Physical Distance, Genetic Relationship, Age, and Leprosy Classification Are Independent Risk Factors for Leprosy in Contacts of Patients with Leprosy

TLDR

Close contacts of leprosy patients face a higher risk of developing the disease, with known risk factors including genetic relationship and physical distance. The study aimed to quantify the independent contributions of age, disease classification, physical distance, and genetic relationship to leprosy risk among contacts. The authors performed logistic regression on intake data from a prospective cohort of 1,037 newly diagnosed leprosy patients and 21,870 contacts. They found that age, disease classification (PB2‑5 or MB), physical proximity, and close genetic relationship were independently associated with higher leprosy risk, with core household contacts and consanguineous relatives at greatest risk.

Abstract

Close contacts of patients with leprosy have a higher risk of developing leprosy. Several risk factors have been identified, including genetic relationship and physical distance. Their independent contributions to the risk of developing leprosy, however, have never been sufficiently quantified.Logistic-regression analysis was performed on intake data from a prospective cohort study of 1037 patients newly diagnosed as having leprosy and their 21,870 contacts.Higher age showed an increased risk, with a bimodal distribution. Contacts of patients with paucibacillary (PB) leprosy with 2-5 lesions (PB2-5) and those with multibacillary (MB) leprosy had a higher risk than did contacts of patients with single-lesion PB leprosy. The core household group had a higher risk than other contacts living under the same roof and next-door neighbors, who again had a higher risk than neighbors of neighbors. A close genetic relationship indicated an increased risk when blood-related children, parents, and siblings were pooled together.Age of the contact, the disease classification of the index patient, and physical and genetic distance were independently associated with the risk of a contact acquiring leprosy. Contact surveys in leprosy should be not only focused on household contacts but also extended to neighbors and consanguineous relatives, especially when the patient has PB2-5 or MB leprosy.