Global genetic diversity of Aedes aegypti.

Mosquitoes, especially Aedes aegypti, are becoming important models for studying invasion biology. We characterized genetic variation at 12 microsatellite loci in 79 populations of Ae. aegypti from 30 countries in six continents, and used them to infer historical and modern patterns of invasion. Our results support the two subspecies Ae. aegypti formosus and Ae. aegypti aegypti as genetically distinct units. Ae. aegypti aegypti populations outside Africa are derived from ancestral African populations and are monophyletic. The two subspecies co-occur in both East Africa (Kenya) and West Africa (Senegal). In rural/forest settings (Rabai District of Kenya), the two subspecies remain genetically distinct, whereas in urban settings, they introgress freely. Populations outside Africa are highly genetically structured likely due to a combination of recent founder effects, discrete discontinuous habitats and low migration rates. Ancestral populations in sub-Saharan Africa are less genetically structured, as are the populations in Asia. Introduction of Ae. aegypti to the New World coinciding with trans-Atlantic shipping in the 16th to 18th centuries was followed by its introduction to Asia in the late 19th century from the New World or from now extinct populations in the Mediterranean Basin. Aedes mascarensis is a genetically distinct sister species to Ae. aegypti s.l. This study provides a reference database of genetic diversity that can be used to determine the likely origin of new introductions that occur regularly for this invasive species. The genetic uniqueness of many populations and regions has important implications for attempts to control Ae. aegypti, especially for the methods using genetic modification of populations.

Molecular Phylogenetics and Population Genetics of the Dengue Vector Aedes aegypti From the Arabian Peninsula.

Aedes aegypti mosquito is the principal dengue vector in the Kingdom of Saudi Arabia (KSA); however, no study has addressed its ecology and population structure yet. Therefore, we report on Ae. aegypti phylo- and population genetics using three DNA markers: COI, ND4, and rDNA-ITS2. Sampling the immature stages of Ae. aegypti revealed that water storage tanks (34.3% of habitats) were the most productive and contained 33% of immatures stages. Other important habitats included containers for wastewater drainage (including air-conditioning and water cooler trays) and containers associated with ornamentation. Shallow water leakage spots (2.7% of habitats, 8% of immatures) can be considered rare-but-epidemiologically-important containers. Neighbor-joining (NJ) phylogenetic analysis of Ae. aegypti identified 8, 14, and 9 haplotypes of COI, ND4, and ITS2, respectively, and revealed high levels of genetic variation in Ae. aegypti populations of KSA. Global distribution of haplotypes also indicated multiple gene introductions into these populations, with high levels of intra-population genetic variation and continuous gene exchange. The neutrality values indicated a deficiency of alleles and suggested that the KSA Ae. aegypti loci tested did not follow a neutral model of molecular evolution. Fst values and AMOVA indicated that most of the genetic variation in the KSA Ae. aegypti populations is due to intra- rather than inter-population differences. This is the first comprehensive report on the phylo- and population genetics of Ae. aegypti from the Arabian Peninsula. This information expands our understanding of the ecology and population dynamics of this important arboviral vector for informed control efforts.

Potency and persistence of the bacterial mosquitocide Bacillus sphaericus against culicine mosquitoes under field conditions.

The biopesticide Bacillus sphaericus represents one of the important tools used in the control of mosquito larvae after chemical insecticides. The present study was conducted to investigate the efficacy B. sphaericus 2362 (VectoLex) in two different technical powders, ABG-6232 and ABG-6491 against larvae of two mosquitoes, Culex pipiens and Aedescaspius in El-Arish city, North Sinai, Egypt. The mosquito larvae were collected from polluted and fresh water (Cx. pipiens) and saline water (Ae. caspius). The physicochemical characteristics of larval breeding water sites were measured as salinity, conductivity, pH values and temperature. Susceptibility bioassays showed that Cx. pipiens larvae from polluted water sites have high susceptibility to B. sphaericus 2362 formulation ABG-6232 (LC50 0.150.33 ppm, LC90: 0.73-9.68 ppm). In case of ABG-6491 formulation, the values were LC50: 0.15-0.33 ppm and LC90: 1.73-9.83 ppm. Cx. pipiens larvae collected from fresh water habitat in ElQusiema, outside El-Arish city, susceptibility to B. sphaericus 2362 ABG-6232 had LC50 values ranging between 0.12 and 0.28 ppm, while LC90 ranged between 1.59 and 4.13 ppm. In case of ABG-6491, the LC50 values ranged between 0.13 and 0.28 ppm, while LC90 values ranged between 1.46 and 8.93 ppm. For Ae. caspius larvae from saline water and treated with B. sphaericus 2362 ABG-6232, LC50 values ranged between 0.31 &1.36 ppm, while LC90 ranged between 1.92 & 9.75 ppm. In case of ABG- 6491, the LC50 values ranged between 0.34 & 0.59 ppm, while LC90 values ranged between 1.79 and 11.56 ppm.

Life table characteristics of Aedes aegypti (Diptera:Culicidae) from Saudi Arabia.

Aedes aegypti (= Stegomyia aegypti) mosquito is a world vector of important arboviral diseases like dengue and Rift Valley fever. Despite its wide distribution in the western and southern regions of Saudi Arabia, where dengue outbreaks have occurred, its ecology is largely unknown. In this study we report on the main life table developmental attributes of a laboratory colony of Ae. aegypti reared from field-collected larvae from Madinah Province, west of Saudi Arabia. Females were maintained on daily blood meal and sugar. The female fecundity was ~62 eggs/female at an overall rate of 72% hatchability. The mean time needed for eggs to hatch into larvae was 4.5 d. The mean pupation time (P50) was 11.53 days (d). The proportion of immature survivorships were 0.69 for 1(st) larva to pupa (P/I), 0.98 for pupa to adult (A/P) and an overall 0.67 for 1(st) larva to adult (A/I). Males emerged faster than females with mean emergence time (E50) of 12.83 and 15.31 d, respectively. The average developmental velocity (V) showed that males (V= 0.081) developed faster than females (V= 0.068). The male/female sex ratio at adult emergence was 0.48, and insignificantly different from the 1:1 ratio. The adult mean life expectancy at emergence (eo) was 17.14 d for females compared to 9.59 d for males. The net reproductive rate (Ro) was 101.04 and the intrinsic rate of increase (rm) was 0.15 with a mean generation time (G) of 30.7 d. The instantaneous mean of birth (B) and death rate (D) were 0.30 and 0.15, respectively, with rm/B of 0.529 and B/D of 2.281. Compared to other Ae. aegypti strains from different geographic and ecological settings, the Saudi strain had a relatively low colonization potential. This is the first report on life table characteristics for Ae. aegypti from the Arabian Peninsula, and provides base-line information for wider studies on its natural populations. This is particularly important for understanding its population dynamics in relation to dengue transmission and control under regional conditions.

Environmental factors underlying spatial patterns of sand flies (Diptera: Psychodidae) associated with leishmaniasis in southern Sinai, Egypt.

Although Leishmania major is endemic in parts of the Sinai of Egypt, the ecology and distribution of Leishmania sand fly vectors in southern Sinai has not been well characterized. Accordingly, additional sand fly samples were obtained at 41 sites in the southern Sinai region during 1996-1997, and analyzed to improve the characterization of risk of sand fly-borne pathogens. Using a Geographic Information System (GIS), species-specific spatial distributions that might suggest zoonotic cutaneous leishmaniasis (ZCL) risk areas were determined in relation to contextual environmental factors, including geology, hydrogeology, climate variables and elevation. Southern Sinai was characterized by a diverse sand fly fauna (eight Phlebotomus species), probably attributable to highly variable landscape and environmental factors. Phlebotomus alexandri, Phlebotomus kazeruni and Phlebotomus sergenti were widespread and abundant, Phlebotomus papatasi and Phlebotomus bergeroti were less frequent, and Phlebotomus arabicus, Phlebotomus major and Phlebotomus orientalis had highly restricted distributions. Logistic regression models indicated that elevation and climatic conditions were limiting determinants for the distributions of sand flies in southern Sinai. Based on the predicted distribution of P. papatasi, a recognized vector of L. major, about one-quarter of southern Sinai may be at high risk of ZCL. Risk areas for the suspected ZCL vector P. bergeroti had a more patchy distribution. Results suggest that future studies should include other factors related to vector abundance, vector competence, human population, and parasite and reservoir host(s) to produce more comprehensive ZCL transmission risk maps, thus helping in planning effective prevention and control strategies.

The biological effects of the insect growth regulators; pyriproxyfen and diflubenzuron on the mosquito Aedes aegypti.

The biological effects of two insect growth regulators (IGRs), pyriproxyfen and diflubenzuron against larvae of the mosquito Aedes aegypti (L.) have been evaluated. Mosquitoes were collected from Jeddah governorate, west of the Kingdom of Saudi Arabia and maintained in the laboratory. According to IC50 values obtained (concentrations which inhibit the emergence of 50% of adults), diflubenzuron (0.00036 ppm) proved to be more effective by 11.4 fold of pyriproxyfen (0.0041 ppm). In addition to the delayed lethal action, larval treatment with the two IGRs, pyriproxyfen and diflubenzuron led to pronounced reduction in the reproductive potential of mosquito adults that emerged from these treatments. Pyriproxyfen caused a 33.2% decrease in egg production compared to 25.5% for diflubenzuron. The reduction in egg hatchability was by 40.6 and 36.2% for pyriproxyfen and diflubenzuron, respectively, with up to 4 fold higher reduction rates than in the control tests. These results shed light on the extended biological effects of IGRs on mosquitoes and encourage further testing of IGRs for wider use in the control of Ae. aegypti and other important disease vectors in Arabia and the world.

Human zoonotic cutaneous leishmaniasis and associated sand flies (Diptera: Psychodidae) in Sheikh Atiya village, southern Sinai, Egypt.

Zoonotic cutaneous leishmaniasis is endemic in Sinai Peninsula. Human cases were recorded from the northern Sinai, however little was known about the disease in southern Sinai. During entomological surveys conducted southern Sinai in summers of 1997-1999, a clinically confirmed ZCL case was encountered for the first time in Sheikh Atiya village in June 1999. The parasite was isolated and identified as L. major using cellulose acetate electrophoresis. A total of 784 phlebotomine sand flies were collected. Sand fly species composition at Sheikh Atiya village showed that P. papatasi and P. alexandri were the most abundant species in the area and each comprises about 47 % of the flies collected. P. sergenti and P. kazeruni occurred in very low numbers. All the female flies dissected (N = 304) were negative for any Leishmania-like flagellates. When the identified isolate was inoculated in the footpads of a clean laboratory colonized Acomys cahirinus dimidiatus, a lesion was developed on the site of inoculation 9 months post injection. The role of P. alexandri and A. c. dimidiatus in transmission of leishmaniasis in southern Sinai remains questionable. Environmental factors contributed to the appearance of ZCL in the area are discussed.