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Ticks represent a risk to humans, farm and pet animals and recent climatic changes have allowed a marked increase in numbers. Find out more...

Ticks are parasitic arachnids. They feed on blood withdrawn by direct penetration of the skin and in the process transfer anticoagulants into the puncture wound as well as transmitting many viral, bacterial and protozoal diseases. They attach tightly inserting their mouthparts deep into the skin tissue and remain attached for a considerable period withdrawing large quantities of blood which is concentrated within the tick by excretion of water through the tegument. Rubbing attached ticks from their biting site often results in the mouth parts remaining in the skin and acting as a focus for skin infection to occur. Their unique ability to transmit disease is a direct result of the life cycle. Most temperate climate ticks have a prolonged development cycle which may last as long as three years and involves obtaining three blood meals from three separate hosts (three host ticks). They are not particular as to the species of host and so also can transmit infection between species.

The life cycle of the most comon UK tick Ixodes ricinus or castor bean tick, begins when a recently engorged female falls from its last host and burrows into a moist organic vegetation mat where she lays about 2,000 eggs.

These hatch the next year in spring or autumn (“seed” ticks with only 6 legs) and are then in a race to acquire a host before succumbing to dehydration. They achieve this by ascending up a plant to the top and “questing” which involves waiting for a host to pass and sensing movement, heat and carbon dioxide emissions. Most fail to find a host and perish, but in favourable conditions there is an enormous biotic potential to increase in numbers. The fed tick falls back to the ground mat to survive until feeding the next year. This means that ticks often are most numerous along tracks where animals move regularly.

The second year the larval tick, now with eight legs repeats the feeding process and in the third year the female mates with a male tick on the final host. The male tick then dies, the female engorges removing about 7 ml of blood before falling off to complete the cycle.

Ticks spread diseases in two ways. Firstly they may be infected from the blood on which they feed transferring the infection between hosts or the infection may pa...