Medication Summary
Ivermectin is the drug of choice in the treatment of onchocerciasis. The addition of 6 weeks of doxycycline to ivermectin has been shown to be effective in reducing the microfilarial load, which may affect transmission and may prevent or reduce onchocerciasis-related blindness.
Moxidectin is an antiparasitic drug indicated for the treatment of onchocerciasis due to O volvulus in patients aged 12 years and older.
Suramin may be indicated for use only if ivermectin cannot adequately control the disease. Amocarzine has not been shown to be effective in treating onchocerciasis. [29] Both suramin and amocarzine are capable of destroying adult worms. DEC therapy is no longer recommended.
When used concurrently with ivermectin therapy, tetracycline antibiotic therapy (eg, with doxycycline) depletes Wolbachia endosymbionts and may decrease transmission and reduce or prevent onchocerciasis-related blindness secondary to disruption of female nematode embryogenesis. [30]
Anthelmintics
Class Summary
Biochemical pathways in parasites are sufficiently different from those in the human host to allow selective interference by using chemotherapeutic agents in relatively small doses.
Ivermectin (Mectizan, Stromectol)
Ivermectin is an oral, semisynthetic, broad-spectrum anthelmintic agent isolated from S avermitilis. It binds selectively with glutamate-gated chloride-ion channels in invertebrate nerve and muscle cells, causing cell death. Its half-life is 16 hours, and it is metabolized in the liver. The usual frequency is every 12 months for mass treatment programs, but individual therapy may be given in intervals as short as 3 months.
Suramin (Metaret)
Suramin is a polyanionic compound developed as an antiparasitic drug for the treatment of CNS trypanosomiasis. It is an intravenous antiparasitic agent effective against African trypanosomiasis and onchocerciasis. Most often, a 10% solution is used. Administration of a test dose of 100-200 mg is advised before initiating treatment.
Moxidectin
Moxidectin, a macrocyclic lactone, is an anthelmintic indicated for the treatment of onchocerciasis due to O volvulus in patients aged 12 years and older. Plasma half-life is 20-43 days, and thereby reduces and maintains low skin microfilarial density effectively. Moxidectin does not kill adult O volvulus. Follow-up evaluation is advised. Safety and efficacy of repeat administration has not been studied.
Antibiotics
Class Summary
When used concurrently with ivermectin therapy, tetracycline antibiotic therapy (eg, with doxycycline) depletes Wolbachia endosymbionts and may decrease transmission and reduce or prevent onchocerciasis-related blindness secondary to disruption of female nematode embryogenesis.
Doxycycline (Doryx, Vibramycin)
Doxycycline is a broad-spectrum, synthetically derived bacteriostatic antibiotic in the tetracycline class. It is almost completely absorbed, concentrates in bile, and is excreted in urine and feces as a biologically active metabolite in high concentrations.
Doxycycline inhibits protein synthesis and, thus, bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria. It may block dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.
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Leopard-spot pattern of depigmentation on the shins. Courtesy of Brooke Army Medical Center teaching file. All images are in the public domain.
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Dermatitis associated with microfilaria. Courtesy of Brooke Army Medical Center teaching file. All images are in the public domain.
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Hanging groin sign. Courtesy of Brooke Army Medical Center teaching file. All images are in the public domain.
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Hanging groin sign. Courtesy of Brooke Army Medical Center teaching file. All images are in the public domain.
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Onchocercoma. Courtesy of Brooke Army Medical Center teaching file. All images are in the public domain.
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Onchocercoma. Courtesy of Brooke Army Medical Center teaching file. All images are in the public domain.
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Photomicrograph of a skin biopsy specimen from a patient with onchocerciasis. A worm is shown in cross-section. Courtesy of Brooke Army Medical Center teaching file. All images are in the public domain.
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Photomicrograph from a gravid female worm (hematoxylin and eosin]). Courtesy of Brooke Army Medical Center. All images are in the public domain.
