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article imageHealth warnings after toxic caterpillar outbreak in London

By Karen Graham     Apr 29, 2018 in Science
London - The British Forestry Commission is warning London residents to beware white-haired caterpillars, the larvae of the oak processional moth (OPM). The hairs on the caterpillars contain a toxic protein that can make humans and pets very ill.
The outbreak of the toxic caterpillars can cause vomiting, asthma attacks, and skin rashes. People are being warned to not touch or approach nests or caterpillars, or let children touch or approach nests or caterpillars. The warning includes pets and livestock.
The Forestry Commission is reporting the biggest infestations of OPM were recorded in Greater London, stemming from Kingston upon Thames to Brent, with some infestations found in Bracknell Forest, Slough and Guildford, reports the BBC.
The OPM caterpillars were first spotted emerging from egg plaques in mid-April, and the agency began treating the infested oak trees with an approved biopesticide around April 23, 2018. This type of treatment will continue to around late May or early June.
Thaumetopoea processionea in procession around an oak tree.
Thaumetopoea processionea in procession around an oak tree.
The caterpillars can make you violently ill
One gardener was clearing some overgrown weeds in a lot and didn't notice the oak tree above her was infested with the OPM caterpillars. She ended up "suffering severely" after coming into contact with the species.
"My first symptom was a rash on my tummy. I was unaware of what it was and thought at first it was a heat rash," she said. "During this time I had spells of feeling violently sick. I thought I might have shingles."
"I contacted my doctor and it was confirmed I had been severely affected by OPM and must keep away from the source as over time I had developed a severe allergic reaction."
Typical uritcaria rash from OPM.
Typical uritcaria rash from OPM.
UK Forestry Commission
The oak processional moth
As its name implies, the oak processionary (Thaumetopoea processionea) is a moth whose caterpillars can be found in oak forests. They are widely distributed in central and southern Europe but have been found as far north as Sweden.
They get their name from the unusual way the creatures move about the oak trees - in distinctive nose-to-tail processions, and the fact that they live and feed almost exclusively on oak trees. They can sometimes be seen in processional lines across the ground between oak trees, and clustering together as they feed on oak leaves.
In the southern countries of Europe, the OPM populations are controlled by natural predators, but these predators do not exist in northern Europe. The expansion of the OPM caterpillars is possibly due to global warming. Years ago, if OPM larvae were brought in on imported oak, the climate was such that they could not survive in northern climes.
An egg plaque on an oak tree. The caterpillars emerge in mid-April.
An egg plaque on an oak tree. The caterpillars emerge in mid-April.
UK Forestry Commission
OPM was first accidentally introduced into Britain in 2005, almost certainly as eggs which had been laid on live oak plants imported from continental Europe. Since that time, the range of the species in the UK has been steadily expanding despite efforts to eradicate it.
The moths pose an increasing threat to humans as their range is extended. The backs of the caterpillars can be covered with up to 63,000 pointed defensive bristles containing an urticating toxin (thaumetopoein. The setae break off easily and become airborne.
Transmission of urticaria from the toxic hairs can be airborne, by ground contact via plants or grass or even by water contact in still water like garden ponds. The toxicity of the hairs remains active beyond the normal life cycle of the moth and in some cases could remain a problem for several seasons
More about london UK, Oak processional, toxic caterpillars, Infestation, Health warning
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