Persistence of phlebotomine Leishmania vectors in urban sites of Catania (Sicily, Italy)

Abstract

Background: Pioneering research on "Mediterranean Kala-Azar" carried out by Adler and Theodor early in the past century (~1930s) had identified Catania city (Sicily) as a major focus of the disease nowadays known as zoonotic visceral leishmaniasis (VL). Despite the fact that disease in both humans and dogs has continued to be highly prevalent in the Catania province up to the present times, research on Leishmania vectors in this urban focus dates back to that distant period. This study aimed to evaluate the persistence and current composition of the sand fly fauna in urban environments of Catania in recent years, 2006 and 2013. Methods: In 2006 fifty-one suitable collecting sites were identified within 44 sub-units of a grid drawn to include the urban Catania area. In 2013 the survey was restricted to four of the most productive and representative sites resulting from the 2006 survey. In both periods 3 collections per month were performed using standard sticky traps set for 3 days in wall holes/cavities along public roads, from the end of April through December. Results: 43/51 sites (84.3%) were found positive for sand flies. The 2006 collections accounted for a total of 4341 specimens including six species. Among competent Leishmania vector species, P. perniciosus was the most prevalent (36.5%) being identified in all sand fly-positive sites, with significant abundance in those of the old city centre. Other species of interest were P. sergenti (2.5%) and P. neglectus (1.5%). The 2013 survey produced 1130 sand flies, of which 39.5% were P. perniciosus, 1.6% P. sergenti and 0.7% P. neglectus. A search for Leishmania DNA in a small sample of 72 P. perniciosus females revealed 11% infection prevalence. Conclusions: Our findings from an old urban focus of leishmaniasis demonstrate that phlebotomine sand flies have adapted fairly well to the drastic environmental changes that have occurred in cities of the Western world in the past century and still represent a potential risk for Leishmania transmission.

Seasonal Dynamics of Phlebotomine Sand Fly Species Proven Vectors of Mediterranean Leishmaniasis Caused by Leishmania infantum

“…perniciosus was found the behave in the same way at similar latitudes (around 37° N, e.g. in Tunis [ 61 ], Almeria [ 28 ] and Catania [ 31 ]).…”

“…Although several investigations on this subject were performed over the past 50 years, they included mostly one season—rarely 2 or 3—and were performed in single sites at different periods [e.g. 11 , 25 – 31 ]. Hence, recent and accurate knowledge of Mediterranean vectors dynamics would be required as a starting baseline for continuing investigations on changes that may have an impact on leishmaniasis transmission.…”

Canine Antibodies against Salivary Recombinant Proteins of Phlebotomus perniciosus: A Longitudinal Study in an Endemic Focus of Canine Leishmaniasis

“…Even in the southernmost region of Italy (Sicily) the earliest collection of P . perniciosus was recently reported to be in April [ 40 ]. The marked increase in antibody levels in the second transmission season is much probably caused by re-exposure of dogs to sand flies following antigenic priming in the previous season.…”

Recent advances in phlebotomine sand fly research related to leishmaniasis control

“…Other concerns about the emergence of transmission cycles include the potential establishment of Le. tropica in Sicily, where the vector Phlebotomus (Paraphlebotomus) sergenti is locally abundant (Luigi Gradoni and colleagues, abstract 45-O; http://www.isops8.org/en/libro-de-resumenes-2/ ) [ 30 ].…”