Mycobacterium leprae-Helminth Co-Infections and Vitamin D Deficiency as Potential Risk Factors for Leprosy: A Case-Control Study in Southeastern Brazil.

BACKGROUND: Evidence suggests that biological mechanisms involved in helminth infections and vitamin deficiencies increase susceptibility to other infections. Our aim was to investigate the associations of helminth co-infection and select micronutrient deficiencies with leprosy through a case-control study design.

METHODS: From 2016-2018, individuals ages 3 years and older were recruited at clinics in and around Governador Valadares, Minas Gerais, Brazil in 3 groups: cases of leprosy, household contacts and community-matched controls. Helminths were diagnosed through stool Kato Katz exams and serum reactivity to anti-SWAP IgG4. Serum ferritin, 25-OH vitamin D, and retinol concentrations were measured. Multivariate logistic regression was conducted to identify associations with active leprosy.

RESULTS: We recruited 79 cases of leprosy, 96 household contacts, and 81 non-contact controls; 48.1% male with a median age of 40 years old. Helminths were found in 7.1% of participants by Kato Katz with all but one S. mansoni, and 32.3% were positive for S. mansoni serology. In multivariate analysis, cases were more likely be infected with helminths (diagnosed by stool) compared to contacts (aOR: 8.69 95% CI 1.50, 50.51). Vitamin D deficiency was common and associated with leprosy when compared to non-contact controls (aOR=4.66, 95% CI 1.42, 15.33). Iron deficiency was not associated with leprosy and we did not detect vitamin A deficiency.

CONCLUSION: These associations suggest that the immune consequences of schistosomiasis and vitamin D deficiency may increase the risk of active leprosy disease. Co-morbid conditions of poverty deserve further study as addressing co-infections and nutritional deficiencies could be incorporated into programs to improve leprosy control.