Genetic diversity and population structure of Phlebotomus argentipes: Vector of Leishmania donovani in Sri Lanka

Abstract

Phlebotomus argentipes is the vector of Leishmania donovani which causes the disease leishmaniasis, a neglected tropical disease and a growing health problem in Sri Lanka. A proper understanding of the population genetic structure of sand fly vectors is considered important prior to planning and implementation of a successful vector control program. Thus, the present study was conducted to determine the population genetic structure of sand fly vectors in Sri Lanka. Two mitochondrial genes namely Cytochrome c oxidase subunit 1 (Cox 1) and Cytochrome b (Cytb), and the internal transcribed spacer 2 (ITS2) region from the nuclear ribosomal DNA were used for molecular characterization. Analyses included maximum likelihood method, network analysis and DNA polymorphisms. The outcome revealed unique sequences of all genomic regions studied except the cox 1 gene had a relationship with sand flies isolated previously from Sri Lanka, India and Israel and cytb gene of 4 sand flies that aligned with those isolated earlier from Sri Lanka and 3 from Madagascar. Furthermore, cox 1 gene and ITS 2 region analyses based on FST values indicated a possible gene flow between the study sites whereas cytb gene analysis favoured the existence of genetically distinct populations of P. argentipes in each of the study sites. Poor population differentiation of P. argentipes, a possible consequence of a gene flow, is indeed of concern due to the risk imposed by promoting the spread of functionally important phenotypes such as insecticide resistance across the country, making future vector control efforts challenging.

Impact of climatic factors on temporal variability of sand fly abundance in Sri Lanka: Longitudinal study (2018 to 2020) with two-stage hierarchical analysis.

“…Previous studies conducted in Sri Lanka have also reported Ph. argentipes as the predominant species of sand flies [ 20 , 33 , 34 ]. However, this current study is significant in that it demonstrates the widespread presence of Ph.…”

“…Among the factors investigated, wind speed has the potential to influence the dynamic behavior of sand flies, particularly in terms of gene flow between populations without geographical barriers. This gene flow can facilitate the transfer of genes that promote sand fly survival, such as insecticide resistance genes [ 34 ], which can have negative implications for vector control programs. However, the present study did not find any relationship between sand fly density and wind speed.…”

Genetic diversity and phylogeography of Phlebotomus argentipes (Diptera: Psychodidae, Phlebotominae), using COI and ND4 mitochondrial gene sequences

“…In this context, Phlebotomus argentipes Annandale and Brunetti (1908), one of the 1060 sandfly species globally, emerges as a main vector for VL and CL in Sri Lanka and India [7]. In Sri Lanka, P. argentipes is currently recognized as a species complex, and its distribution has been documented across all three climatic zones in the country [10,11]. The distribution pattern of P. argentipes over the country highlights the epidemic risk of the disease, emphasizing the significance of vector control in effective disease management [8].…”

“…The extensive utilization of insecticides like DDT and malathion, had been identified as effective control of other vectors, also it indirectly influences the development of insecticide-resistant P. argentipes populations [12]. As the P. argentipes vector species is well established in arid regions where malaria is prevalent, non-targeted control strategies are likely to have an effect on the development of insecticide resistance in these communities [11]. However, as a consequence of these factors, changes in the genetic composition of the P. argentipes community in Sri Lanka led to an increase in their genetic diversity.…”

“…However, as a consequence of these factors, changes in the genetic composition of the P. argentipes community in Sri Lanka led to an increase in their genetic diversity. Several molecular studies of P. argentipes in Sri Lanka have been conducted and revealed the availability of higher genetic diversity [10,11].…”