# Impact of Climatic Factors on the Incidence of Cutaneous Leishmaniasis in Essaouira, Morocco: A Decadal Analysis (2014–2023)

## TL;DR

This study examines how climate factors affect the spread of cutaneous leishmaniasis in Morocco's Essaouira region over ten years.

## Contribution

The study reveals a biphasic seasonal climate influence on CL incidence, with distinct winter and summer drivers.

## Key findings

- CL incidence increased sharply in 2022–2023 after being stable from 2014 to 2021.
- Warm and dry years are linked to higher CL incidence, with temperature positively and humidity/precipitation negatively correlated.
- Minimum temperature in summer and January rainfall are key seasonal drivers of CL transmission.

## Abstract

Background/Objectives: Cutaneous leishmaniasis (CL) remains a major public health and economic challenge in Morocco, where its transmission dynamics are increasingly influenced by climatic variability. This study aimed to evaluate the impact of meteorological factors on CL incidence in the province of Essaouira, a high-incidence region, to identify the environmental drivers behind recent epidemic trends. Methods: Epidemiological data (N = 834 cases) were collected from the Hygiene and Health Laboratory of Essaouira for the period between January 2014 and December 2023. Climatic variables were obtained from the Moroccan Directorate of National Meteorology. Data were analyzed at annual, seasonal, and monthly scales using the Spearman rank correlation in R 4.5.0 software to account for non-normal distributions and non-linear associations. Results: CL incidence remained stable from 2014 to 2021 before an unprecedented surge in cases during 2022–2023. Annual analysis indicated that warm and dry years pose a higher risk, with incidence positively correlated with temperatures and negatively associated with humidity and precipitation. Monthly results identified a biphasic regulatory mechanism: a winter hydric constraint phase with strong negative correlations with January rainfall and humidity (p < 0.05), followed by a summer thermal promotion phase where minimum temperature (Tmin) emerged as the dominant driver (rho = 0.53), peaking in September (rho = 0.59). Conclusions: Our findings confirm the significant influence of climatic factors on CL incidence through complex seasonal dynamics. These results highlight the necessity of integrating high-resolution meteorological monitoring and predictive modeling into public health surveillance to anticipate future outbreaks in the context of increasing Mediterranean aridification.