Leprosy as a challenge to science on the ability to decode its enigma. A hypothesis on how to respond

In world leprosy nowadays, a favorable epidemiologic trend has been provided due to the best effort of the worldwide campaign with chemotherapy providing a bright but one-sided look at the future. However, the numbers of new patients are still higher than those under chemotherapy, leaving a concern over the remaining non-human source of infection. To overcome that plausibility, overall understanding of the etiology of the disease should be improved. The author discussed this by the analyses of historical and scientific legitimacy of the current idea about the etiology of leprosy that have unreasonably rejected the possibility of dual infections in relation to that of Mycobacterium leprae. The analyses also consider the author's ongoing effort to know the feasibility of artificial culture of M. leprae by improving of the former methods reported by Skinsnes et al. and has been rejected as it contained Mycobacterium scrofulaceum, without attention to the coexistent M. leprae at that time. The bacillus thus maintained with the modification of the medium still shows PGL-1 immunoreactivity and the pathogenicity to cause neuropathy in mice. These strongly suggest the coexistence of the above two bacilli throughout past years. The genomic study is in progress to prove that hypothesis, the genomes should be alike in nature if proven.