13,836 nests. That is the number of bags of pine processionary moths that have been removed from Madrid parks since the beginning of 2023, as confirmed by the City Council itself. If the number is impressive, it is even more so by providing an important piece of information: in each of these nests there may be between 100 and 200 specimens. That is, approximately between 1.4 and 2.7 million. The good news? This year the figure is almost 79% less than that of 2022, when 65,000 bags were withdrawn in Madrid. That is, between 6.5 and 13 million caterpillars.
The pine processionary moth is considered the most important defoliating insect in Spanish pine forests and, furthermore, an important public health problem. The reason is simple: when these caterpillars, between 25 and 40 millimeters in length, come down to earth, after spending the winter in their nest feeding on the pine tree they inhabit, they have thousands of stinging hairs that they can release if something gets close to them and bothers them. . And that something is usually a child or a dog (cats are usually more cautious). The effects in minors translate into hives and dermatitis, while in animals it can cause death if ingested.
The habitat that favors the processionary: mild temperatures and extensive pine forests
The risk of encountering these characteristic animals that circulate in rigorous single file used to start in March, with the end of winter, but climate change is bringing their arrival forward. “We have observed that the cases come earlier, before they appeared already in the spring, they began more or less in March, and the definitive hatching in April. But, for some time now, we are seeing cases of processionary moths in winter,” says Ignacio Molina Angulo, veterinarian and professor at AEVA Veterinary Training. This year, according to the Catalan platform Alerta Forestal, in the first weeks of 2023 there have been observations of processions of this caterpillar in eight Catalan regions.
“In general terms, the processionary is being favored by the increase in temperatures, particularly in winter,” explains José A. Hódar, doctor and professor of Ecology at the University of Granada, who defines the best conditions for the processionary to thrive: “Food availability (pines), low specific and structural diversity in plant formation, and (relatively) mild temperatures during winter.” Climate change is helping, but the increase in artificial pine forests is another fundamental aspect. “Although pines are known species in almost all the habitats of the peninsula, human activity has increased their relative importance in plant formations, coming to constitute the dominant species,” argues Hódar. Spain is plagued with places where the pine should be a companion species to holm oaks, oaks, gall oaks, cork oaks, maples and beeches, instead of dense, closed and almost monospecific plantations of pines, the ideal home of the processionary moth. “There are, of course, pine forests that can be considered natural, but they are a minority,” says the professor.
How to avoid contact with the processionary
Those pine forests are precisely the ones that any dog guardian should avoid between February and May to avoid scares. “And if they go out through these areas, it is very important that the dogs are on a leash and not let them run loose, because they are very curious and the first thing they are going to do is approach the processions of the caterpillars,” warns Molina.
They know a lot about this curiosity at Weimaraner Rescue, an association dedicated to rescuing and adopting pointers, a breed of dog with an important tracking instinct, which makes them especially vulnerable to running into this caterpillar. “We had the case of two dogs that were up for adoption and had contact with the processionary. Both suffered necrosis in the tongue, so the affected piece had to be cut out,” explains Goiuri Cerezo, one of the five volunteers that make up this entity, which since it was born in 2019 has managed 336 adoptions, 17 so far this year. . The risk is usually higher in this type of breed and also in puppies, who are more curious and tend to eat everything they find, although not only. “They do not always have to interact directly with them, go smell them or bite them, it can also happen, and this is usually the most common, that they step on them involuntarily and by contact with their feet, they sting and lick themselves,” alerts Cerezo.
Those who can be calmer are cat owners. “They tend to be more selective and don’t usually have much contact with caterpillars. In my professional career, I have seen a case with a leg injury because they play with the caterpillar, but not with processionary urticaria”, Molina points out.
What to do if my dog has contact with the processionary?
Any veterinarian or ethologist will say that it is important to watch the dog while it is walking. This, which is always essential, becomes vital between February and May and especially if there is an area of pine trees nearby. But there are times when, although it has not been possible to see the contact of the animal with the caterpillar, symptoms do begin to occur, so you have to go to the vet quickly. “The symptoms that should make the owner suspicious are excessive salivation and an inflammatory reaction with redness and swelling of the part with which they have come into contact,” explains María Luisa Medina de Zafra, veterinarian and vice president of the Official College of Veterinarians of Murcia, a community that has been suffering the effects of the processionary for years.
The caterpillar’s hairs contain thaumatopin, a stinging substance. “The effects can be very varied depending on the contact that has been made. It can range from an allergic reaction with skin erythema, itching and other related effects, to, if there has been very direct contact with the oral mucosa and even ingestion of the processionary, the death of the animal occurs,” explains Molina, who He also points out that the most common consequence is necrosis of the contact area, so it is common for the dog to lose part of the tongue. If swallowed, it can cause necrosis of the digestive system and, therefore, death.
For all these reasons, it is essential to act quickly, as soon as symptoms are noticed or contact with the caterpillar has been seen. You have to go quickly to the vet and avoid as much as possible that the effect of the toxin expands. “Wash, always with gloves, the tongue or affected parts with hot water (without burning), without rubbing excessively and then apply cold or cold water to minimize inflammation,” explains Medina de Zafra. Care must be taken so that the dog does not drink the water used to wash it and Molina points out one more piece of information: “If Urbason is available, administer it, above all, to those dogs that are allergic where exposure to urticating substances can provoke a more severe process”.
It should be remembered that if an animal comes into contact with the processionary moth it is a veterinary emergency and that early diagnosis is essential so that the condition does not progress and the subsequent sequelae are limited.