This clinical trial compares two treatments - ivermectin and moxidectin - to learn which is better at reducing the proportion of people with onchocerciasis (river blindness) when given through mass drug administration (MDA) in Angola. Both drugs are approved by the United States Food and Drug Administration (FDA) to treat this disease. The study also explores how these treatments affect other infections common in the region, including intestinal worms (soil-transmitted helminths) and scabies.

The trial aims to answer the following key questions:

• How do moxidectin and ivermectin compare in reducing the prevalence (how common the disease is) and intensity (amount of parasites per person) of onchocerciasis in the community?
• Do the treatments differ in their effect on the prevalence and intensity of soil-transmitted helminths and the prevalence of scabies?
• Does moxidectin reduce transmission of onchocerciasis more effectively than ivermectin, based on genetic testing of parasites in people and lab testing of the blackflies that carry the infection?
• How many more years of treatment would be needed to reach elimination with each drug, based on mathematical disease modelling?
• How do communities feel about receiving moxidectin versus ivermectin, and what factors help or make it harder to carry out MDA programs with moxidectin versus ivermectin?

The study takes place in Bié Province, Angola, and involves 20 groups of villages randomly assigned to receive either moxidectin or ivermectin once a year for four years. Prior to every round of MDA, researchers will collect skin, stool and blood samples from a sample of the people living in the study area. We believe the results will help guide global policy on the use of moxidectin in efforts to eliminate onchocerciasis and control related diseases.

Inclusion Criteria:

• Male or female children and adults
• Residents in the villages selected for MDA treatment

Exclusion Criteria:

• Arm 1 (ivermectin): children under the age of 5 and/or under 90 cm of height
• Arm 2 (moxidectin): children under the age of 12 years (who will receive ivermectin if they are at least 90 cm in height/5 years of age and above).
• Arm 1 (ivermectin): Women breast-feeding babies under 45 days of age
• Arm 2 (moxidectin): All breastfeeding women (who will be offered ivermectin if their infants is at least 45 days old)
• Know allergy to ivermectin or moxidectin
• Attending other clinical trials during the study
• Pregnant
• Arm 2 (moxidectin): Women planning to become pregnant in the 3 months post-treatment
• Refusal to receive one or both study drugs, i.e. participants in villages allocated to receive moxidectin who refuse to receive moxidectin will be given the option to receive ivermectin; if they refuse to receive both drugs they will be excluded from the MDA altogether
• Has an illness that makes them too sick or weak to get out of bed
• Currently hospitalized