Leprosy Mailing List – April 8, 2019
Ref.: (LML) Number and proportion of PB Leprosy cases reported
From: Joel Almeida, London and Mumbai
Dear Pieter,
Most persons newly developing perceptible signs of Hanseniasis are known to be self-healing and non-infectious. Only when a population is frequently examined are these transient signs detected. Otherwise the signs disappear before detection, and sequelae in these affected persons are vanishingly rare.
Therefore, more frequent examination of a population leads to a higher proportion of self-healing PB cases among newly detected cases, and consequently a higher new case detection rate.
This explains why the introduction of MDT resulted in an increasing trend in the new case detection rate until about the year 2000. Intensive case-finding was implemented. Most of those newly detected showed PB signs. In the early 2000s the policies changed. Active case-finding was discouraged. This changed policy worked to reduce the new case detection rate while reducing the PB proportion among newly detected cases.
The decline in PB proportion and decline in new case detection rate are both probably artefacts. Both of them can be boosted merely by increasing the frequency with which a population is examined. The underlying epidemiology usually remains relatively unchanged. All the more so because persons with polar LL Hanseniasis have been denied prolonged anti-microbial protection against re-infection.
One unprotected person with polar LL Hanseniasis is known to harbour and shed more M. leprae than hundreds of thousands of persons with transient PB signs. It is useful to protect persons with PB signs, but it is critical to protect persons with polar LL Hanseniasis. Otherwise transmission of M. leprae can continue with near full force.
We have cut back on skin smear services in some large endemic countries, Instead, we rely on the number of lesions for classifying newly diagnosed patients. Polar LL Hanseniasis tends to produce a single large lesion covering most of the body. Often this lesion is no more than diffuse infiltration of the skin (and palpation often reveals bilateral thickening of nerves). Merely counting skin patches, as our health workers are trained to do, guarantees that we either miss or misclassify persons with polar LL Hanseniasis. M. leprae is the winner.
In endemic areas, M. leprae re-infect the rare persons who have polar LL Hanseniasis once anti-microbial protection is withdrawn. Such persons are so rare that "relapse rates" or re-infection rates remain deceptively low after MDT. Our policy has been to withdraw anti-microbial protection from patients with polar LL Hanseniasis. That leaves them exposed to re-infection. This error is sufficient to maintain the transmission of M. leprae despite our other efforts, innovations and predictions.
M. leprae have been highly successful at deceiving us. Not only do they conceal their presence in persons harbouring the most M. leprae, but also, they produce clearly defined and visible skin patches in persons harbouring relatively few M. leprae. We have responded by training health workers to chase skin patches while neglecting skin smears and overlooking diffusely infiltrated skin. M. leprae is the winner.
If infectious diseases are like fires, and infectious agents like arsonists, then M. leprae is the deadliest of arsonists. It creates smoke to divert the fire brigade, while keeping the real flames hidden. Our various innovations tend to be like smoke extinguishers. Our predictions tend to be over-optimistic. But the real flames are overlooked. The fire keeps spreading, transmission of M. leprae continues. This can be explained, in large part, by our failure to protect persons with polar LL Hanseniasis against re-infection.
Until we start providing skin smear services and prolonged anti-microbial protection to persons with polar LL Hanseniasis, M. leprae will continue to win. Only places such as Shandong Province in China (1) defeated M. leprae using anti-microbial treatment. This was an unexpected and sustained victory, starting in the year 1955 and continuing relentlessly until near-zero transmission. It can be explained, in important part, by the skin smear services and prolonged anti-microbial protection provided to persons with polar LL Hanseniasis.
Meanwhile, we continue to do the opposite. We deny skin smear services and deny prolonged anti-microbial protection to persons with polar LL Hanseniasis. M. leprae is the winner.
M. leprae is the winner, but that need not remain so. If Shandong Province could interrupt transmission, then so can all of us. First, it would be good to open our eyes to the underlying epidemiology.
We can win. But probably only if we start providing skin smear services and prolonged anti-microbial protection to persons with polar LL Hanseniasis. Wouldn't it be good to win?
केवल चीन में शेडोंग प्रांत (1) जैसे स्थानों ने एंटी-माइक्रोबियल उपचार का उपयोग करके एम लेप्रै को हराया। यह जीत वर्ष 1955 में शुरू हुई और लगभग शून्य संचरण तक निरंतर रूप से जारी रही। यह skin smear सेवाओं द्वारा, और लंबे समय तक एल.एल. वाले व्यक्तियों को प्रदान की गई एंटी-माइक्रोबियल सुरक्षा द्वारा, समझाया जा सकता है। हम भी शायद इस तरह से जीत सकते हैं।
Apenas locais como a província de Shandong na China (1) derrotaram o M. leprae usando tratamento antimicrobiano. Esta foi uma vitória inesperada e sustentada, começando no ano de 1955 e continuando implacável até a transmissão quase zero. Isso pode ser explicado, em parte importante, pelos serviços de baciloscopia e proteção antimicrobiana prolongada fornecida a pessoas com hanseníase LL polar. Nós também provavelmente podemos vencer dessa maneira.
Seuls des endroits tels que la province chinoise du Shandong (1) ont vaincu M. leprae par un traitement antimicrobien. C'était une victoire inattendue qui a débuté en 1955 et qui s'est poursuivie sans relâche jusqu'à une transmission presque nulle. Cela peut s'expliquer, en grande partie, par les services de bacilloscopie cutanée et la protection antimicrobienne prolongée fournis aux personnes atteintes de hanséniose LL polaire. Nous aussi, nous pouvons probablement gagner de cette façon.
Joel Almeida
Reference
1. 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.
LML - S Deepak, B Naafs, S Noto and P Schreuder
LML blog link: http://leprosymailinglist.blogspot.it/
Contact: Dr Pieter Schreuder << editorlml@gmail.com
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