Trombidiosis B88.0

Infestation of humans by bites of the larvae of certain runner mites (Trombidiae). S.a.o. mites, gamasidiosis, cereal dross, grocer's dross.

In Europe, the most common pathogen is Trombicula autumnalis (Trombidia, autumn mite, also called harvest mite, autumn louse or gooseberry mite). Humans are a false host for Trombidiae, so the mites (larvae) persist on the skin only for hours and then fall off. The preferred habitat of mites is gardens, fields, meadows and forest edges. They require a relative humidity of > 75% and are therefore only found at ground level (max. 30 cm height). Their larvae are responsible for the mite bites. They sit at the ends or tips of grasses and wait until a suitable host removes them. These are usually mice, rabbits, hedgehogs or small birds. In humans, it is mainly the feet and ankles that come into contact. However, the mite larvae usually do not remain there but migrate to the preferred warm and humid skin areas. Once there, the approach begins with the stinging and sucking mouth parts.

The most common representative of this mite family is Neotrombicula autumnalis.

Occurrence of red, very itchy, 0.1-0.3 cm large spots and wheals, which appear 3-4 hours after exposure. After about 24-48 hours, papules, papulovesicles usually with a hemorrhagic centre, develop at the injection sites. The skin changes persist for about 2 weeks. Itching persists for about one week. Residual pigmentation may occur.

The mite infestation itself does not require therapy.

Indifferent external therapy with lotio alba, if necessary with the addition of 5% polidocanol lotio R200, for persistent itching also glucocorticoid-containing lotions or creams such as 0.05% betamethasone lotion, e.g. Betamethasone valerate emulsion hydrophilic 0.025/0.05 or 0.1% (NRF 11.47.), 0.25% prednicarbate (e.g. Dermatop cream), 0.1% triamcinolone cream e.g. triamcinolone acetonide cream hydrophilic 0.025/0.05/0.1% (NRF 11.38.).

Other species of the autumn mite are found worldwide (South America, USA). In Japan, they act as carriers of Rickettsia tsutsugamushi, the causative agent of tsutsugamushi fever (Japanese river fever).