ThePigSite Pig Health
Aujeszkys disease - Pseudorabies virus (AD or PRV)
See also chapter 12.(202) This is an important disease of pigs, caused by a herpes virus. Once introduced into a herd the virus usually remains there and it can continually affect reproductive performance at varying levels. The virus can survive for up to three weeks outside the pig.
Clinical signs
Acute disease These reproductive problems may occur in up to 20% of dry sows. However these are not the only clinical signs seen in the herd. Dogs and cattle may become infected, show nervous signs and die.
Chronic disease
Carrier state
Methods of spread between herds
Treatment
Acute outbreaks of disease occur when virulent strains of the virus first infect an unvaccinated susceptible herd. The virus crosses the uterus and placenta and infects the foetuses. Often the first clinical signs are abortions, stillbirths and the birth of weak litters which soon die. Abortions may rise to 5% over about 6 weeks followed by reproductive failure at all stages of the cycle. Embryos are killed and absorbed and sows return to heat.
In an unvaccinated herd, when the early acute phase of the disease is over and the herd has developed an immunity clinical signs are sporadic and milder. The signs may also be difficult to associate with an infertility problem because of their insidious nature. Depression of reproductive efficiency across all parameters is a feature of the chronic infection with increased levels of repeats, mummification, stillbirths and piglet mortality. Young carrier females that are stressed shed virus thus maintaining infection throughout the herd. Spread of infection in the breeding herd is low with immunity and infection waning and rising over one to two year cycles.
After the acute phase clinical signs of disease may die out altogether and this is often seen in small herds of less than 100 sows. Sometimes the virus itself may disappear. However it is more likely to persist in a few animals sporadically.
Diagnosis
When a susceptible breeding herd first breaks down with this disease the clinical signs described above strongly suggest aujeszky's disease and are almost diagnostic. Laboratory tests are required to confirm the diagnosis. The common ones are as follows:
Similar diseases
When disease is first introduced into a susceptible breeding herd there are few other diseases except possibly swine fever that would be confused with AD. Once the disease has become chronic it could be confused with PRRS and chronic swine fever. Laboratory tests would be required to differentiate them.
Management control and prevention
