Walking through fields and woods involves brushing against low vegetation. Sometimes unwanted guests will hitch a ride and become attached to you. They are ticks, blood-sucking parasites related to the mites. They not infrequently fix themselves to dogs and cats as well and can be seen in great profusion on hedgehogs (these poor animals support the greatest range of external parasites of any mammal, including fleas, ticks and mites of various species).
These small, pea-sized, brownish creatures may at first appear wrinkled but before too long they expand to resemble shiny little peas - full of blood. They are found on a wide range of both wild and domestic animals but they will on occasion attach themselves to people, especially if they have bare legs or lay down in the grass. Unfortunately, sheep ticks can transmit Lyme Disease, a potentially serious condition in humans caused by the bacteria Borrelia burgdorfi. Most ticks do not carry the bacteria but in some areas, particularly where there are high populations of wild deer, there is a chance of infection. Fortunately, it is unlikely that a tick will transmit the disease in the first few hours of feeding and, so long as it is properly removed as soon as discovered after being in the field (see below), the chances of catching it are very low. However, the site of tick bites should be checked occasionally after being bitten. The first symptom of the disease is a pink or red rash around the site of the bite that is not normally itchy, raised or painful. If medical attention is sought at this stage, the condition will clear up rapidly with suitable antibiotic treatment. More serious symptoms may develop if the disease is left untreated for longer periods, often because the patient has not realised a tick bit him or her.
Sheep ticks can also carry a disease of sheep called 'louping-ill' as well as diseases of cattle.