can affect cattle at any age. The virus that causes it is a bovine herpes virus (BHV-1) and, as with human herpes viruses, once an animal is infected, they will always have the virus. This is known as latency. Once the initial infection is over the virus retreats to the nerve cells in the face. When the animal goes through a period of stress, eg calving or weaning, the virus can start replicating and cause disease again. Around 40% of farms in the UK have IBR on farm.
IBR is highly contagious and is spread from cow to cow via contact with secretions, through the air and uncommonly by sexual transmission. The most common form of the disease is the respiratory form, but it also has a reproductive form.
Clinical signs vary and often occur 2-3 weeks after a stressful event. When the disease is mild, signs are non-specific and can be confused with other causes of pneumonia. More severe signs include fever, thick discoloured nasal discharge, ocular discharge, coughing, panting, foul breath (halitosis) from pus in the back of the throat and windpipe, decreased appetite, severe milk drop, abortion and, occasionally, death.
Outbreaks on naïve farms can have morbidity (loss of production) of up to 100% in the group but rarely cause mortality (around 2%).
As IBR is a virus, treatment is focused on supportive therapy with anti-inflammatories and nutritional support through periods of inappetence. Antibiotics are indicated if a secondary bacterial pneumonia has infected the lungs.
Diagnosis of IBR in acute cases detects the virus itself from swabs of the back of the nose or the eyes. To detect latently infected animals blood samples are taken for antibodies.
Management of IBR on farm is best done through vaccination. There are a number of vaccines available and it is best to vaccinate animals when the protection from the dam’s antibodies wanes. This usually occurs from four to six months of age.
The vaccines are either intranasal or intramuscular and usually cover other infectious causes of pneumonia. Vaccination strategies are important as full protection is usually achieved up to 3 weeks after injection. Vaccines should therefore be given at least 3 weeks before a period of stress, eg weaning. In the face of an outbreak or widespread latent IBR on farm, an intra-nasal vaccine can be given from 2 weeks of age.
Marker vaccines are available which differentiate vaccinated animals from those infected naturally. Annual vaccination of all animals in the herd can be a useful part of IBR management, however on farms with little to no exposure, biosecurity and only buying in from accredited herds is advisable. Testing of all incoming animals will also help to prevent widespread outbreaks in naïve herds.
In summary, IBR is a disease that is often overlooked but can make a big impact on productivity. Westpoint Farm Vets can advise on vaccination, biosecurity and how to prevent infection entering your herd.
Written by Charlotte Hockings BVetMed MRCVS