Development of a degree-day model to predict the growth of Anopheles stephensi (Diptera: Culicidae): implication for vector control management.

Anopheles stephensi is an efficient vector of malaria parasites in Iran. Despite its importance in malaria transmission, there is a scarcity of accurate predictive models of its rates of development at different temperatures. A laboratory colony of An. stephensi, collected from Bandar Abbas County, southern Iran, was established, and all its developmental stages were maintained in temperature-controlled incubators so that the water temperature set at 5, 8, 10, 12.5, 14, 28, 38, 39.5, 42, and 45(±0.2) °C for different treatments until subsequent adult emergence. The Lower and Upper Developmental Temperatures (LDT and UDT) and the growth degree-day (GDD) were calculated for each development stage. A 12-mo population dynamics survey of the larvae and adults of An. stephensi was performed in 3 malaria-endemic villages (Geno, Hormoodar, and Sarkhoon) of Bandar Abbas County, and the obtained data were matched with the constructed GDD model. Based on the field meteorological and dynamics data, the model was verified in the field and used to determine the appropriate date to start spraying. The LDT was determined to be 8.19, 9.74, 8.42, 5.6, 13.57, and 10.03 °C for egg hatching, first, second, and third ecdysis, pupation, and eclosion events, respectively. The UDT was 38 °C for all developmental stages. The thermal requirement for the development of all immature stages of An stephensi was determined to be 187.7 (±56.3) GDD above the LDT. Therefore, the appropriate date to start residual spraying is when the region's GDD reaches 187.7 (±56.3). Given the climatic conditions in Bandar Abbas County, it is expected that the first activity peak of adult An. stephensi would be in March. Field observations showed that An. stephensi activity starts in February and peaks in March. The GDD model can provide a good estimate for peak An. stephensi activity and indicate the optimal deployment time of residual spraying operations against the multiplication and development of malaria parasites inside the vector.

First detection of Leishmania infantum DNA in wild caught Phlebotomus papatasi in endemic focus of cutaneous leishmaniasis, South of Iran.

OBJECTIVE: To identify the vectors and reservoirs of cutaneous leishmaniasis in the endemic focus of Farashband, Fars Province, South of Iran. METHODS: Sticky papers and Sherman trap were used for collection of sand flies and rodents, respectively. Polymerase chain reaction (PCR) of kDNA, ITS1-rDNA were used for identification of Leishmania parasite in sand flies as well as rodents. RESULTS: Totally 2 010 sand flies were collected and the species of Phlebotomus papatasi Scopoli was the common specimen in outdoors and indoors places. PCR technique was employed on 130 females of Phlebotomus papatasi. One of them (0.76%) was positive to parasite Leishmania major (L. major) and one specimen (0.76%) was positive to Leishmania infantum. Microscopic investigation on blood smear of the animal reservoirs for amastigote parasites revealed 16 (44%) infected Tatera indica. Infection of them to L. major was confirmed by PCR against kDNA loci of the parasite. CONCLUSIONS: The results indicated that Phlebotomus papatasi was the dominant species circulating two species of parasites including L. major and Leishmania infantum among human and reservoirs. Furthermore, Tatera indica is the only main host reservoir for maintenance of the parasite source in the area.

Larvicidal activity of essential oil and methanol extract of Nepeta menthoides against malaria vector Anopheles stephensi.

OBJECTIVE: To investigate the larvicidal activity of essential oil and methanol extract of the Nepeta menthoides (N. menthoides) against main malaria vector, Anopheles stephensi (An. stephensi). METHODS: The essential oil of plant was obtained by Clevenger type apparatus and the methanol extract was supplied with Percolation method. Larvicidal activity was tested by WHO method. Twenty five fourth-instar larvae of An. stephensi were used in the larvicidal assay and four replicates were tested for each concentration. Five different concentrations of the oil and extract were tested for calculation of LC(50) and LC(90) values. RESULTS: The LC(50) and LC(90) values were determined by probit analysis. LC(50) was 69.5 and 234.3 ppm and LC(90) was 175.5 and 419.9 ppm for the extract and essential oil respectively. CONCLUSIONS: According to the results of this study methanolic extract of plant exhibited more larvicidal activity than essential oil. This could be useful for investigation of new natural larvicidal compounds.

Phlebotomus papatasi and Meriones libycus as the vector and reservoir host of cutaneous leishmaniasis in Qomrood District, Qom Province, central Iran.

OBJECTIVE: To determine the sand flies species responsible for most transmission of Leishmania major (L. major) to human, as well as to determine the main reservoir hosts of the disease. METHODS: Sand flies were collected using sticky papers and mounted in Puri's medium for species identification. Rodents were trapped by live Sherman traps. Both sand flies and rodents were subjected to molecular methods for detection of leishmanial parasite. RESULTS: Phlebotomus papatasi (P. papatasi) was the common species in outdoor and indoor resting places. Employing PCR technique only three specimens of 150 P. papatasi (2%) were found naturally infected by parasites with a band of 350 bp which is equal to the L. major parasite. Forty six rodents were captured by Sherman traps and identified. Microscopic investigation on blood smear of the animals for amastigote parasites revealed 1 (3.22%) infected Meriones libycus (M. libycus). Infection of this animal to L. major was confirmed by PCR against rDNA loci of the parasite. CONCLUSIONS: This is the first molecular report of parasite infection of both vector (P. papatasi) and reservoir (M. libycus) to L. major in the region. The results indicated that P. papatasi was the primary vector of the disease and circulating the parasite between human and reservoirs and M. libycus was the most important host reservoir for maintenance of the parasite source in the area.