Loiasis

Loiasis is a filarial infection also called Calabar swelling or African eyeworm disease. Worms can migrate to the skin and bulbar conjunctiva. Initial symptoms are itching and transient areas of subcutaneous swelling several centimeters in diameter all over the body. Urticaria and fever may develop.

CASES/YEAR
0 (US); 20,000,000 (Global)
CATEGORY
AGENT TYPE
Helminths
OTHER NAMES
Loa loa; Calabar swelling; African eyeworm disease;
ACUITY
Subacute/Chronic
INCUBATION
Symptoms: 4 months to several years; Microfilariae in blood: 6 months; [CCDM, p. 362]
INITIAL SYMPTOMS
Itching and transient areas of subcutaneous swelling several centimeters in diameter all over the body; [CCDM]
PRECAUTIONS
Protect patients with microfilariae from deer fly bites to prevent transmission; [CCDM]
COMMENTS
FINDINGS
In this filarial infection, allergic reactions with urticaria and fever may develop. Eye swelling and pain may occur when the worm migrates in the bulbar conjunctiva. [CCDM, p. 361] Hematuria and proteinuria are present in about 30% of patients. Renal failure is uncommon. Encephalitis is a complication seen in some heavily infected patients. Loiasis is the possible cause of endomyocardial fibrosis. Hypergammaglobulinemia and marked eosinophilia is associated with this infection. [Guerrant, p. 735-8, 943] Calabar swellings are non-erythematous. Preceded by pruritus and pain, they typically occur on the face and extremities. They last for a few days and can reach a size of 5-20 cm. Adult worms can live for up to 17 years. [Cecil, p. 2138-9] Renal complications (proteinuria and hematuria) and encephalitis are usually precipitated by treatment with diethylcarbamazine. [PPID, p. 3448]

EPIDEMIOLOGY:
Loiasis is transmitted by deer flies. The only reservoir is humans. [CCDM, p. 361-2] Temporary residents have an immune hyperresponsiveness (hypereosinophilia and severe symptoms) not seen in long-term natives with the disease. [Cohen, p. 945]
DIAGNOSTIC
Identify microfilariae in blood; May be visible in eye; Serology (LIPS) & PCR available from NIH (301-496-5398); [Harrison ID, p. 1040t] Infected visitors: eosinophilia & +serology; Natives: +blood smears (collect @ 10am-2pm; [Cecil, 24th Ed, p. 2075]
SCOPE
African rain forests, especially in central Africa; [CCDM] Highest risk in southeastern Nigeria, Cameroon, Gabon, Central African Republic, Equatorial Guinea, and the Democratic Republic of Congo; [ID, p. 2372]
SIGNS & SYMPTOMS
  • >arthralgia
  • >fever
  • H eosinophilia
  • H hypergammaglobulinemia
  • O conjunctivitis, acute
  • S lymphadenitis, acute
  • S skin or subcutaneous nodule
  • S urticaria
  • U hematuria
  • X pleural effusions
  • *acute renal failure
  • *arthritis
  • *blindness
  • *encephalitis
  • *glomerulonephritis
  • *peripheral neuropathy
  • *uveitis
ANTIMICROBIC

Yes

VACCINE

No

ENTRY
VECTOR
Biting Flies
RESERVOIR
Human
RISK FACTORS
  • Travel to endemic area
REFERENCES FOR CASES/YEAR
1.
2. (Global) Estimated 20 million people infected in the rain forests of equatorial West and Central Africa; [ID, p. 2372]