Case 36: Tick bite
Monday, November 7th, 2011
A 68 year old female attended A&E with a letter from a GP. This referred to a tick attached behind the knee, asked for it to be removed, and assessment for Lyme Disease to be undertaken. The patient had been on a long walk in the Kent countryside three days earlier.
1. How should ticks be removed?
Click to see the answerThe mouthparts of ticks are barbed, so can easily be left behind in the skin, to become a source of infection. If the tick is pulled by the body, then the head and mouthparts may separate off. So the mouthparts need to be grasped close to the skin, fine forceps are ideal, with a good light and magnification (eg from an otoscope) . It is not clear whether twisting, or gradual traction are best – strong views are held on both options. However it is likely that simple traction is adequate, and that this will cause the tick to release its grasp.
2. Is Lyme disease a real risk?
Click to see the answerThere are a large number of different tick species across the UK, the majority of which do not transmit Lyme Disease. See Link. However several types can, and are not fussy what they bite. The commonest tick to bite humans in the UK is the Sheep Tick, a species of Ixodid ‘hard’ tick, which can transmit Lyme Disease. Although at one time Lyme Disease was considered a risk only around the New Forest, it is now known to occur more widely, particularly in areas where deer are found. So many areas of the UK are at risk, although around 50% of cases arise in Southern England. The tick waits on the tip of a blade of grass, and attaches to passing animals or clothing.
3. What is Lyme Disease, and how can you assess the risk in this patient?
Click to see the answerLyme Disease is caused by a spirochaete, Borrelia burgdorferi. About 1,500 laboratory diagnoses of this condition are made in the UK each year, and the incidence has been increasing. It starts as a expanding raised red rash around the bite site, after an incubation of 3 to 30 days. Other symptoms vary widely but generally include feeling unwell, flu-like, with muscular aches and pains. If untreated chronic problems may develop, including cardiac conduction disorders, skin atrophy, joint swelling and neurological complications. Neurological complications can be subtle, like those of neurosyphilis, another spirochaete. See Link. Diagnosis can be difficult, and is clinical in the early stages. Serology can help later. A number of antibiotics are effective, including doxycycline.