Leprosy Mailing List – April 17, 2023
Ref.: (LML) Is it a bad idea to reduce transmission rapidly?
From: Joel Almeida, Mumbai, India
Dear Pieter and colleagues,
Transmission of HD (leprosy) continues largely as it did two decades ago, even in places that have used single dose rifampicin among contacts of HD patients and BCG. Does it matter whether or not LL (lepromatous) HD patients in endemic areas are protected?
A study in India (1) reported recurrences of HD (leprosy) in two groups of patients treated regularly with MDT. One group had fixed duration treatment (24 months of MDT). The other group had MDT prolonged until skin smear negativity. In highly bacillated patients, skin smear negativity is typically delayed for several years beyond 24 months of MDT.
An increase in bacillary index (BI) of 2 log units or more at any site was taken as recurrence.
Among patients with a pre-treatment BI of 4+ or more, the recurrence rate differed according to whether MDT was prolonged or withdrawn after only 24 months, A recurrence rate of only 1.27/100 patient-years of follow-up was found in the prolonged MDT group compared to 4.29/100 patient-years in the fixed 24 months MDT group (p<0.01).
In other words, withdrawing anti-microbial protection from highly bacillated patients in endemic areas after only 24 months vastly increases their risk of recurrent HD (in this study, by over 230%).
Interestingly, the reported observations suggest that as many as 40% of recurrences would have been missed, or perhaps discovered only belatedly, if regular smear microscopy had been omitted. Without regular skin smears, diagnosis of reinfection can be difficult.
In an area of Brazil, the risk of recurrence was shown to be associated with the local endemicity of HD (2). For each new case among children under 15 years old, 2.41 cases of HD recurrence were reported among adults. This relationship between endemicity and risk of recurrence in a non-isolated non-endogamous population is more consistent with exogenous reinfection than with endogenous relapse.
Ensuring that highly bacillated patients in endemic areas receive anti-microbial protection against reinfection seems wise. Otherwise reinfection can maintain transmission despite all other efforts. Further, premature withdrawal of MDT from highly bacillated patients is known to boost the risk of painful ENL neuritis (as discussed in LML 26 March 2023).
The disappointing epidemiological impact of currently fashionable approaches contrasts with the rapid decline in new MB (multibacillary)and LL HD documented in Karigiri (India), Uele (DR Congo) and Weifang/Shandong (China), of the order of 16% to 20% per year (3-5). Prolonged anti-microbial protection for LL patients is the common thread in highly impactful projects in endemic areas. Without prolonged anti-microbial protection for LL patients, each patient is forced to incur an elevated risk of painful ENL and in case of reinfection to become a walking factory generating and shedding tens of millions of viable bacilli per day or even per nose blow (6)
It seems wiser, and more humane, to emulate impactful projects of great colleagues in endemic areas than to oppose protection of LL patients against reinfection in endemic areas.
Is it a bad idea to reduce transmission rapidly?
Joel Almeida
References
1. Girdhar BK, Girdhar A, Kumar A. Relapses in multibacillary leprosy: effect of length of therapy. Lepr Rev. 2000 Jun;71(2):144-53
2. Gonçalves FG, Belone AFF, Rosa PS, Laporta GZ.Underlying mechanisms of leprosy recurrence in the Western Amazon . BMC Infectious Diseases (2019) 19:460
3. Norman G, Bhushanam JDRS, Samuel P. Trends in leprosy over 50 years in Gudiyatham Taluk, Vellore, Tamil Nadu. Ind J Lepr 2006. 78(2): 167-185. reviewed and analysed further in: 3a. Almeida J. Karigiri, India: How transmission rapidly was reduced in a low-income population. LML 29 Oct 2020
4. Tonglet R, Pattyn SR, Nsansi BN et al. The reduction of the leprosy endemicity in northeastern Zaire 1975/1989 J.Eur J Epidemiol. 1990 Dec;6(4):404-6 reviewed in: 4a. Almeida J. Reducing transmission in poor hyperendemic areas - evidence from Uele (DRC). LML 29 Nov 2019
5. Li HY, Weng XM, Li T et al. Long-Term Effect of Leprosy Control in Two Prefectures of China, 1955-1993. Int J Lepr Other Mycobact Dis. 1995 Jun;63(2):213-221. reviewed & analysed further in: 5a. Almeida J. What really happened in Shandong? LML 16 Nov 2019
LML - S Deepak, B Naafs, S Noto and P Schreuder
LML blog link: http://leprosymailinglist.blogspot.it/
Contact: Dr Pieter Schreuder << editorlml@gmail.com
--You received this message because you are subscribed to the Google Groups "Leprosy Mailing List" group.
To unsubscribe from this group and stop receiving emails from it, send an email to leprosymailinglist+unsubscribe@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/leprosymailinglist/bd834575-65c0-4b67-93d5-b5f482d8652dn%40googlegroups.com.
No comments:
Post a Comment