Bornavirus infection

Lisa Vogel studied departmental journalism with a focus on medicine and biosciences at Ansbach University and deepened her journalistic knowledge in the master's degree in multimedia information and communication. This was followed by a traineeship in the editorial team. Since September 2020 she has been writing as a freelance journalist for

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The Bornavirus BoDV-1 is the causative agent of Borna's disease - an animal disease that rarely occurs in humans. The viruses infect field shrews, but can also spread to other mammals such as horses, cats and even humans. A life-threatening encephalitis can result. Where is the Borna virus spread? What are the symptoms? How can you protect yourself from infection? You can read the answers here!

ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. G05

Brief overview

• What is the Borna virus? BoDV-1 (Borna disease virus 1), also called “classic” Bornavirus, belongs to the Bornaviridae family and causes Borna's disease (BoDV-1 meningoencephalitis).
• Distribution: Bavaria, Thuringia, Saxony, Saxony-Anhalt and neighboring federal states as well as Austria, Liechtenstein and Switzerland
• Transmission: Presumably via excretions (saliva, feces, urine) from infected animals.
• Symptoms: initially mostly unspecific complaints (such as headache, fever), then neurological symptoms (such as language disorders, gait disorders) and encephalitis (usually fatal).
• Therapy: No specific therapy available. Only supportive treatment and intensive medical care are possible.
• Prevention: no contact with field shrews and their excretions; Hygiene measures

What is the Borna virus?

The Bornavirus (BoDV-1) is a so-called RNA virus. It triggers Borna’s disease, which is usually fatal in inflammation of the brain (encephalitis).

Borna disease is a zoonosis, an infectious disease that can be transmitted from animals to humans and vice versa. The BoDV-1 pathogen attacks field shrews and can then spread to other mammals, including humans. This virus has long been known to be the cause of Borna disease, especially in horses and sheep. In 2018, BoDV-1 was first detected in humans as the cause of encephalitis.

However, Bornavirus infections are rare and isolated cases in humans. On average, two people across Germany are infected with BoDV-1 each year. However, the number of unreported cases is likely to be significantly higher. An examination of tissue samples from the brain of already deceased encephalitis patients has shown that at least 14 people died of the Bornavirus infection between 1995 and 2019. To what extent the virus could be behind brain inflammation with unknown cause is still unclear.

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 responsible health department.

The virus is named after the district town of Borna in Saxony. Hundreds of horses died there in 1885 from initially unknown causes. It was not until almost 100 years later that scientists were able to identify the virus as the cause of death.

Red squirrel Bornavirus

Known a few years longer as the Bornavirus BoDV-1 is the Bunthörnchen-Bornavirus. variegated squirrel bornavirus 1 (VSBV-1). It has been found in colored and beautiful squirrels as well as a few other exotic squirrels in Germany, the Netherlands and Croatia. In recent years there have been isolated cases of VSBV-1 infections among breeders and zookeepers who had contracted infected squirrels and then developed encephalitis, which usually ended in death.

How the red squirrel Borna virus found its way into European croissant holdings and whether wild squirrels (e.g. Central America, Asia) are infected is not yet known.

The transmission routes between the croissants and to humans are also still unknown. VSBV-1 can probably be transmitted directly via bite or scratch injuries as well as via excretions from infected animals. It is considered impossible that an infected person can pass the pathogen on to other people.

VSBV-1 has not yet been found in native wild squirrels.

Spread of the Bornavirus

The natural occurrence of the classic Bornavirus (BoDV-1) is limited to regions in Germany, Austria, Liechtenstein and Switzerland where the field shrew - the natural host of the pathogen - is widespread. In Germany, these BoDV-1 risk areas can be found in:

• Bavaria
• Baden-Wuerttemberg
• Thuringia
• Saxony
• Saxony-Anhalt
• Share in neighboring federal states

The field shrew is true to its location and rarely leaves its territory. Therefore, there is rarely an infection between animals from two different populations. As a result, the Borna virus can only spread slowly - the spread is limited to these areas.

An accumulation of Bornavirus infections can be observed in Bavaria.

Routes of transmission of the Bornavirus

The field shrew is the natural host of BoDV-1. If the mice are infected with the Borna virus, they presumably excrete contagious virus particles in saliva, urine and feces. Other mammals can presumably be infected by smear infection through these excretions. However, the exact transmission route is not yet known.

It is also still unclear how the Borna virus is transmitted to humans. However, different transmission routes are conceivable, such as:

• Ingestion of the virus through contaminated food or water
• Inhaling the virus through contaminated dust
• direct contact with or being bitten by a field shrew

BoDV-1 is optimally adapted to the field shrew. The pathogen can multiply and spread in this host. The mouse can be infected with the virus for life without becoming ill itself.

In addition to field shrews, the Borna virus can also attack other species as so-called "false hosts". According to the current state of knowledge, these are:

• Horses
• Sheep
• Alpacas
• Cats
• people
• Mice and rats (infected in experiments)

In contrast to the field shrew, the Borna virus cannot spread throughout the body of these false hosts. Because it is not optimally adapted to these living beings and thus provokes an immune reaction.

The Borna virus cannot multiply in these false hosts and is probably not excreted again. As a result, infected horses, sheep, or humans are unlikely to be contagious to others.

Transmission via donor organs

The first BoDV-1 infections detected in humans in 2018 concerned transplant recipients: organs were removed from a dead organ donor who was undetected with the Borna virus and implanted in several people. Three of the transplant recipients then fell ill with Borna's disease, two of whom died.

How high is the risk of infection?

Overall, the Borna virus rarely occurs in humans. According to current knowledge, the greatest likelihood of infection comes from contact with infected shrews or their excretions in the above-mentioned risk areas. However, these contacts rarely occur. A possible risk of infection exists, for example, with outdoor activities such as gardening or camping trips.

Even when working in agriculture, forestry and construction, people can potentially come into contact with infected animals or their excretions. The same applies to staying in and, above all, cleaning buildings in which shrews live or lived.

Borna virus: symptoms

Most of the known BoDV-1 patients initially developed unspecific symptoms:

• headache
• fever
• general feeling of illness

After a few days, neurological symptoms may appear in the case of a Bornavirus infection, for example:

• Behavioral problems
• Speech disorder (aphasia)
• Gait disorders

These complaints arise because the Bornaviruses withdraw into the cells of the central nervous system. As the disease progresses, severe inflammation of the brain (encephalitis) can develop. Affected patients often fall into a coma within a few days to weeks. Borna's disease is fatal if left untreated.

All of the above symptoms can also have other causes. In fact, a Bornavirus infection is very rarely behind it. Nevertheless, they should be taken seriously, especially neurological symptoms. Acute aphasia, for example, is usually caused by a stroke - to be on the safe side, call the emergency doctor immediately!

Borna virus: diagnosis

If you experience 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 complaints and, if necessary, refer you to a specialist.

anamnese

The anamnesis includes a detailed doctor-patient discussion to collect the medical history. The doctor can ask you the following questions, among others:

• Which complaints do you have exactly?
• Do you notice insecurities while walking or speaking?
• Since when are you having those complaints?
• Do you work with animals?
• Was the last time you were out in nature?
• Have you had any contact with wildlife?

If encephalitis is suspected, the patient is immediately admitted to hospital. Every encephalitis must be taken seriously because it can be life-threatening.

Laboratory tests

Laboratory tests to diagnose Bornavirus infection in humans and animals can be carried out at the Bernhard Nocht Institute for Tropical Medicine and at various university clinics. The Friedrich Loeffler Institute (FLI) has developed two methods for detecting viruses:

PCR detection

Using a PCR test, nerve water (liquor) or brain tissue from deceased persons can be examined for the genetic material of the Borna virus. Even the smallest RNA snippets can be tracked down and - after sufficient replication - identified.

Antibody detection

To do this, the scientists examine the blood or nerve water of potentially infected people or animals: As soon as the Borna virus has penetrated the organism, the immune system of the false host reacts to the foreigners and forms specific antibodies against it. These can then be detected in the blood.

In living patients, antibody detection is usually the only way to confirm a BoDV infection.

Bornavirus: treatment and prognosis

There is still no approved therapy against Bornavirus infections in humans. Experiments with the antiviral agent (virostat) 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.

Most people infected with Borna virus die within two to six months of the onset of symptoms.

There is currently no effective therapy for infected animals either. If the Borna virus has infected horses, sheep or cats and Brona’s disease actually breaks out, most animals die within a few weeks or months after the onset of symptoms.

Borna virus: prevention

Because Bornavirus infections are so rare, the chances of getting infected are rather low. However, the following measures can help to further reduce the risk of BoDV-1 infection:

• Avoid contact with shrews and their excretions.
• Do not keep shrews as pets.
• Do not touch dead (wild) animals with your bare hands.
• If you find live shrews at home, use dog or cat food to lure them outside.
• After contact with the animals, clean contaminated surfaces (such as floors, door handles, work surfaces, surfaces) thoroughly with household cleaner.
• After dusty work, you should shower and wash your hair immediately. You should also wash the work clothes you have used.
• Correct hand washing: After every contact with animals, you should wash or disinfect your hands thoroughly.

Cats & Bornavirus: Correct use

Cats can also be infected with the Borna virus. So far, however, only a few such cases are known. Since cats are also a false host, they do not excrete the virus according to previous 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:

• Never touch the mice with your bare hands.
• Spray dead shrews and their excretions thoroughly with a commercially available cleaning agent. This prevents virus-containing dust from being whirled up during disposal.
• Wear gloves when disposing of it and - if it gets dusty - also wear a mouth and nose cover.
• Dispose of the carcass in a sealed plastic bag with household waste.

Cats, like humans, are a false host for the Borna virus. Infection from an infected cat is therefore unlikely.

Investigation of infected animals

Since hardly any people have been infected with Borna virus so far, the examination of infected animals is an important part of research into the virus. The Friedrich-Loeffler-Institut (FLI) therefore recommends taking saliva and blood samples in suspected cases and sending them to the institute. Talk to your veterinarian about this.

In the case of deaths (especially from croissants) with an unclear cause, you can send the entire animal carcass in a cooled or frozen state to the institute (Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald-Insel Riems). The contact person there for Bornavirus diagnostics is Dr. Dennis Rubbenstroth ([email protected]).

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