Contagious porcine paralysis (Teschen's disease) is an infectious disease of domestic and wild pigs caused by highly virulent strains of porcine teschovirus serotype 1 (PTV-1, Picornaviridae), although mild forms of the disease can also be caused by other PTV serotypes such as PTV-2, -3, -4, -5, -6, -9 and -10.

Infections with virulent strains of porcine teschovirus (PTV-1) have become very rare nowadays (only on the islands of Haiti, Madagascar and La Réunion). They no longer occur in Western Europe, where predominantly mild strains and courses prevail.

Domestic and wild boars

Directly from animal to animal (faecal-oral) or indirectly via contaminated infection carriers (objects, contaminated pig feed, etc.).

1 to 2 days

Severe forms of the disease in domestic pigs are initially characterised by high fever, exhaustion, inappetence and ataxia (especially weakness of the hindquarters) and then usually progress to encephalomyelitis, which is often associated with signs of paralysis (paraplegia or quadriplegia). Diarrhea may occur before the onset of central nervous disturbances. The disease is fatal in 20-100% of cases, with death occurring 3-4 days after the onset of the first symptoms. The subacute forms ("Talfan disease") with low mortality are common and symptoms such as fever, ataxia, and afterhand paralysis also occur; however, the paralysis symptoms are usually reversible. In addition to these two clinical pictures, inapparent forms have also been described.

There is no therapy

Contagious porcine paralysis is a notifiable animal disease according to the Animal Diseases Act. Vaccination is not permitted in Austria. Inactivated and attenuated vaccines exist, but are not used in the EU area either.

In Austria, there is an obligation to report infectious porcine paralysis (infection with porcine teschovirus 1 (PTV 1)) in accordance with Section 16 of the Animal Diseases Act (Tierseuchengesetz - TSG). Suspicion of Teschovirus encephalitis must be reported to the official veterinarian. In the event of corresponding clinical symptoms and the diagnostic detection of PTV-1, the official veterinarian will decide whether lockdown/culling measures are necessary - depending on the virulence/course of the disease. In the past 10 years, only rare mild CNS forms caused by other Teschovirus strains and/or porcine sapelovirus 1 (species Sapelovirus A) or porcine enteroviruses G1 and G2 (species Enterovirus G) have been detected.

Synonyms: Teschovirus Encephalomyelitis, Teschen Disease, Teschen/Talfan Disease, Polioencephalomyelitis enzootica suum, Porcine Enterovirus Encephalomyelitis, Benign Enzootic Paresis Teschen disease was first identified in the Czech town of Teschen in 1929. In 1957, a PTV-1 virus with a milder clinical form was detected in Talfan (Wales).

Porcine teschovirus A is an RNA virus belonging to the genus Teschovirus A of the family Picornaviridae. Previously, teschoviruses were classified in the enterovirus group with a total of 13 serotypes. Based on cytopathic effect (CPE), replication characteristics in different host cell lines, serological assays and sequence data, the porcine enteroviruses (PEV) have been continuously reclassified and are currently divided into 3 groups: Teschovirus A (formerly Porcine Teschovirus), Sapelovirus A (formerly Porcine Enterovirus A, PEV-8), and Enterovirus G (formerly Porcine Enterovirus B, PEV-9 and PEV-10).

Differential diagnoses include infections with Sapelovirus A (PSV-A), Porcine Enterovirus G (PEV-G), Porcine Parvovirus, PRRSV, Aujeszky's disease, European swine fever, African swine fever, colienterotoxemia, selenium poisoning or other intoxications, spinal canal abscesses, trauma, bacterial meningo(encephalitides).

Transmission

The first replication occurs in the tonsils as well as in the intestinal epithelium (especially ileum, colon). The enteric phase is not clinically significant and is not accompanied by morphological changes. The enteric phase is followed by viremia and invasion of the CNS with the typical picture of non-pituitary (encephalo)myelitis (inflammation of the brain or spinal cord). During the viraemic phase, some serotypes show affinity for the uterus. Colonization of uterine tissue with the pathogens can lead to intrauterine fetal death.

Infection is most common in weanling piglets due to the decline in maternal immunity as well as the common co-location of animals of different origins at this age. After 24 hours the virus is detectable in large quantities in the tonsils and cervical lymph nodes, after 48 hours in the mesenteric lymph nodes and in the faeces. Co-infections of teschoviruses with other Picornaviridae, e.g. PSV-1 and PEV-G, occur.

Symptomatology

Teschen disease (severe, fatal/lethal form)

• Pathogen: virulent strains of porcine teschovirus 1 (PTV 1)
• Occurrence: originally in Europe, sporadically Africa, China, Haiti, Brazil, Canada
• High morbidity (individuals of a population), high mortality (up to 90 %), in all age groups
• clinical signs: convulsions, opisthotonus, nystagmus, coma, death after 3-4 days, survivors show residual paralysis

Talfan disease (mild forms are predominant today)

• Pathogen: less virulent teschovirus strains, including PTV-1
• Occurrence: Occurs worldwide and more frequently than Teschen disease
• Paresis, ataxias, rarely paralysis, often asymptomatic, 95 % of animals exposed to infection develop latent or inapparent infections

Suitable sample materials are

• Blood (EDTA/serum)
• Brain incl. spinal cord and trigeminal ganglion
• organs

Detection of PTV from the above materials is possible using the following methods:

• PTV real-time RT-PCR, conventional RT-PCR (if necessary supported by sequencing)
• Virus isolation in cell culture
• Histopathological examination

The clinical symptoms only allow a tentative diagnosis. Suspicion of teschovirus encephalitis must be reported to the official veterinarian. A definitive diagnosis can only be made taking into account the clinical symptoms and epidemiology, the pathomorphological changes (non-purulent (encephalo)myelitis) and successful detection of the pathogen (detection of PTV-1).

If other teschovirus or enterovirus serotypes are detected, these are mild forms of the disease with no need for further action, as the disease cannot be treated. Severely affected animals should be euthanised if the disease progresses, but in many cases the disease heals itself.