At this time of the year Pine Processionary Moth caterpillars leave their silken nests in the pine treetops to begin en masse migration downwards. As many as three hundred caterpillars may travel long distances from the natal tree, looking for soft soil in which to bury themselves and form cocoons, forming the most spectacular processions.
So far I was unable to confirm if this species was ever officially recorded in Malta. Nevertheless, dog owners should be very careful during early spring if visiting areas with pine forests, as this little creature presents considerable threat to our canine companions. Cats, on the other hand, seem to have an inherent fear of the larvae and it is quite unusual for a cat to be poisoned.
The hairy processional caterpillar itself is not a killer, nor is it considered danger to the public. But the defense system of this creature is where the problems begin. The caterpillar is covered in approximately 60,000 extremely fine hairs, which break off if they are disturbed.
Each hair carries a toxin, which can cause skin rashes, conjunctivitis, and in sensitive individuals it can cause anaphylactic reaction, which - if not treated can lead to death by asphyxiation.
Dogs find these caterpillars irresistible; it is believed by some veterinarians that dogs have no second thoughts about putting them on their menu because they find their smell very enticing. Unfortunately, even just sniffing the line or group of caterpillars and inhaling their hairs can cause serious problems in our canine companions.
The contact of mucous membranes with caterpillar’s hairs is within minutes followed by dramatic inflammatory reaction and swelling of the tissue. The swelling of the tongue and gums can be so severe that it is impossible for the dog close its mouth. If the swelling occurs in the throat there is a danger of asphyxiation so urgent veterinary assistance is required. As a first aid measure flush the dog's mouth with plenty of water, wiping the mucous membranes with the tissue, but make sure to weare some sort of protective gloves.
Normally the first aid for swellings would be applying cold packs but in this case, as most of the biological toxins are thermolabile it would be more beneficial to apply heat (same as with jelly fish stings). Applying heat should only be alleviating measure until you reach your veterinarian, because heat will do nothing to stop the allergic reaction.
In these unfortunate encounters, even after the proper veterinary care was given, it happens very often that the part of the tongue that was exposed to the toxin will becomes necrotic, turnins grey and eventually falls off.
Since dogs seem to be unable to stay away from processionary caterpillars the best protection is to be vigilant when around the pine trees during this time of the year. If the encounter happens and you notice hyper salivation (drooling form the mouth) you should rush the dog to your vet as soon as possible. After the dog has been treated it is recommended to give it a bath as caterpillar hairs remaining on dogs coat may cause skin rash or allergic reaction to the owner.
Following are the photos (courtesy of my Croatian colleague - Tamara Ferrari) showing changes very similar to suspect caterpillar poisoning case I have seen recently:
