Trombiculiasis: The uninvited trekker.

A 38-year-old, otherwise healthy, Caucasian woman complained of itching skin eruption during a trekking in Aspromonte mountain in Calabria, Italy. On clinical examination, intensely pruritic, erythematous papules and nodules on abdomen, hips, buttocks and upper legs were noted, together with small hyperpigmented skin wounds along the waist area, probably due to scratching. (Fig. 1A and B). She recalled that her dog was also affected by intense itching after the trip, thus developing dermatitis of the abdomen, limbs, chin and ears. With the suspicion of a link between the human and the animal conditions, we obtained some specimens for microscopic examination revealing reddish-orange mites that were identified as larvae of Neotrombicula autumnalis (Fig. 2).

Fig. 1

A and B. Clinical picture of trombiculiasis: multiple erythematous papules and nodules of the trunk and buttocks.

Fig. 2

Microscopic view of the mite Neotrombicula autumnalis (magnification ×200).

Trombiculiasis is an epizoonosis that occurs worldwide, caused by various types of chiggers. Because of the favoring warm and humid environment, larvae are always present in tropical climates whereas they are abundant in the late summer and autumn in Europe and North America. The life cycle of Neotrombicula autumnalis starts from eggs deposited on the soil, then hatching in ten days as six-legged larvae; at this stage, they are able to climb onto warmblood-hosts, feeding for 2–10 days, and to inject lytic enzymes in the upper layers of the skinusing chelicerae. Larvae then return to the soil, developing into eight-legged-nymphae and feeding on plant fluids or small insects [1].

Human infestation by chigger mites, although rarely reported in medical literature, has probably a not-negligible incidence. The reason of underreporting probably relies on the lack of attention to some neglected parasites, including life characteristics and way of transmission [1], [2]. Formulations of combined permethrins and insect growth regulators achieved optimal responses in eradication of mites in animals. Natural permethrins have been used in humans in cases of massive infestation, together with treatment of symptoms and adequate disinfection of clothes [2].

Funding source

None.

Conflict of interest

None to be declared.