Harvest Mites (as pictured above, under the microscope) are tiny spider-like creatures that only emerge in August and September every year. They are never seen at other times of the year. To find out more, listen to the podcast at the foot of this page, or read on.
What are Harvest Mites?
The mites are correctly called Trombicula autumnalis, but most people know them by their colloquial names: Harvest Mites or Red Spider Mites.
How do Harvest Mites cause a problem?
Adult Harvest Mites do not cause problems: it is the younger larvae that are the parasitic phase of the life cycle. The larvae hatch out in meadows and scrubland. Harvest Mites are present all over Ireland, in open fields in the countryside as well as in town gardens and parks. They are active during the day, especially when it is dry and sunny. They wait for passing warm-blooded animals, and then launch themselves towards them. After grabbing hold with their spidery legs, they crawl into a secure part of the animal’s body, sticking themselves to the underside of dogs, cats and wild animals. They remain attached for several days while they feed on the skin of their host.
Which parts of an animal’s body get itchy?
Unlike many parasites, Harvest Mites do not suck blood. Instead, their saliva digests the outer layers of the skin. They feed by thrusting their small hooked fangs into the skin, injecting a fluid that breaks down the cells underlying the horny outer layer of the skin. The liquid food resulting from this process is sucked back into the digestive system of the larva. The mites feed for two to three days then they fall to the ground where they develop into the next phase of their life cycle. Eventually they develop into an adult mite that eats plants and small insects.
The mites most commonly attach to the underside of the feet, between the toes. The skin here is very thin, sensitive and easily irritated. The mites can also cause itchiness in other parts of the body – the abdomen and the sides of the head can be affected, particularly in cats.
If an pet starts to itch around the lower parts of their body towards the end of the summer, Harvest Mites are prime suspects.
What do Harvest Mites look like?
Harvest Mites are tiny, but they tend to cluster together, and they can be seen like a sprinkling of red dust between the animal’s toes. When they are examined under magnification, it is possible to see their tiny legs sticking out from their bulging little bodies, as in the photo that I took last week of a sample collected from a cat’s feet (see at the top of this page). Sometimes Harvest Mites are impossible to see with the naked eye, and vets may take a scrape from affected areas of skin and look at it under the microscope to find them.
How do Harvest Mites cause a problem?
Many animals are not particularly bothered by the presence of Harvest Mites. It is common to find the pin-point sized orange mites hiding between the toes of many dogs and cats at this time of year, but only a small proportion of pets develop sore feet.
The itchy problem only occurs when an animal is allergic to the mite.
In these cases the skin between the toes becomes red and swollen. The unfortunate allergic animals can be driven demented by their itchy feet. They lick their feet, they chew their toes, but they just cannot get relief from the discomfort. In fact the licking and chewing usually just makes things worse, by making the itchy skin even more red and sore.
Some breeds are more prone than others to developing allergies, eg West Highland White Terriers seem to be particularly vulnerable. Westies can develop allergies to all sorts of things, from grass pollens in the atmosphere, to wheat in their diet, to parasites such as fleas and harvest mites.
Treatment of Harvest Mites
- Removing the parasites using insecticide sprays seems logical but the mites seem to be difficult to prevent completely so this is often not enough to solve the problem.
- When vets are presented with pets that are itching due to the mites, they are likely to suggest anti-inflammatory medications to block the animal’s allergic reaction so that the red sore areas stop feeling so itchy. This is prescription only medication so that means that if your pet is bothered by harvest mites, you need to visit the vet
- If your pet has a regular problem, try to avoid fields etc where the harvest mites live during August and September.
Questions from listeners about pets
The following questions were asked this week:
- My collie hates having his nails clipped. He runs away as soon as he sees the clippers. How can we get him used to this?
- Our Beagle is overweight. What diet can we use to trim him down?
- My Pug rolled around in nettles yesterday and he has a rash today. Should I take him to the vet?
- I am putting my Border Terrier into boarding kennels next week for the first time. How can I make it easier for her?
Please note that I am unable to answer veterinary questions in comments. If you have questions or concerns about your pet's health it is always better to contact your vet.