Mites are extremely small and are barely visible unless viewed under a microscope or magnifying glass. Most mites feed on plants, or attack and feed on other mites and insects, although some feed on animals. The most common mite associated with feeding on humans as an alternate host is the tropical rat mite. On rare occasions, two species of bird mites, the northern fowl mite and tropical fowl mite, and the larval stage of the chigger mite can be significant pests. Mites will frequently invade structures when their primary host nests in or on structures. Mites are attracted to carbon dioxide (a product of breathing) and heat, and use these to locate hosts. Mites cannot jump or fly and must crawl. Mites are usually found in rooms such as kitchens, family rooms, bedrooms, and work areas that contain the highest concentrations of carbon dioxide. Mites are also attracted to furniture and will bite the occupants as they rest or sleep. Their bites can cause irritation and sometimes painful dermatitis. For unknown reasons, some persons are more susceptible to bites than others. After feeding, mites drop off their host; they do not burrow under or remain on the skin so the cause of the bites may not be readily apparent. Rodent and bird mites are small (about the size of a period at the end of this sentence) and grayish in color unless they have fed recently, in which case they will be 2-3 times larger and look red or black.

Tropical Rat Mite

This type of mite occurs on rats and in their nests and frequently feeds on people living in rat infested buildings. Tropical rat mites can become serious pests when there are many rats living within a structure, but usually only bite people if their primary host dies. If control measures are initiated to remove the primary host (rats) or if trapped or poisoned animals fail to return to their nests, the mites may migrate into the living areas of the structure to feed on humans or other animal hosts. Migrating mites are extremely active and will crawl long distances in search of a blood meal. Since rodent mites can live up to six weeks without an animal host, they may persist for some time after the rodents have been eliminated.

Controlling Tropical Rat Mites

The primary way of controlling tropical rat mites in a home is abatement of the rodent infestation. Rats can be controlled with bait or traps, but baits are not recommended when rodents inhabit dwellings because rats may die within wall voids or behind cabinets, and the resulting odor may be present for a week or longer. Placement of traps is crucial. Snap traps should be used in areas where rodents or droppings have been seen to control rodents indoors. Trapping or poisoning rats may increase the activity of the mites as they search for alternative hosts. Be sure to remove rodent food and harborage. Refer to Contra Costa Mosquito & Vector Control District’s Rats or Mice pamphlets for additional rodent prevention and control. Mites that have invaded the home can be eliminated by vacuuming carpets and furniture. Indoor aerosol insecticides or foggers may provide temporary relief, but generally do not penetrate to the source of the mites (empty rodent nests in attics, crawlspaces, or wall voids). Before using a fogger in a bedroom, remove all linens from the bed and launder. Cover the mattress with a sheet to prevent pesticide from settling on the mattress. After treatment, remove sheet and replace linens. A licensed professional exterminator can treat these spaces. ALWAYS read and follow label directions and remember: the key to successfully controlling tropical rat mites is abatement of the rodent infestation.

Bird Mites

Mites associated with birds are very similar in size, appearance, and behavior to tropical rat mites. Problems with bird mites usually develop in the spring and summer months, during bird nesting times, and are often associated with nesting house sparrows, pigeons, and doves in or on homes. When the mother and young birds are in the nests, mites remain in the nest and on the birds. When the young mature and the nest is abandoned, mites migrate into the structure in search of an alternative host. Residents of a home infested with bird mites as a result of bird nesting activity often experience an excessive number of bites. Occasionally, intermittent bites may be experienced as a result of congregating pigeons utilizing roofs and eaves as resting sites.

Controlling Bird Mites

If you suspect birds are nesting on or in your home, locate the nest and dispose of it. Signs of bird nesting include the accumulation of droppings beneath the nest or the presence of nesting material. Spray the area that the nest occupied with a household pesticide to eliminate any mites that may remain after nest removal. Control of bird mites that have entered a dwelling is the same as previously mentioned for rat mites. Seal openings where birds may build nests with hardware cloth or chicken wire. If structural modifications are necessary, pest management companies specializing in vertebrate control can provide assistance.

Chigger Mites

Chigger mites are rarely encountered in our area and are most common in warm humid states like Florida or Texas. Chigger larvae attach to the skin of vertebrates where they normally feed just once. They are found outdoors in grassy areas and do not infest homes. They feed on skin tissue and lymph, but not blood and do not burrow into the skin. There is no sensation of being bit; the mites drop off and itching begins 2-3 hours after bite. Chiggers often attach to humans around the ankles, armpits, and waistline. Repellants with DEET work well at repelling chiggers.