Entering the herd, the Aujeszky’s disease virus continues to circulate in it until appropriate measures of eradication are taken. What is virus cunning, what are the specialties of modern means of its control and why Ukrainian pigmen should stay alert — details are in the article.

The etiology and ways of expanding

Aujeszky’s disease (AD) is a highly contagious disease that causes significant economic losses. It run superacute in nervous form in suckling piglets with nearly 100% mortality, in adult pigs it is in pulmonary form, often with fur of secondary bacterial infection.

ADv has a wide range of ways of spread. It is very stable in the environment; it forms in a non-sterile immunity in convalescent pigs. The virus does not infect people, but is always fatal for other susceptible mammals (including cattle, goats, sheep and cats, dogs and rodents). For these reasons AD is included into the list of diseases that are on mandatory registration.

Pathogenesis, clinical features and characteristics of immunity

The virus transmits through the lymphatic system to the lymph nodes where secondary viraemia lasts for 7–10 days. The incubation period for suckling piglets is usually lasts for 2–4 days, for weaned piglets and adult pigs it takes 3–6 days. Virus transmission in the environment with all animal’s secretions begins on the second and fifth day after infection and lasts more than for two weeks.

The clinical appearance of AD depends on the virus strain, the way infecting and pig’s age. The younger the animal, the heavier disease runs and the higher percentage of mortality are.

After clinical recovery, pigs turn into lifelong latently infected carriers of ADv. As soon as the virus sat in the trigeminal nerve, any vaccine is able to eliminate it. Pathogens may be present in a latent state in the central nervous system, in leukocytes and other organs and systems as infected, so vaccinated and unvaccinated pigs.

Pathoanatomical changes

While AD, pigs have macroscopically pathoanatomical changes, absent or difficult to find. There are no lesions, specific to the VHA. At post-mortem examination the serosal or fibrinous-necrotic rhinitis, necrotic tonsillitis, hemorrhage mediastinal lymph nodes are shown. Besides, the oedema and pulmonary involvement, caused by secondary bacterial pathogens can be observed.

Diagnostics

The diagnosis of the Aujeszky’s disease is established only by a complex epizootic, clinical, pathoanatomical data and laboratory reports.

The virus neutralization reaction (NR) and immunoenzymatic assay (IEA) are the obligatory tests for laboratory diagnosis of AD, according to the guidelines of the World Organization for Animal Health (OIE). NR is less sensitive and doesn’t distinguish vaccinal immunity from infection. At the same time, if for AD control are used marker vaccines (with deletions of individual virus genes, most often gE), discriminatory IEA determines not only positive, but latently infected pigs.

Control and eradication are modern approach

For prevention the Aujeszky’s disease, in endemic zones is organized quarantine and testing of new-come replacement animals as well as biosecurity measures to prevent virus entry with stock, clothes, people and stray animals, excluding the contact between domestic pigs with wild.

It is impossible to cure pigs, infected with AD. The disease can only be controlled through vaccination. However it is necessary to remember that vaccination soften the clinical symptoms of the disease and reduces the number and duration of virus isolation by infected animals, but it doesn’t provide sterile immunity and doesn’t prevent the transfer of infection in a latent state.

A number of programs are developed for eradication ADv. Full depopulation, partial depopulation (isolated piglets growing), and also the analysis strategy and culling are among effective approaches. Complete depopulation is reliable, but it is the most expensive method, and therefore unpopular among pig producers.

Now the acute and superacute forms of AD are uncommon in Ukrainians pig units as the virus is widespread and there are very few intact farms. However, native pig producers should stay alert and notice dangerous and treacherous enemy under the respiratory and reproductive herd’s problems in time.

1. Why AD virus must be mandatory registered? What are its characteristics? Who is the main carriers of the disease?
2. How to detect Aujeszky desease? Why is it dangerous?
3. How long does the incubation period last? How does it differ in different age groups of pigs?
4. What measures are used to prevent and control the disease?

You can find answers for these and other questions in the full version of the article in the magazine «Profitable Pig Production», № 6 (24) 2014