Mucosal leishmaniasis in Brazil: spatiotemporal patterns from a 23-year retrospective study

Mucosal/mucocutaneous leishmaniasis (ML) is a severe form of tegumentary leishmaniasis (TL). This study analyzed spatiotemporal patterns in the occurrence of ML in Brazil between 2001 and 2023. All ML cases reported to the Brazilian national surveillance system were included. Joinpoint regression models were used to assess temporal trends in ML incidence and in the percentage of ML cases among TL cases (%ML). Spatial scan statistics identified spatial and spatiotemporal clusters of ML incidence at the municipal level, while global and local (LISA) Moran's I statistics evaluated spatial autocorrelation of smoothed municipal %ML. Cases of ML accounted for 6.1% (n=30,192) of all TL cases reported in Brazil. The cumulative incidence of ML was 0.67 cases/100,000 inhabitants. Although ML incidence declined over time, %ML increased markedly between 2020 and 2023. ML occurred in 53.2% of Brazilian municipalities, with higher ML incidence in the Legal Amazon region, where spatial and spatiotemporal high-incidence scan clusters were identified. The smoothed municipal %ML ranged from 0.0% to 52.3% and showed moderate positive spatial autocorrelation (I=0.395; p=0.001). Approximately 10% (n=554) of Brazilian municipalities were located in High-High LISA clusters for this indicator, including areas outside the Legal Amazon, suggesting that a high relative burden of ML is not restricted to this region. Despite its widespread occurrence, ML showed a heterogeneous spatial distribution, with high-incidence areas concentrated in relatively few municipalities. The increasing %ML is concerning and may reflect changes in disease detection and surveillance practices, as well as factors related to diagnosis and treatment, warranting further investigation.