ABSTRACT
Background & objectives: Malaria is the most important mosquito-borne disease in Iran. It is endemic in south to southeastern part of the country. Knowledge about bio-ecology of vectors will support authorities for appropriate management of the disease. Bashagard district is one of the main endemic areas for malaria in south of Iran. This study was conducted to determine anopheline fauna, diversity and affinity in the area, characterization of larval habitats, and mapping their potential distribution across the district. Methods: The potential aquatic habitats for Anopheles larvae were extracted from Indian Remote Sensing Satellite (IRS) image and digital elevation model of the area using GIS. Surface water bodies were sampled monthly during 2009–10 for anopheline larvae, while characteristics of their physical environment were recorded and water samples were analyzed. Results: A total of 4511 Anopheles larvae were found during the year with the lowest and highest frequencies in February and April, respectively. Dominant species was Anopheles culicifacies. The Shanon diversity index ranged from 0.570–0.829 at fixed collection sites, while the affinity index was significant among some vector species. Conclusion: Riversides and riverbeds were the main breeding places which provided sandy, rocky, and clay beds for different species. The potential breeding places as well as distribution of collected species were mapped. Knowledge about ecology of malaria vectors provides information to health sector for effective control programs.
ABSTRACT
BACKGROUND & OBJECTIVES: Most of autocidal control of malaria vectors relies on the rearing and release of large numbers of sterile male into a wild population and it would be crucial to separate the males from females before release. This could result in enormous economic benefits in the mass rearing and raise the efficiency of the field operations. The development of genetic sexing of mosquitoes, enabling the release of males only, but impairing the overall fitness of the released insect has been considered greatly. Here we report on a morphological sexing method for the preferential diagnosis and separation of males in late III and IV instar larvae for the mosquitoes Anopheles stephensi Liston and An. culicifacies s.l. (Diptera: Culicidae), the principal vectors of human malaria in Asia and Indian subcontinent. METHODS: Male mosquitoes are identified by their tube like organ at the 9th abdomen segment which originates from segment parallel to the spiracles. Length and width of this organ is measured as 66.66 +/- 9.5 and 14.3 +/- 1.5 microm respectively. The whole length of the organ is 201.63 +/- 23.4 microm. Two fried eggs in the anterior portion of the segment are apparent in males. The length of tube in female is shorter than the male (almost half of the length--37.95 +/- 4.0 microm), its width is slightly stout and wider than the male (16.72 +/- 1.4 microm). Two fried eggs in the anterior portion of the segment are absent. After separation of live male larvae by those characteristics, they were transferred into the trays and emerged adults were identified to ascertain correct identification of sex. RESULTS: All the larvae with male organs developed into male adults with hairy antennae and club shaped palpi, whereas all the female larvae developed into adult females. INTERPRETATION & CONCLUSION: The sex separation at the larval stage will provide a clue for embryonic origin of sex organs, insecticide selection at the larval stage, sex related genes, male sterility and other measures.