Download Report

Investigations on sand fly bionomics and Leishmania natural infections in
Eastern Sicily, Italy, with particular reference to Phlebotomus sergenti
Bongiorno G1, Lisi O2, Severini F1, Vaccalluzzo V2, Khoury C1, Di Muccio T1, Gradoni L1, Maroli M1, D’Urso V2, Gramiccia M1
1
Section of Vector-borne Diseases & International Health, Istituto Superiore di Sanità, Rome; 2Section of Animal Biology, University of Catania - Italy
Background
Visceral and cutaneous leishmaniasis (CL) by Leishmania infantum have long been known to be
endemic in Sicily. Fig. 1 shows the distribution of Leishmania strains from 146 autochthonous cases
of leishmaniasis (29 from Catania province) identified by MLEE from 1978 through 2004 (ISS), from
which a total of 15 zymodemes of L. infantum were identified among VL, CL and HIV co-infected
patients. Canine leishmaniasis is also widespread; strains from 65 Sicilian dogs were identified as L.
infantum zymodeme MON-1, one strain as L. infantum MON-24.
A
B
Fig. 1. Distribution of human strains typed as Leishmania infantum in Sicily (A)
and in Catania province (B)
Catania province, sited on the eastern coast of the island, represents also an old endemic territory
for the sand fly Phlebotomus (Paraphlebotomus) sergenti Parrot, 1917, the main vector of
Leishmania tropica (Wright, 1903). This species has been conclusively incriminated in several
countries such as Afghanistan, Algeria, Ethiopia, Iran, Israel, Tunisia, Morocco and Saudi Arabia,
and strongly suspected to be a vector in other countries such as Syria, Turkey and Uzbekistan. The
presence of P. sergenti in L. tropica-free areas may suggest the existence of cryptic populations with
different vectorial capacities. However, the Sicilian population of P. sergenti was found genetically
very similar to the Moroccan populations known to be competent for L. tropica transmission.
Aims
Because of the increase in human migration - the refugee population landed in Sicily from 2011
through 2014 have increased from 57,181 to 120,239 (Tab. 1) - there is a related risk for the
introduction of exotic Leishmania species in these territories. For this reason, our work has focused
on the investigation of sand fly fauna composition, seasonal dynamics and Leishmania natural
infections, with particular reference to P. sergenti. In addition, active surveillance and etiological
characterization of recent human CL cases has been performed in CL endemic territories.
Fig. 3. Location of peri-urban/rural sites north of Catania, and trapping methods
Results
Among 4,105 specimens collected, 2,545 (62.0%) were Sergentomyia minuta. Out of 1,560
Phlebotomus specimens, P. perniciosus (65.4%) and P. sergenti (20.8%) were the most prevalent,
followed by P. papatasi, P. neglectus and P. mascittii. P. sergenti was confirmed to be endemic, being
recorded in 3 urban and 5 periurban/rural sites of which those located at the slopes of mount Etna
were the most productive. The comparative dynamics of P. sergenti and P. perniciosus showed that
they peaked in different months, July and August respectively (Fig. 4). Females captured alive from P.
sergenti-positive sites (143 P. sergenti and 34 P. perniciosus) were found negative at dissection. In a
P. sergenti-negative site dominated by P. perniciosus, 3/118 specimens of this species (2.5%) were
detected with promastigotes subsequently identified as L. infantum. Among 175 dead females from all
sites, 17 (9.7%) were found positive by Leishmania n-PCR (13 P. perniciosus and 4 P. sergenti).
Tab. 1. Boat people (refugees) landings in Italy from 2011 through 2014
(data from the Italian Ministry of Interior)
Fig. 4. Early peak of P. sergenti (July), late peak of P. perniciosus (August)
The study
Four urban (Catania city, Fig. 2) and eleven periurban/rural sites, located in an area previously
recorded for P. sergenti presence and located at different elevations (Fig. 3), were investigated.
Sand flies were collected by sticky traps from April through December and by CDC light traps from
June through October 2013. Live females were dissected and examined for Leishmania
promastigotes identified by ITS1 PCR-RFLP, whereas dead females were analyzed by Leishmania
sp. nested(n)-PCR.
Active surveillance and etiological characterization of recent human CL cases in Catania province
resulted in the detection of 4 CL cases during the entomological study, 3 of which were identified
by ITS1 PCR-RFLP as belonging to L. infantum (Fig. 5). Furthermore, retrospective evaluation of
CL cases occurred in 2011-2013 was performed through n-PCR and ITS1 PCR-RFLP on the DNA
extracted from archived skin smears. Twenty-three additional CL cases were confirmed by n-PCR
and 11 of them could be identified as caused by L. infantum.
Fig. 4. Twin and multiple papular CL lesions caused by L. infantum
Conclusions
While P. perniciosus has been confirmed as a vector of autochthonous CL, P. sergenti does not seem to
play any vectorial role for leishmaniasis in Sicily.
Fig. 2. Presence of P. sergenti in sites of Catania city
This work was supported by EDENext, a collaborative project of the 7th FP (2011-2014) funded by the European Commission under the DG Health; Contract Number: 261504