Household and Dwelling Contact as Risk Factors for Leprosy in Northern Malawi

Abstract

Data on household and dwelling contact with known leprosy cases were available on more than 80,000 initially disease-free individuals followed up during the 1980s in a rural district of northern Malawi. A total of 331 new cases of leprosy were diagnosed among them. Individuals recorded as living in household or dwelling contact with multibacillary patients at the start of follow-up were at approximately five- to eightfold increased risk of leprosy, respectively, compared with individuals not living in such households or dwellings. Individuals living in household or dwelling contact with paucibacillary cases were both at approximately twofold increased risk. The higher risk associated with multibacillary contact and the fact that dwelling contact entailed a greater risk than household contact if the association was with multibacillary, but not with paucibacillary, disease suggest that paucibacillary cases may not themselves be sources of transmission, but rather just markers that a household has had contact with some (outside) source of infection. When household contact was considered alone, the risks of disease were appreciably higher for younger than for older contacts and for male compared with female contacts. Despite the elevated risk of leprosy associated with household or dwelling contact, only 15% of all incidence cases arose among recognized household contacts. Given the dynamic nature of household membership and consequent misclassification of contact status, the true contribution to overall incidence of contact within household or dwelling settings is likely to be much higher than this, perhaps 30% or higher. Considering the predilection of males for infectious multibacillary forms of the disease, the transmission of Mycobacterium leprae at an early age, in particular to males, may be of particular importance for the persistence of leprosy in endemic communities. Although residential contact with a multibacillary case is the strongest known determinant of leprosy risk, the vast majority of such contacts never manifest disease, which indicates a crucial role for genetic and/or environmental factors in the transmission of M. leprae infection and/or the pathogenesis of clinical leprosy.

Armadillo meat intake was not associated with leprosy in a case control study, Curitiba (Brazil)

“…There are many cases of leprosy of unknown origin in various countries, climates and topographies on the planet, even in regions that are considered free of the disease. Our study confirms this observation because 65% of all cases did not present any acknowledged contacts (de Wit et al 1993, Fine et al 1997, Richardus et al 2005, Deps et al 2008.…”

“…In Bangladesh, up to 75% of patients do not report contact with leprosy patients and, in Malawi, southern Africa, this was true for 85% of all cases. Perhaps the presence of bacillus in the environment or in asymptomatic carriers may help to explain such cases (de Wit et al 1993, Fine et al 1997, Matsuoka et al 1999, Richardus et al 2005, Lavania et al 2008.…”

Identification of serological biomarkers of infection, disease progression and treatment efficacy for leprosy

“…A number of these antigens, including ML2028, ML2038 ) and the fusion protein LID-1 (Duthie et al 2010 have been shown to induce very strong antibody responses in virtually all BL/LL cases. A previous study in which HHCs of MB patients were bled four years prior to clinical diagnosis showed that seven/11 (64%) developed antibody re- A number of studies have shown that family members living in close contact with an untreated MB index case have the highest risk for developing this disease (Fine et al 1997, Cunanan et al 1998, van Beers et al 1999. In a large study involving 1,396 HHCs of index cases (79% of the index cases were MB) in Uberlândia, Brazil over a five-year period, 28 individuals were eventually diagnosed with leprosy, with 75% of those cases occurring within the first year of enrolment (Goulart et al 2008).…”

Interleukin-10 promoter single-nucleotide polymorphisms as markers for disease susceptibility and disease severity in leprosy

“…Household contacts of multibacillary (MB) patients are at the highest risk to acquire the disease. 1 Host susceptibility to disease and to specific disease manifestations, notably severe (MB) or mild (paucibacillary (BP)) leprosy, is influenced by both host genetic and environmental factors. 2,3 Several genomic regions have been implicated in genetically controlled susceptibility to and severity of leprosy.…”