Environmental, Climatic, and Parasite Molecular Factors Impacting the Incidence of Cutaneous Leishmaniasis Due to Leishmania tropica in Three Moroccan Foci

Abstract

Cutaneous leishmaniasis (CL) occurring due to Leishmania tropica is a public health problem in Morocco. The distribution and incidence of this form of leishmaniasis have increased in an unusual way in the last decade, and the control measures put in place are struggling to slow down the epidemic. This study was designed to assess the impact of climatic and environmental factors on CL in L. tropica foci. The data collected included CL incidence and climatic and environmental factors across three Moroccan foci (Foum Jemaa, Imintanout, and Ouazzane) from 2000 to 2019. Statistical analyses were performed using the linear regression model. An association was found between the occurrence of CL in Imintanout and temperature and humidity (r2 = 0.6076, df = (1.18), p-value = 3.09 × 10−5; r2 = 0.6306, df = (1.18), p-value = 1.77 × 10−5). As a second objective of our study, we investigated the population structure of L.tropica in these three foci, using the nuclear marker internal transcribed spacer 1 (ITS1). Our results showed a low-to-medium level of geographic differentiation among the L.tropica populations using pairwise differentiation. Molecular diversity indices showed a high genetic diversity in Foum Jemaa and Imintanout; indeed, 29 polymorphic sites were identified, leading to the definition of 13 haplotypes. Tajima’s D and Fu’s F test statistics in all populations were not statistically significant, and consistent with a population at drift–mutation equilibrium. Further analysis, including additional DNA markers and a larger sample size, could provide a more complete perspective of L. tropica’s population structure in these three regions. In addition, further research is needed to better understand the impact of climatic conditions on the transmission cycle of Leishmania, allowing both for the development of effective control measures, and for the development of a predictive model for this parasitosis.

Climate Variables Related to the Incidence of Human Leishmaniosis in Montenegro in Southeastern Europe during Seven Decades (1945–2014)

“…Leishmaniosis is a climate-sensitive disease, since the reproduction and behavior of its vector, the sandfly, is under strong impact of meteorological parameters: precipitation, air temperature, and humidity [24][25][26][27]. Our study demonstrated that per every degree of air temperature rise in the coastal and central region yearly, there was a statistically significant positive correlation with the increase in the number of people affected by leishmaniosis.…”

The Impact of Climatological Factors on the Incidence of Cutaneous Leishmaniasis (CL) in Colombian Municipalities from 2017 to 2019

“…Climate impacts CL dynamics through its effect on vector population density and ecological behavior; meteorological parameters influence vector reproduction and behavior [ 68 ], with vector abundance linked to CL cases [ 12 ]. Vectors show sensitivity to abrupt temperature changes, suggesting an optimal development temperature range identified in experimental studies across various sandfly and Leishmania species [ 16 , 69 ], which respond differently to environmental stimuli.…”

Entomological, parasitological and molecular investigations in a new focus of cutaneous leishmaniasis in Youssoufia region, Morocco

“…In other study, the highest rates of both active lesions and scars were found in the age group of 10 years or under with significant differences (Fazaeli et al., 2009). This result can be explained by the fact that the prevalence of the infection tends to increase with age up to 15 years, after which it becomes stable, probably indicating the development of a protective immune status (Daoui et al., 2022).…”