Loa loa

Background

Transmitted by Chrysops silacea and Chrysops dimidiata flies
- Day biting flies, more common in rainy season and in rain forests
- Attracted by fires and to rubber plantations
Present in West and Central Africa, primarily in Equatorial Guinea, Gabon, Cameroon, Central African Republic, Congo (Brazzaville), DRC, Nigeria, Chad, Sudan, Angola, Ethiopia

Often asymptomatic
Most common symptom is Calabar swellings, a 10- to 20-cm painful, itchy subcutaneous swelling caused by migration of the adult worms
- The lesions are essentially angioedema in response to the worm
Worms can also migrate to the conjunctiva, where they are visible
Infection can be complicated by hematuria and proteinuria

Treatment with antiparasitics may cause an increase in symptoms such as Calabar swellings or pruritis
With treatment of high-level parasitemia, can cause fatal encephalopathy

Demonatration of microfilaria on Giemsa-stained blood film collected during daytime (10 am to 2 pm)
- Also provides quantification of microfilarial burden

Not all infections require treatment
Before treatment
- Must rule out high-level microfilaremia (>2500-8000 microfilariae/mL) before considering medical treatment, due to the risk of encephalopathy
- Rule out Onchocerca volvulus coinfection, as treatment with DEC can lead to blindness or exacerbation of skin disease
If microfilaremia <8000 MF/mL
- First-line treatment is diethylcarbamazine 8-10 mg/kg/day po divided tid for 21 days
  - Kills both the adult worms and microfilaria
- After failing 2 rounds of DEC, albendazole 200 mg bid for 21 days
If microfilaremia ≥8000 MF/mL, either:
- Albendazole as above to decrease levels below 8000, followed by DEC as above
- Apheresis to decrease levels below 8000, followed by DEC as above
Can consider concomitant antihistamines or corticosteroids during the first week of treatment to decrease symptoms associated with treatment