Pine Processionary Caterpillars: Risks, Symptoms, and What to Do

Pine processionary caterpillars are dangerous for dogs and cats. Learn how to recognise the symptoms of contact, what to do in an emergency, and how to protect your pet.

Lagartas do Pinheiro: Riscos, Sintomas e o Que Fazer

The pine processionary caterpillar is one of the most underestimated dangers for dogs and cats in Portugal. Contact with these insects can cause severe reactions within minutes, especially when many pet owners do not know how to recognize the warning signs.

With the arrival of good weather, walks and nature trails become increasingly common. Walks in wooded areas with pine trees can expose our animals to the pine processionary caterpillar (Thaumetopoea pityocampa), which is responsible for severe allergic reactions and, in extreme cases, tissue loss or fatal complications. In this article, we explain everything you need to know to protect your animal.

What is the pine processionary caterpillar?

The pine processionary caterpillar is the larval stage of a moth common in Mediterranean countries. They are easily identified by the white silk nests they form in the treetops during winter, and by the single-file processions they make on the ground looking for soil to burrow into.

The danger lies in the urticating hairs covering the caterpillar's body. These microscopic hairs release a protein called thaumetopoein, which is highly irritating to the skin, mucous membranes, and eyes, in both humans and animals.

Attention: Urticating hairs can be released into the air even without direct contact with the caterpillar. A dog sniffing the ground near a procession can inhale the hairs and suffer a severe reaction.

Symptoms of contact in dogs and cats

Symptoms appear quickly after contact, often within 30 minutes. The tongue is often the most affected organ in dogs, due to their tendency to sniff and lick everything they find on the ground.

👅Tongue inflammation
Severe swelling of the tongue and lips, which can make breathing and swallowing difficult.
🤤Excessive salivation
Intense and sudden hypersalivation, often one of the first visible signs.
🤢Vomiting and nausea
The animal may vomit and show signs of general malaise and agitation.
👁️Eye irritation
Red eyes, tearing, and even conjunctivitis or corneal lesions.
🫁Respiratory distress
In severe cases, swelling can compress the airways and make breathing difficult.
🩹Tissue necrosis
In prolonged and intense contact, tissue death may occur on the tongue, which may require partial amputation.

What to do if my pet comes into contact with the pine processionary caterpillar?

Prompt action is crucial. Follow these steps while heading to the vet:

Do not touch the caterpillar with unprotected hands: the urticating hairs also affect humans. Use gloves or a cloth.

Wash the mouth and affected area with plenty of water: do so carefully to avoid spreading the hairs to other areas.

Do not let the animal lick the affected area: instinctive behavior can worsen the reaction.

Go to the vet: even if the symptoms seem mild, the situation can deteriorate rapidly.

Do not administer medication without veterinary guidance: human antihistamines can be toxic to certain animals. 

How to prevent contact with pine processionary caterpillars

Prevention is the best protection. Adopt these measures during the months of greatest risk, from November to April in Portugal.

  1. Avoid walking in areas with pine trees during the processionary period (early morning and late afternoon).
  2. Keep your dog on a leash in wooded areas to control what it sniffs and touches.
  3. Identify white silk nests in the pine treetops and avoid those areas.
  4. After walks in risky areas, observe the animal's behavior for 30 to 60 minutes.
  5. Alert other pet owners: especially in parks and gardens where there are pine trees.
Highest risk season in Portugal: January to April. Processions mainly occur during the warmest hours of the day on sunny days.

Frequently asked questions

Are pine processionary caterpillars dangerous to humans?
Yes. Contact with the urticating hairs can cause skin rashes, eye irritation, and allergic reactions in people. Children and people with allergies are especially vulnerable.
Are cats also at risk?
Yes, although cases in cats are less frequent than in dogs, as cats tend to be more cautious about what they sniff and touch. However, the risk exists, and the symptoms are similar.
Can my animal have sequelae?
It depends on the severity and rapidity of treatment. In cases treated promptly, recovery is usually complete. In severe cases with tongue necrosis, surgery may be necessary, and the animal may have permanent sequelae.
Is it possible to find pine processionary caterpillars in urban gardens?
Yes. Any area with pine trees, including urban parks, gardens, and tree-lined avenues, can be a habitat for the pine processionary caterpillar.

Conclusion

The pine processionary caterpillar is a real and present danger in Portugal. Knowing the risks, recognizing the symptoms, and knowing how to act quickly can save your animal's life. Be vigilant during walks, keep your dog on a leash in risky areas, and do not hesitate to go to the vet at the first sign of contact.


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