Coarse-resolution Ecology of Etiological Agent, Vector, and Reservoirs of Zoonotic Cutaneous Leishmaniasis in Libya

Cutaneous leishmaniasis ranks among the tropical diseases least known and most neglected in Libya. World Health Organization reports recognized associations of Phlebotomus papatasi, Psammomys obesus, and Meriones spp., with transmission of zoonotic cutaneous leishmaniasis (ZCL; caused by Leishmania major) across Libya. Here, we map risk of ZCL infection based on occurrence records of L. major, P. papatasi, and four potential animal reservoirs (Meriones libycus, Meriones shawi, Psammomys obesus, and Gerbillus gerbillus). Ecological niche models identified limited risk areas for ZCL across the northern coast of the country; most species associated with ZCL transmission were confined to this same region, but some had ranges extending to central Libya. All ENM predictions were significant based on partial ROC tests. As a further evaluation of L. major ENM predictions, we compared predictions with 98 additional independent records provided by the Libyan National Centre for Disease Control (NCDC); all of these records fell inside the belt predicted as suitable for ZCL. We tested ecological niche similarity among vector, parasite, and reservoir species and could not reject any null hypotheses of niche similarity. Finally, we tested among possible combinations of vector and reservoir that could predict all recent human ZCL cases reported by NCDC; only three combinations could anticipate the distribution of human cases across the country

Natural Infection of Phlebotomus sergenti by Leishmania tropica in Libya.

International audienceCutaneous Leishmaniasis (CL) is a public health concern caused by Leishmania (L.) major and L.tropica in Libya. Information on sandfly vectors, as well as their associated Leishmania species, is of paramount importance because vector dispersion is one of the major factors responsible for pathogen dissemination. A number of 515 sandflies (275 males and 240 females) were collected during June-November 2012 using the Centers for Disease Control miniature light traps from Al Rabta, northwest of Libya. Two hundred and forty unfed females were identified; Phlebotomus (Ph.) papatasi (N = 97), Ph. sergenti (N = 27), Ph. longicuspis (N = 32), Sergentomyia (Se.) minuta (N = 38), and Se. fallax (N = 46). These flies were screened for Leishmania DNA using the polymerase chain reaction-restriction fragment length polymorphism analysis of the internal transcribed spacer 1 and sequencing. Two Ph. sergenti were found positive to L. tropica DNA. This finding should be considered for any further vector surveillance and epidemiological studies of CL in endemic areas across Libya

Thresholded potential distribution maps for <i>Leishmania major</i>, <i>Phlebotomus papatasi</i>, and four candidate mammal reservoir species potentially associated with the zoonotic transmission of cutaneous leishmaniasis.

<p>Models were calibrated across sampled areas (S), and transferred across all Libya. Blue points are occurrences, pink areas are modeled suitable conditions, and gray areas are unsuitable conditions.</p

Relationship of additional independent human case records to the areas where pairs of vector <i>Phlebotomus papatasi</i> and mammal reservoir species can occur.

<p>Green areas are areas of overlap between <i>P</i>. <i>papatasi</i> and each of the potential mammal reservoirs; white dotted circle represent localities where human cases were predicted successfully; blue dotted circles indicate case records not predicted successfully by the model combination.</p

Visualization of ecological niches of <i>Leishmania major</i>, <i>Phlebotomus papatasi</i>, and animal reservoir in three environmental dimensions (PC1, PC2, and PC3).

<p>Niches are represented as minimum volume ellipsoids to illustrate the limits under which the species has been sampled. Gray shading represents environmental background, green ellipsoid represents the potential mammal reservoir, yellow is the vector <i>Phlebotomus papatasi</i>, and purple represents <i>Leishmania major</i>.</p

Example background similarity tests showing overall niche overlap between ecological niche models for pairs of species: (A) <i>Leishmania major</i>—<i>Phlebotomus papatasi</i> and (B) <i>Leishmania major</i> –<i>Meriones libycus</i>.

<p>The vertical purple line shows observed niche overlap, and the histograms show the distribution of the background similarity values among 100 random replicates, for the <i>I</i> and <i>D</i> similarity metrics. On the maps, red and blue shading indicates the modeled suitable areas for the two species; purple shading shows areas of overlap between the two species. Results for other species are given in the <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0004381#sec010" target="_blank">Supporting Information</a> (<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0004381#pntd.0004381.s005" target="_blank">S5 File</a>).</p

Development of polymorphic EST microsatellite markers for the sand fly, Phlebotomus papatasi (Diptera: Psychodidae)

Abstract Background Phlebotomus papatasi is a widely distributed sand fly species in different tropical and sub-tropical regions including the Middle East and North Africa. It is considered an important vector that transmits Leishmania major parasites, the causative agents of cutaneous leishmaniasis. The development of microsatellite markers for this sand fly vector is of high interest to understand its population structure and to monitor its geographic dispersal. Results Fourteen polymorphic microsatellite markers were developed with simple di-, tri- and tetra-nucleotide repeats. The F statistics calculated for the 14 markers revealed high genetic diversity; expected heterozygosity (He) ranged from 0.407 to 0.767, while observed heterozygosity (Ho) was lower and ranged from 0.083 to 0.514. The number of alleles sampled fall in the range of 9–29. Three out of 14 markers deviated from Hardy-Weinberg expectations, no significant linkage disequilibrium was detected and high values for inbreeding coefficient (F IS) were likely due to inbreeding. Conclusions The development of these functional microsatellites enable a high resolution of P. papatasi populations. It opens a path for researchers to perform multi locus-based population genetic structure analyses, and comparative mapping, a part of the efforts to uncover the population dynamics of this vector, which is an important global strategy for understanding the epidemiology and control of leishmaniasis

Population genetics analysis of Phlebotomus papatasi sand flies from Egypt and Jordan based on mitochondrial cytochrome b haplotypes

Abstract Background Phlebotomus papatasi sand flies are major vectors of Leishmania major and phlebovirus infection in North Africa and across the Middle East to the Indian subcontinent. Population genetics is a valuable tool in understanding the level of genetic variability present in vector populations, vector competence, and the development of novel control strategies. This study investigated the genetic differentiation between P. papatasi populations in Egypt and Jordan that inhabit distinct ecotopes and compared this structure to P. papatasi populations from a broader geographical range. Methods A 461 base pair (bp) fragment from the mtDNA cytochrome b (cyt b) gene was PCR amplified and sequenced from 116 individual female sand flies from Aswan and North Sinai, Egypt, as well as Swaimeh and Malka, Jordan. Haplotypes were identified and used to generate a median-joining network, F ST values and isolation-by-distance were also evaluated. Additional sand fly individuals from Afghanistan, Iran, Israel, Jordan, Libya, Tunisia and Turkey were included as well as previously published haplotypes to provide a geographically broad genetic variation analysis. Results Thirteen haplotypes displaying nine variant sites were identified from P. papatasi collected in Egypt and Jordan. No private haplotypes were identified from samples in North Sinai, Egypt, two were observed in Aswan, Egypt, four from Swaimeh, Jordan and two in Malka, Jordan. The Jordan populations clustered separately from the Egypt populations and produced more private haplotypes than those from Egypt. Pairwise F ST values fall in the range 0.024–0.648. Conclusion The clustering patterns and pairwise F ST values indicate a strong differentiation between Egyptian and Jordanian populations, although this population structure is not due to isolation-by-distance. Other factors, such as environmental influences and the genetic variability in the circulating Le. major parasites, could possibly contribute to this heterogeneity. The present study aligns with previous reports in that pockets of genetic differentiation exists between populations of this widely dispersed species but, overall, the species remains relatively homogeneous