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NE61
2.4.3 Trombidiosis
Grading & Level of Importance: B
ICD-11
Synonyms
Harvest itch, chigger itch
Epidemiology
Larvae are most prevalent in forests and long and overgrown grass in fields and gardens in late summer and fall. In tropical areas, the infection may occur at any time of the year. The natural hosts are small rodents.
Definition
Pruritic skin lesions caused by mite larvae (chiggers) of the Trombiculidae family.
Aetiology & Pathogenesis
Larval mites (Trombicula autumnalis): 0.3 mm, transfer from vegetation to skin, usually late summer, bite human as accidental host, inject proteolytic agent then suck up debris and drop off.
Signs & Symptoms
Intensely pruritic papules and macules with haemorrhagic central punctae (site of bite), sometimes vesicles.
Localisation
Sites where clothing is tight (belt line, tight cuffs), proximal thighs, popliteal fossae, ankles. Often several lesions in a linear pattern.
Classification
None.
Laboratory & other workups
Not required.
Dermatopathology
Lymphomononuclear cell infiltrate with eosinophiles in the dermis. Focal parakeratosis and spongiosis in the epidermis, sometimes vesicles around sting.
Course
Usually resolves spontaneously.
Complications
Bacterial superinfection; “summer penile syndrome”.
Diagnosis
Clinical features and history (exposure in known endemic areas). Almost impossible to find larva on human. Sometimes larva found outdoors.
Differential diagnosis
Prurigo, other arthropod bites.
Prevention & Therapy
Topical antipruritic agents (zinc or corticosteroid lotion). Systemic antihistamines. Prophylaxis: avoidance of risk areas (gardens, parks, compost piles), insect repellents for garden work.
Special
None.
Differential Diagnosis
Podcasts
Tests
- What helps to diagnose trombiculiasis?
- Which findings are typical for trombiculiasis?
- Which descriptions fit with trombiculiasis?
- Statement 1 Prurigo simplex subacuta is part of the differential diagnosis of trombiculiasis
- Statement 1 Symptomatic treatment is all that is required for trombiculiasis
- What is the recommended therapy for trombiculiasis?
- Where is trombiculiasis most often acquired?
- Trombiculiasis is caused by:
- The larva of Neotrombicula autumnalis is a:
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