Tick carries more than just Lyme disease

The number of Lyme disease cases and other diseases carried by ticks rises. RIVM researchers Agnetha Hofhuis and Seta Jahfari, who both did a PhD on ticks and pathogens that might be carried by ticks, came to this conclusion.

Number of EMs multiplied

With her PhD, Angnetha Hofhuis shows that the number of erythema migrans (the famous bullseye rash) after a tick bite has quadrupled between 1994 and 2014. Hofhuis also concludes that the chance of getting Lyme disease after a tick bite is about 2,6%. When the tick is engorged with blood, the chance of getting Lyme disease after a tick bite even rises to a maximum of 14,4%.

Half of the ticks carry pathogens

Seta Jahfari concludes with her research that about half of the ticks carries one or multiple pathogens. Besides, Jahfari showed tick-borne encephalitis virus and Borrelia miyamotoi in the Dutch ticks for the first time. Both can cause meningitis.  

Don’t rule-out co-infections

Both researchers found traces of one or multiple pathogens in the blood of 2,5% of the people who had a tick bite. According the researchers, the infections caused by the pathogens can’t be distinguished very well by a clinic, because the symptoms are (wrongly) attributed to Lyme disease most of the time.

The advice of both PhD students is, therefore, that the treating physician should also pay attention to co-infections. Especially when a patient still has symptoms after a tick bite.


Hofhuis, A. Epidemiology of Lyme borreliosis and other tick-borne diseases in the Netherlands. 2017

Jahfari, S. Tick-Borne Disease: Opening Pandora’s Box. 2017