Experts are warning that a walk in the countryside could end up being a health hazard.

The Health Protection Agency says cases of Lyme disease are on the rise and areas such as the South Downs and parts of West Sussex are particularly at risk.

The disease is transmitted through tick bites which are more common at this time of year.

More people are expected to be out and about in the warmer weather over the Easter weekend and following week, leading to a greater risk of being bitten.

The tiny spider-like insects are found in most parts of the Downs, forests and heathland areas around Sussex and the rest of the South East.

Most Lyme disease cases reported in the UK are acquired in this country rather than overseas, often through activities such as walking, trekking and mountain-biking.

A spokeswoman for the HPA in Sussex and Surrey said: “It's important that people take preventive measures against tick bites and also look out for ticks after visiting affected areas.

“Ticks that can transmit Lyme disease are very small – about the size of a poppy seed – and can easily be overlooked, so it is important to check regularly for attached ticks on the skin.

“Most ticks do not carry the infection but if one is found it should be removed promptly, as infected ticks are unlikely to transmit the organism if they are removed in the early stages of attachment.

“Ticks can be removed with tweezers or special tick hooks, pulling gently upwards away from the skin.

“People who develop a rash or other symptoms after a tick bite should consult their GP.”