Harvest Mite Allergy in Cats

Harvest mites are also called red bugs, berry bugs, and trombiculid mites.  Harvest mites can be found in grasslands, berry patches, woody areas, pine straw, bark, and mulch. Chigger infestation usually occurs in the fall.   Adult harvest mites feed on decaying vegetation; their larvae feed on people, mammals, amphibians and birds. The larva pierces the skin and forms a hole called a stylostome (hardened skin cells).  The digestive enzymes in their saliva “travel” down the stylostome and then break down skin tissue cells, which they ingest. They do not feed on blood; they ingest dissolved skin cells. Chiggers feed for two to three days and then drop off the host to continue their life cycle. In cats chiggers can mostly found around their ears, between their toes, and other areas with a thin covering of hair.

Adult harvest mites are harmless but their larvae cause allergic reactions in people and pets. Harvest mites lay their eggs in the soil; the larvae that hatch are referred to as chiggers.  Chiggers attach to a host and use their fangs to pierce the skin.  The saliva of the chigger contains a digestive enzyme that causes an allergic reaction; the severity of the allergy varies in individual cats.

Symptoms may include:

• Skin lesions
• Crusted skin
• Hair loss
• Bleeding sores
• Severe itching
• Biting of the skin
• Hives
• Blisters
• Change in behavior
• Orange dots or orange clusters ( the larva is orange in color)
• Secondary bacterial infection

Harvest mite allergies in cats are caused by the bite and the secretion of a digestion enzyme of chiggers (harvest mite larvae).  Cats that are allowed to explore the outside can be exposed to the microscopic chiggers. The mite that is responsible for this condition is Trombicula autumnalis.

The veterinarian will want to go over your cat’s medical records.  He may want to know if your cat is up to date with vaccinations and if he is on a flea and tick preventative.  It may be helpful for the veterinarian to know if your cat is allowed to go outside.  Please let the doctor know what symptoms you have observed and describe the evolution of the allergy.

The veterinarian will then perform a physical examination on your pet.  The exam may include taking the cat’s temperature, weight, pulse and blood pressure.  He will check the overall appearance of your cat, taking note of sores or lesions that may be present due to the harvest mite allergy and subsequent skin reaction, making sure no secondary infection has set in..  

A complete blood count and a serum chemistry test may be suggested.  Blood is usually drawn from the side of the neck; from the jugular vein.  The veterinarian may also want to take a skin scrape from the surface of the skin. The sample of skin is then placed on a slide and viewed under a microscope; the presence of mites may be confirmed on the slide.

To alleviate the itchiness caused by the allergen the veterinarian may prescribe an antihistamine and inflammatory medication.  If the complete blood count or physical examination determined that there is a secondary bacterial infection, antibiotics will be prescribed.  Topical cream may also be prescribed and the patient may need to wear an Elizabethan collar (cone). The cone will help prevent the cat from licking at the lesions and/or topical medication. The veterinarian may also recommend a pyrethrin based dip or shampoo to help eliminate the chiggers.

An old wive’s tale is to pour rubbing alcohol on the clusters of chiggers.  This will not kill the chiggers but will cause your pet extreme pain and irritation to his skin. It is important to follow the veterinarian’s treatment plan.

The recovery prognosis of harvest mite allergies in cats is very good.  The patient will need follow up visits to ensure that he is responding well to the medications.  If your cat was diagnosed with a bacterial infection, the veterinarian will want to retake the complete blood count.  The use of a regular monthly parasite preventative may help prevent the recurrence of harvest mites.  

It is recommended that cats under 10 years of age should be seen annually for wellness checks and for annual vaccinations.  Cats that are older than 10 years of age should be seen every six months. Please be aware that cats that are allowed to be outdoors are exposed to potential health hazards such as parasites, wild animals, toxins, vehicular impact and animal abuse. In addition, outside cats can be responsible for the hunting and killing of birds and other small animals. The killing of prey can expose your pet to infections and diseases.  Cats kept inside can be very happy with lots of love, attention, interactive toys, climbing posts, cat perches and scratching posts.