Map shows everywhere OPM caterpillars are in Essex

However, humans are not the only ones.

Oak Processionary Moth (OPM) caterpillars are typically seen from May to July and this toxic caterpillar can be bad news for both animals and humans.

It's important to note these caterpillars may be spotted outside of this time frame and you should keep away from them at all times.

What is an oak processionary moth caterpillar?

OPM caterpillars are a species of moth and their caterpillars are found during the spring in nests on oak trees.

These caterpillars have a grey body, black head and long white hairs which are more noticeable than the shorter ones.

The name comes from the way they move around together in a procession.

They’ll sit together on a branch or inside a tree trunk and create a white, silk-like nest.

Jim Yiangou spotted the moths on his way back from Heybridge in 2021 (Image: Jim Yiangou)

The OPM was first accidentally introduced to England in 2005 and is subject to a government-led programme of survey and control to minimise its population, spread and impacts.

What makes it toxic?

It’s the hairs on these creatures which cause irritation as they contain a substance called thaumetopoein which can be harmful to animals and humans.

You might not have to touch a caterpillar to come into contact with its hairs though as they can become detached and blow about on a windy day.

When travelling from oak tree to oak tree, they walk along the ground in a procession.

Cats are at risk of coming across these caterpillars because they often run up into trees while dogs may meet the caterpillars during one of their processions along the ground.

The hairs can easily stick to a dog’s face or paws when they’re out and about.

What happens if humans or pets come into contact?

Your dog or cat may have the following symptoms if they have sniffed, touched, licked, picked up or tried to eat a caterpillar or its nest:

• Excessive drooling
• Swollen tongue
• Conjunctivitis
• Gagging
• Vomiting
• Difficulty breathing
• Inflamed or swollen mouth

OPM caterpillars are often spotted on or in oak trees but they also move between trees by walking along the ground (Image: Canva)

You should call your vet for advice if your pet has come into contact with an OPM caterpillar and is suffering any of the above symptoms or is uncomfortable.

Keep an eye on your pet for a couple of days even though serious allergic reactions are rare.

No vaccine or spot-on treatment exists for these toxic caterpillars but you should try to keep your dog or cat away from them and any nests if you see them before it’s too late.

Try calling them so they come back to you and hopefully avoid running into trouble.

If your dog has an OPM caterpillar attached to its coat and you need to remove it, don’t touch it with bare hands.

Blue Cross suggests wearing rubber gloves or using a thick pile of tissues to make sure you can keep away from hairs of the caterpillar.

What happens if humans touch an OPM caterpillar?

Humans who come into contact with an OPM caterpillar could get a rash or experience breathing difficulties.

They might also get sore, itchy or irritated eyes and throat.

For humans, the symptoms are usually not medically serious and are likely to pass in a few days but you should speak to a pharmacist who can help you with relief of the symptoms.

While serious allergic reactions are rare, you should speak to a doctor if you experience them.

Where can they be found?

A map by the Forestry Commission shows everywhere in Essex they may be found.

They are mostly around the London area in what is called an “established area”, however are also found in a “buffer zone”, which covers parts of Essex.

Basildon, Billericay and Wickford find themselves in a hotspot, with registered infested oak trees found all over the towns.

Elsewhere in Essex, infested oaks have been recorded in Southend, Chelmsford, Maldon and Braintree areas.

Jim Yiangou spotted the moths on his way back from Heybridge (Image: Jim Yiangou)

They have been previously spotted in Frinton and also in Heybridge.

The map also shows an infected oak near to Colchester.

To view the full map, visit HERE.

Residents are advised to report sightings to by emailing opm@forestrycommission.gov.uk or calling 0300 067 4442.

For more information, visit HERE.