Molecular detection ofLeishmania donovani, Leishmania major, andTrypanosomaspp. inSergentomyia squamipleurissandflies from a visceral leishmaniasis focus in Merti sub-County, eastern Kenya
Abstract:BackgroundVisceral leishmaniasis (VL) and zoonotic cutaneous leishmaniasis (ZCL) are of public health concern in Merti sub-County, Kenya, but epidemiological data on transmission, vector abundance, distribution, and reservoir hosts remains limited. To better understand the disease and inform control measures to reduce transmission, we investigated the abundance and distribution of sandfly species responsible for Leishmania transmission in the sub-County, and their blood-meal hosts.MethodsWe conducted an entomo… Show more
“…In most geographic areas, L. tropica is transmitted by its most common vector, the female Phlebotomus sergenti sandfly (17). Although other vectors like P. arabicus in northern Israel (18) and P. guggisbergi in Kenya (19) also are known. Phlebotomus spp.…”
Section: Introductionmentioning
confidence: 99%
“…Phlebotomus spp. can be infected by different Leishmania spp., including P. perniciosus (20), P. tobbi by L. tropica and L. infantum (20,21) and P. guggisbergi by L. tropica and L. major (19). Hybrids capable of transmitting have formed in all these vectors (22).…”
Background
The kinetoplastid protozoan Leishmania tropica mainly causes cutaneous leishmaniasis in humans in the Middle East, and relapse or treatment failure after treatment are common in this area. L. tropica's digenic life cycle includes distinct stages in the vector sandfly and the mammalian host. Sexual reproduction and genetic exchange appear to occur more frequently than in other Leishmania species. Understanding these processes is complicated by chromosome instability during cell division that yields aneuploidy, recombination and heterozygosity. This combination of rare recombination and aneuploid permits may reveal signs of hypothetical parasexual mating, where diploid cells fuse to form a transient tetraploid that undergoes chromosomal recombination and gradual chromosomal loss.
Methodology and Findings
The genome-wide SNP diversity from 22 L. tropica isolates showed chromosome-specific runs of patchy homozygosity and extensive chromosome copy number variation. All these isolates were collected during 2007-2017 in the Middle East and included isolates from a patient possessing two genetically distinct leishmaniasis infections three years apart with no evidence of re-infection.
We found on the same chromosomes (chr36) in different samples ancestries matching the reference genome with few derived alleles, followed by blocks of heterozygous SNPs, and then by clusters of homozygous SNPs with specific recombination breakpoints at the inferred origin of replication. Other chromosomes had similar marked changes in heterozygosity at strand-switch regions separating polycistronic transcriptional units.
Conclusion
These large-scale intra- and inter-chromosomal changes in diversity driven by recombination and aneuploidy suggest multiple mechanisms of cell reproduction and diversification in L. tropica, including mitotic, meiotic and parasexual processes. It underpins the need for more genomic surveillance of Leishmania, to detect emerging hybrids that could spread more widely and to better understand the association between genetic variation and treatment outcome. Furthering our understanding of Leishmania genome evolution and ancestry will aid better diagnostics and treatment for cutaneous leishmaniasis caused by L.tropica in the Middle East.
“…In most geographic areas, L. tropica is transmitted by its most common vector, the female Phlebotomus sergenti sandfly (17). Although other vectors like P. arabicus in northern Israel (18) and P. guggisbergi in Kenya (19) also are known. Phlebotomus spp.…”
Section: Introductionmentioning
confidence: 99%
“…Phlebotomus spp. can be infected by different Leishmania spp., including P. perniciosus (20), P. tobbi by L. tropica and L. infantum (20,21) and P. guggisbergi by L. tropica and L. major (19). Hybrids capable of transmitting have formed in all these vectors (22).…”
Background
The kinetoplastid protozoan Leishmania tropica mainly causes cutaneous leishmaniasis in humans in the Middle East, and relapse or treatment failure after treatment are common in this area. L. tropica's digenic life cycle includes distinct stages in the vector sandfly and the mammalian host. Sexual reproduction and genetic exchange appear to occur more frequently than in other Leishmania species. Understanding these processes is complicated by chromosome instability during cell division that yields aneuploidy, recombination and heterozygosity. This combination of rare recombination and aneuploid permits may reveal signs of hypothetical parasexual mating, where diploid cells fuse to form a transient tetraploid that undergoes chromosomal recombination and gradual chromosomal loss.
Methodology and Findings
The genome-wide SNP diversity from 22 L. tropica isolates showed chromosome-specific runs of patchy homozygosity and extensive chromosome copy number variation. All these isolates were collected during 2007-2017 in the Middle East and included isolates from a patient possessing two genetically distinct leishmaniasis infections three years apart with no evidence of re-infection.
We found on the same chromosomes (chr36) in different samples ancestries matching the reference genome with few derived alleles, followed by blocks of heterozygous SNPs, and then by clusters of homozygous SNPs with specific recombination breakpoints at the inferred origin of replication. Other chromosomes had similar marked changes in heterozygosity at strand-switch regions separating polycistronic transcriptional units.
Conclusion
These large-scale intra- and inter-chromosomal changes in diversity driven by recombination and aneuploidy suggest multiple mechanisms of cell reproduction and diversification in L. tropica, including mitotic, meiotic and parasexual processes. It underpins the need for more genomic surveillance of Leishmania, to detect emerging hybrids that could spread more widely and to better understand the association between genetic variation and treatment outcome. Furthering our understanding of Leishmania genome evolution and ancestry will aid better diagnostics and treatment for cutaneous leishmaniasis caused by L.tropica in the Middle East.
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