(LML) Classification of patients and interruption of transmission

Leprosy Mailing List – April 14,  2019

Ref.:  (LML)  Classification of patients and interruption of transmission

From:  Joel Almeida, London and Mumbai

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Dear Pieter,

Following discussion about the proportion of PB cases among newly detected cases, I performed the following analysis on data from China (1)

The Figure. Analysis of the proportion MB according to proportion detected by active case-finding, in China 1949-1998.

Active case-finding is observed to increase the proportion of PB patients (and correspondingly decrease the MB proportion) among newly detected patients. For every 10% increase in the proportion of patients detected by active case-finding, the proportion of PB patients among newly detected patients increased by roughly 7.5%.

PB patients harbour relatively few bacilli. Many of these persons are completely non-infectious, with single lesions that tend to self-heal without any sequelae. Self-healing patients are better off, in every way, without any treatment. We detect and treat PB patients only because some of them tend to downgrade to MB leprosy if left untreated. However, our preoccupation with detecting PB patients can sometimes divert attention from untreated LL patients. Yet untreated LL patients are critical to keeping the endemic alive.

Further, among newly detected patients in India, MB patients were observed to be about 5 to 10 times more likely than PB patients to suffer visible deformities before diagnosis. (2)  Therefore, prompt detection of MB patients is doubly important. It is particularly helpful not only to reduce transmission but also to avert visible deformity. That's why slit skin smears are so important. They enable quicker detection and classification of LL patients even when signs of disease are not prominent. If MB patients are detected promptly and LL patients correctly classified at diagnosis, we know thereafter how to protect nerves and how to protect LL patients against re-infection. It has been demonstrated before and it can be done again.

Transmission is maintained largely from one LL patient to another LL patient, including via the environment. Once an LL patient can no longer directly or indirectly infect another LL patient, the entire endemic tends to decline. The reproduction ratio of LL patients falls below one. That was how Shandong Province achieved lasting success. (3, 4)

Our critical mistake in endemic areas has been to leave LL patients unprotected against re-infection. (5, 6) Our job is to protect all known LL patients and ensure that they never re-enter the pool of infection. Then they cannot contribute to the environmental reservoir of bacilli. That's how the endemic starts its steady and terminal decline. Instead, we have failed to remove them reliably from the pool of infectious persons. Shandong Province avoided that serious mistake.

Merely observing LL patients after MDT, and delaying re-treatment until obvious signs appear, is insufficient. That's because signs of re-infection in LLp patients tend to be subtle and delayed. By the time treatment is re-started, the environmental reservoir of bacilli is already replenished. That replenishment is sufficient to infect another person with LLp genetics. That enables the endemic to be maintained despite all our heroic efforts, innovations and predictions.

Therefore, prolonged anti-microbial protection for "cured" LL patients in endemic areas is likely to be the most important and effective form of chemoprophylaxis. It worked in Shandong Province, yielding near-zero transmission. We neglect it at the cost of the nerves, eyes, limbs, livelihoods and relationships of the lay people who trust us.

Our discussions point us increasingly towards victory. We can be optimistic because endemic countries including India and Brazil have many bright, energetic and committed professionals who keep questioning assumptions, discarding past errors, making improvements continuously at the front-lines, and ploughing ahead towards success. More power to them. We can assist by opening our minds and improving the quality of our technical advice.

एमडीटी के बाद एलएल रोगियों के लिए लंबे समय तक एंटी-माइक्रोबियल सुरक्षा केमोप्रोफाइलैक्सिस का सबसे महत्वपूर्ण और प्रभावी रूप है। यह पहले से ही शेडोंग प्रांत में लगभग शून्य संचरण हासिल किया।

A proteção antimicrobiana prolongada para pacientes com LL após a MDT é provavelmente a forma mais importante e eficaz de quimioprofilaxia. Já resultou em transmissão quase zero na província de Shandong.

La protection antimicrobienne prolongée des patients LL après la PCT est probablement la forme de chimioprophylaxie la plus importante et la plus efficace. Cela a déjà entraîné une transmission presque nulle dans la province du Shandong.

Joel Almeida

P.S. Thanks to LML founders and editors for LML's unique and invaluable role as a platform for rapid and continuous improvement.

References

1) Xiang-Sheng Chen, Wen-Zhong Li, Cheng Jiang, & Gan-Yun Ye. Leprosy in China: epidemiological trends between 1949 and 1998. Bulletin of the World Health Organization, 2001, 79: 306–312

2) Kiran Katoch, Abha Aggarwal, Virendra Singh Yadav, Arvind Pandey. National sample survey to assess the new case disease burden of leprosy in India. Indian Journal of Medical Research, 2017; 146(5): 585-605.  

3) Li Huan-Ying, Pan Yu-Lin, and Wang Yang. Leprosy Control in Shandong Province, China,1955-1983; Some Epidemiological Features. Int J Lepr (1985) 53(1): 79-85.

4) Shumin Chen, Yunchun Zheng, Min Zheng, Demin Wang. Rapid survey on case detection of leprosy in a low endemic situation, Zhucheng County, Shandong Province, The People's Republic of China. Lepr Rev (2007) 78, 65–69.

5) da Silva Rocha A, Cunha Dos Santos AA, Pignataro P et al. Genotyping of Mycobacterium leprae from Brazilian leprosy patients suggests the occurrence of reinfection or of bacterial population shift during disease relapse. J Med Microbiol. 2011 Oct;60(Pt 10):1441-6. doi: 10.1099/jmm.0.029389-0.

6) Stefani MMA, Avanzi C, Bührer-Sékula S et al. Whole genome sequencing distinguishes between relapse and reinfection in recurrent leprosy cases. PLoS Negl Trop Dis (2017) 11(6): e0005598.

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

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

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