Previous Malaria Exposure and Early Tuberculosis Infection Outcomes among Household Contacts in Malawi: A Narrative Review
Chifundo Lusungu Milanzi
*
Malawi University of Science and Technology, Thyolo, Malawi.
*Author to whom correspondence should be addressed.
Abstract
Background: Tuberculosis (TB) and malaria remain major public health challenges in sub-Saharan Africa. Although many people are exposed to Mycobacterium tuberculosis (Mtb), the bacterium that causes TB, not all individuals develop a detectable infection. The reasons why some highly exposed individuals remain negative on TB infection tests are not fully understood.
Aim: This review examines differences in early Mtb infection outcomes and examines whether previous exposure to Plasmodium falciparum, the parasite that causes malaria, may influence these outcomes through lasting changes in innate immunity.
Methods: A narrative literature review was conducted using PubMed/MEDLINE, Google Scholar, Web of Science, and relevant institutional and international sources. The review focused on household contacts of TB patients, early Mtb infection outcomes, malaria-associated immune changes, and trained immunity, with particular attention to Malawi and similar settings. Findings were synthesised thematically.
Results: Evidence shows that some household contacts remain negative on TB infection tests despite substantial exposure, and this pattern has been associated with differences in innate immune responses. Studies also indicate that malaria can alter monocyte function, gene regulation, and cytokine responses, with some changes persisting beyond acute infection. Research from Malawi supports the presence of malaria-associated immune changes, while studies of malaria and TB co-infection suggest that malaria can modify immune responses to Mtb. However, direct evidence linking previous malaria exposure to subsequent Mtb infection outcomes remains limited. Most studies have examined concurrent infections rather than previous malaria exposure followed by longitudinal assessment of TB infection.
Conclusion: Previous malaria exposure may influence early Mtb infection outcomes through lasting changes in innate immunity, but this relationship has not been established. Further longitudinal studies in Malawi are needed to determine whether previous or repeated malaria exposure is associated with persistent negative TB infection tests or subsequent conversion to a positive interferon-gamma release assay (IGRA) result.
Keywords: Plasmodium falciparum, mycobacterium tuberculosis, tuberculosis, household contacts, innate immunity, trained immunity