Loa loa: Difference between revisions

Revision as of 21:44, 11 September 2020

Background

Epidemiology

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

Clinical Manifestations

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

Complications of Treatment

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

Diagnosis

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

Management

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

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 ==Background==
 ===Epidemiology===
-* Transmitted by ''[[Chrysops silacea]]'' and ''[[Chrysops dimidiata]]'' flies
+*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
 ==Clinical Manifestations==
-* Often asymptomatic
+*Often asymptomatic
-* Most common symptom is '''Calabar swellings''', a 10- to 20-cm painful, itchy subcutaneous swelling caused by migration of the adult worms
+*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
+**The lesions are essentially angioedema in response to the worm
-* Worms can also migrate to the conjunctiva, where they are visible
+*Worms can also migrate to the conjunctiva, where they are visible
-* Infection can be complicated by [[Causes::hematuria]] and [[Causes::proteinuria]], as well as as [[Causes::encephalitis]], precipitated by treatment during high-level microfilaremia
+*Infection can be complicated by [[Causes::hematuria]] and [[Causes::proteinuria]]
+=== Complications of Treatment ===
+* 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
+== Diagnosis ==
+* Demonatration of microfilaria on Giemsa-stained blood film collected during daytime (10 am to 2 pm)
+** Also provides quantification of microfilarial burden
 ==Management==
-* Must rule out high-level microfilaremia (>2500 microfilariae/mL) before considering medical treatment, due to the risk of encephalitis
+*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
 {{DISPLAYTITLE:''Loa loa''}}