Abstract
We evaluated the distribution expansion of important human visceral leishmaniasis (HVL) and sporadic cutaneous leishmaniasis (SCL) vector species, Phlebotomus perfiliewi and P. perniciosus, throughout central Tunisia. Both visceral and cutaneous leishmaniasis are important vector-borne diseases in Tunisia. With the increase of irrigation in arid areas of Tunisia over the last twenty years there have been increases in the number of visceral cases reported. More than 10,000 wells have been developed throughout arid areas of Tunisia. However, entomological investigations on the effects of irrigation on the abundance and distribution of important sand fly vectors have not fully been explored. In this study we demonstrated that the abundance of P. perfiliewi, important human visceral leishmaniasis vector, is associated with the development of irrigated areas in the governorate of Sidi Bouzid while the abundance of P. perniciosus is not influenced by irrigation. These findings suggest that the expansion of P. perfiliewi is most likely associated with the increase in the number of HVL and SCL cases reported. With the continued development of irrigation we predict that this important species will continue to expand its distribution into more arid regions of Tunisia. The development of integrated vector management approaches targeting these developed irrigation sites could reduce vector populations and promote public health.
•Investigated the impact of irrigation on the distribution of leishmaniasis vectors.•Remote sensing approaches were used to predict the density of sand fly vectors.•The density of P. perfiliewi is predicted to be high in arid regions of Tunisia.•P. perfiliewi is associated with the establishment of irrigation.
The distribution expansion of important human visceral leishmaniasis (HVL) and sporadic cutaneous leishmaniasis (SCL) vector species, Phlebotomus perfiliewi and P. perniciosus, throughout central Tunisia is a major public health concern. This study was designed to investigate if the expansion of irrigation influences the abundance of sand fly species potentially involved in the transmission of HVL and SCL located in arid bioclimatic regions. Geographic and remote sensing approaches were used to predict the density of visceral leishmaniasis vectors in Tunisia. Entomological investigations were performed in the governorate of Sidi Bouzid, located in the arid bioclimatic region of Tunisia. In 2012, sand flies were collected by CDC light traps located at nine irrigated and nine non-irrigated sites to determine species abundance. Eight species in two genera were collected. Among sand flies of the subgenus Larroussius, P. perfiliewi was the only species collected significantly more in irrigated areas. Trap data were then used to develop Poisson regression models to map the apparent density of important sand fly species as a function of different environmental covariates including climate and vegetation density. The density of P. perfiliewi is predicted to be moderately high in the arid regions. These results highlight that the abundance of P. perfiliewi is associated with the development of irrigated areas and suggests that the expansion of this species will continue to more arid areas of the country as irrigation sites continue to be developed in the region. The continued increase in irrigated areas in the Middle East and North Africa region deserves attention, as it is associated with the spread of L. infantum vector P. perfiliewi. Integrated vector management strategies targeting irrigation structures to reduce sand fly vector populations should be evaluated in light of these findings.
