Tungiasis

Tungiasis is a parasitic skin infestation caused by the female sand flea (Tunga penetrans), which burrows into the epidermis, usually of the feet, grows 2000-fold in size over about 2 weeks, expels eggs, and dies in situ. It is a neglected tropical disease of poor communities in sub-Saharan Africa (including the Kenyan coast and western regions), Latin America and the Caribbean.

• Spread: fleas live in dry, sandy soil and floors of houses, schools and animal pens; people walking barefoot or in open shoes are bitten; domestic animals (pigs, dogs, cats, cattle) act as reservoirs.
• Risk factors: poverty, earth floors, overcrowding, lack of footwear, poor hygiene, dry season, and children, older adults, and disabled people.
• Prevalence in endemic communities is 20 to 50 percent of children; heavy infestation with over 30 lesions can occur.
• Complications are serious: secondary bacterial infection (including Staphylococcus aureus, streptococci, and clostridia), abscess, lymphangitis, cellulitis, gangrene, tetanus, nail loss, deformed toes, walking difficulty, school absenteeism, and, rarely, auto amputation.

• Sites: around and under toenails, between toes, sole and heel, and less often the hands, elbows and genitalia.
• Five clinical stages: stage 1, flea penetrating (small red or brown macule with itch); stage 2, early lesion with a white halo and black central dot, 1 to 2 mm, becoming pea sized as the abdomen enlarges (day 1 to 3); stage 3, mature "watch glass" lesion, 4 to 10 mm, a white disc with a dark central pore from which eggs are expelled, painful and itchy (days 3 to 14); stage 4, dying flea with a crust (after 2 to 5 weeks); stage 5, residual scar or pigmented area.
• Symptoms: intense itching, pain on walking, burning, sleep disturbance; in heavy infestation, many lesions on toes and soles producing a typical honeycomb pattern.
• Complications: pus, swelling, redness, erysipelas, ulcers, lymphadenopathy, fever; tetanus (trismus, spasms), gas gangrene.
• Examination: all four limbs, the groin lymph nodes, signs of malnutrition, and vaccination history.

• Clinical diagnosis from the typical lesions in an endemic setting; dermoscopy (a dark pore, a white halo and egg clusters) confirms.
• Microscopy of extracted flea or biopsy rarely needed.
• Swab and culture of infected lesions if purulent; FBC and CRP if systemic infection.
• Check tetanus immunisation status; test for HIV, malnutrition and anaemia in heavily infested people.
• Differentials: plantar warts, corns, foreign body, scabies, cutaneous larva migrans, myiasis, impetigo, pyoderma, ingrown toenail, and paronychia.

Remove the flea (definitive treatment for stage 2 to 4 lesions)

• Wash the foot with soap and water, then clean with an antiseptic (povidone iodine 10 percent, chlorhexidine 0.5 percent in alcohol, or 70 percent alcohol).
• Using a sterile needle or sharp forceps, enlarge the opening at the pore, loosen the flea along its body edge with gentle circular motion, and lift the whole flea out in one piece, avoiding rupture (rupture increases infection); extract eggs.
• Disinfect the cavity with antiseptic and cover with a clean, dry dressing; leave small cavities open; remove nail margins only if necessary.
• Use sterile instruments for every patient (never reuse needles); gloves; treat in a clean, well lit setting.
• Local anaesthetic (lidocaine 1 percent, 1 to 2 mL) for large or painful lesions.

Topical treatment (alternative to extraction; particularly for heavy infestation)

• Dimeticone (a mixture of low- and high viscosity dimeticone, 2 cSt and 100 cSt) lotion applied to the affected areas twice daily for 3 days, which suffocates the fleas; very effective, painless, and suitable for children and mass treatment.
• Potassium permanganate 1:10 000 foot soak (0.01 percent) for 10 minutes daily for 5 days, to dry and kill the flea; ivermectin 1 percent topical lotion twice daily (evidence limited); oral ivermectin 200 micrograms/kg single dose (variable effect and not for children under 15 kg or pregnancy).
• Avoid petroleum jelly, paraffin and unsterile home remedies, hot oils, or burning; avoid improvised razor blades.

Treat and prevent secondary infection

• Mild infection: wash and apply mupirocin 2 percent ointment three times daily for 7 days.
• Cellulitis or purulent infection: flucloxacillin 500 mg orally four times daily for 7 days (children: 25 mg/kg four times daily, maximum 500 mg a dose); penicillin allergy: clarithromycin 500 mg twice daily for 7 days (children 7.5 mg/kg twice daily); add metronidazole 400 mg three times daily for 5 days for deep or necrotic infection.
• Severe sepsis, gangrene, extensive abscess: hospital admission, intravenous antibiotics (flucloxacillin or ceftriaxone 1 to 2 g daily with metronidazole 500 mg every 8 hours) and surgical debridement.

Tetanus prevention (essential)

• Give tetanus toxoid containing vaccine (tetanus diphtheria 0.5 mL intramuscularly) if the last dose was over 10 years ago (over 5 years ago for a dirty wound) or the vaccination status is unknown; give tetanus immunoglobulin 250 IU intramuscularly (500 IU if over 24 hours since injury or heavy contamination) if unvaccinated or incompletely immunised.

Symptom relief

• Paracetamol 1 g every 6 hours (children 15 mg/kg), antihistamine for itching such as cetirizine 10 mg daily (children 2 to 6 years 2.5 mg daily; 6 to 12 years 5 mg daily).

Prevention and community control

• Wear closed shoes; wash feet daily with soap and water and dry them; keep nails short; inspect and treat all household members and animals.
• Treat floors (use sealed, hardened surfaces and cement); sweep and spray with insecticide; keep animals out of living areas; avoid sitting or lying on sand where fleas live; treat and control dogs and pigs.
• Apply repellent (coconut oil based repellents) or dimeticone lotion regularly in endemic communities; community education and school based programmes.
• Repeat treatment of all infested people (monthly) because reinfestation is common.

Follow up

• Review in 3 to 7 days to check healing, infection and tetanus status; refer for deformity, chronic ulcers, malnutrition, or when vaccination is not available.