There are over twenty different species of tick found in the UK, some are highly specialised and only live in specific habitats or feed on specific animals. The most likely species to bite humans is the Sheep tick Ixodes ricinus, however bites from the Hedgehog tick (Ixodes hexagonus) are also reported. This study is concerned with Ixodes ricinus because it is the main vector of Borrelia burgdorferi, the causative agent of Lyme disease in the UK. Not all ticks will carry the bacteria but they are capable of harbouring other pathogens.
Ixodes ricinus has four stages to its life cycle; egg, larva, nymph and adult.
Most bites on humans tend to be from nymphs, although both larvae and adults do bite humans.
Video showing Ixodes ricinus tick female and nymh
Depending on when it hatches and its success in finding a suitable host, the tick’s life cycle can last between 1.5 and 4.5 years. Once hatched, the larva seeks a small mammal or bird host and feeds for 3 to 5 days, before dropping off to moult. Usually later in the year or the following year the newly moulted nymph seeks a host (often a small or medium mammal) to feed on and engorges for 4 to 6 days, and will moult into a male or female. The male feeds intermittently on a newly acquired host, whilst mating with females found on the same host. The adult female feeds for 7 to 11 days, engorging and then dropping off the host to find a suitable habitat to lay her (up to 2000!) eggs.
All feeding stages can be seen with the naked eye – larvae have six legs, are slightly smaller than a poppy seed and glisten slightly in the light –Nymphs are slightly bigger, about the size of a pin head, dark in colour and have 8 legs. Sex cannot be determined at the nymphal stage. Adult females and males resemble small spiders but appear flatter and have a distinctive tick crawling movement. Males are slightly smaller than females and dark in colour. Females are the largest and have a distinctive two tone reddish brown/black appearance.