Also known as harvest mites, berry bugs, scrub-itch mites or red bugs, trombiculid mites are tiny parasitic mites that live in decaying vegetation. Cats become infected while roaming these areas.
The life cycle of the trombiculid mite is in four development stages, egg, larval, nymph and adult. Only the larval form (known as chiggers, hence the name) are parasitic to cats, the nymph and adult are free living.
Chiggers don't actually bite your cat, once on the host, they pierce the skin and inject saliva containing digestive enzymes to break down the skin cells (known as cellular autolysis), they then feed on the blood serum. Once they have fed, they fall drop back onto the ground and passes unto the nymph stage. Chiggers feed on a wide variety of vertebrates, including humans and dogs as well as reptiles and birds. They are most prevalent between spring and autumn when conditions are hot and humid.
Geographical distribution of chiggers:
There are approximately 10,000 species of chiggers and their distribution is worldwide. It would appear they are a bigger issue for cats in the United States (most commonly called chiggers or red bug) and Europe (where they are known as harvest mites). In Australia, they are known as scrub-itch mites but don't seem to be a particularly big issue for cats.
What do chiggers look like?
The larval form of chiggers are minute and barely visible to the eye. They are red/orange in colour and have six legs. The nymph and adult trombiculid mites have eight legs.
What are the symptoms of chiggers in cats?
An enzyme produced by the mite during feeding causes the tissues to disintegrate (known as cell autolysis), the cat's skin becomes hardened, forming a tube called a stylostome from which the mite feeds from (similar to a straw). It is the digestive enzyme produced by the mite that causes the typical reaction seen in affected animals.
Common symptoms of chiggers include:
Intense itching and swelling, especially on parts of the cat that come into contact with the ground such as the feet, head, ears, and legs. In cats, the ears are most commonly affected. Itching occurs a few hours after the chigger has fed.
A red pimple like bump where the chigger has fed.
Dry, crusty lesions, especially along the ear margins.
Some cats may develop a secondary bacterial infection but to scratching and damaging the skin further. The skin may become red and inflamed if an infection is present.
How are chiggers diagnosed?
Your veterinarian will perform a complete physical examination of your cat and obtain a history from you. Diagnosis may be made on the basis of the following:
A history of roaming outdoors.
If a large number of mites are on your cat, your veterinarian will be able to see them as clumps of red/orange on the affected area.
Identifying the six-legged chigger on skin scrapings.
How are chiggers treated?
Infection with chiggers is usually self-limiting and treatment is not always necessary.
When treatment is required, it involves the administration of an appropriate parasiticide for cats. There are currently no treatments which are licensed for use on cats to treat chiggers, however, most flea treatment products are also effective in killing these mites.
Glucocorticoids may be prescribed for severe pruritus (itching).
If your cat has developed a secondary skin infection, he may require a course of antibiotics.
Can my cat pass on chiggers to other cats or humans?
It is not likely that your cat can pass chiggers on to other cats or yourself. Most cases of chiggers are acquired from walking outdoors in infested areas.
Do chiggers transmit diseases?
Chiggers in the United States and Europe aren't believed to transmit any diseases to cats (or humans), however in parts of Asia they can transmit scrub typhus to humans, which is a rickettsial disease.
Keep your cat indoors, or confined to a cat enclosure if possible. Avoid allowing him to roam, especially in areas where infestation of the mites occur, such as grasslands and wooded areas.
If he must go outdoors, check him carefully for the presence of chiggers. Pay attention to the face, ears and feet. If you see mites, gently remove them.
Speak to your veterinarian about a monthly topical treatment which may help reduce the chances of your cat being fed on.
Humans should wear insect repellent when outside, especially in high-risk areas.
Chigger image courtesy of Peter Fender.
Updated: 23rd May 2016.