Medical Information Cards N°06.Envenomation by the pine processionary caterpillars

The pine processionary caterpillar (thaumetopoea pityocampa) is an insect responsible for envenomations in our domestic carnivores.

It is found in regions with a climate favorable to their development (they are found mainly on the Mediterranean coast, in Corsica and on the Atlantic coast) and rich in thorns (the larvae feed on needles of various kinds of pines).

The dog is more concerned about these envenomations because he is less suspicious than the cat and places all kinds of objects in his mouth.


¤ Envenomation occurs mostly in late winter and early spring: the caterpillars then descend from the pines and move to the ground in single file before burying to make a cocoon and turn into pupae.

¤ The dog comes into contact with the toxin:

- either directly: the dog licks a caterpillar and thus breaks the stinging hairs it carries on the back, releasing the toxin (thaumatopoein) that they contain

- or indirectly: by contact with a nest fallen to the ground or by simple inhalation of hairs carried in the air during high winds.


The symptoms of envenomation result from the inoculation of the venom contained in the stinging hairs through the skin or mucous membranes of the animal concerned.
Thaumatopoein may be responsible for local lesions (at the area of ​​contact between the stinging hairs and the skin or mucous membranes of the animal) but also of general symptoms.

¤ Local lesions

- Eye injuries: when contact between the stinging hairs and the eyes, conjunctivitis or corneal ulcers may appear. An ophthalmological examination must therefore be carried out in the face of any suspicion of envenomation by the processional caterpillars.

- Cutaneous lesions: Thaumatopoein can cause significant skin lesions, especially around the lips and in all areas where the skin is thin.

- Buccal and digestive lesions: A few minutes to a few hours after a contact between a caterpillar and the mouth of the animal, a very important inflammation appears. The dog suffers from itching, it can no longer swallow and begins to salivate enormously. His face swells as well as his tongue that gradually bluish. Ulcers can then develop. A few days after the envenomation, the part of the tongue that has been in contact with the stinging hairs may die: the affected area will darken and then detach from the healthy part. These lesions are all the more marked as the area of ​​contact between the stinging hairs and the mucous membranes has been significant.
If caterpillars have been swallowed, inflammation will also affect the esophagus and stomach of the animal. Vomiting may occur.

¤ General disorders

To these local symptoms may be added general disorders linked to a direct action of thaumatopoein on the major functions of the organism or resulting from the local lesions.

- The animal is very often feverish (hyperthermia at 40 °)
- Swelling of the tongue and throat may cause severe respiratory distress.
- Bleeding disorders are sometimes noted with the appearance of a very high hemorrhagic risk.
- Envenomation can cause kidney failure
- Finally, an allergic shock can occur as well as convulsions or coma.

The various complications associated with envenomation may lead to the death of the animal.

The life prognosis depends on two factors:

- The speed of intervention after the envenomation to fight the general repercussions: oxygenation in case of respiratory distress, fight against the renal insufficiency, treatment of the disorders of coagulation ...

- The severity of the local lesions (which can only be evaluated after a few days). Indeed, in case of important contact with the toxin, some animals lose a large part of their tongue, which makes any food intake very difficult.


As we have just mentioned, the speed of intervention and the implementation of a treatment will play a big role in the prognosis.

If you suspect that your pet has touched processional caterpillars, it is better not to manipulate it: the stinging hairs of the processionary caterpillars behave like tiny harpoons that are planted in the mucous membranes. Any friction will increase the release of thaumatopoein, aggravating the symptoms.
Avoid any contact of your skin with the stinging hairs because the toxin also causes cutaneous lesions in humans.

You should go as soon as possible to your veterinarian where various treatments will be made according to the symptoms.
- Emergency is the oxygenation of the animal in case of edema of the throat to avoid choking
- The veterinarian will then rinse the dog's mouth with a solution adapted to eliminate without breaking as much stinging hairs and the toxin they contain (limiting the local lesions and the general repercussions by reducing the passage of the toxin in the blood).
- An injection of cortisone is practiced by the veterinarian to fight edema and inflammation
- A suitable treatment is in place to treat any kidney or hemorrhagic disorders.
- The administration of antacid and gastrointestinal dressings helps to limit the digestive disorders associated with the ingestion of a caterpillar.
- If the animal is unable to feed after a long time (because of a mechanical discomfort linked to the edema of the tongue or a very important pain ...), the veterinarian may, if he judges Necessary, decide to put in place a replenishment probe.


Prevention of contact with the pine processionary caterpillars is essential since there is no active antitoxin against thaumatopoein.

In addition, humans are also susceptible to envenomation. Contact with the toxin occurs:

Either directly (inhalation of the hair, ingestion of a caterpillar by a child),

Or indirectly (contact with remains of stinging spines when caring for an affected dog).

Itching and patches such as stinging of nettles appear at the areas of contact with the stinging hairs (hands most often). Allergic shocks have also been described in humans.

The prevention of envenomation is carried out at several levels:

- By the destruction of the eggs:
During summer, egg-sleeve-carrying needles can be removed.

- By the destruction of the larvae:
In the areas concerned, the municipality generally carries out an annual treatment to limit the progression of these butterflies.

Biological control is preferred: a bacterium (Bacillus thuringiensis) is sprayed on the trees in late summer / early autumn. This bacterium produces a lethal toxin for the early larval stages of the future butterfly.

The following larval stages (L4 and L5) in late autumn and early winter can be eliminated by the spraying of certain chemicals, but their use must be limited because these molecules are toxic to the environment.

Cocoons can also be collected and incinerated (in this case, wearing protective clothing (gloves, goggles) is essential to limit the risk of irritation by stinging hairs)

Finally, in early spring, the caterpillars can be trapped on the trunks with glu before they descend to the ground and the caterpillar processions marked on the ground are destroyed (always with wearing protective clothing) But these latter methods are much more tedious and unpredictable.

- By respecting certain precautions:
In risky areas (coniferous soils), during the critical period of the spring, vigilance must be increased and animal walks only on a leash to avoid contact with caterpillars or remnants of moult.

Despite the implementation of these various means of control, the total elimination of the caterpillars remains very difficult because of the mobility of butterflies capable of moving for miles before laying and the possibility of underground survival of buried forms for several years .

Envenomations by processional caterpillars are relatively frequent. It is therefore advisable in the areas concerned to be particularly vigilant at the end of winter and early spring when walking near conifers or strolling through pine forests.
If you suspect that your pet may have been in contact with processional caterpillars, immediately consult your veterinarian so that he can limit the effects of envenomation as soon as possible.