Health alert as march of toxic caterpillars gathers pace

TOXIC caterpillars that cause severe allergic reactions and asthma attacks are spreading outside London, where the pest has been multiplying in large numbers.

Experts warned the public about the larva of the oak processionary moth, which sheds poisonous hairs that can cause health problems.

The hairs, which are shed when the insect becomes stressed, can cause skin and eye irritations, sore throats and breathing difficulties.

The larva can be identified by its distinctive long white hairs which contrast markedly with other shorter hairs and the fact it mainly lives on oak trees, on which it feeds. Unlike other caterpillars, it is not found on fences, walls or similar structures.

It was accidentally brought into the UK in 2005 from southern Europe, almost certainly as eggs on live oak plants imported from the Continent.

Dr Glynn Percival, from the Bartlett Tree Research Lab, told the BBC: “There really has been intensive management regimes put in place, but it is still spreading on an annual basis. It has now spread beyond the M25, it is just going to spread further and further.”

Officials have treated oak trees in Richmond, west London, where there is a large concentration of caterpillars, but this has not quelled the population’s rise. People have been warned not to touch the caterpillars, but if they accidentally do and start to suffer a severe allergic reaction, they should go to hospital or contact their doctor.

The caterpillars are a threat to oak trees, as they feed on the leaves and can strip trees bare, which makes them weakened and vulnerable to other threats.