Thaumetopoea pityocampa as common pruritus


Although it is an important allergen, Thaumetopoea pityocampa, which is common in our country, is not well known by physicians. Especially for our country, March-June is the period when itching due to pine processionary beetle can be seen. Based on this, we examined the biology of the pinewood beetle and the disease it causes.

Key words: pine louse beetle, pine locust beetle, airborne allergy-related dermatosis, thaumetopoein.

Thaumetopoea pityocampa, a member of the Lepidoptera family, is an important forest pest and a source of allergenicity that can lead to angioedema for humans and animals.

Geographical Distribution:

It occurs in Central and Southern Europe, the Middle East (north of Palestine), North Africa (especially Algeria). In Turkey, it is available in the Marmara, Aegean, Mediterranean and Black Sea regions.(1)


The generation period of T. pityocampa is one year. Biological periods during this period;

Adult (butterfly) period:
Its wings are ashen-colored, there are transverse zigzag stripes on the fore wings, the hind wings are white with a gray spot on each side, the wingspan is up to 4 cm. At the end of the female’s abdomen are hairs that serve to cover the egg cob. (pic 1)

Egg period: The hands are arranged in a spiral pattern and are covered with scales. Each cob usually contains between 100-300 eggs.

Larval (caterpillar) period:
It has a color ranging from blue to black and has a lot of hair on it, the hairs on the side are silvery white, the ones on the back are yellow and brown. (pictures 2 and 3)

Pupal (chrysalis) period: It is found in the soil, the cocoons are blackish brown. The insect spends the first three of these four periods outside the soil and the last one in the soil.

The larval (caterpillar) period, which is medically important, is the longest period of life of T. pityocampa. It lasts from autumn to the beginning of summer, depending on the ecological conditions of the region. Unlike many other Lepidopterans, the larval stage of this butterfly coincides with the winter months. In order to protect themselves from the winter cold, the caterpillars live in colonies and take shelter in a pouch-shaped nest that they weave from a secreted silky substance. (picture 4) The sacs of caterpillars in the first and second larval stages are sparsely textured and small, and they are often not noticed. The caterpillars in this period migrate en masse and look for new feeding places on the tree. After the third larval stage, they make the first big nest, but this nest is also temporary. In the fourth larval stage, they usually make their wintering nest on the top shoots or in a suitable shoot in the sun-drenched direction of the tree. This nest has features that can protect the fifth instar larvae.

The larvae pass through 5 stages until they become pupae, hairs with itchy properties are formed in the third larval period. Wintering takes place in the 4th and 5th larval stages. (one)
The sacs that the caterpillars knit as a nest serve as a solar heater in winter, especially on sunny days. For this reason, branches and shoots that see the sun well are selected to build winter nests. Top shoots and shoots on the south-facing side of the tree are preferred for winter scrubs in Turkey. The pine processionary caterpillar period of the pine processionary caterpillar ends with the caterpillars leaving the sacs in the spring and entering the soil in trains to enter the pupa stage, depending on the geographical location of the pest, the latitude and the climatic conditions of that place.

The larvae, which have completed their development, leave the trees they feed on as trains from the end of March and descend to the soil. The caterpillars, which leave the sacs to enter the soil, move forward in single rows. (1) The number of caterpillars in motion can be a few or hundreds.

Allergenicity of T. Pityocampa:

48 out of 63 people who attended an all-day training meeting under the pines in the open area on the first weekend of May applied to us with complaints of itching on Monday. At first we thought that the situation might be a food poisoning, but when the patients stated that there were many caterpillars in their environment, when we went to see the place where the meeting was held, we observed many caterpillars and pine sacs on the pines. Another patient of ours said that there were many caterpillars under a pine tree where they sat for a picnic with their family, and all of them had itching half an hour after they sat down. Two weeks later, one of our patients, who went to a picnic and stayed in an environment with plenty of caterpillars, presented with complaints of severe conjunctivitis and a widespread rash on his face. Another patient of ours reported that itching appeared in all children who went under the pine tree near their home, and they found the salvation by cutting the tree. In addition, we witnessed many people who had itching after going to the pine groves in May and June. While it is possible to reach thousands of articles from the forestry community about T. pityocampa in our literature review, there are also a limited number of medical articles. We have come to the conclusion that our medical community is unfamiliar with the subject, in classical dermatology books and on the internet.

Pine beetle T. pityocampa is an insect of medical importance. The hairs on the back of the caterpillar during the larval stage may cause an itching reaction as well as ocular problems such as temporary blindness and even anaphylactic reactions. (2,3) It is important to know that the reactions seen in humans can also be seen in animals (4) and to be knowledgeable about the life cycle, population and ecological status of the insect in order to prevent possible morbidity. (2)
The disease caused by T. pityocampa is an HTAD (airborne) dermatosis caused by airborne agents (5). When HTAD is mentioned, it is understood that all skin reactions caused by chemicals and numerous other agents mixed with the air and carried by air. In order for a dermatosis to be called HTAD, it is important to evaluate the patient’s history, clinical appearance of the lesions, the presence of a volatile agent that is encountered incidentally or unintentionally, during occupational or hobby activities, and the evaluation of the epicutaneous test results.(6)

Symptomatology due to T. pityocampa occurs by two mechanisms; In mechanical phenomena, there is penetration of hairs, while in chemical phenomena there is the release of toxic substances. (7)
It has been shown that a substance separated from the hair of the caterpillar probably causes a reaction by directly affecting the mast cells with the mediators released from the mast cells.

The allergen fraction, which can be separated from the caterpillar’s hair by various electrophoretic and immuno-electrophoretic techniques, is a soluble protein. These proteins are also seen in the cuticle and hemolymph. This protein, which weighs 28,000 doltons, consists of subunits of 13,000 and 15,000 daltons. This itchy protein thaumetopoein ” and was found abundantly in the glands of caterpillar hairs. (8)

T. pityocampa is also common in our country, which is a Mediterranean country. T. pityocampa, which is an important forest pest and can cause drying of trees, can cause serious allergic reactions in humans and animals during the larval period. Its threat to human health is limited only to the larval period. Although the feathers showing allergenicity in the larval period, which is divided into 5 sub-stages, show the most pathogenicity especially in the L3 period, the feathers in the L4 and L5 periods may also show pathogenicity.(1,7)

Considering that the larval period is affected by geographical and climatic conditions, the health-threatening period is March – June, and itching can be seen as an epidemic during this period.

Diagnosis Treatment and Prevention

A detailed anamnesis of the patient must be taken for diagnosis. The season is important when taking anamnesis. The place where the person lives, his job, his hobbies, whether he goes to a pine place, whether he sees pine grouse in pine trees and caterpillars on the ground should be questioned. The whole body of the patient, especially the exposed parts such as hands, face, arms and neck, should be thoroughly examined in a well-lit environment. Forest workers, forest villagers, picnickers and those who have taken a walk in the forest area should be carefully questioned and examined.
It is thought that caterpillar hairs cause contact urticaria by a nonimmunological mechanism. Specific IgE tests by prick test and immunoblotting were performed in 16 suspected patients: prick test against caterpillar extract was positive in 87% of the patients. Angioedema was observed in 79% of the patients, conjunctivitis in 36%, and anaphylaxis in 14% of the patients together with urticaria. The locations of the lesions are 100% in the neck, 93% in the forearm, angioedema is common and mostly seen in the eyelids in 79%.(5)

In the itchy areas of the patient, there may be linear nail marks or even bleeding due to severe itching. There may be redness of the eye conjunctiva and edema of the eyelids. The most important element for diagnosis is detailed anamnesis and examination. If the months are March, April, May, June; If there are pine sacs on the pine trees in the region, if the person who comes with itching is a forest villager, forest worker or has gone to the forest area for a picnic or trip, it would be a right decision to consider T. pityocampa as a factor in the patients.

Local and systemic antihistamines are sufficient for treatment. In severe cases, if there are no contraindications, complaints can be controlled with a few doses of parenteral corticosteroids. With treatment, the symptoms disappear within a few days.

Presence of pollen and feathers and reserve and meteorological conditions in the region are important for protection. T. pityocampa is a serious forest pest. It is followed closely by the forestry community, especially since it causes significant yield loss and drying of pine trees, and it is tried to be destroyed by various methods of struggle. Sometimes an epidemic envelops the forests and it is necessary to continue the struggle for several years. (1) As a matter of fact, the cases that were common in Bursa in 2003 were also the result of such an epidemic.

If necessary, information should be obtained from the Regional Directorate of Forestry about the pinewood beetle population, and people should not be allowed to enter the epidemic areas. In March-June, it should be avoided to go to places where there are pine roaches, and if you do, clothing that exposes the body should be avoided.


  1. Özay F, Pineapple Beetle and its Control Methods,
  2. Soltz I, Mendel Z. The pine processionary caterpillar Thaumetopoea pityocampa. Harefuah. 2002 Sep;141(9):810-4, 857. Hebrew
  3. Vega JM, Moneo I, Armentia A, Fernandez A, Vega J, De La Fuente R, Sanchez P, Sanchis ME. Allergy to the pine processionary caterpillar (Thaumetopoea pityocampa). Clin Exp Allergy. 1999 Oct;29(10):1418-23
  4. Lamy M, Vincendeau P, Ducombs G, Pastueaud MH. Irritating substance extracted from Thaumetopoea pityocampa caterpillar; mechanism of action. Experientia 1983 Mar 15;39(3):299
  5. Vega JM, Moneo I, Armentia A, Vega J, De La Fuente R, Fernandez A.Contact Dermatitis. 2000 Sep;43(3) 129-32
  • Taşkapan O, Harmanyeri Y. Dermatoses caused by airborne agents. Turkderm 2001;35:(2)91-98
  • Ducombs G, Lamy M, Bergaud JJ, Tamisier JM, Gervais C, Texier L. Thaumetopoea pityocampa caterpillar and man. Morphology of its venom apparatus. epidemiological investigation. Ann Dermato Venerol. 1979 Oct;106(10);769-78
  • Lamy M, Pasturreaud MH, Ducombs G. Thametopoein, an urticating protein of processionary hairs of the caterpillar (Thaumetopoea pityocampa Schiff) (Lepidoptera, Thaumetopodeidae) CR Acad Sci Ш. 1985;301(5): 173-6

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