Brief overview
- What is Bornavirus? BoDV-1 (Borna disease virus 1), also called “classical” Bornavirus, belongs to the Bornaviridae family and causes Borna’s disease (BoDV-1 meningoencephalitis).
- Distribution: in parts of eastern and southern Germany, Austria, Switzerland and Liechtenstein.
- Symptoms: initially mostly nonspecific complaints (such as headache, fever), then neurological symptoms (such as speech disorders, gait disturbances) and encephalitis (usually with fatal course).
- Therapy: no specific therapy available. Only supportive treatment and intensive medical care possible.
- Prevention: avoid contact with field shrews and their excreta; observe hygiene measures.
What is Bornavirus?
Since March 2020, there has been an obligation to report bornavirus infections. If the virus has been detected in humans, the laboratory concerned must report the case to the relevant health authority.
The virus is named after the district town of Borna in Saxony. Hundreds of horses died there in 1885, initially of unknown causes. It was not until nearly 100 years later that scientists were able to pinpoint the virus as the cause of death.
Bunthörnchen Bornavirus
How the variegated squirrel hornavirus found its way into European squirrel husbandries and whether wild squirrels (e.g., Central America, Asia) are also infected is not yet known.
VSBV-1 has not yet been found in wild native squirrels.
Distribution of the Bornavirus
The natural occurrence of classical bornavirus (BoDV-1) is restricted to regions in Germany, Austria, Liechtenstein and Switzerland, where the field shrew – the natural host of the pathogen – is common. In Germany, these BoDV-1 risk areas are found in:
- Bavaria
- Baden-Wuerttemberg
- Thuringia
- Saxony
- Saxony-Anhalt
- Parts of bordering federal states
In addition to the countries mentioned above, the field shrew is also found in Italy, France and the Czech Republic. However, there has been no evidence of the classic bornavirus (BoDV-1) there to date.
Transmission routes of the Bornavirus
How the Bornavirus is transmitted to humans is also still unclear. However, various transmission routes are conceivable, such as:
- Ingestion of the virus via contaminated food or contaminated water
- inhalation of the virus via contaminated dust
- direct contact with or bite by a field shrew
In addition, cases have been described in which the virus was transmitted as part of an organ transplant (see below).
In addition to field shrews, bornavirus can also infect other species as so-called “false hosts”. According to current knowledge, these are:
- Horses
- Sheep
- Alpacas
- Cats
- Humans
- Mice and rats (infected in experiments)
Unlike the field shrew, bornavirus cannot spread throughout the body of these maladaptive hosts. This is because it is not optimally adapted to these creatures and thus provokes an immune response.
Transmission via donor organs
The first BoDV-1 infections detected in humans in 2018 involved transplant recipients: organs had been removed from a dead organ donor undetected as infected with Borna virus and transplanted into several people. Three of the transplant recipients subsequently contracted Borna disease, and two of them died.
How high is the risk of infection?
People can also potentially come into contact with infected animals or their excreta when working in agriculture, forestry and construction. The same applies to staying in and especially cleaning buildings where shrews live or have lived.
Bornavirus: symptoms
Most of the known BoDV-1 patients initially developed nonspecific symptoms:
- Headache
- fever
- general feeling of illness
- Behavioral disorders
- Speech disorder (aphasia)
- Gait disorders
These symptoms are caused by the Bornaviruses retreating into the cells of the central nervous system. In the further course, a severe brain inflammation (encephalitis) can develop. Affected patients often fall into a coma within a few days to weeks. Borna’s disease is fatal if left untreated.
Bornavirus: Diagnosis
If you notice the symptoms described above in yourself or someone close to you, you should consult a doctor. The family doctor is the first point of contact. He can classify the symptoms and refer you to a specialist if necessary.
Medical history
The anamnesis includes a detailed doctor-patient discussion to obtain the medical history. The physician may ask you the following questions, among others:
- Do you notice any unsteadiness when walking or talking?
- How long have you had the complaints?
- Do you work with animals?
- Have you been out in nature recently?
- Have you had any contact with wildlife?
If encephalitis is suspected, you will be admitted to a hospital immediately. Any encephalitis must be taken seriously because it can become life-threatening.
Laboratory tests
PCR detection
PCR tests can be used to examine cerebrospinal fluid (CSF) or brain tissue from deceased persons for the genetic material of the bornaviruses. Even the smallest RNA fragments can be detected and – after sufficient amplification – identified.
Antibody detection
In living patients, antibody detection is usually the only way to confirm BoDV infection.
Bornavirus: treatment and prognosis
There is not yet an approved therapy for bornavirus infections in humans. Experiments with the antiviral agent (virostatic agent) ribavirin, which is actually approved for the treatment of other viral diseases, have shown that it is also effective against BoDV-1 – at least at the cellular level and in animal experiments.
There is also no effective therapy for infected animals as yet. If bornavirus has infected horses, sheep or cats and Borna’s disease actually breaks out, most animals die within a few weeks or months after the onset of symptoms.
Bornavirus: Prevention
Because Bornavirus infections are so rare, the likelihood of becoming infected is rather low. However, the following measures can help further reduce the risk of BoDV-1 infection:
- Do not keep shrews as pets.
- Do not touch dead (wild) animals with your bare hand.
- If you find live shrews at home, you should lure them outside with dog or cat food.
- After contact with the animals, clean contaminated surfaces (such as floors, doorknobs, countertops, surfaces) thoroughly with household cleaner.
- You should shower and wash your hair immediately after dusty work. In addition, you should wash the used work clothes.
Cats & Bornavirus: Correct handling
Also cats can become infected with the Bornavirus. So far however only few such cases are well-known. Since cats are also a false host, they do not excrete the virus according to current knowledge and thus cannot transmit it to humans.
However, you should be careful if you live in a BoDV-1 risk area and your cat brings home dead mice. Then the following advice applies:
- Spray dead shrews and their droppings thoroughly with a commercial cleaning agent. This prevents dust containing viruses from being stirred up during disposal.
- Wear gloves and, if dusty, mouth-to-nose coverings during disposal.
- Dispose of the carcass in a sealed plastic bag in household trash.
