Trachoma is caused by repeated Chlamydia trachomatis infection in the eye. Routes of infection include close person-to-person contact and contaminated clothing. In addition, the bazaar fly Musca sorbens has been implicated in transmission. These flies frequently visit the faces of children and have been found positive for C. trachomatis, which may be transferred from the body of the flies or their regurgitated or defecated material.

This study aims to give recruited healthy volunteers a safe dose of oral ivermectin. Their faeces will be collected over subsequent days to determine whether ivermectin excreted from the body results in faecal concentrations that are high enough to prevent emergence of M. sorbens developing in faeces. It will also quantify ivermectin concentrations in tears secretions and faecal samples for up to 30 days post-treatment.

Inclusion Criteria:

• Able and willing to give fully informed consent
• Able to understand and comply with the study procedures
• Able to produce a stool on most days
• Consider themselves to be in good general health
• Aged 18 to 65 years

Exclusion Criteria:

• Suspected or known to be sensitive or allergic to ivermectin
• Women who are pregnant, nursing or intending to become pregnant
• Aware of having any neurological disorders or recent history of seizures
• History of travel to a region endemic for Loa loa.
• Currently taking acenocoumarol, warfarin or levimasole

Study outcomes are not related to the participant.

Investigators exposing flies to the faeces of volunteers will be masked as to the treatment (whether the sample is pre- or post-treatment).