Rodent mite dermatitis (also known as rat mite dermatitis) is an often unrecognized ectoparasitosis occurring after human contact with haematophagous mesostigmatid mites that infest rodents, such as house mice,^[1] rats^[2] and hamsters.^[3] The condition is associated with the tropical rat mite (Ornithonyssus bacoti), spiny rat mite (Laelaps echidnina) and house mouse mite (Liponyssoides sanguineus)^[4] which opportunistically feed on humans. Rodent mites are capable of surviving for long periods without feeding and travelling long distances when seeking hosts.^[4] Cases have been reported in homes, libraries,^[5] hospitals^[6] and care homes.^[7] A similar condition, known as gamasoidosis, is caused by avian mites.^[8]

Symptoms and signs

Rodent mite bites leave multiple groups or individual small itchy papules (around 1–2 mm in diameter)^[7] on the skin (papular urticaria).^[9][10] These are found mostly "on the upper extremities, neck, upper trunk and face".^[7]

Diagnosis

Diagnosis requires species identification of the parasite, which will be likely to be found in the environment of its host rather than on the host's skin.^[10] Rodent mites are very small, for O. bacoti "female mites reach a size between 0.75 and 1.40 mm, males are a little smaller".^[7]

Treatment

The original rodent host of the mites must be located and eradicated,^[11] and their nests removed.^[12] Steps should also be taken to prevent future infestations, such as by blocking the rodents means of entry into the building. The patient's environment should then be treated,^[10] using both non-residual and residual insecticides, mites crawling in the open can be removed by vacuuming or with a cloth moistened with alcohol.^[12]

Bites can be treated with antihistamines and corticosteroids, to relieve the associated itching and allergic reactions.^[7]

Epidemiology

L. sanguineus has been implicated in the spread of Rickettsialpox.^[13]

See also

• Acariasis
• Gamasoidosis

References