Mapping the global distribution of Buruli ulcer: a systematic review with evidence consensus

Abstract

Background: Buruli ulcer can cause disfigurement and long-term loss of function. It is underdiagnosed and under-reported, and its current distribution is unclear. We aimed to synthesise and evaluate data on Buruli ulcer prevalence and distribution.

Methods: We did a systematic review of Buruli ulcer prevalence and used an evidence consensus framework to describe and evaluate evidence for Buruli ulcer distribution worldwide. We searched PubMed and Web of Science databases from inception to Aug 6, 2018, for records of Buruli ulcer and Mycobacterium ulcerans detection, with no limits on study type, publication date, participant population, or location. English, French, and Spanish language publications were included. We included population-based surveys presenting Buruli ulcer prevalence estimates, or data that allowed prevalence to be estimated, in the systematic review. We extracted geographical data on the occurrence of Buruli ulcer cases and M ulcerans detection from studies of any type for the evidence consensus framework; articles that did not report original data were excluded. For the main analysis, we extracted prevalence estimates from included surveys and calculated 95% CIs using Byar's method. We included occurrence records, reports to WHO and the Global Infectious Diseases and Epidemiology Network, and surveillance data from Buruli ulcer control programmes in the evidence consensus framework to grade the strength of evidence for Buruli ulcer endemicity. This study is registered with PROSPERO, number CRD42018116260.

Findings: 2763 titles met the search criteria. We extracted prevalence estimates from ten studies and occurrence data from 208 studies and five unpublished surveillance datasets. Prevalence estimates within study areas ranged from 3·2 (95% CI 3·1-3·3) cases per 10 000 population in Côte d'Ivoire to 26·9 (23·5-30·7) cases per 10 000 population in Benin. There was evidence of Buruli ulcer in 32 countries and consensus on presence in 12.

Interpretation: The global distribution of Buruli ulcer is uncertain and potentially wider than currently recognised. Our findings represent the strongest available evidence on Buruli ulcer distribution so far and have many potential applications, from directing surveillance activities to informing burden estimates.

Funding: AIM Initiative.

Figure 1. Evidence consensus framework used to assess strength of evidence for Buruli ulcer presence and absence at national level

(A) Framework for all countries. (B) Framework for countries with no evidence of reported cases. Numbers in bold show each constituent’s maximum score. GIDEON=Global Infectious Diseases and Epidemiology Network. *Score was adjusted post-hoc for countries from which Mycobacterium ulcerans strains had been isolated, if no cases meeting inclusion criteria were identified.

Figure 2. Evidence consensus framework used to assess strength of evidence for Buruli ulcer presence at subnational level

Numbers in bold show each constituent’s maximum score.

Figure 3. Selection of eligible studies

Figure 4. Evidence consensus for Buruli ulcer presence and absence worldwide

Figure 5. Evidence for Buruli ulcer endemicity at national and upper subnational levels in Africa

ADM0=national administrative division. ADM1=upper subnational administrative division.

Figure 6. Evidence for Buruli ulcer endemicity at national and upper subnational levels in Central and South America and the Pacific Region

ADM0=national administrative division. ADM1=upper subnational administrative division.

Figure 7. Evidence for environmental occurrence of Mycobacterium ulcerans at upper subnational level and for Buruli ulcer endemicity at national level in west and central Africa, the western Pacific region, and South America