Processionary caterpillars: symptoms, bite, what to do?

At spring, THE pine processionary caterpillars are moving in procession towards the ground to bury themselves (this is where we can come into contact with them and where we must therefore open our eyes) while the oak processionary caterpillars begin to hatch. You don’t have to not touch or even approach dare processionary caterpillars because their stinging hairs can cause serious allergic reactions: pimples, itching, edema and even retinal detachments if the hairs come into contact with the eyes. We fear them especially in children And with the animals because they are within reach, on grass and near trees in forest. Processionary caterpillars have been classified as “species harmful to human health” since April 2022. What are the dangers of a sting processionary caterpillar? What to do in case of a nest? Before a ride? What treatment if we are stung?

Definition: what is a processionary caterpillar?

The processionary caterpillar is the larva of a moth. We meet in France two types of processionary caterpillars which each have their biological cycle: the pine processionary caterpillar which is present in fall and winterand the oak processionary caterpillar which is present from spring to summer.

What are the symptoms of a processionary caterpillar bite?

Each caterpillar has volatile microscopic hairs which contain a stinging protein, “thaumetopoein”. These hairs cling easily to the skin and mucous membranes and can cause various reactions in humans:

• Appearance within eight hours of a painful rash with severe itching. Stinging hairs are easily dispersed by sweat, scratching and rubbing or through clothing.
• Appearance of buttons,
• Development after 1 to 4 hours of a conjunctivitis (red, sore, watery eyes).
• Respiratory tract irritation. This irritation manifests as sneezing, sore throat, difficulty swallowing, and possibly difficulty breathing.
• sore throat.

More seriously, contact with the hairs of a processionary caterpillar can lead to anaphylactic shock with:

• urticaria,
• edema in the mouth and throat,
• difficulty in breathing,
• low blood pressure,
• loss of consciousness.

What to do in the event of a processionary caterpillar bite?

In case of skin contact:

• Remove clothing with gloves, wash at high temperatures and tumble dry to get rid of hair.
• Wash affected area with soap and water.
• “We can possibly use sticky paper to unhook the stinging hairs from the skin, a bit like hair removal” indicates theGrand-Est Regional Health Agency.
• To brush hair.
• Consult a doctor to receive antihistamine treatment to calm allergic signs such as itching and the eruption of pimples.

In case of eye contact: rinse the eyes and consult an ophthalmologist who will carry out a meticulous examination to decide on the consequences of the treatment to be administered.

In case of contact with the respiratory tract: consult a doctor who can prescribe the treatments indicated according to the symptoms observed (antihistamines, corticosteroids).

If swallowed: drink a large glass of water, consult a doctor or call 15 directly.

In case of vomitingdizziness and fever, breathing difficulties, oedema, consult the nearest emergency department.

Photo and map of the pine processionary caterpillar

The pine processionary caterpillar (winter) (Thaumetopoea pityocampa): lhe reproductive cycle lasts 1 year. The first caterpillars hatch in October. They leave their nest around March-April and move by clinging to each other, in procession, towards the ground to bury themselves a few centimeters deep and turn into a nymph and then a butterfly during the summer. This is where you can come into contact with them and so you have to keep your eyes peeled!

Photo and map of the oak processionary caterpillar

The oak processionary caterpillar (summer) (Thaumetopoea processionea): eggs hatch around March-April. The caterpillar moves at the end of the day and at night in procession on the leaves to feed. Around the month of June-July, the caterpillars make their nest in the trunk and the strongest branches. This nest will contain the chrysalises which will metamorphose into butterflies in August. The butterflies will then mate, lay eggs and give birth to new ones. stinging caterpillars.

What signs in case of allergy to a processionary caterpillar?

Contact with the hairs of processionary caterpillars can cause physical urticaria called “contact” which is not linked to an immunological mechanism and is therefore not a sign of an “allergy” as such. It can affect all people, whereas the real allergy concerns only those who are “sensitized.” Only certain subjects present a real allergy to stinging hairs.

→ The most affected parts of the body are the uncovered parts: wrists, forearms, back of the hands, spaces between the fingers, face, eyelids, neck.

→ The eyes can be affected : The stinging hairs penetrate the cornea causing ocular discomfort, tearing, conjunctivitis.

→ The attack of the respiratory tract is a more serious sign which imposes a medical consultation. : it can be a small difficulty breathing or more seriously an asthma attack.

Nest of processionary caterpillars : what to do ?

If a nest of processionary caterpillars has settled in your garden, be aware thatdon’t go near it let alone touch them.

• In the presence of a nest of processionary caterpillars, do not seek to destroy it immediately and seek advice from professionals. If you have any doubt, do not shake the branches of the tree and do not stir the ground to make the possible nest fall. Do not eat the fruit that is underneath.
• Do not walk under a tree carrying a nest.
• If you live next to an infested tree: do not dry clothes outside especially if it is windy, carefully wash the fruits and vegetables in the garden, be careful when mowing the lawn.
• Do not let children play near an infested tree and from a distance, provide them with protective clothing (even a hat and goggles as well).
• Thoroughly wash fruits and vegetables from the garden.
• Take care when mowing the lawn.

Prevention advice in case of walks, walks in the forest

• Wear covering clothes when walking in the forest (long sleeves, long pants)
• Avoid rubbing your eyes in case of exposure but also during and after a walk.
• If in doubt about exposure to caterpillar hair, take a shower and change your clothes when you get home.

To destroy processionary caterpillarsThere are several solutions :

• Either destroying their nestfollowing the advice of a professional or calling on a specialist who will destroy the nest for you.
• Either by applying a suitable treatment based on Bacillus thuringiensis to the nesta product available in garden centres.
• Either by introducing its natural predators, thanks to nesting boxes, such as the cuckoo or the tit which feed on processionary caterpillar larvae.

What is the period and season of the processionary caterpillar?

• The pine processionary caterpillar is stinging from October to March.
• The oak processionary caterpillar is stinging from april to june.

Sources:

“Progress in dermato-allergology” in 1999.

Stinging caterpillars, ARS Grand Est, June 2020.

Thanks to Dr Jérôme Langrand, Head of the Paris Poison Control Center CHU Lariboisière-Fernand Widal, for his proofreading.