Pathophysiology

Ticks are small, spider-like creatures that feed on the blood of animals, including humans (Figure 1).  Once they have fed on an animal infected with one of the four Borrelia species of bacteria that cause Lyme Disease they remain infected for life.

In the UK, the most important tick species to human health is Ixodes ricinus, more commonly known as the sheep, castor bean or deer tick. This species can be found feeding on humans and is the principle vector of Lyme disease. They are commonly found in areas with high humidity and ground vegetation (including urban gardens and parks).

Figure 1: Image of a tick

Figure 2: Lyme Disease: Tick and Host Lifecycle

Humans are at risk of infection throughout the year. Different stages peak at different times of the year (figure 2). The larva and adult stage are high during summer whereas the nymph stage increases during spring and autumn.  Most tick bites will not transmit Lyme disease.

Learning Bite:

Lyme disease can occur anywhere in the UK, although the south of England and the Scottish Highlands are particularly high-risk areas.