Yaser Salim Abadi

Mosquitoes play a predominant role in the transmission of parasitic and viral diseases which are today among the greatest health problems in the world. Currently, synthetic insecticides are the most commonly used compounds for the control of larval mosquitoes. Nevertheless, the continuous and indiscriminate use of synthetic larvicides has also induced adverse effects. Essential oils obtained from plants can be an alternative to synthetic insecticides because they are highly effective, safe, and environmentally acceptable. In this study, the larval stage of Anopheles stephensi, and Culex quinnquefaciatus were exposed to serial concentrations of essential oils from Tanacetum persicum and Achillea kellalensis for 24 h under laboratory condition. In addition, the chemical composition of essential oils were determined and identified by Gas chromatography (GC) and GC-mass spectrometry (MS) analysis. Both plant oils exerted significant larvicidal activity against An. stephensi and Cx. quinquefasciatus. The LC values of T. persicum and A. kellalensis against An. stephensi larvae were 48.64 and 35.42 ppm, and for Cx. quinquefasciatus were 28.53 and 21.79 ppm, respectively. In A. kellalensis, 36 components were identified, representing 97.26 % of the oil, of which βocimene (17.72 %), linalyl acetate (15.98 %), linalool (10.83 %) and α-pinene (10.3 %) were found to be the major constituents. Twenty components were identified in the oil of T. persicum, making up 89.60 % of total composition. The main constituents were Borneol (26.4 %), chrysanthenone (16.48 %), bornyl acetate (10.68 %) and βfarnesene (9.89 %). Our results suggested that both examined oils may be explored as a natural larvicide to control vector mosquitoes.

Mosquitoes play an important role in transmission of large number of diseases including malaria, filariasis and arboviral diseases. Increasing application of synthetic insecticides may be resulted in resistant to insecticides. Furthermore, it may have adverse effects on the environment and human health. Currently, one of the most effective alternative approaches under the biological control programs is using of natural larvicidal agents derived from plants. The larvicidal properties of essential oil obtained from the aerial parts of an indigenous plant, Satureja bachtiarica was evaluated against two mosquito vector, Anopheles stephensi and Culex quinquefasciatus. In addition, the analysis of essential oil was investigated by Gas chromatography-Mass spectrometry (GC-MS). Forty-one compounds, representing 98.42% of the essential oils have been identified. The main constituents were carvacrol (22.66%), p-cymene (15.89%), borneol (14.05 %), 1,8-cineole (10.45%) and thymol (7.27%). Five different concentrations of essential oil were evaluated against the late 3^rd and early 4^th instars larvae of An. stephensi and Cx. quinquefasciatus. The LC₅₀ and LC₉₀ values against An. stephensi larvae were 24.27 and 54.24 ppm and for Cx. quinquefasciatus were 44.96 and 114.45 ppm after 24 hours of exposure, respectively. In conclusion, results of study clearly indicated that the essential oils of S. bachtiarica possessed remarkable larvicidal properties and could serve as an alternative to synthetic insecticides for control of mosquito larvae.

Background: During recent years transmission of Dirofilaria immitis (dog heart worm) by Culex pipiens and West Nile virus have been reported from Iran. The present study was preformed for evaluating the susceptibility status of Cx. pipiens collected from capital city of Tehran, Iran. Methods: Four Insecticides including: DDT 4%, Lambdacyhalothrin 0.05%, Deltamethrin 0.05% and Cyfluthrin 0.15 % according to WHO standard methods were used for evaluating the susceptibility status of Cx. pipiens from Tehran moreover For comparison susceptibility status a Laboratory strain also was used. Bioassay data were analyzed using Probit program. The lethal time for 50% and 90% mortality (LT50 and LT90) values were calculated from regression line. Results: The susceptibility status of lab strain of Cx. pipiens revealed that it is susceptible to Lambdacyhalothrin, Deltamethrin, Cyfluthrin and resistant to DDT. Moreover cyfluthrin with LT50=36 seconds and DDT with LT50=3005 seconds had the least and most LT(50)s. Field population was resistance to all tested insecticides and DDT yielded no mortality. Conclusion: Highly resistance level against all WHO recommended imagicides were detected in field populations. We suggest more biochemical and molecular investigations to detect resistance mechanisms in the field population for further decision of vector control.

Background: Anopheles mosquitoes are an important group of arthropods due to their role in transmission of malaria. The present study was conducted for determination of susceptibility status of Anopheles stephensi to different imagicides collected from malarious area in Chabahar city, Iran. Methods: In the present study seven insecticides including: DDT 4%, lambdacyhalothrin 0.05%, deltamethrin 0.05%, permethrin 0.75%, cyfluthrin 0.15% and etofenprox 0.5% were tested based on WHO method. Regression line was plotted for each insecticide using mortality of different exposure times. Bioassay data were analyzed using Probit software and the lethal time for 50% and 90% mortality (LT50 and LT90) values were calculated. Results: The susceptibility levels of field strain of An. stephensi to the discriminative dose of different imagicides were determined 100, 98, 96, 89, 82 and 62% for etofenprox, permethrin, deltamethrin, lambdacyhalothrin, cyfluthrin and DDT, respectively. Our finding indicated that An. stephensi is resistant to DDT, lambdacyhalothrin and cyfluthrin, and susceptible to etofenprox and permethrin and candidate of resistant to deltamethrin based on WHO criteria. Conclusion: Our findings indicated that An. stephensi is resistant to DDT and some pyrethroid insecticides which can be developed due to application of insecticides in health and agriculture. These results can provide a clue for future chemical control program in the study area.

The use of natural products derived from plants in mosquitoes control is an alternative method for minimizing the side effects of chemical pesticides on the environment. In the current study chemical composition of essential oil extracted from an indigenous plant, Zhumeria majdae was determined and identified by gas chromatography (GC) and GC-mass spectrometry (MS) analysis. In addition, the larvicidal activity of essential oil was evaluated against two important mosquito vectors, Anopheles stephensi and Culex quinquefasciatus. Thirty constituents, representing 97.86 % of the oil, were identified. The main constituents of the oil were camphor (38.84 %), linalool (31.18 %) and camphene (7.73 %). Z. Majdae volatile oil showed significant toxicity against larvae of both species. The LC₅₀ and LC₉₀ values against An. stephensi larvae were 61.34 and 135.81 ppm and for Cx. quinquefasciatus were 88.51 and 191.56 ppm after 24 hours, respectively. Our findings indicated that the essential oil from Z. majdae leaves may be explored as a potential mosquito bio-larvicide.

Insecticide resistance is one of the serious problems for German cockroach control program. This study was conducted to determine the bendiocarb and Carbaryl resistance mechanisms in German cockroaches using the piperonyl butoxide (PBO). Bioassay tests were conducted with 4 to 6 different concentrations of both insecticides with four replicates of 10 susceptible strain cockroaches per concentration to determine of discriminative concentration. After determining discriminative concentration, the result was compared to wild strain. The levels of susceptibility and resistance ratio (RR) and synergism ratio (SR) were calculated for each five wild strains. Moreover resistance mechanisms in wild strains were determined using PBO synergist in vivo. Hospital strains showed different levels of resistance to bendiocarb and carbaryl compared to susceptible strain. The bendiocarb and carbaryl resistance ratios ranged from 2.11 to 7.97 and 1.67 to 2 at LD50 levels, respectively. The synergist PBO significantly enhanced the toxicity of bendiocarb and carbaryl to all strains with different degrees of synergist ratio, 1.31, 1.39, 3.61, 1.78, 1.62 and 2.1 fold for bendiocarb, 1.19, 1.18, 1.12. 1.29, 1.45 and 1.11-fold for carbaryl, suggesting monooxygenase involvement in bendiocarb and carbaryl resistance. The synergetic effect of PBO had the highest effect on bendiocarb and resistance level was significantly reduced, which indicates the important role of monoxidase enzyme in creating resistance to Bendiocarb. Piperonyl butoxide did not have a significant synergistic effect on carbaryl and did not significantly break the resistance.

Background: Aquatic insects are the major groups of arthropods that spend some parts of their life cycle in the water. These insects play an important role for transmission of some human and animal diseases. There is few information about the aquatic insects fauna of Iran. Methods: To study the aquatic insects fauna, adult, nymphal and larval collections were carried out from different habitats using the standard technique in Zayandeh Roud River, Isfahan Province, central Iran, during summer 2011. Results: In total, 741 speimens of aquatic insects were collected and morphologically identified. They include 7 families and 12 genera representing 2 Orders. The order of Diptera ( 92.31%) and Coleoptera ( 7.69%). The families Culicidae, Syrphidae and Chironomidae from Diptera order, Gyrinidae, Dytiscidae, Haliplidae, Hydrophilidae from Coleoptera order were identified. Conclusion: Some aquatic insects play an important role for transmission of human and animal diseases. These insects also are important for biological control. Therefore ecological study on aquatic insects can provide information about ecology of insects in an area for any decision making.

Plant extracts and oils may act as alternatives to conventional pesticides for malaria vector control. The aim of this study was to evaluate the larvicidal activity of essential oils of three plants of Apiaceae family against Anopheles stephensi, the main malaria vector in Iran. Essential oils from Heracleum persicum, Foeniculum vulgare and Coriandrum sativum seeds were hydro distillated, then their larvicidal activity were evaluated against laboratory-reared larvae of An. stephensi according to standard method of WHO. After susceptibility test, results were analysis using Probit program. Essential oils were separated from H. persicum, F. vulgare and C. sativum plants and their larvicidal activities were tested. Result of this study showed that F. vulgare oil was the most effective against An. stephensi with LC50 and LC90 values of 20.10 and 44.51 ppm, respectively. All three plants essential oil can serve as a natural larvicide against An. stephensi. F. vulgare oil exhibited more larvicidal properties.

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.