Tick-borne diseases

Ticks can carry pathogens that can be transmitted to humans or animals when they are bitten. Lyme disease (or Lyme borreliosis) is the most common tick-borne disease in humans. 

What are tick-borne diseases? 

A tick bite is usually harmless, only causing a local reaction with some redness and itching. In some cases, however, the tick can carry pathogens (bacteria, viruses or parasites) that can be transmitted through the tick’s saliva and thus cause disease in humans or animals. 

Lyme disease

Lyme borreliosis, or Lyme disease, is an infectious disease caused by the bacteria Borrelia burgdorferi sensu lato, which can be transmitted to humans through a tick bite, when the tick itself is infected.

Tick-borne encephalitis

Tick-borne encephalitis (or TBE) is an infectious disease caused by the tick-borne encephalitis virus (TBEV).


Human granulocytic anaplasmosis (HGA) is an infectious disease caused by the bacterium Anaplasma phagocytophilum.

Other tick-borne diseases in humans

In addition to the pathogens that cause Lyme borreliosis, tick-borne encephalitis or anaplasmosis (see above), ticks can also carry other bacteria or parasites (including Neoehrlichia mikurensis, Borrelia miyamotoi, Rickettsia spp., Francisella tularensis and Babesia spp.).

In general, pahtogens other than the Borrelia burgdorferi s.l. bacteria are found much less frequently in ticks, and human disease caused by infection with these other pathogens is rarely diagnosed in Belgium. The infections often present without symptoms or with flu-like symptoms, whereby the cause is not usually sought. However, the diseases can sometimes be serious, especially in people with a weakened immune system.

Sciensano is responsible for the epidemiological surveillance of various human diseases transmitted by ticks and monitors the population’s exposure to tick bites (via the TekenNet project). We also conduct research through specific studies, including on ticks and in animals. 

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