The impact of climatic variables on the population dynamics of the main malaria vector, Anopheles stephensi Liston (Diptera: Culicidae), in southern Iran

Objective: To determine the significance of temperature, rainfall and humidity in the seasonal abundance of Anopheles stephensi in southern Iran. Methods: Data on the monthly abundance of Anopheles stephensi larvae and adults were gathered from earlier studies conducted between 2002 and 2019 in malaria prone areas of southeastern Iran. Climatic data for the studied counties were obtained from climatology stations. Generalized estimating equations method was used for cluster correlation of data for each study site in different years. Results: A significant relationship was found between monthly density of adult and larvae of Anopheles stephensi and precipitation, max temperature and mean temperature, both with simple and multiple generalized estimating equations analysis (P<0.05). But when analysis was done with one month lag, only relationship between monthly density of adults and larvae of Anopheles stephensi and max temperature was significant (P<0.05). Conclusions: This study provides a basis for developing multivariate time series models, which can be used to develop improved appropriate epidemic prediction systems for these areas. Long-term entomological study in the studied sites by expert teams is recommended to compare the abundance of malaria vectors in the different areas and their association with climatic variables. Abbasi Madineh 1 Deparment of Medical Entomology & Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran; Infectious and Tropical Diseases Research Center,Tabriz University of Medical Sciences, Tabriz Rahimi Foroushani Abbas 2 Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran Jafari-Koshki Tohid 3 Molecular Medicine Research Center; Department of Statistics and Epidemiology, Faculty of Health, Tabriz University of Medical Sciences, Tabriz Pakdad Kamran 4 Department of Parasitology & Mycology, Paramedical School, Shahid Beheshti University of Medical Sciences, Tehran Vatandoost Hassan 5 Deparment of Medical Entomology & Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran Hanafi-Bojd Ahmad 6 Deparment of Medical Entomology & Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran WHO. Malaria report 2019. Geneva: WHO; 2019. 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A physiological time analysis of the duration of the gonotrophic cycle of Anopheles pseudopunctipennis and its implications for malaria transmission in Bolivia. Malar J 2008; 7: 141. Simon-Oke IA, Olofintoye LK. The effect of climatic factors on the distribution and abundance of mosquito vectors in Ekiti State. J Biol Agri Healthcare 2015; 5(9): 142-146. Jemal Y, Al-Thukair AA. Combining GIS application and climatic factors for mosquito control in Eastern Province, Saudi Arabia. Saudi J Biol Sci 2016; 25(8):1593-1602. Msugh-Ter MM, Aondowase DA, Terese AE. Association of meteorological factors with two principal malaria vector complexes in the University of Agriculture Makurdi community, Central Nigeria. Am J Entomol 2017; 1(2): 31-38. [31 ]Kabbale FG, Akol AM, Kaddu JB, Ambrose W. Biting patterns and seasonality of Anopheles gambiae sensu lato and Anopheles funestus mosquitoes in Kamuli District, Uganda Onapa. Parasit Vectors 2013; 6: 340. 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The Ecology of Anopheles mosquitoes under climate change: Case studies from the effects of environmental changes in East Africa highlands. Ann Acad Sci 2012; 1249: 204-210. Abbasi F, Babaeian I, Malboosi SH, Asmari M, Mokhtari LG. Climate change assessment over Iran during future decades, using statistical downscaling of ECHO-G model. J Geogr Res 2012; 104: 205-230 (In Persian).

Resistance status of main malaria vector, Anopheles stephensi Liston (Diptera: Culicidae) to insecticides in a malaria Endemic Area, Southern Iran

Objective: To evaluate the susceptibility of Anopheles stephensi (An. stephensi) Liston, the main malaria vector in southern Iran, to WHO recommended insecticides. Methods: Larvae of An. stephensi were collected from three different larval habitats in both urban and rural area of Bandar Abbas city and one rural area in Rudan county southern Iran. WHO standard method was used for evaluation of adult and larval mosquito susceptibility. Bendiocarb, permethrin, lambda-cyhalothrin, deltamethrin as insecticide and temephos and chlorpyriphos as larvicide were used at the diagnostic dosages recommended by WHO. Results: Findings of this study showed all larval populations of An. stephensi were completely susceptible to temephos and candidate for resistance to chlorpyriphos. Adult mosquitoes in rural areas of Bandar Abbas city were resistant to pyrethroid and carbamate insecticides. Conclusion: Comparison of the results of this survey with previous studies indicates that the resistance to pyrethroids and carbamates in this malaria endemic region is increasing. Wide use of pesticides in agriculture is certainly effective in increasing resistance. The inter-sectoral coordination and collaboration in health and agriculture seem to be necessary to manage insecticide resistance in malaria vectors.

Bioassay evaluation on the efficacy of α-cypermethrin impregnated into long lasting insecticide treated nets using Anopheles stephensi.

OBJECTIVE: To evaluate the bioefficacy of α-cypermethrin impregnated into long lasting insecticide treated nets (LLITNs-INTERCEPTOR®) against main malaria vector, Anopheles stephensi (An. stephensi). METHODS: The effectiveness of bed net impregnated with α-cypermethrin (INTERCEPTOR®) with washing was evaluated. The washing procedure and bioassay tests were carried out according to the WHO-recommended methods. Malaria vector, An. stephensi was exposed to impregnated bed net for three minutes and then mortality measured after 24 h recovery period. Knockdown was also measured according to the logarithmic times. RESULTS: Result of cone bioassay method showed that bioefficacy of α-cypermethrin decreased from 100% in unwashed to 15% in 20 washes. KT(50) was measure as one minute in one wash and increased to 40 min in 20 washes. DISCUSSION: Findings of this study provide guideline for malaria vector control authorities and people using pyrethroid-impregnated bed nets.

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.

Wash resistance and bio-efficacy of Olyset

Objective To determine the wash resistance of Olyset

Astrodaucus persicus as a new source of bioinsectisides against malaria vector, Anopheles stephensi

OBJECTIVE@#To determine the larvicidal activities of petroleum ether, chloroform, ethyl acetate and methanol fractions of roots and fruits extracts of Astrodaucus persicus from Apiaceae family against malaria vector, Anopheles stephensi (An. stephensi).@*METHODS@#Twenty five third instar larvae of An. stephensi were exposed to various concentrations (10-160 g/L) of fractions and were assayed according to World Health Organization protocol. The larval mortality was calculated after 24 h treatment.@*RESULTS@#Among tested fractions, the highest larvicidal efficacy was observed from ethyl acetate fraction of fruits extract with 50% and 90% mortality values (LC and LC) of 34.49 g/L and 108.61 g/L, respectively. Chloroform fraction of fruits extract was the second larvicidal sample with LC of 45.11 g/L and LC of 139.36 g/L. Petroleum ether fractions of fruits and roots and methanol fraction of fruits showed moderate toxicity against An. stephensi.@*CONCLUSIONS@#Astrodaucus persicus is a potential source of valuable and natural larvicidal compounds against malaria vector, An. stephensi and can be used in mosquitoes control programs as an alternative to synthetic insecticides.

Wash resistance and bio-efficacy of Olyset Plus, a long-lasting insecticide-treated mosquito net with synergist against malaria vector, Anopheles stephensi

OBJECTIVE@#To determine the wash resistance of Olyset Plus using World Health Organization Pesticide Evaluation Scheme standard washing procedure and to assess the value of knock down and mortality rates of Anopheles stephensi at different regimens of long lasting insecticide treated nets washings.@*METHODS@#The study was conducted at the Bioassay Laboratory of Culicidae Insectary, School of Public Health, Tehran University of Medical Sciences, Iran. The net was made of polyester impregnated with permethrin and piperonyl butoxide at a ratio of 2:1. The washing resistance was assessed using Le Chat soap and a shaker incubator set at a speed of 155 r/min, 30 °C for 10 min. The cone bioassay test was carried out according to World Health Organization recommended guideline with tolerant field strain of female Anopheles stephensi to pyrethroids.@*RESULTS@#The knockdown and mortality rates of female mosquitoes exposed to Olyset Plus from un-washed nets to 2 washings were 79.7% and 88.8% respectively. Mortality was dropped to zero while active ingredient estimated 0.532 μg/100 cm to 0.481 μg/100 cm after 15 washings. A positive correlation was seen between residues of permethrin on nets, knockdown rate and mortality rate of female Anopheles stephensi exposed to different regimes of washed Olyset Plus (r = 0.954, P = 0.001).@*CONCLUSIONS@#It is recommended that a preliminary survey conducted on resistance level of Anopheles vectors before the distribution of Olyset Plus in malaria endemic communities.

Astrodaucus persicus as a new source of bioinsectisides against malaria vector, Anopheles stephensi

Objective To determine the larvicidal activities of petroleum ether, chloroform, ethyl acetate and methanol fractions of roots and fruits extracts of Astrodaucus persicus from Apiaceae family against malaria vector, Anopheles stephensi (An. stephensi). Methods Twenty five third instar larvae of An. stephensi were exposed to various concentrations (10–160 g/L) of fractions and were assayed according to World Health Organization protocol. The larval mortality was calculated after 24 h treatment. Results Among tested fractions, the highest larvicidal efficacy was observed from ethyl acetate fraction of fruits extract with 50% and 90% mortality values (LC

Crimean--Congo hemorrhagic fever: a molecular survey on hard ticks (Ixodidae) in Yazd province, Iran.

OBJECTIVE: To determine the rate of Crimean--Congo hemorrhagic fever virus (CCHFV) infection in hard ticks (Ixodidae) in Yazd province of Iran. METHODS: A molecular survey on hard ticks (Ixodidae) was conducted in Yazd province during 2008-2009. A total of 140 hard ticks (three genera and 7 species) were collected from randomly selected villages and were exanimate for presence of CCHFV reverse transcription--polymerase chain reaction (RT-PCR) method. RESULTS: CCHFV genome was found in 5.71% of hard ticks. All positive ticks were from Hyalomma genus. Positive ticks including: Hyalomma dromedarii, Hyalomma marginatum, Hyalomma anatolicum, Hyalomma detritum, Hyalomma asiaticum. We were not able to find virus in in Rhipicephalus sanguineus and Dermacentor marginatus. Results exhibited that Hyalomma is the main vector in the study area. CONCLUSIONS: Due to the presence of virus in 24 provinces' out of 31, we recommend the use of acaricides and repellent to prevent disease transmission among humans. Greta care should be taken by the people who are working in slaughter houses.

Demonstration of malaria situation analysis, stratification and planning in Minab District, southern Iran.

OBJECTIVE: To demonstrate malaria situation analysis, stratification and planning for an endemic area in southern Iran. METHODS: Data on health system, population, meteorological parameters, malaria cases, anopheline vectors, and control activities during 2005-2007 was obtained from Minab Health Center, Minab Meteorological Station and published documents about malaria elements in the study area. A datasheet was created in excel 2003 for analysis. RESULTS: There were 644 health staff working in Minab District including 99 health staff in malaria control program. The health facilities are distributed as follow: 1 hospital with 96 beds, 23 health centers including private centers (10 in Minab city and 13 in rural area of Minab District) and 119 health houses in rural areas of Minab District. A nopheles stephensi was the dominant species in Minab District, however, Anopheles dthali, Anopheles superpictus, Anopheles fluviatilis, Anopheles multicolor, Anopheles pulcherrimus and Anopheles turkhudi can also be found in the area. Anopheles stephensi was reported susceptible to malathion, propoxur, primphos-methyl, lambda-cyhalothrin permethrin and deltamethrin, and resistant to DDT and dieldrin in the area. During the study period a total of 10 665 positive cases were reported, mainly due to local transmission (99.6%). Plasmodium vivax was the main causative agent followed by Plasmodium falciparum. There were reports about drug resistance of Plasmodium falciparum in the area. CONCLUSIONS: Using different parameters, Minab was classified into 3 strata. A plan was designed based on described goal, objectives and targets. The approaches of this plan were categorized into: health education, early detection and correct treatment, and vector control. Main constraints of these approaches are population movement between Iran, Pakistan and Afghanistan; vector control challenges at district, inadequate skilled medical staff in malaria case management and weak inter-sectorial coordination for malaria control, especially in urban areas.

Susceptibility of Anopheles maculipennis to different classes of insecticides in West Azarbaijan Province, Northwestern Iran

OBJECTIVE: To determine the susceptibility status of Anopheles maculipennis (An. maculipennis) against the major insecticides used in the health sectors in West Azarbaijan Province, Northwestern Iran. METHODS: Unfed 3-5 days old adult females of An. maculipennis were collected across the West Azarbaijan Province and were subjected to evaluation of their susceptibility following World Health Organization recommended protocol against six insecticides (permethrin, deltamethrin, propoxur, bendiocarb, malathion and dieldrin) belonging to four different classes. RESULTS: In this study, 916 specimens of An. maculipennis were examined against the insecticides which indicated that An. maculipennis was tolerant to permethrin, deltamethrin and dielderin, but displayed resistance against propoxur, bendiocarb and malathion. CONCLUSIONS: The pattern of resistance in An. maculipennis could be attributed to the agricultural landscapes, agricultural pesticides used and the exposure of the mosquitoes to insecticides. Logical cooperation is needed between the agriculture and health sectors to ensure the judicious use of pesticides in each sector and the management of probable resistance.

Characterization of larval habitats for anopheline mosquitoes in a malarious area under elimination program in the southeast of Iran

<p><b>OBJECTIVE</b>To determine the effects of environmental characteristics of larval habitats on distribution and abundance of anopheline mosquitoes in Bashagard county, a malarious area in southeast of Iran.</p><p><b>METHODS</b>Larvae were collected monthly using the standard dipping method and identified using a morphological-based key. Environmental characteristics of the larval habitats were recorded. Water samples were taken from habitats during larval collection for physico-chemical characterization. Statistical analyses were performed.</p><p><b>RESULTS</b>In total 5 150 anopheline larvae from 36 larval habitats were collected and identified. They comprised of six species: Anopheles culicifacies (29.36%), Anopheles moghulensis (25.20%), Anopheles dthali (18.02%), Anopheles superpictus (17.24%), Anopheles turkhudi (5.17%) and Anopheles stephensi (5.01%). The most common larval habitats were natural and clear water bodies such as riverbeds with sandy substrates and still water. Furthermore, the anopheline larvae were abundant in permanent and full sunlight habitats without vegetation and algae. Larval density was positively correlated with water temperature. Chemical characteristics including conductivity, total alkalinity, sulphate and chloride had significant effects on distribution and abundance of anopheline species.</p><p><b>CONCLUSIONS</b>The result of this study indicates a correlation between some environmental characteristics and anopheline larvae abundance which can be considered for effective planning and implementing malaria elimination program in Iran.</p>

The insecticidal effect of diatomaceous earth against adults and nymphs of Blattella germanica

<p><b>OBJECTIVE</b>To evaluate the insecticidal effect of diatomaceous earth (DE) against adults and nymphs of Blattella germanica.</p><p><b>METHODS</b>This cross sectional study has been done on the laboratory strain of German cockroaches. Two stages, nymph and adult, were exposed to six dose rates of the DE, 2.5, 5, 10, 15, 20 and 25 g/m(2), at 24, 48 and 72 h exposure period. Mortality (number of dead cockroaches) was assessed after 24 h. Other exposed specimens were transferred to the beakers contained food and water for counting the retard mortality rate after 1 week.</p><p><b>RESULTS</b>Increasing in dose rates of DE increased mortality rate, so that the lowest and highest mortality rates were observed in 2.5 and 25 g/m(2), respectively. The results of the statistical analysis showed no significant difference in the lethality of 50% of DE plus water on the German cockroach nymphs.</p><p><b>CONCLUSIONS</b>Due to the resistance of German cockroach against organochloride, organophosphorus, carbamate and pyrethriodes insecticides, it is suggested to use DE for insect's control.</p>

Environmental characteristics of anopheline mosquito larval habitats in a malaria endemic area in Iran

OBJECTIVE@#To determine the effects of environmental parameters of larval habitats on distribution and abundance of anopheline mosquitoes in Rudan county of Iran.@*METHODS@#This cross-sectional study was conducted during the mosquito breeding season from February 2010 to October 2011. The anopheline larvae were collected using the standard dipping method. The specimens were identified using a morphological-based key. Simultaneously with larval collection, environmental parameters of the larval habitats including water current and turbidity, sunlight situation, and substrate type of habitats were recorded. Water samples were taken from breeding sites during larval collection. Before collection of samples, the water temperature was measured. The water samples were analysed for turbidity, conductivity, total alkalinity, total dissolved solid, pH and ions including chloride, sulphate, calcium, and magnesium. Statistical correlation analysis and ANOVA test were used to analyze the association between environmental parameters and larval mosquito abundance.@*RESULTS@#In total 2 973 larvae of the genus Anopheles were collected from 25 larval habitats and identified using morphological characters. They comprised of six species: An. dthali (53.21%), An. stephensi (24.22%), An. culicifacies (14.06%), An. superpictus (4.07%), An. turkhudi (3.30%), and An. apoci (1.14%). The most abundant species was An. dthali which were collected from all of the study areas. Larvae of two malaria vectors, An. dthali and An. stephensi, co-existed and collected in a wide range of habitats with different physico-chemical parameters. The most common larval habitats were man-made sites such as sand mining pools with clean and still water. The anopheline mosquitoes also preferred permanent habitats in sunlight with sandy substrates. The results indicated that there was a significant relationship between mean physico-chemical parameters such as water temperature, conductivity, total alkalinity, sulphate, chloride, and mosquito distribution and abundance.@*CONCLUSIONS@#The results of this study showed a correlation between certain environmental parameters and mosquito larvae abundance, and these parameters should be considered in planning and implementing larval control programs.

Irritability of malaria vector, Anopheles sacharovi to different insecticides in a malaria-prone area

OBJECTIVE@#To determine the susceptibility and irritability level of malaria vector Anopheles sacharovi (An. sachrovi) to different insecticides in a malaria-prone area.@*METHODS@#Susceptibility and irritability levels of field collected strain of An. sacharovi to WHO standard papers of DDT 4%, dieldrin 0.4%, malathion 5%, fenitrothion 1%, permethrin 0.75%, and deltamethrin 0.05% were determined in East Azerbaijan of Iran during reemerging of malaria as described by WHO.@*RESULTS@#Results showed that at the diagnostic dose of insecticides this species exhibited resistance to DDT, tolerant to dieldrin and but somehow susceptible to fenitrothion, malathion, permethrin and deltamethrin. The results of irritability of this species to DDT, lambdacyhalothrin, permethrin cyfluthrin and deltamethrin revealed that DDT had had the most and deltamethrin the least irritancy effect. The average number of take offs/fly/minutes for DDT was 0.8±0.2. The order of irritability for permethrin, lambdacyhalothrin, cyfluthrin and deltamethrin were 0.7±0.2, 0.5±0.2, 0.5±0.3, and 0.2±0.1, respectively.@*CONCLUSIONS@#Results of this study reveals the responsiveness of the main malaria vector to different insecticides. This phenomenon is depending on several factors such as type and background of insecticide used previously, insecticide properties, and physiology of the species. Careful monitoring of insecticide resistance and irritability level of species could provide a clue for appropriate selection of insecticide for malaria control.

Indication of pyrethroid resistance in the main malaria vector, Anopheles stephensi from Iran

OBJECTIVE@#To investigate insecticide resistance in target species for better insecticide resistance management in malaria control programs.@*METHODS@#The status of insecticide resistance to different imagicides in Anopheles stephensi (An. stephensi) including DDT 4%, lambdacyhalothrin 0.50%, deltamethrin 0.05%, permethrin 0.75%, cyfluthrin 0.15% and etofenprox 0.50% was performed according to WHO standard method.@*RESULTS@#The mortality rate to lambdacyhalothrin, permethrin, cyfluthrin, deltamethrin, etofenprox and DDT was (88.0 ± 3.2), (92.0 ± 2.7), (52.0 ± 5.0), (96.0 ± 2.2), (90.0 ± 3.0) and (41.0 ± 5.7) percent, respectively at diagnostic dose for one hour exposure time followed by 24 h recovery period.@*CONCLUSIONS@#These results showed first indication of pyrethroid resistance in An. stephensi in a malarious area, from southern Iran. There is widespread, multiple resistances in the country in An. stephensi to organochlorine and some report of tolerance to organophosphate insecticides and recently to pyrethroids. However, results of this paper will provide a clue for monitoring and mapping of insecticide resistance in the main malaria vector for implementation of any vector control.

Spatio-temporal distribution of malaria vectors (Diptera: Culicidae) across different climatic zones of Iran

Malaria is a main vector-borne public health problem in Iran. The last studies on Iranian mosquitoes show 31 Anopheles species including different sibling species and genotypes, eight of them are reported to play role in malaria transmission. The objective of this study is to provide a reference for malaria vectors of Iran and to map their spatial and temporal distribution in different climatic zones. Shape files of administrative boundaries and climates of Iran were provided by National Cartographic Center. Data on distribution and seasonal activity of malaria vectors were obtained from different sources and a databank in district level was created in Excel 2003, inserted to the shape files and analyzed by ArcGIS 9.2 to provide the maps. Anopheles culicifacies Giles s.l., Anopheles dthali Patton, Anopheles fluviatilis James s.l., Anopheles maculipennis Meigen s.l., Anopheles sacharovi Favre, Anopheles stephensi Liston, and Anopheles superpictus Grassi have been introduced as primary and secondary malaria vectors and Anopheles pulcherrimus Theobald as a suspected vector in Iran. Temporal distribution of anopheline mosquitoes is restricted to April-December in northern Iran, however mosquitoes can be found during the year in southern region. Spatial distribution of malaria vectors is different based on species, thus six of them (except for Anopheles maculipennis s.l. and Anopheles sacharovi) are reported from endemic malarious area in southern and southeastern areas of Iran. The climate of this part is usually warm and humid, which makes it favorable for mosquito rearing and malaria transmission. Correlation between climate conditions and vector distribution can help to predict the potential range of activity for each species and preparedness for malaria epidemics.

A Survey of Dung Beetles Infected with Larval Nematodes with Particular Note on Copris lunaris Beetles as a Vector for Gongylonema sp. in Iran

Dung beetles (family Scarabaeidae) are one of the largest families of beetles worldwide. Due to biological behavior of these arthropods, they are considered to play an important role in the life cycle of some helminths. In the present study, dung beetles collected from cattle pastures in rural areas of Ardabil province, north-west of Iran were examined for infection with larval stages of helminths. According to the results, nematodes of 2 genera were identified including Rhabditis and Gongylonema. The more common species was Rhabditis sp. which was found in 9 species of beetles. Out of 15 different species of dung beetles, Copris lunaris was the only scarabaeid to be found naturally infected with the larval stages of Gongylonema sp. Our new findings introduce C. lunaris as a potential biological vector for transmission of Gongylonema sp. to vertebrates in the surveyed region.