Also known as Pseudorabies
Aujeszky's disease is eradicated and notifiable in some countries. It occurs in pigs of all ages.
Pigs younger than 3 weeks, inco ordination, appetite loss, depression, vomiting, diarrhea and convulsions may occur, then death of entire litters.
Older pigs often have fever, appetite loss, sneezing, coughing, pneumonia, Convulsions and sometimes blindness. Abortion, stillbirths and mummified pigs can also occur. Respiratory signs, abortion, stillbirths, mummies, pre-weaning deaths with nervous signs.
- Causes of Aujeszky's disease >
- Effects of Aujeszky's disease >
- Diagnosis of Aujeszky's disease >
- Treatment & Control of Aujeszky's disease >
Causes of Aujeszky's disease
Aujeszky's disease is caused by infection with a herpes virus, Suid herpesvirus 1 (SHV) which multiplies in the nuclei of the cells of the pig to lyse (kill) them, to form syncytia (merge them) or to produce a characteristic intra-nuclear inclusion body . It can be grown in tissue culture in the laboratory. It is a DNA virus.
The glycoproteins (gp) and thymidine kinase (TK) of the virus are important in the disease, in vaccines and in diagnosis and their genes have been sequenced. Only one major antigenic types of the virus occurs.
Aujeszky's disease virus infects the upper respiratory tract and travels along the virus invades the brain and cranial nerves.
Strains found in Northern Ireland and Central Europe also produce pneumonia.
Invasion of the uterus, maternal and fetal placentas and foetuses occurs and can cause abortion, fetal death, fetal resorption and Mummification.
The virus can be adsorbed onto the zona pellucida of embryos and can infect recipient embryo transfer in sows and may be shed in the semen for up to 10 days. Virus is shed from 2 days post-infection until 10-14 days post-infection in most cases and exceptionally until 19-20 days. Latent (undemonstrable) infections commonly develop.
Effects of Aujeszky's disease
Clinical signs in piglets under 4 weeks of age start within 3.7 days of infection and they may vomit and become depressed or show diarrhea, with fever (41.5 ° C, 107 ° F), trembling, in-coordination (including Circling) the adoption of a dog-sitting position, spasms followed by prostration and death in newborn animals or 100% after 12 hours, but that only 40-60% by 4 weeks of age.
The disease lasts 4.8 days in animals aged 1.5 months. Anorexia (inappetence) with occasional vomiting occurs within 3 days of the onset of fever and from the 4th day, tremor and inco ordination of the hind limbs to progress to muscle spasms and convulsions followed by short prostration and death in up to 15% of animals.
Finishing periods may be extended by 10-14 days. Severe pneumonia in weaned pigs has been recorded in addition to the nervous signs described above. Infection in adults may be inapparent, transient inappetence or result in a rise in temperature accompanied by mild respiratory and nervous signs.
Up to 50% of affected pregnant animals to abort or give birth or macerated mummified foetuses. Reproductive failure may follow. Semen quality may decline from 10-14 days post-infection for a period of 1-2 weeks.
Diagnosis of Aujeszky's disease
Abortion, neonatal deaths, nervous signs in piglets and coughing and listless ness in finishing pigs spreading through a non-immune herd should suggest Aujeszky's disease.
Clinical signs may be slight or undetectable in vaccinated, partially immune herds in breeding herds or those with only finishers.
Pruritus and death in farm cats and dogs, cattle or sheep is a common early sign. Post-mortem findings such as necrosis of the tonsils and turbinates or nasal septum may indicate Aujeszky's disease.
The characteristic intra-nuclear inclusions seen by microscopic examination are diagnosed, but occur in less than half the cases. Confirmation of disease is by laboratory tests for virus in tissues of infected pigs or for antibody in sera.
Virus can be grown from the brain, lung and spleen of affected pigs, demonstrated in the brain or tonsil using a fluorescent antibody, immunoperoxidase, DNA probes, in situ DNA hybridisation and the Polymerase Chain Reaction (PCR), a DNA test which detects tiny especially in amounts of latent virus infections.
The origin of virus can be determined and Whether it is a wild or vaccine type. ELISA for serum antibody tests are widely used on pigs and recovered in herd diagnosis. They, too, can distinguishing wild and vaccine type infections.
Treatment & Control of Aujeszky's disease
There is no treatment although hyper-immune serum may protect piglets less than 4 weeks old in some countries.
Control is by herd vaccination in countries where the disease is widespread and by prevention of re-infection has tasks where eradication place.
Vaccination is with live or killed vaccines made from virus lacking one of the glycoproteins or the thymidine kinase. These protect, and antibody to them can be distinguished from that in ELISA tests to wild type virus. Sow vaccination prevents disease in young pigs and abortion, but maternal antibody may prevent successful vaccination of piglets and 3 vaccinations, the last at 14 weeks of age may be needed to prevent disease in finishers. Serum profiles determining the proper time to vaccinate a herd when antibody is absent.
Aujeszky's disease has been eradicated by slaughtering herds containing infected animals or by vaccinate herds to reduce disease and then slaughtering pigs with antibody to wild type virus. Wind can spread virus for 2-17 km on land and 70 km over water, so eradication is best carried out on an area basis. Disease free stock, semen and embryos must be available and depopulated units must be disinfected or left empty for 10.12 weeks.
