The virus that causes IBR is called bovine herpes virus -1 but is often more commonly called IBRV. There is sufficient evidence to suggest that 70% of Irish cattle have been exposed to the virus associated with IBR.
IBR can cause a respiratory disease in all ages of cattle, severe cases can result in death or long term ill health. The following symptoms may be associated with IBR. However it is important to note that they are not unique to IBR and all suspect animals should be examined by your vet.
The following clinical signs may be associated with (but are not unique to) IBR infections:
• Dullness and reducedappetite
• High body temperature
• Rapid and loud breathing, sometimes with coughing
• Inflammation inside the nose and in the pink of the eye (conjunctiva) or less commonly on lining of male or female reproductive tracts
• Fluid discharge from nose and eyes
• Pharyngitis (inflammation of the throat)
• Sudden reduced milk production
• Nervous signs (normally only in young calves).
(Adopted from AHIinformation leaflet on IBR)
The virus is spread mainly by direct or close contact between animals. The virus can also spread over short distances in the air.
Overall the virus is very contagious. After primary respiratory infection a susceptible animal can shed high levels of virus in fluid from their eyes, nose and mouth for anything up to 14 days. It is estimated that an infected animal can infect up to 7 other individuals. The virus can also be shed by semen. Moving or sharing contaminated equipment or personnel is another source of infection. Immunity is developed as a recovery to primary infection but this does not lead to elimination of the virus. Instead the virus enters a sleeping state and is not re awakened until episodes of stress caused by transport, calving, nutritional stress or mixing of animals. This re-activated source of infection leads to further spreading of the virus and in turn more animals that will become carriers of the disease. Figure 1 shows the spread of IBRV through a herd.
Several different vaccines containing either live or dead virus are available in Ireland. These are marker vaccines which means that when used with an appropriate test it’s possible to distinguish animals that test positive due to vaccination or infection. Vaccines can be used for various reasons. A decision on which product and strategy to use should be discussed with your vet. Animal’s blood or milk samples can be tested to determine their IBR status.
When deciding on implementing a control programme the three recommended steps are, investigate, control and monitor. It’s important to investigate herd status where the level of infection is unknown the results will in turn help with selecting a control programme.
Figure 2 shows the three general principles and there effectiveness under various situations that can form the herd control plan.
For further information including information leaflets and frequently asked questions visit the Animal Health Ireland website.