A case of Borna virus reported in Bavaria…

In Germany, a very rare case of Borna virus has been detected in Bavaria in the district of Mühldorf am Inn. No further information available. The disease, which is often fatal, has occurred only in isolated cases in people in Germany.

Two other cases of Borna virus have been known in the district in the past three years. According to the Bavarian State Office for Health and Food Safety (LGL), seven cases of infection have been reported across Germany in 2021, including five in Bavaria. On average, two infections are reported each year in Germany. However, scientists assume that the number of unreported cases is higher – up to six cases per year.

Reminder about Borna virus :

Borna virus is an enveloped RNA virus belonging to the family Bornaviridaeorder of Monogavirus. The genus Bornavirus includes 8 species and 16 viruses.

  • five species including 12 avian influenza viruses;
  • a species consisting of a reptile virus;
  • Two species include three viruses that cause disease in mammals: mammal species 1 bornavirus including Borna viruses 1 and 2 (BoDV-1 and BoDV-2) and mammal species 2 bornavirus where a species found in the Mammal Bornavirus species 2 bornavirus 1 (VSBV-1).

The bicolor white-toothed shrew (Crocidura leucodon) has been suggested as a natural source of BoDV-1. The presence of BoDV-1 in reservoir hosts has been demonstrated for Germany, Austria, Switzerland and Liechtenstein.

Borna disease in animals

Borna disease was first described in the 18th century and is named after the town of Borna, near Leipzig, Germany, where a military horse suffering from fatal neurological disease was described in 1885. Borna disease was described reported most frequently in horses and sheep. However, many species of mammals, including farm animals (cattle and goats), zoo animals (lamps, hippos, alpacas, monkeys, etc.) cats) may also be affected. Disease has been observed in psittacines, Canadian geese, trumpeters and mute swans, canaries and reptiles.

In animals, the incubation period varies from two weeks to several months. Infection can lead to acute or subacute illness with meningitis, or mild manifestations with impaired or impaired neuronal function. Most animals become paralyzed and die within 1 to 5 weeks. Recovery is possible with lifelong behavioral changes.

Borna disease in humans

The first demonstrated human infections with a member of the Bornavirus genus were reported in 2015. The virus involved is VSBV-1. Between 2011 and 2013, three men in the same geographic area (Sachsen-Anhalt, Germany) developed fatal progressive encephalitis and died 2 to 4 months after the onset of symptoms (fever and/or chills, confusion, unsteady gait, myoclonus and/or eye paralysis, psychomotor retardation and coma). The three men were breeders of multicolored squirrels (Sciurus variegatoides) and they traded their animals on different occasions. VSBV-1 was detected in central nervous system samples from three patients, as well as in a squirrel that had been exposed to them. Possible routes of transmission are a bite or scratch, but direct transmission to mucous membranes or inhalation of particles contaminated with feces or urine from an infected animal cannot be ruled out. of infected animals are not excluded.

In 2018, Germany reported four cases of people with encephalitis or acute encephalopathy associated with infection BoDV-1. Three of the cases involved a group of snake organ recipients who fell ill about 100 days after transplantation from a single donor in southern Germany (two recipients died) and another BoDV-1 encephalitis, also deceased, was found. in southern Germany. Apart from the fact that these three cases received organs from a single donor, no other common risk factors were identified.

The overall incidence of human bornavirus encephalitis is unknown. However, a retrospective study performed in the endemic area of
The German federal state of Bavaria has demonstrated that BoDV-1 can cause a significant proportion of fatal encephalitis cases. Therefore, all cases of severe encephalitis of unknown cause should be tested for this virus, especially in endemic areas. However, the absolute number of infections and therefore the risk of infection is estimated to be very low.

Infection may be suggested by contact with infected white-toothed shrews or their droppings, however, the exact route of transmission is unknown. Natural human-to-human, equine-to-horse, or equine-to-human transmission can be excluded according to current knowledge. Viruses are the cause of neurological disorders. The so-called classical Borna virus causes encephalitis, which ends in death in most cases. Survivors often leave serious sequelae

References: (1) ECDC. 26 March 2018. Acute encephalitis associated with infection with Borna’s disease andirus 1, Germany. (2) Clap et al. Infectious Diseases BMC (2021) 21: 787

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