eMedicine Specialties > Infectious Diseases > Parasitic Infections

Onchocerciasis: Treatment & Medication

Author: Mary Nettleman, MD, MS, Chair, Department of Medicine, Michigan State University
Coauthor(s): Apoorv Kalra, MD, Assistant Professor of Medicine, Michigan State University
Contributor Information and Disclosures

Updated: Apr 16, 2009

Treatment

Medical Care

Because most of the pathogenesis of onchocerciasis is secondary to microfilariae, the goal of therapy is to eliminate the microfilarial stage of disease to improve symptoms, to prevent progression of eye lesions, and to interrupt disease transmission.

  • Ivermectin is considered to be the drug of choice as a microfilaricidal agent.29,30
    • Repeated dosing at intervals of 3–12 months is recommended for at least 10-12 years.
    • More frequent dosing is reserved for patients who experience frequent symptomatic recurrences.
    • Ivermectin is usually well-tolerated. Dying microfilaria may result in pruritus and adenopathy (Mazzotti reaction), leading to angioedema in rare cases. Ocular inflammation may also be triggered by dying microfilariae. To minimize this in individuals with microfilariae observed during slit-lamp examination, some experts recommend using a short course of prednisone (2-3 d) along with ivermectin. More frequent dosing with ivermectin (every 3 mo instead of every 12 mo) may reduce inflammatory complications because it does not permit microfilarial numbers to build, thus reducing the number of dead organisms after treatment.
    • Concomitant infection with L loa should be ruled out, as ivermectin may precipitate toxic encephalopathy in these patients.
    • Ivermectin has little effect on adult worms. It reduces the burden of microfilaria and the risk of complications but does not cure the disease.
  • Targeting endosymbiotic Wolbachia species has emerged as an exciting new approach in the control of onchocerciasis. Studies of doxycycline therapy (100–200 mg/d for 6 wk) have shown great promise.31,32,33 Doxycycline interrupts microfilarial embryogenesis, dramatically decreasing or eliminating microfilaria for at least 18 months after treatment. The drug has modest activity against adult worms, reducing numbers by approximately 50%-60%. Investigators have also studied rifampin and azithromycin, but early results appear to be inferior to those of doxycycline.34,35

Surgical Care

Nodulectomy can result in cure only if excision eliminates all adult worms. Thus, this is not a practical choice in patients with multiple nodules or in patients in whom nodules are not clinically evident.

Consultations

  • Infectious disease specialist
  • Ophthalmologist
  • Dermatologist

Medication

Treatment involves microfilaricidal or macrofilaricidal agents. No known nontoxic macrofilaricidal agent is available to kill adult worms.

Antiparasitics

These agents inhibit growth and proliferation of parasites.


Ivermectin (Mectizan, Stromectol)

Drug of choice for onchocerciasis. Derived from the soil actinomycete Streptomyces avermitilis. Metabolized in liver and excreted in feces over 12 d. Plasma half-life is 18 h. Its activity is the result of increased nerve and muscle cell permeability to chloride channels, leading to hyperpolarization and paralysis due to the drug's high affinity binding to glutamate-gated and gamma aminobutyric acid–gated chloride ion channels.

Adult

150 mcg/kg PO as single dose every 3-12 mo

Pediatric

<5 years: Not established
>5 years: Administer as in adults

Elevated INR with warfarin coadministration reported

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Some patients with hyperactive onchodermatitis may worsen after starting ivermectin, developing edema, pruritus, arthralgias, and postural hypotension; toxic encephalopathy in patients coinfected with L loa (rare); teratogenic in mice, rats, and rabbits; excreted in low levels in human milk (not recommended in breastfeeding mothers)


Diethylcarbamazine (Hetrazan)

Diethylcarbamazine (DEC) is never used in the treatment of onchocerciasis. DEC is rarely used for diagnostic purposes, when low test doses are given and patients are observed for the Mazzotti reaction, which, in mild cases, results in pruritus, dermal edema, maculopapular eruptions, lymphadenopathy, and fever and, in severe cases, results in meningismus, severe prostration, and/or death. The mechanism of action of DEC is secondary to direct effect on microfilariae by causing organelle damage and apoptosis.

Adult

6 mg PO once (Mazzotti test)

Pediatric

Not established

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

In heavily infected patients with onchocerciasis, severe reactions may occur following a single dose of diethylcarbamazine

Antibiotics

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.


Doxycycline (Bio-Tab, Doryx, Doxy, Periostat, Vibramycin, Vibra-Tabs)

May be used to reduce or eliminate the endosymbiotic bacteria Wolbachia. This disrupts production of microfilariae by the adult female worm.

Adult

Several regimens under study; 100-200 mg/d for 6 wk suggested

Pediatric

Not established

Bioavailability decreases with antacids containing aluminum, calcium, magnesium, iron, or bismuth subsalicylate; tetracyclines can increase hypoprothrombinemic effects of anticoagulants; tetracyclines can decrease effects of oral contraceptives, causing breakthrough bleeding and increased risk of pregnancy

Documented hypersensitivity; severe hepatic dysfunction

Pregnancy

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Photosensitivity may occur with prolonged exposure to sunlight or tanning equipment; reduce dose in renal impairment; consider drug serum level determinations in prolonged therapy; tetracycline use during tooth development (last one-half of pregnancy through age 8 y) can cause permanent discoloration of teeth; Fanconi-like syndrome may occur with outdated tetracyclines

More on Onchocerciasis

Overview: Onchocerciasis
Differential Diagnoses & Workup: Onchocerciasis
Treatment & Medication: Onchocerciasis
Follow-up: Onchocerciasis
Multimedia: Onchocerciasis
References
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References

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Further Reading

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Keywords

onchocerciasis, onchocercosis, river blindness, volvulosis, craw-craw, Robles disease, Onchocerca volvulus, O volvulus, Simulium fly, blinding disease, papular dermatitis, leopard skin, sowda, sowdah, Nakalaga syndrome, ocular onchocerciasis, ocular onchocercosis, onchodermatitis, onchocercomata

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Contributor Information and Disclosures

Author

Mary Nettleman, MD, MS, Chair, Department of Medicine, Michigan State University
Mary Nettleman, MD, MS is a member of the following medical societies: American College of Physicians, Association of Professors of Medicine, Central Society for Clinical Research, Infectious Diseases Society of America, and Society of General Internal Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Apoorv Kalra, MD, Assistant Professor of Medicine, Michigan State University
Disclosure: Nothing to disclose.

Medical Editor

Daniel R Lucey, MD, MPH, Chief, Fellowship Program Director, Department of Internal Medicine, Division of Infectious Diseases, Washington Hospital Center; Professor, Department of Internal Medicine, Uniformed Services University of the Health Sciences
Daniel R Lucey, MD, MPH is a member of the following medical societies: Alpha Omega Alpha and American College of Physicians
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

John W King, MD, Professor of Medicine, Section of Infectious Diseases, Louisiana State University Health Sciences Center; Director, Viral Therapeutics Clinics for Hepatitis; Consulting Staff, Department of Infectious Diseases, Overton Brook Veterans Affairs Medical Center
John W King, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Association of Subspecialty Professors, Infectious Diseases Society of America, and Sigma Xi
Disclosure: emedicine $50.00 author of chapter

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

 
 
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