Serological Evidence of Soil-Transmitted Helminth Infections as a Potential Risk for Severity in Leprosy Patients.

Leprosy presents a broad clinical spectrum influenced by the host's immune response, and co-infections may further modulate disease progression. This study evaluated clinically diagnosed leprosy patients (n = 251) from Sergipe and Minas Gerais, Brazil, along with healthy controls (n = 43), soil-transmitted helminths-positive controls (n = 15), and household contacts (n = 176). Enzyme-linked immunosorbent assays were performed using predicted B-cell epitopes from immunogenic proteins of Ascaris sp., Trichuris trichiura, Strongyloides stercoralis, Ancylostoma duodenale and Necator americanus. Among leprosy patients, 123 (49%) were IgG seropositive for at least one soil-transmitted helminths antigen. Nine (7.3%) had optical density (OD) values exceeding 2-fold the cut-off, six (4.9%) surpassed 3-fold and one exceeded 7-fold. In patients with documented reactions (n = 34), seropositivity was observed in 6 with neuritis, 14 with type 1 reaction (T1R) and 14 with type 2 reaction (T2R), totaling 61.8%. Among household contacts, 96 (54.5%) were seropositive. Stratified analyses revealed significant differences in IgG levels between soil-transmitted helminths-seropositive and seronegative individuals within both paucibacillary and multibacillary groups, despite no overall association with operational classification. These findings suggest that helminth exposure may influence immune responses within leprosy subtypes and contribute to reactional episodes. The high seroprevalence observed in both patients and household contacts highlights shared environmental exposure and supports the inclusion of helminth monitoring in leprosy control strategies. Early detection and treatment of co-infections may reduce immune imbalances and severe inflammatory outcomes. Further studies are needed to elucidate the immunological mechanisms underlying helminth-leprosy interactions and to strengthen integrated approaches in public health.