Uncommon Infections

PARASITES

We will consider 3 main groups - Arthropods: insects e.g. lice, ticks, arachnids   Worms: roundworms e.g. hookworm, pinworm, onchocerciasis, schistosomiasis   Protozoa: leischmaniasis, trypanosomiasis 

Anthropods- Lyme disease is caused by borrelia burgdorferi (a spirochaete - a variant of a bacteria) transmitted by tick bites from deer/woodland animals. This is rare in the UK except around the New Forest or parks with lots of deer. The rash is called erythema chronicum migrans and which is a slow growing annular rash occurring at the site of the tick bite. If undiagnosed the patient may go on to develop neurological complications and rarely arthritis and cardiac disease. A late manifestation in skin is acrodermatitis chronica atrophicans (scleroderma like rash). Check for Borrelia serology (may take several months to become positive). Treatment is with tetracyclines, e.g. Doxycycline. Erythema chronicum migrans – annular erythematous plaque on the palm

 
Worms and skin disease - Pruritus is a common symptom and eosinplhila may be seen on the full blood count. There may be a history of foreign travel but note the incubation period can be more than 10 years.

Onchocerciasis - central Africa and central / Southern America. Pruritus e.g. buttocks, shoulders, legs initially urticarial, then papular, then lichenified and finally atrophic. Diagnosis on skin snips. Treat with ivermectin.

Schistosomiasis - Schistosoma mansoni – endemic in Africa and South America Schistosoma japonicum – Far East Schistosoma haematobium – Africa and South-West India dermatitis (swimmers itch), urticaria + eosinophilia. Skin lesions are more common on the trunk and may take on a zosteriform appearance. Diagnosis on stool ova/cysts/parasites or organisms may be seen on a skin biopsy. Treat with praziquantel.

Threadworms - nocturnal anal, perianal & vulval pruritus. Sellotape test. Treat with mebendazole.

Larva currens - strongyloides urticaria following path of larva parasite. Travels several cm/day. Raised IgE & check stool for ova/cysts/parasites. Infestation may last 50+ years. Treat with albendazole.

Larva migrans - dog/cat hookworm in faeces. Found in sandy areas e.g. beaches. Affects hands, feet and buttocks i.e. exposed skin. Pruritic serpiginous eruption. Parasite travels several mm/day. Self-resolving but can treat with cryotherapy, albendazole or single dose of ivermectin.

Annular plaque of Cutaneous larvae migrans on the exposed shoulder. Note the lichenified appearance from scratching

Protozoa - Leishmaniasis Mediterranean, Africa (Old world), South and Central America (New world). Currently cutaneous epidemics in Afghanistan and Pakistan. Initially nodule, then crust, then ulcer and finally spontaneous healing. Treatment: pentavalent antimony.

Cutaneous leishmaniasis – crusted ulcerated nodule on the cheek