Hidden burden of leprosy in incarcerated populations in northeast Brazil: active case detection and serological...

Leprosy remains a public health challenge in Brazil's Northeast, where prison overcrowding may facilitate transmission. Limited data exist on leprosy screening strategies in incarcerated populations.

This observational, cross-sectional study was conducted at Baldomero Cavalcante Male Penitentiary in Maceió, Alagoas, Brazil. A total of 915 inmates were approached using the Leprosy Suspicion Questionnaire (LSQ) as an active case-finding tool. Neurodermatological examinations were performed on 260 participants, and serological testing for anti-PGL-I (IgM) and anti-Mce1A antibodies (IgA, IgM, IgG) was conducted on 244 plasma samples using indirect ELISA.

Of 842/915 returned questionnaires (92%), 240/842 (28.5%) were positive in the LSQ. Clinical examination revealed 8 new leprosy cases among 260/842 evaluated inmates with positive and negative LSQ, yielding an overall new case detection rate (NCDR) of 3.08%, which increased to 6.52% among symptomatic individuals. All diagnosed patients were classified as having multibacillary disease, with 100% presenting some grade of physical disability at diagnosis, and 75% LSQ were positive (p = 0.0249), while only 34.1% in the non-leprosy group. Anti-Mce1A IgM showed 37.7% seropositivity rate, and 19.9% for anti-PGL-I among clinically unaffected individuals. IgA (100%), IgM (37.5%), and IgG (25%) anti-Mce1A antibodies were positive in the leprosy group.

The LSQ may be effective as a screening tool. The study confirms significant underdiagnosis of leprosy in prison populations and highlights that anti-Mce1A serology showed higher positivity among diagnosed cases than anti-PGL-I, particularly for the detection of early-stage and neural forms of the disease. These findings support enhanced active surveillance strategies in high-risk populations to achieve leprosy elimination goals.