Ecology and habitat characterization of mosquitoes in Saudi Arabia.

The Kingdom of Saudi Arabia (KSA) contains many of the world's mosquito vectors of parasitic and arboviral diseases. However, few studies addressed their geographic distribution and larval habitat characteristics. We carried out a 14-months mosquito survey in three KSA regions: Makkah and Al-Baha (western) and Jezan (south-western). Larvae were collected by dipping from various water habitats and adults by CDC light and BG sentinel traps. Climatic conditions and physicochemical characteristics of collection sites were recorded. We collected a total of 3331 mosquitoes {larvae (n= 2766, 83%) and adults (n= 565, 17%)} of 21 species from six genera (8 Anopheles, 8 Culex, 1 Aedes and 3 others). Larval water habitats included streams, rocky pits, seepage, leakage and containers (plastic and concrete). Of the total larvae collected, 52% (n= 1439) were Anopheles, 44.3% (n= 1226) were Culex, 0.51% (n= 14) were Aedes aegypti and 3.1% (n= 87) were from four other species. The most abundant species were Culex tritaeniorhynchus (n=1008, ~36.3%) and Anopheles dthali (n= 976, ~35.3%). The medically-important species were Anopheles arabiensis (n= 128) and Anopheles sergenti (n= 58), vectors of malaria and Culex tritaeniorhynchus, Culex quinquefasciatus (n= 53) and Ae. aegypti (n= 14), vectors of arboviral diseases. Three species are new records in KSA and all from Jezan: Anopheles superpictus (n= 3), Culex duttoni (n= 1) and Culex mimeticus (n= 1), however the numbers were very low, which requires further investigations. Only two species were collected in the adult stage, Cx. quinquefasciatus (n= 561: 551 females and 10 males) from Makkah and Culex theileri (n= 4, all females) from Al-Baha. Only 3.8% (n= 21) of Cx. quinquefasciatus females were blood-fed. This study provides new information on the bionomics of 21 mosquito species in KSA including six dominant vector species and thus adds to the scarce data available on them. This information is essential to better understand mosquito population dynamics in relation to disease transmission and control.

GIS-based prediction of malaria risk in Egypt.

Environmental variables in a malaria geographic information system (GIS) database were analysed to discriminate between governorates at high and low risk of malaria. Only Fayoum governorate was categorized as a high risk area for malaria during the last 2 decades. Discriminant models correctly classified 96.3% of the risk categories and indicated that the most important predictor of risk is hydrogeology. Further GIS spatial analysis indicated that the high malaria risk in Fayoum is associated with a unique environmental envelope of biotic (presence of both efficient malaria vectors) and abiotic (hydrogeology and soil) variables. Recommendations for surveillance and control are discussed.

GIS-based prediction of malaria risk in Egypt

Environmental variables in a malaria geographic information system [GIS] database were analysed to discriminate between governorates at high and low risk of malaria. Only Fayoum governorate was categorized as a high risk area for malaria during the last 2 decades. Discriminant models correctly classified 96.3% of the risk categories and indicated that the most important predictor of risk is hydrogeology. Further GIS spatial analysis indicated that the high malaria risk in Fayoum is associated with a unique environmental envelope of biotic [presence of both efficient malaria vectors] and abiotic [hydrogeology and soil] variables. Recommendations for surveillance and control are discussed

Preliminary observations on cross-mating of the malaria vector, Anopheles sergentii from two Egyptian oases.

Intra- and inter-strain crosses were made between randomly collected adults Anopheles sergentii originated from Tersa village (El-Faiyum Governorate) and Siwa oasis (Matruh Governorate). The success of such crosses and their effects on fecundity and fertility of the parental females and on survival and development velocities of the F1 immatures were examined. No overall heterosis effects on such attributes were detected suggesting absence of genetic differences between the vector populations in these two malarious areas.

The ecological characteristics of Anopheles mosquitoes associated with low malaria transmission in Siwa oasis, Egypt.

The ecology of Anopheles sergentii and An. multicolor was investigated over eight months to examine the entomological factors maintaining the low Plasmodium vivax transmission in Siwa oasis. The two species were encountered as larvae while the dominant species, Anopheles sergentii was also collected as adults. Breeding sites were characterized for the two species in six localities. Larvae of both species were common during June and November. In Bahi El Din as an indicator village with a higher endemicity, An. sergentii females were endophilic but more common inside animal sheds than in houses, attracted more to donkey-baited traps than to human hosts, more endophagic as human biters and were more common in May/June and November. Female survivorship was higher in November than in the other months. Vector potential of An. sergentii was predicted and revealed that the species characteristics (low human contact, short survival and zoophilic feeding behavior) are responsible for maintaining such low and unstable malaria in Siwa oasis.