Rodent mites are tiny parasitic arachnids that primarily live on and feed from rats and mice. They are highly dependent on their rodent hosts, but they will readily leave the host or its nest to seek a new blood meal when necessary. A human encounter with rodent mites often signals a nearby or recently resolved rodent infestation within a structure. This migration occurs when the primary host population dies, is removed, or the existing mite population grows so large that it overwhelms the original host.
Physical Description of Rodent Mites
Rodent mites are extremely small, making them barely visible to the unaided eye. Adult mites typically measure between 0.5 and 1.5 millimeters in length, approximately the size of a period in 12-point font. They possess an oval or pear-shaped body.
When a mite has not recently fed, its body is often pale, translucent, or grayish-white. Following a blood meal, the mite’s body swells and changes color to a reddish-brown or dark black. As arachnids, they have eight legs, which distinguishes them from insects that only have six.
Mite Behavior and Habitat
Rodent mites are obligate parasites. They spend most of their time in or around their host’s nest, which is typically found in secluded areas like attics, wall voids, crawlspaces, and behind appliances. The entire life cycle, from egg to adult, can be completed in as little as ten to twelve days under favorable conditions.
The mites only venture out when their host source is disrupted, such as when the rodent dies or leaves the area. They can survive for several days to a few weeks without a blood meal. When searching, they are often seen crawling slowly across floors, walls, and ceilings, unlike other common household pests.
Distinguishing Rodent Mites from Other Common Pests
Rodent mites are slow-moving and crawl, which is a key difference from fleas, which are known for their distinct jumping ability and laterally compressed bodies. Unlike fleas, rodent mites are generally found crawling on vertical surfaces like walls and window sills as they search for a host.
Another common confusion is with bed bugs, but rodent mites are much smaller and are often seen wandering far from bedding. Bed bugs are flatter and typically hide in tight cracks and crevices very close to where a host sleeps. It is also important to distinguish them from dust mites, which are microscopic, do not bite humans, and primarily cause allergic reactions from their waste products. Furthermore, rodent mites do not burrow into the skin like scabies mites do.
Human Health Impact of Rodent Mite Bites
When rodent mites cannot find their preferred host, they will opportunistically bite humans. These bites often result in small, red, raised welts that can resemble a rash or pimple. The primary symptom is intense itching and skin irritation.
The bites can remain itchy for up to a week, and severe scratching may lead to secondary bacterial infections. Rodent mites in North America are not generally known to transmit diseases to humans. If bites occur, the affected area should be cleaned, and medical attention should be sought for severe or prolonged reactions.