Cohort study of the seasonal effect on nasal carriage and the presence of Mycobacterium leprae in an endemic area in the general population

Abstract

Leprosy continues to be a significant health problem in certain pockets in developing countries. Better understanding of the transmission and source of the infection would help to decipher the transmission link, leading to control of the spread of the disease. The nose is considered to be a portal of entry, suggesting an aerial route for transmission through droplet infection. The evidence suggests that many individuals from endemic countries carry Mycobacterium leprae in their nasal cavities without having obvious symptoms of leprosy. The objective of the present study was to assess the presence of M. leprae on the nasal mucosa in the general population from a leprosy-endemic pocket. M. leprae detection was carried out using PCR targeting RLEP. Four hundred subjects from an area highly endemic for leprosy were included in the study and followed up during three different seasons--winter, summer, and monsoon--for evidence of nasal exposure to M. leprae. PCR positivity for M. leprae was observed in 29%, 21% and 31% of the samples collected in winter, summer and the monsoon season, respectively. Twenty-six individuals from the cohort showed amplification for M. leprae for all seasons. Our results are consistent with reports in the literature showing widespread exposure to M. leprae in the endemic community. The results also suggest possible association of the environmental conditions (climate) with the transmission pattern and levels of exposure to M. leprae. However, the present study indicated that the population from highly endemic pockets will have exposure to M. leprae irrespective of season.

Leprosy in Brazil and its association with characteristics of municipalities: ecological study, 2009–2011

“…Studies have suggested that the population living in endemic areas with poor conditions is at highest risk for acquiring Mycobacterium leprae irrespective of season (Bhat & Prakash ; Lavania et al . ). Future studies, including field‐collected validation data (temperature, rivers, water sources, humidity), may help to identify the environmental factors associated with the incidence rate of leprosy.…”

Recent laboratory advances in diagnostics and monitoring response to treatment in leprosy

“…[838485] Several studies in Indonesia, India, and Brazil have indicated that in an endemic community as population are exposed to infection, the biological samples such as blood, nasal swabs, saliva, and slit-skin smears of contacts of patients remain positive either for ML-specific antibody or for specific component of ML. [868788899091] How many of these biomarker-positive contacts of the population will transform into cases is generally uncertain and depends on the immune status of the individual having subclinical infection. These diagnostic tests are performed only once in individuals who pass through a dynamic state of the immune system, and therefore every individual who test positive to these assays do not develop leprosy in future.…”

Leprosy Diagnosis: An Update on the Use of Molecular Tools Lucrecia

“…The extraction and amplification of M. leprae DNA from nasal secretions can be very useful in both screening of potential contacts and leprosy control [43,49,85,88]. On the other hand, it has also demonstrated the importance of identifying healthy and subclinical carriers [50,83,84,87,[89][90][91][92]. In endemic countries, some studies have shown that there are no differences in being a nasal carrier of M. leprae DNA between contacts and non contacts (controls) of a leprosy patient [83,87].…”

“…In endemic countries, some studies have shown that there are no differences in being a nasal carrier of M. leprae DNA between contacts and non contacts (controls) of a leprosy patient [83,87]. But, none of these studies have consistently associated the presence of the M. leprae DNA in nasal secretion with further development of the disease: it only indicates nasal carriage, which may imply active leprosy transmission [43,92].…”

“…The definitive identification of M. leprae is possible through the development of methods for the extraction, amplification, and identification of M. leprae DNA in clinical specimens using PCR [106]. A few studies have compared several genetic targets [26,27,38,40,52] employing several protocols standardized in small groups of patients [21,33,58,92]. The use of a repetitive sequence (RLEP) as a PCR target, provides the advantage of higher sensitivity because it is present at multiple sites in the genomic DNA, especially, in clinical samples, with low concentration of bacilli and/or degraded genomic material (PNL, IL and PB patients) [27,38,46,50,51,86].…”