Tick saliva inhibits the skin's defense function, thereby increasing the risk of diseases such as tick-borne encephalitis or Lyme disease.

Tick saliva inhibits the skin's defense function, thereby increasing the risk of diseases such as tick-borne encephalitis (TBE) or Lyme disease, according to new research in the Journal of Clinical Investigation.

The researchers carried out their investigations on skin samples from volunteers and also on models of human skin, mimicking the bite of the most common European tick (Ixodes ricinus). In both cases, the team led by Georg Stary, an associate professor of dermatology at the Medical University of Vienna in collaboration with the research group of Hannes Stockinger of the Center for Pathophysiology, Infectiology and Immunology at the Medical University of Vienna identified rapidly occurring patterns of immunomodulation. For example, it was found that the function of immune cells, especially T cells, which are important for immunological memory, was disrupted by contact with tick saliva.

Tick saliva modulates immune system

The scientists made similar observations in the early stages of model infection by Borrelia burgdorferi, the most common cause of Lyme disease. They found that pre-incubation of Lyme disease-transmitting bacteria (B. burgdorferi spirochetes) with tick salivary gland extracts impedes the accumulation of immune cells in the skin and increases the pathogen burden. "Overall, we found that tick feeding causes profound changes in the skin's immune system inhibiting the local immune response. This means that dangerous pathogens that are introduced into the skin together with tick saliva, can multiply more easily, leading to infection," says study author Johanna Strobl, PhD, of the department of dermatology at the Medical University of Vienna.

Climate change increases danger of ticks

Austria is one of the countries with the greatest prevalence of ticks. Nearly every second European tick is infected with pathogens, Lyme disease and tick-borne encephalitis (TBE) being the most common tick-borne diseases. The arachnids become active at a temperature of seven degrees. Due to rising temperatures associated with climate change, ticks now also pose a threat in higher-altitude regions of Austria and well into late autumn.

PHOTO CREDIT:Medical University of Vienna