Borna is a zoonosisCurrent cases show: Human infections must also be expected in the northern part of the animal endemic area. Borna disease virus 1 was first identified as a cause of encephalitis in humans as recently as 2018.
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– BoDV1 is a zoonotic pathogen. – The virus can cause a fatal brain inflammation. – Transmission from horse or sheep to humans is unlikely.
A possible infection of humans with the Bornavirus has long been discussed. Studies that postulated a connection with mental illnesses such as depression or schizophrenia are now considered disproved. But in January 2020, a publication in The Lancet showed: the virus (BoDV-1) causes brain inflammation in humans. The causative agent of Borna disease in horses, sheep, and some other domestic animals may be behind a high percentage of serious to fatal human encephalitides of unknown cause in endemic areas.
Brain inflammation and neurological symptoms
In 2018/19, the first six cases of encephalitis caused by BoDV-1 were reported. As a result, researchers at the Regensburg Institute for Clinical Microbiology and Hygiene tested 56 samples from encephalitis patients between 1999 and 2019 for the virus. They were able to identify six new patients, and two more cases are reported from other institutes. The virus has been found exclusively in patients in whom the cause of the disease was previously unknown.
The animal endemic area covers the eastern part of southern and central Germany, Switzerland, Austria and Liechtenstein. Human cases were first detected in Bavaria, then also in Thuringia and Brandenburg. In the fall of 2021, the first human BoDV1 infection in humans was reported in Saxony-Anhalt.
The disease started with headache and fever in most of the affected people, then neurological symptoms appeared: Gait disturbances, confusion, memory lapses, seizures and progressive loss of consciousness. The lethality is very high. In light of the new data, human patients with acute meningoencephalitis should be tested for BoDV-1, especially in the endemic area. At the end of March 2020, compulsory registration in veterinary medicine was reintroduced. Bornavirus is also notifiable in humans.
Vaccinate horses now against West Nile virus
The Standing Veterinary Vaccination Committee recommends vaccinating horses in central Germany against West Nile virus before the mosquito season really gets going.
Transmission from horses to humans?
It is not yet known how the infected people became infected. But there's no need to worry about contracting it from animal Borna patients. Pets are false hosts and are unlikely to transmit the virus. Human-to-human transmission is also unlikely to occur naturally. However, in two of the cases reported in 2018, the virus was transmitted through organ transplantation. The infection is rare overall. The risk therefore to be regarded as small. The main host and reservoir of the Borna virus is the field shrew. Horses probably become infected through feed contaminated with mouse droppings. It is most likely that humans also become infected in endemic areas through direct or indirect contact with shrews. A large proportion of patients were from rural areas or were outdoors a lot. A conspicuous number were cat owners. Researchers believe the cats may have brought shrews into the house or been contaminated by hunting mice.