Dog owners: What you need to know about oak processionary moth caterpillars

If you own a dog and you’ve never heard of oak processionary moth caterpillars, you’re probably not alone. However, oak processionary moth caterpillars pose a seasonal danger to dogs in the UK and can cause them harm, and because dogs tend to be quite inquisitive animals that don’t always abide by the principle of “look before you leap,” they are something that all dog owners should be aware of.

In this article, we’ll tell you what oak processionary moth caterpillars are, and why they pose a danger to dogs. Read on to learn more.

What is the oak processionary moth caterpillar, and where are they found?

The oak processionary moth caterpillar is the caterpillar form of the oak processionary moth, and they can usually (but not exclusively) be found on and around oak trees. It is usually between May and July that they’re in their caterpillar form, and so, this is when they pose a danger to dogs, although their exact seasonality can vary from year to year, and in different parts of the country.

The greatest concentration of them can be found around the South East region, but they are found in other areas of the country too and are spreading out ever-further each year.

I’ve never heard of the oak processionary moth caterpillar or them being a danger to dogs before; why?

The oak processionary moth (and so their caterpillar form too) is in fact an invasive species that has only been found in the UK since 2005, when it was accidentally brought into the UK on trees imported from Europe.

Between 2005 and today, they’ve grown in numbers year on year, and spread ever more widely across the UK. The caterpillar has very long white hairs on their body alongside of shorter hairs, but they’re not particularly brightly coloured or unique-looking compared to caterpillars in general, so you might actually have seen them loads of times without realising it.

Why is the oak processionary moth caterpillar dangerous to dogs?

The hairs on the body of the oak processionary moth caterpillar contain a substance that irritates the eyes and skin – of dogs, and also of people, cats, and most other animals too. The substance itself is called thaumetopoein, and it can make areas it comes into contact with highly itchy and uncomfortable, causing more acute issues in some cases too.

Every oak processionary moth caterpillar has thousands of these irritating hairs, and direct contact with such a caterpillar will result in contact with them; but they are also shed and blown around and fall on the ground and other surfaces, so your dog needn’t ever come into physical contact with an oak processionary moth caterpillar to come into contact with their hair.

However, direct contact with a caterpillar will tend to generate more acute symptoms than passing contact with loose or shed hair; for instance, conjunctivitis, and irritation of the throat and nasal passages, as well as tongue swelling and even swelling of the throat too, causing respiratory distress.

How likely is it that a dog will come into contact with an oak processionary moth caterpillar?

Oak processionary moth caterpillars are called this because they move around in long lines nose to tail, and can be found in nests on trees too as groups; so contact will usually involve a dog facing lots of them, not just one.

They usually dwell on oak trees, and so are perhaps more of a risk to cats that climb trees than to dogs, but dogs may see or brush past them on the lower part of trees, and they can be found on the ground between trees too.

Dogs are very inquisitive animals and can be very gung-ho about getting up close and personal with things before considering the consequences, which means that if a dog spots a procession, they’re apt to stick their nose in the middle of it or even lick or try to pick up caterpillars in their mouths, all of which is a problem!

As mentioned too, loose hairs in the environment can cause irritation with contact as well, but generally to a lesser extent.

What should I do if my dog has had contact with oak processionary moth caterpillars?

In the first instance, bear in mind that their hairs are irritating to human skin and eyes too, so don’t do anything hasty! When safe to do so, try to wipe and wash your dog’s face and body to remove hairs.

If you know or suspect that your dog got their nose right into a procession or licked, mouthed, or even ate a caterpillar or two, they might suffer from a high degree of irritation and potentially, swelling of the mouth, tongue, and inflammation of the respiratory system; so take them to the vet to be checked out and monitored.

If you know that oak processionary moths can be found in a certain park or area, try to use other places to walk your dog during the season for them, and a month or two either side just to be safe.