The parasitic mites that infest rodents can affect humans. While rat mites primarily target their rodent hosts, they are opportunistic feeders that will readily bite people when their preferred meal source is no longer available. This usually happens after a rat population has been eliminated or died off, forcing the mites to seek a new blood meal. Humans are considered accidental hosts; the mites do not live or reproduce on us, but they will bite, leading to uncomfortable skin reactions.
The Rat Mite Species and Transmission Pathway
The primary species responsible for biting humans is the Tropical Rat Mite, Ornithonyssus bacoti. This mite is an arachnid and a blood-feeding parasite of rats. It lives most of its life in the rodent’s nest rather than continuously on the host. The entire life cycle, from egg to adult, can be completed in about two weeks, allowing populations to grow rapidly.
Transmission to humans occurs when the mites are separated from their primary host. This separation is typically triggered by the death, removal, or abandonment of the rat or mouse, which leaves the mites without a food source. These tiny parasites, only about 1 millimeter long, can travel significant distances to find a new host.
Once displaced, the mites actively seek out any nearby mammal, including humans and pets, for a blood meal, particularly at night when they are most active. They do not burrow into the skin like scabies mites. The mites can survive without a blood meal for several weeks, meaning they pose a threat even after the initial rodent problem has been addressed.
Recognizing Symptoms of a Rat Mite Bite
The condition resulting from human infestation is often called rat mite dermatitis. The bites are typically not felt at the moment of the bite, but they quickly lead to an intensely itchy skin reaction. This reaction presents as small, raised, red bumps, or papules, which may resemble a rash.
The pattern of bites often helps distinguish them from other insect bites. Rat mite bites frequently occur in clusters or groups on the skin, most commonly appearing on the upper extremities, neck, face, and trunk. They are also concentrated in areas where clothing fits tightly against the body, such as the waistline or under the armpits.
A challenge with rat mite dermatitis is misdiagnosis, as the symptoms can be easily confused with those of bed bug bites, mosquito bites, or scabies. The mites themselves are very small and move quickly, making visual confirmation difficult without professional help. Unexplained, intensely itchy bites, especially following known or suspected rodent activity in the home, should prompt suspicion of a rat mite infestation.
Treatment and Environmental Eradication
Addressing a rat mite problem requires a two-part approach: treating the human symptoms and eliminating the environmental source. For the skin reaction, over-the-counter anti-itch creams containing hydrocortisone or oral antihistamines can help relieve the severe itching and irritation. In cases where the reaction is severe or if scratching has led to a secondary bacterial infection, a consultation with a doctor may be necessary for stronger topical corticosteroids or antibiotics.
The most effective treatment is the complete eradication of the mites’ host and habitat. This begins with the immediate and complete removal of the rat population and their nesting materials, which should ideally be handled by professional pest control services. Sealing all entry points into the structure is a necessary step to prevent future rodent infestations.
Once the rodents are gone, the environment must be treated, as mites can persist for weeks without a host. Thorough cleaning of all infested areas is necessary, including using a vacuum cleaner with a HEPA filter to remove mites and eggs from carpets and cracks. This must be followed by the application of residual insecticides targeting the cracks, crevices, wall voids, and any areas where the nests were located, as surface treatments alone are insufficient to reach all hiding mites.