Genetic structure of Phlebotomus (Larroussius) ariasi populations, the vector of Leishmania infantum in the western Mediterranean: epidemiological implications.

In recent years there has been growing interest in analyzing the geographical variations between populations of different Phlebotomus spp. by comparing the sequences of various genes. However, little is known about the genetic structure of Phlebotomus ariasi. In this study, we were able to sequence a fragment of the mitochondrial Cyt b gene in 133 sandflies morphologically identified as P. ariasi and proceeding from a wide geographical range covering 35 locations in 11 different regions from five countries. The intra-specific diversity of P. ariasi is high, with 45 haplotypes differing from each other by one to 26 bases and they are distributed in two mitochondrial lineages, one limited geographically to Algeria and the other widely dispersed across Mediterranean countries. The Algerian lineage is characterized by having 13 fixed polymorphisms and is made up of one sole haplotype. The European/Moroccan P. ariasi lineage is characterized by being made up of a great diversity of haplotypes (44) which display some geographical structuring. This could be one of the multiple factors involved in the epidemiological heterogeneity of the foci of leishmaniasis. Phlebotomus chadlii is the sister group of European/Moroccan P. ariasi. The separation of the Algerian haplotype, H45, from the rest of the specimens, European/Moroccan P. ariasi and P. chadlii, is well supported by the bootstrap analysis.

Sero-epidemiological study of canine Leishmania spp. infection in the municipality of Alijó (Alto Douro, Portugal).

Visceral leishmaniosis caused by Leishmania infantum is a zoonotic disease in the Mediterranean basin. We report an epidemiological survey carried out in dogs from the municipality of Alijó in the endemic region of Alto Douro (north Portugal). Performance of the direct agglutination test (DAT) was assessed in 205 matching samples of blood collected on filter paper and serum. A high degree of agreement (97.6%; k = 0.83) was found between the results obtained from both types of samples. DAT was then used to test more blood on filter paper (B-FP) samples from other dogs of the same municipality. The detected sero-prevalence was 18.7% (288/1540), with values ranging from 0.0 to 81.1% in each of the 19 parishes of Alijó. Three distinct geographical zones of mean sero-prevalence could be defined: northwestern (2.5%), intermediate (11.4%) and southern (49.9%). No statistically significant difference was observed between male (19.1%) and female (17.8%) sero-prevalences (P = 0.560). Dogs of 9-11 years of age showed the highest sero-prevalence (28.4%), but all the other age-intervals (0-2, 3-5, 6-8 and 12-17 years) presented values (15.0-22.3%) not significantly different from the mean of the whole study population. Risk factors for canine Leishmania infection were age and geographical zone. Only 5.9% of the sero-positive animals had clinical signs of canine leishmaniosis and the overall prevalence of disease was 1.1%. This study validates the use of B-FP samples and confirms DAT as a simple and sensitive serological test to evaluate the level of canine Leishmania infection in areas of high sero-prevalence.

ITS 2 sequences heterogeneity in Phlebotomus sergenti and Phlebotomus similis (Diptera, Psychodidae): possible consequences in their ability to transmit Leishmania tropica.

An intraspecific study on Phlebotomus sergenti, the main and only proven vector of Leishmania tropica among the members of the subgenus Paraphlebotomus was performed. The internal transcribed spacer 2 (ITS2) sequences of 12 populations from 10 countries (Cyprus, Egypt, Italy, Lebanon, Morocco, Pakistan, Portugal, Spain, Syria, and Turkey) were compared. Samples also included three species closely related to P. sergenti: Phlebotomus similis (three populations from Greece and Malta), Phlebotomus jacusieli and Phlebotomus kazeruni. Our results confirm the validity of the taxa morphologically characterised, and imply the revision of their distribution areas, which are explained through biogeographical events. At the Miocene time, a migration route, north of the Paratethys sea would have been followed by P. similis to colonise the north of the Caucasus, Crimea, Balkans including Greece and its islands, and western Turkey. Phlebotomus sergenti would have followed an Asiatic dispersion as well as a western migration route south of the Tethys sea to colonise North Africa and western Europe. This hypothesis seems to be well supported by high degree of variation observed in the present study, which is not related to colonisation or to intra-populational variation. Two groups can be individualised, one oriental and one western in connection with ecology, host preferences and distribution of L. tropica. We hypothesise that they could be correlated with differences in vectorial capacities.