Fw: Ref.: (LML) Discussion Paper: Revisiting Bacillary Persistence, Viability, and Transmission in Leprosy

 

 

Leprosy Mailing List – 23 June,  2026

 

Ref.:  (LML) Discussion Paper: Revisiting Bacillary Persistence, Viability, and Transmission in Leprosy

From: Joel Almeida, Mumbai, India

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Dear Pieter and colleagues,

Thanks to Dr. Isabela Goulart for a thought-provoking contribution (LML 19 June 2026).

 Ref.: (LML) Discussion Paper: Revisiting Bacillary Persistence, Viability, and Transmission in Leprosy

The questions can be discussed further by the many learned colleagues here. 
Would it be disrespectful of me to focus on this specific aspect:

"What direct biological evidence supports the assertion that epidemiologically relevant transmission is interrupted after the first dose of MDT?" 

MDT continues beyond the first dose, so complete sterilisation by the first dose is not required. The inclusion of "epidemiologically relevant" is helpful in terms of focusing on what is most important. Would it be wrong to ask, for practical purposes, whether anti-microbials are capable of interrupting transmission in a geographical area?

The answer is: Yes. Malta demonstrated this. (1) Weifang (China) also illustrated what is possible with reliable diagnosis and prolonged protection against reinfection. (2) 

Dr. Ben Naafs disclosed earlier that in Malta the late Dr. Leiker identified M. leprae (or at least AFB, acid fast bacilli) in the scrotum of a patient, despite the epidemiologically relevant elimination of transmission. If that person is still alive, the M. leprae (or AFB) might still be lurking in their scrotum. That is not necessarily epidemiologically relevant.

If every autopsy in an endemic area attempted to rule out the presence of M. leprae components, or even viability, the prevalence might approach the frequency of the positive lymphocyte transformation test for subclinical infection. (3) Extremely frequent, often >24% and in some subsets of the local population even >50%. 

None of that is necessarily important for epidemiologically relevant transmission. 

Is it wrong to look for concentrated viable bacilli across a village or neighbourhood and hit the bacilli hard and long? Or to do this simultaneously across a human cluster so that the risk of reinfection of polar LL after withdrawal of anti-microbials is greatly reduced? (e.g. nasal swabs from ALL asymptomatics for semi-quantitative mLAMP to distinguish high-shedding cryptic LL from transient carriers of trivial numbers of bacilli, followed by full treatment of all clinical cases and all cryptic LL high-shedders, backed by regular check-ups to preserve nerve function). Why not do this in parallel or in sequence across an endemic area, with periodic mop-up rounds?

Together with steady socio-economic improvements that uphold natural macrophage defences and minimise contact with concentrated viable bacilli in the environment, is there a quicker way to eliminate concentrated viable bacilli from the human population? Find, treat, end.

The inclusion of the word "concentrated" is critical in this context. We might miss some bacilli, but that is not necessarily epidemiologically relevant.

For the individual patient, the calculations are not necessarily identical. They want freedom from all signs of disease, all sequelae, all prejudice, all suffering, all unemployment, all hunger, all destitution (and to enjoy prosperity if possible). We try to assist as best we can given the current state of scientific knowledge and the resources available.

Is there no merit in simply eliminating concentrated viable bacilli rapidly from human populations? Like turning off at source an important cause of harm. Few if any persons in Malta (or Weifang, Chile, Jordan) have reason now to worry about the M. leprae complex and its potentially devastating consequences. Why not do our best to make that happen everywhere?

Esteemed colleagues will have even more insights. Apologies for the focus on "epidemiologically relevant transmission". The topic illustrates how valuable this group is for informed discussion by experts such as Dr. Isabela Goulart.

With all sincerity,

Joel Almeida

References

1.     Jacobson RR, Gatt P. Can leprosy be eradicated with chemotherapy? An evaluation of the Malta Leprosy Eradication Project. Lepr Rev 2008; 79(4):410-5

2.      Li HY, Weng XM, Li T et al. Long-Term Effect of Leprosy Control in Two Prefectures of China, 1955-1993. Int J Lepr 1995 Jun;63(2):213-221.

3.      Godal T, Negassi K (1973). Subclinical infection in leprosy. Br Med J. 3 (5880): 557-559
____________________________________________________________________________

LML - S Deepak, B Naafs, S Noto and P Schreuder

LML blog link: http://leprosymailinglist.blogspot.it/

Contact: Dr Pieter Schreuder << edit...@gmail.com

 

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