Mass treatment with ivermectin (Mectizan, Merck & Co) is the mainstay of the current efforts to control onchocerciasis, but the drug is not lethal to adult Onchocerca volvulus parasites. Wolbachia, an endosymbiotic bacterium necessary for the fecundity of O. volvulus, can be eradicated with four-six week courses of doxycycline, but this cannot be implemented in current mass drug administration programs. The purpose of this study is to evaluate if a shorter course (five days) with antibiotics that could be used in children and potentially pregnant women would likewise be effective.

Guatemalan patients with onchocercal nodules will be enrolled in an open label trial with four treatment groups: Group A (rifampin 20 mg/kg po (maximum 600 mg/day)); B (azithromycin 12 mg/kg po (maximum 500 mg/day)); C (combination of rifampin 20 mg/kg po (maximum 600 mg/day) and azithromycin 12 mg/kg po (maximum 500 mg/day)); D (control group, multivitamin). At the end of the five day treatment course all participants will receive a single dose of ivermectin (150 mcg/kg).

Nodulectomies will be performed 9 months after treatment and the O. volvulus will be analyzed by immunohistochemical staining specific for Wolbachia .

Inclusion Criteria:

• Males and non-pregnant/non lactating females >5 years of age
• One onchocercal nodule in an anatomical position where it can be easily removed surgically

Exclusion Criteria:

• pregnancy (based on urine pregnancy test)
• breast-feeding
• women taking oral contraceptives
• allergy or other adverse reaction to either medication
• use of other medications (See Appendix 5) that might interact with rifampin
• clinical evidence of liver disease (jaundice, swollen abdomen)
• clinical evidence of chronic disease/alcoholism