Linking Climate to Incidence of Zoonotic Cutaneous Leishmaniasis (L. major) in Pre-Saharan North Africa

Abstract

Shifts in surface climate may have changed the dynamic of zoonotic cutaneous leishmaniasis (ZCL) in the pre-Saharan zones of North Africa. Caused by Leishmania major, this form multiplies in the body of rodents serving as reservoirs of the disease. The parasite is then transmitted to human hosts by the bite of a Phlebotomine sand fly (Diptera: Psychodidae) that was previously fed by biting an infected reservoir. We examine the seasonal and interannual dynamics of the incidence of this ZCL as a function of surface climate indicators in two regions covering a large area of the semi-arid Pre-Saharan North Africa. Results suggest that in this area, changes in climate may have initiated a trophic cascade that resulted in an increase in ZCL incidence. We find the correlation between the rainy season precipitation and the same year Normalized Difference Vegetation Index (NDVI) to be strong for both regions while the number of cases of ZCL incidence lags the precipitation and NDVI by 2 years. The zoonotic cutaneous leishmaniasis seasonal dynamic appears to be controlled by minimum temperatures and presents a 2-month lag between the reported infection date and the presumed date when the infection actually occurred. The decadal increase in the number of ZCL occurrence in the region suggests that changes in climate increased minimum temperatures sufficiently and created conditions suitable for endemicity that did not previously exist. We also find that temperatures above a critical range suppress ZCL incidence by limiting the vector’s reproductive activity.

Truncated seasonal activity patterns of the western blacklegged tick (Ixodes pacificus) in central and southern California

“…A number of large-scale anthropogenic changes, such as land use and climate change, are contributing to the amplification of emerging infectious zoonotic diseases. For example, the distribution of vector species may shift or expand as a result of climate change, and lead to subsequent shifts in vector-borne disease burden (Bounoua et al, 2013;Ogden et al, 2008b). In the case of pathogens with complex transmission cycles involving multiple hosts and vector life stages, changing host ecology resulting from land use or environmental change may also alter human disease risk through vector abundance (Ogden et al, 2014), infection prevalence with the pathogen (Allan et al, 2003;Patz et al, 2004), or vector activity patterns (Ogden et al, 2008a).…”

Effect of temperature, rainfall and relative density of rodent reservoir hosts on zoonotic cutaneous leishmaniasis incidence in Central Tunisia

“…The work of Kassem et al [25] in the Nile Delta revealed that sand fly densities were strongly correlated to temperature but not to relative humidity or wind velocity. However, the study of Bounoua et al [26] in Algeria demonstrated that the establishment of new endemic foci in regions that were not previously endemic was related to sufficient increase in minimum temperatures.…”

Spatial relations among environmental factors and phlebotomine sand fly populations (Diptera: Psychodidae) in central and southern Morocco

“…To analyze some environmental variables related to disease incidence, geoprocessing is becoming very important for landscape epidemiology (Hugh‐Jones , Washino and Wood , Beck et al The transmission profile of leishmaniasis includes landscape elements and in Morocco, previous studies have suggested several environmental factors that may influence, directly or indirectly, the distribution of sand flies, including altitude (Guernaoui et al biotopes (Guernaoui and Boumezzough ), aspect (Boussaa et al climate (Rispail et al Bounoua et al and soil type (Boussaa and Boumezzough ).…”