PICTURE THIS: Bull’s eye! A bizarre effect of a tick bite

THIS impressive ‘bull’s eye’ rash was caused by a tiny tick. The patient remembers brushing a bug off his leg, and a few days later woke up to this dramatic reaction.

The cause? Lyme disease, one of the fastest-growing infections in the Western world. It occurs after a bite from a tick carrying the Borrelia burgdorferi bacteria. Symptoms include fatigue, headaches and a temperature.

One of the classic early signs is this rash. It appears in roughly 65 per cent of cases between three and 30 days after the bite. But you may not have noticed the tick itself, says Dr Sandra Pearson, medical director of the charity Lyme Disease Action.

‘They can be very small, even as small as a poppy seed, and difficult to spot if there is a lot of hair on the leg — as in this case.’ Dr Pearson adds that a tick can remain attached for five days, partly due to a cement-like substance it injects.

And they don’t strike only in the countryside. ‘Ticks can be found in urban parks and gardens — even in Central London,’ she says.

The image here was posted on Figure 1, a website where doctors around the world share medical snaps and canvass colleagues’ opinions.

The rash is the result of an immune response to the bacteria. ‘People bitten by ticks in the U.S. — as in this case — may have a more florid rash, possibly due to a different species of bacteria,’ says Dr Pearson

Diagnosis is a problem because only one in three patients recalls being bitten by a tick — and not everyone gets a rash, or at least not one as dramatic as this (sometimes it’s paler or bruise-like).

This means people with other common symptoms of Lyme disease — fever and joint pain — may have no idea they are due to a tick bite. Experts advise seeking medical help immediately if you suspect Lyme disease because if left undiagnosed, the long- term effects can be crippling — in 25 per cent of cases, the nervous system is affected, causing numbness and memory problems.

There is a blood test for Lyme disease, but it’s not always accurate. ‘Unfortunately, early in the infection these tests may be negative, as antibodies may take weeks to develop,’ says Dr Pearson. And even after the infection has developed the tests may not pick it up.

But treated at an early stage, a 14 to 21-day course of antibiotics is effective ‘in most cases’, she adds.