Incrimination of Phlebotomus kandelakii and Phlebotomus balcanicus as Vectors of Leishmania infantum in Tbilisi, Georgia

A survey of potential vector sand flies was conducted in the neighboring suburban communities of Vake and Mtatsminda districts in an active focus of visceral Leishmaniasis (VL) in Tbilisi, Georgia. Using light and sticky-paper traps, 1,266 male and 1,179 female sand flies were collected during 2006–2008. Five Phlebotomus species of three subgenera were collected: Phlebotomus balcanicus Theodor and Phlebotomus halepensis Theodor of the subgenus Adlerius; Phlebotomus kandelakii Shchurenkova and Phlebotomus wenyoni Adler and Theodor of the subgenus Larroussius; Phlebotomus sergenti Perfil'ev of the subgenus Paraphlebotomus. Phlebotomus sergenti (35.1%) predominated in Vake, followed by P. kandelakii (33.5%), P. balcanicus (18.9%), P. halepensis (12.2%), and P. wenyoni (0.3%). In Mtatsminda, P. kandelakii (76.8%) comprised over three fourths of collected sand flies, followed by P. sergenti (12.6%), P. balcanicus (5.8%), P. halepensis (3.7%), and P. wenyoni (1.1%). The sand fly season in Georgia is exceptionally short beginning in early June, peaking in July and August, then declining to zero in early September. Of 659 female sand flies examined for Leishmania, 12 (1.8%) specimens without traces of blood were infected including 10 of 535 P. kandelakii (1.9%) and two of 40 P. balcanicus (5.0%). Six isolates were successfully cultured and characterized as Leishmania by PCR. Three isolates from P. kandelakii (2) and P. balcanicus (1) were further identified as L. infantum using sequence alignment of the 70 kDa heat-shock protein gene. Importantly, the sand fly isolates showed a high percent identity (99.8%–99.9%) to human and dog isolates from the same focus, incriminating the two sand fly species as vectors. Blood meal analysis showed that P. kandelakii preferentially feeds on dogs (76%) but also feeds on humans. The abundance, infection rate and feeding behavior of P. kandelakii and the infection rate in P. balcanicus establish these species as vectors in the Tbilisi VL focus

Epidemiologic Aspects of an Emerging Focus of Visceral Leishmaniasis in Tbilisi, Georgia

Visceral leishmaniasis (VL) has emerged as a public health problem in Tbilisi, the capital of Georgia. Dogs are the main infection reservoirs for transmission by sand flies of Leishmania infantum to humans, many of whom may become infected without developing disease. Since majority of cases are in children we were interested to know the rate of infection in children and in dogs living within the area where cases of VL have been found, and what factors may affect the risk of infection. Using a test that detects the presence of antibodies in blood as a marker of infection, 7.3% of 4,250 children examined were positive at the baseline survey, and 6% became positive after one year. Overall, 18.2% of domestic and 15.3% of stray dogs were seropositive. The infected children were more apt to live in areas where clustered flying insects and stray dogs were observed, and were far more likely to have experienced a persistent fever in the 6 months before the survey. We conclude that there is very active transmission of L. infantum to both humans and dogs in Tbilisi, and that children remain at high risk of developing clinical disease and sub-clinical infection

Natural <i>Leishmania</i> infections in wild-caught sand flies from VL case sites in Tbilisi, Georgia.

<p>Natural <i>Leishmania</i> infections in wild-caught sand flies from VL case sites in Tbilisi, Georgia.</p

Map of the visceral leishmaniasis (VL) focus in Tbilisi, Georgia.

<p>The districts of Vake, Mtatsminda and Krtsanisi are indicated. • = human VL case sites. Inset shows the geographical location of Georgia relative to neighboring countries and the position of its capital Tbilisi.</p

Diversity and relative abundance of sand fly species in Vake and Mtatsminda districts.

<p>Collections were made from May 2006 through September 2008. M = male; F = female; T = species total.</p

Diversity and relative abundance of sand fly species collected in Vake and Mtatsminda districts, 2006–2008. LT = light trap; ST = sticky trap.

<p>Diversity and relative abundance of sand fly species collected in Vake and Mtatsminda districts, 2006–2008. LT = light trap; ST = sticky trap.</p

Molecular characterization of <i>Leishmania</i> isolates from wild-caught sand flies in the Tbilisi VL focus.

<p>(A) Lanes 1 and 11, DNA size marker (100 base pair ladder); lane 2, <i>L. major</i> (MHOM/IL/80/Friedlin); lane 3, <i>L. infantum</i> (MHOM/ES/00/UCM-1); lanes 4–8, <i>Leishmania</i> isolates from <i>P. kandelakii</i>; lane 9, <i>Leishmania</i> isolate from <i>P. balcanicus</i>; lane 10, negative control. bp = basepairs. (B) Phylogenetic analysis of the <i>Leishmania</i> 70 kDa heat-shock protein (HSP70) gene. The sequences are represented by the <i>Leishmania sp.</i>, country of origin in parentheses and GenBank nucleotide accession numbers. Node values indicate branch support.</p

Blood meal sources of <i>Phlebotomus</i> sand flies from VL case sites in Tbilisi, Georgia.

<p>Blood meal sources of <i>Phlebotomus</i> sand flies from VL case sites in Tbilisi, Georgia.</p

Seasonal distribution of sand fly species collected from Vake and Mtatsminda districts, 2006–2008.

<p>Seasonal distribution of sand fly species collected from Vake and Mtatsminda districts, 2006–2008.</p