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

Abstract 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.