Also known as Bovine viral diarrhoea virus (BVDV) or Mucosal disease virus, the introduction of pestivirus into your herd can result in production losses of between 25-40%, with ongoing annual losses of 5-10% experienced if the virus is not then eliminated.
Transmission of the virus requires direct contact with a 'carrier' animal, with these individuals shedding the virus in all secretions and excretions including discharge from the nose, saliva, tears, urine, faeces and semen. The effect of infection on the individual is dependent on both their immune and pregnancy statuses:
1. Previously Unexposed, non- pregnant animal infected with the virus: The healthy immune system responds to the infection and clears the virus from the body within a few weeks. Clinical signs, if any, include transient fever, ill thrift and diarrhoea, with most infections going unnoticed.
2. Previously exposed, pregnant animal infected during gestation: The virus is eliminated by the immune system with no ill effects.
3. Previously UNexposed, pregnant cattle infected during gestation: The virus has the ability to cross the placental barrier and result in various deformities depending on the stage of gestation:
- Early gestation (first month): Abortion only
- Mid gestation (Second-fifth months): Abortion, deformed calf at full term, stillborn calf at full term or perfectly healthy calf at full term that is persistently infected (PI).
- Late gestation (sixth-ninth months): Generally by this stage the foetal immune system can fight off the virus however infection can still result in mild growth retardation.
4. Persistently infected (carrier) cattle: These PI calves usually do not develop equal to other calves of the same age and tend to die before the age of two due to a suppressed immune system, and are known as 'carriers'. If survival ensues, they can develop severe acute or chronic mucosal disease later in life.
Production losses following infection are based on the impacts on reproductive, productive and growth. Reproductive failures include early-term abortions or embryonic loss and temporary infertility, whilst calves are born weak, deformed and lack the growth potential of others of their age. The effect on milk production also has substantial financial impacts, and an increased susceptibility to other diseases can lead to more frequent incidences of diarrhoea, respiratory disease and ill- thrift.
Methods of Prevention:
- Vaccination: Requires 2 doses, 4-6 weeks apart prior to joining.
- Identifying and culling persistently infected cattle
- Isolating newly introduced animals with strict biosecurity protocols
