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Observational Study
. 2019 Jun 7;19(1):501.
doi: 10.1186/s12879-019-4116-y.

Clustering of leprosy beyond the household level in a highly endemic setting on the Comoros, an observational study

Nimer Ortuno-Gutierrez  1 , Abdallah Baco  2 , Sofie Braet  3 , Assoumani Younoussa  2 , Aboubacar Mzembaba  2 , Zahara Salim  2 , Mohamed Amidy  2 , Saverio Grillone  2 , Bouke C de Jong  3 , Jan Hendrik Richardus  4 , Epco Hasker  3
Affiliations
Observational Study

Clustering of leprosy beyond the household level in a highly endemic setting on the Comoros, an observational study

Nimer Ortuno-Gutierrez et al. BMC Infect Dis. .

Abstract

Background: The island of Anjouan (Comoros) is highly endemic for leprosy with an annual incidence of 5-10/10,000. In May/June, 2015 single-dose Rifampicin post-exposure prophylaxis (SDR-PEP) was administered to 269 close contacts of 70 leprosy-patients in four villages as a pilot programmatic intervention. Two years later we revisited the villages for follow-up investigations. The main aim of our study was to quantify spatial associations between reported leprosy cases before and after PEP implementation. A secondary aim was to assess the effect of this single round of SDR-PEP at the individual level.

Methods: We conducted door-to-door leprosy screening in all four villages in August/September, 2017. We screened all consenting individuals for leprosy and recorded geographic coordinates of their household. We also recorded whether they had received SDR-PEP and whether they had been diagnosed with leprosy, before or after the 2015 intervention. We fitted a Poisson model with leprosy as outcome and distance to the nearest pre-intervention case and SDR-PEP as predictors.

Results: During the survey we found 114 new cases among 5760 contacts screened (2.0% prevalence), in addition to the 39 cases detected in the two preceding years. We found statistically significant associations of incident leprosy with physical distance to index cases ranging from 2.4 (95% confidence interval (95% CI) 1.5-3.6) for household contacts to 1.8 (95% CI 1.3-2.5) for those living at 1-25 m, compared to individuals living at ≥75 m. The effect of SDR-PEP appeared protective but did not reach statistical significance due to the low numbers, with an incidence rate ratio (IRR) of 0.6 (95% CI 0.3-1.2) overall, and 0.5 (95% CI 0.2-1.3) when considering only household contacts.

Conclusions: This pilot demonstrated an increased risk of leprosy in contacts beyond the household, therefore a wider circle should be considered for chemoprophylaxis. Baseline surveys and extended contact definitions are essential for improving SDR-PEP effectiveness.

Keywords: Clustering; Leprosy; Mapping; Post-exposure prophylaxis; Single dose rifampicin; Transmission.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Overview map of the Union of Comoros. Map of Comoros and neighboring countries
Fig. 2
Fig. 2
Distribution of index cases (January 2012–June 2015) and incident cases (July 2015–October 2017) in a village on Anjouan (Comoros). Legend: the map plots the household screened, incident leprosy cases households and incident leprosy cases in a village of Anjouan
See this image and copyright information in PMC

References

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