BACKGROUND: Malawi, Uganda, and Zimbabwe have recently adopted a universal 'test-and-treat' approach to the prevention of mother-to-child transmission of HIV (Option B+). Amongst a largely asymptomatic population of women tested for HIV and immediately started on antiretroviral treatment (ART), a relatively high number are not retained in care; they are labelled 'defaulters' or 'lost-to-follow-up' patients. METHODS: We draw on data collected as part of a study looking at ART decentralization (Lablite) to reflect on the spaces created through the instrumentalization of community health workers (CHWs) for the purpose of bringing women who default from Option B+ back into care. Data were collected through semi-structured interviews with CHWs who are designated to trace Option B+ patients in Uganda, Malawi and Zimbabwe. FINDINGS: Lost to follow up women give a range of reasons for not coming back to health facilities and often implicitly choose not to be traced by providing a false address at enrolment. New strategies have sought to utilize CHWs' liminal positionality - situated between the experience of living with HIV, having established local social ties, and being a caretaker - in order to track 'defaulters'. CHWs are often deployed without adequate guidance or training to protect confidentiality and respect patients' choice. CONCLUSIONS: CHWs provide essential linkages between health services and patients; they embody the role of 'extension workers', a bridge between a novel health policy and 'non-compliant patients'. Option B+ offers a powerful narrative of the construction of a unilateral 'moral economy', which requires the full compliance of patients newly initiated on treatment.