2022-04-27 15:30:00
Processionary caterpillars are the larvae of a moth. They present a risk for human health, but also for animals and vegetation. They usually weave their silken nests high up in the middle of tree branches, but pace parks, gardens and forests in search of food, a good part of the year. At our own risk. How to avoid them? What reactions in case of contact with their stinging hairs? Answers from Professor Marie-Sylvie Doutre, dermatologist at the Bordeaux University Hospital and member of the French Society of Dermatology (SFD).
Pine and oak processionary caterpillars, what are the differences?
These caterpillars live in groups and most often move in processions of several meters (in other words, in single file), hence their name: processionary caterpillars. Their body is covered with stinging and allergenic hairs, until they turn into harmless butterflies (pupation). In France, there are two types of processionary caterpillars:
- THE pine processionary caterpillars (Thaumetopoea pityocampa) ;
- THE oak processionary caterpillars (Thaumetopoea processionea).
Note, when they have just hatched, these caterpillars are orange and not stinging. As the days pass, they become greyish and present a black band on the back, strewn with two kinds of hair : silky white hairs, but also tiny, stinging orange hairs, which develop in the third stage of their transformation. In case of stress, when they feel in danger for example, they can throw thousands into the air.
Both can slow down the growth of the trees they colonize, but their biological cycles differ: while the oak caterpillar stays in the tree waiting to turn into a butterfly, the pine caterpillar burrows into the ground to turn into a chrysalis before spreading its wings.
Processionary caterpillars, recognized as harmful to human health
The oak and pine processionary caterpillars have been recognized as pests since April 27, 2022. A decree published in the Official newspaper (source 1) allowed them to be added to the “list of species whose proliferation is harmful to human health “. Since 2012, 1,300 cases of exposure to these caterpillars have been recorded by poison control centres. A number that is probably underestimated.
Classifying these insects as a “harmful species” will thus allow “the prefects, in each department concerned, to warn the population and to detail the measures to be taken” to protect themselves, explains the coordinator of the processionary caterpillar observatory, Marilou Mottet, at Parisian (source 2).
When are processionary caterpillars dangerous? Where to find them?
Pine processionary caterpillars are present on the southern ¾ of French territory. But their migration front goes back a few kilometers each year towards the north, in particular because of global warming. They are stinging from October to Marchbefore migrating underground to initiate their pupation.
The oak processionary caterpillars are rather present in the northeast quarter of France. Their larvae generally hatch between the months of March and April, before run from May to July, as stinging caterpillars. They then make their nest in the heart of summer, on the strongest branches, to guarantee their safety during their transformation.
Vigilance periods may vary each year, depending on the evolution of temperatures. If winter and autumn were mild, pine caterpillars, for example, will tend to bury themselves earlier underground, specifies Pre Doutre.
Nest of processionary caterpillars: how to recognize it?
Caterpillar nests, also called silk shelters, are easily identifiable. They look like large white balls wedged between the branches. Their cottony look leaves no room for doubt, and we often see silk threads protruding from the nest.
Why are these caterpillars so stinging?
The microhairs present on the back of processionary caterpillars contain an stinging toxin, the thaumetopoeinwhich can lead toallergic reactions in some people and animals (dogs, cats, but also horses and sheep can suffer from necrosis in the tongue).
The problem is that these hairs are very volatile and can be transported over long distances. They cling easily to skin, mucous membranes, clothing, etc. We can therefore develop a reaction without having been in direct contact with the caterpillar in question, explains the dermatologist.
A phenomenon all the more deleterious as these stinging microhairs easily dispersed by sweating, scratching, or through clothing.
How to recognize the buttons of processionary caterpillars?
The caterpillars do not “bite”, strictly speaking. THE ENT, dermatological, ocular and even respiratory symptoms manifest themselves simply in contact with their stinging hairs. These can be inhaled, ingested, or, most often, simply come into contact with the skin and eyes.
Victims usually feel a feeling of itching and burning : “we systematically observe the appearance of red patches on the skin, accompanied by severe itching”, indicates the dermatologist. They can appear immediately, or within eight hours.
Other symptoms may alert
- The development of a conjunctivitis (red, sore, watery eyes) after 1 to 4 hours;
- The development of a allergic rhinitis (runny nose, itchy nose, sneezing, etc.);
- And/or a respiratory tract irritation (mainly when inhaled), which is manifested by sneezing, sore throat, difficulty swallowing and possibly difficulty breathing.
If swallowed – “which is exceptional”, specifies the specialist -, there is an inflammation of the mucous membranes of the mouth and intestines, characterized by hypersalivation, vomiting and abdominal pain.
Allergy to processionary caterpillars: beware of anaphylactic shock
More rarely, contact with a processionary caterpillar can lead to anaphylactic shockcharacterized by :
- Hives;
- Edema in the mouth and throat;
- Of the difficulty in breathing;
- hypotension;
- even a loss of consciousness.
Bite of processionary caterpillars: what to do? How to calm them down?
After a bite, or suspicion of a bite, several actions can relieve the symptoms.
In case of skin contact
- Rinse the affected area with soap and water;
- If in doubt, rinse or brush your hair as well;
- Remove clothing with gloves, wash at high temperatures and tumble dry to remove stinging hair;
- Use adhesive paper to lift the stinging hairs from the skin, a bit like hair removal;
- Carefully avoid rubbing your eyes during the entire process.
What cream to use?
“A cream containing cortisone, combined with antihistamine treatmentwill relieve itching and other allergic symptoms,” says Father Doutre.
In case of eye contact
In case of contact with eyes, it is better go to an ophthalmologist who will be able to properly clean your eyes and extract the stinging hairs that sometimes have lodged there. These can penetrate the cornea and cause ocular discomfort, tearing, conjunctivitis, etc.
Which doctor to consult? When should you go to the emergency room?
Symptoms can be overwhelming, but remain mild most of the time. They may require a visit to a GP, although some antihistamines are available without a prescription. According to a report published by ANSES in June 2020 (source 3), the vast majority of people (96.3%) exposed to processionary caterpillar hairs have developed “low severity” issues. Specialists have observed “high severity” ailments in only 0.2% of cases.
“If the extent of the dermatological lesions is significant, if the victim is an infant or a young child, if the eyes or the respiratory tract are affected, it is better to consult a doctor quickly”, warns the dermatologist.
Go to an emergency department, or contact 15 in the event of serious signs: vomiting, dizziness, loss of consciousness, breathing difficulties, oedema.
Prevention: how to avoid processionary caterpillar bites?
If processionary caterpillars have taken up residence in your garden, or if their concentration is particularly high in the surrounding green spaces, keep in mind that you should not approach them and even less touch them! Several preventive measures have been proven:
- Do not dry clothes outside, especially if it is windy;
- Thoroughly wash fruits and vegetables from your garden and not to consume those who would be near a nest;
- Water the lawn before mowing, so that any hairs are flat on the ground and do not fly away when the mower passes;
- Do not let your children play near an infested tree and at a distance, provide them with protective clothing (even a hat and glasses as well);
- Wear covering clothes when walking in the forest (long sleeves, long pants, closed shoes);
- Avoid rubbing your eyes during and after a ride;
- Shower and change after returning from an expedition to a potentially infested area.
How to get rid of processionary caterpillars?
In case of proven infestation, there are two main treatments to overcome these insects:
- A biological treatment made of Bacillus thuringiensis. It is a bacterium that lives naturally in the soil and gradually poisons the caterpillars that ingest it. ;
- chemical treatment, the diflubenzuron. This insecticide disrupts the moulting process and prevents the proliferation of caterpillars. However, it is not recommended for large scale invasions.
How to get rid of a nest of processionary caterpillars?
There are no official regulations, since the processionary caterpillar is not considered an invasive alien species. It is best to contact your town hall to find out how to proceed, or call professionals directlywhich cut the branches concerned, burn the nests and suck up the residues in complete safety.
How to kill processionary caterpillars on the ground?
To trap the caterpillars on the ground, it is possible to use an Écopiège® : we place a kind of collar around the trunk of the infested tree, under which we fix an outlet tube, associated with a bag. The goal? At the time of the procession, the caterpillars arrive in the collar, follow the route of the tube and land in the bag filled with earth and needles. Then just carefully destroy the bag, and repeat the process every year.
Betting on natural predators
The processionary caterpillar has few natural predators. Installation of birdhouses can however be recommended: tits and cuckoos can consume hundreds of them per day.
THE callosome larvae (species of beetle) are also fond of processionary caterpillars and can easily climb trees to feed on them.
1689853335
#Processionary #Caterpillar #Bites #Symptoms #Risks #Solutions