Monograph

Fri, 01/21/2011 - 14:41 — Anonyme

definition:

Teschovirus encephalomyelitis virus are responsible of a contagious and infectious diseases of nervous central system to swine. These virus are classified in a Picornaviridea family, Enterovirus and Teschovirus swine genus.

Previously, Teschovirus are separated in eleven subtypes (PTV-1 to PTV-11), they were classified in 3 groups (I, II and III) in function to citopatogenico effects, serology and site of cells multiplication.

OIE do a differenciation between Teschen disease, with some virulents strains PTV-1, and Talfan disease, with less virulents subtypes. Today, in the Terrestrial Manual 2008 to OIE, the twice diseases are bring together under the name of Teschovirus encephalomyelitis diseases.

Importance

In the origin, the Teschen disease has been described for the first time in 1929 in Czechoslovakia in Teschen district. It expanded then in other countries of Eastern Europe but have disappeared today thanks to medical prophylaxis operations and improving conditions for breeding, including biosafety. However, the disease is enzootic in Madagascar and is responsible of important economic consequences on the familial breeding.

The virus responsible to old Talfan disease, less contagious disease in comparison with Teschen disease, has been identified next to Talfan mountains in Great Britain in 1955. This disease is more present in the world, but it is more minor.

Situation in America:

In the West Indies, only Haïti described encephalomyelitis disease in March 2009. The virus has been described like a strain of Teschovirus subtype PTV-1. This subtype has 97 % of homology with a virus of Madagascar. The origin of introduction of the virus has been never determined.

Susceptible species:

The Teschovirus encephalomyelitis are specifics to swine population, they are not transmissible at human people.

Methods of transmission

Method of contamination:

The contamination sources of this disease are the infected or clinical pigs. The disease transmission is possible by digestive or respiratory ways (when the disease is serious). When the virus is excreted in the exterior medium, it is possible it survives during several months. Transmission can be direct or not direct because the virus can be stay on water or food.

In serious encephalomyelitis disease, when the strains are pathogenics, all the ages groups of animals can be infected and the mortality can be reach 50%. Conversely, when the virus is less pathogenics, between 2 and 5 % of animals are infected and the mortality is weak (between 1 and 2 %).

Symptoms:

The incubation of serious encephalomylitis disease change between 5 and 15 days, however, the infection can be latent, delaying it to up to 35 days.

When the diseases are very serious, the diseases caused a high fever and, then, a gradual degradation of the general condition with earthquakes, paralysis or convulsions. The fatale issue of these diseases appears between 24 and 48 hours by encephalitis.

When the diseases are importants, a gradual degradation of the general condition is possible, the encephalitis symptoms and earthquakes appears and the death arrived between 4 and 5 days after the infection for 30 % at 50 % of animals or keeping an irreversibles consequences.

To conclude, when the diseases are not really importants or chronics, animals doesn't deaths, reversibles paralysis disappears in one or two weeks, however, the animal slimming is important and after-effects can be persists.

Lesions

Macroscopic lesions:

Paralysis of hindquaters frequent

Microscopic lesions:

The principals injuries induced by the serious form of the disease are essentially microscopics, with encephalitis in a grey tissue in brain.

Diagnostics

Clinical diagnosis:

The diagnostic is based on a contagious paralysis and on important mortality and morbidity. It is really important to confirm this diagnostic for not confound with severe form to classical swine fever and or Aujesky disease...

Laboratory diagnosis:

It is based on the observation of poliomyelitis injuries and on the histo-immuno-chimicals techniques, based on a brain swabs and spinal cord swabs. This technique uses a conjugates specifics antibodies.

Virological diagnosis:

It is an isolation of the virus from the nervous center. It is the more reliable techniques, however, the detection of the virus is not easy because this virus is often absent when the clinical signs are declared. When the virus was isolate, this identification is possible by a specifiques serums or antibodies. For that, Primers are create, they permits to amplify and differenciate the subtype PVT-1 by a RT-PCR.

Serological diagnosis:

It is very difficult to do an interpretation to this technical because the infection is often not declared and the same antibodies are presents with other swine Enterovirus.

Prophylaxis:

Sanitary :

When the Teschovirus encephalomyelitis diseases appears in a new country, the control must be based on the stamping-out and disinfection.

Medical :

When the high prevalence, like in Madagascar, it is necessary to use a vaccines campaigns.