Opening a Can of Worms: Leprosy Reactions and Complicit Soil-Transmitted Helminths

Abstract

Background> 94% of new annual leprosy cases are diagnosed in populations co-endemic for soil-transmitted helminths (STH). STH can profoundly dysregulate host immune responses towards Th2 bias, which can be restored over time after deworming. We hypothesize that STH co-infection is associated with leprosy reaction (denoted as simply “reaction” herein) occurrence within a co-endemic population.MethodsA cohort study was performed on a cohort of Nepalese leprosy patients across treatment and diagnostic classifications who were screened by routine fecal smear microscopy and multiplex quantitative PCR (qPCR) for Ascaris lumbricoides (Al), Strongyloides stercoralis (Ss), Ancyclostoma duodenale (Ad) and Necator americanus (Na).ResultsAmong 145 patients, 55% were positive for ≥ 1 STH (STH +): 34% Al +, 18% Ss +, 17% Ad + and 5% Na +. Significant inverse STH and reaction relationships were evidenced by the bulk of cases: 63% reaction-negative were STH + of total cases (p = 0.030) while 65% reaction-positive were STH − in new cases (96; p = 0.023). Strikingly, the majority of STH + were reaction-negative, even when considering each species: 59% Al +, 60% Ss +, 62% Ad + and 67% Na + of new leprosy cases.ConclusionsAbsence of STH co-infection is associated with leprosy reaction at diagnosis within a co-endemic population. This is likely due to immune reconstitution effects after deworming or interruption of chronic STH-mediated immune dysregulation.

Longitudinal assessment of anti-PGL-I serology in contacts of leprosy patients in Bangladesh

“…Furthermore, it is worthy to note that leprosy is a complicated disease with different immunological processes playing a role in disease progression, which in turn are affected by factors such as genetics[ 27 ], co-infections[ 28 ] as well as food-shortage[ 29 ]. The combination of these factors with the long incubation time that elapses before leprosy becomes clinically manifest, makes predicting which M .…”

“…For example, certain helminth-derived proteins can bias the host immune response towards an anti-inflammatory Th2 response, which may facilitate M . leprae growth or progression to MB leprosy[ 28 ]. Furthermore, a period of food shortage can reduce cell mediated immunity of individuals incubating M .…”

Detection ofMycobacterium lepraeDNA in soil; Multiple needles in the haystack?

“…Granting M. leprae transmission is not completely understood, risk factors for development of leprosy have been identified including close contact with untreated, multibacillary patients(3), human susceptibility genes(4, 5), infection with soil transmitted helminths(6), as well as food shortage(7).…”

The Burden of Helminth Coinfections and Micronutrient Deficiencies in Patients with and without Leprosy Reactions: A Pilot Study in Minas Gerais, Brazil

“…13 This study also showed a higher odds of STH in multibacillary (MB) versus paucibacillary leprosy cases, an association which Diniz et al 14 also demonstrated in Brazil. On the other hand, Hagge et al 15 found a lower risk of reactions in STH-positive participants.…”