Larvicidal potential of Trachyspermum ammi essential oil and Delphinium speciosum extract against malaria, dengue, and filariasis mosquito vectors.

Mosquito-borne diseases, such as malaria, dengue, and Zika, pose major public health challenges globally, affecting millions of people. The growing resistance of mosquito populations to synthetic insecticides underscores the critical need for effective and environmentally friendly larvicides. Although chemical pesticides can initially be effective, they often lead to negative environmental consequences and health hazards for non-target species, including humans. This study aimed to evaluate the larvicidal effects of Trachyspermum ammi essential oil and Delphinium speciosum extract on the larvae of three major mosquito species: Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Mosquito larvae of Ae. aegypti, An. stephensi, and Cx. quinquefasciatus were reared under controlled laboratory conditions. The larvicidal activity of T. ammi essential oil and D. speciosum extract was evaluated through standard bioassays, using various concentrations of essential oils (10, 20, 40, 80, and 160 ppm) and extracts (160, 320, 640, 1280, and 2560 ppm) to determine the lethal concentration (LC50) values after 24 h of exposure. Fresh plant materials were collected, with the essential oil extracted via hydro-distillation, and the extract prepared using methanol solvent extraction. The chemical composition of T. ammi essential oil was examined using gas chromatography-mass spectrometry (GC-MS). Additionally, the preliminary analysis of the chemical compounds in D. speciosum extract was carried out using thin layer chromatography (TLC) and nuclear magnetic resonance spectroscopy (NMR) techniques. The results indicated that the essential oil of T. ammi exhibited more effective larvicidal activity compared to the D. speciosum extract. Specifically, the essential oil demonstrated LC50 values of 18 ppm for Cx. quinquefasciatus and 19 ppm for Ae. aegypti. In contrast, the D. speciosum extract showed the strongest larvicidal effect against An. stephensi, with an LC50 of 517 ppm. Concentrations of 40 ppm of the essential oil and 1280 ppm of the extract resulted in 100% mortality across all three species. Both the essential oil of T. ammi and the D. speciosum extract exhibited concentration-dependent larvicidal activity, and these results were statistically significant (p < 0.001) compared to the no-treatment group. GC-MS analysis revealed thymol (88.95%), o-cymen-5-ol (4.11%), and γ-terpinene (2.10%) as the major constituents of the T. ammi essential oil. Additionally, TLC verified the presence of alkaloids in both chloroform and methanolic extracts. Proton NMR identified a diterpene structure for these alkaloids. These findings suggest that T. ammi essential oil is a promising candidate for natural mosquito control strategies. Given its efficacy, further research is warranted to explore its potential in integrated vector management programs.

Evaluation of the Entomopathogenic Fungus Beauveria bassiana on Different Stages of Phlebotomus papatasi (Diptera: Psychodidae), Vector of Zoonotic Cutaneous Leishmaniasis in Iran.

Background: Zoonotic cutaneous leishmaniasis is a major public health problem in Iran with the main vector of Phlebotomus papatasi. The use of entomopathogenic fungi for biological control of the vector is a potential substitute for the current methods which are being used. The purpose of the current study was to assess the virulence of two local isolates of Beauveria bassiana (OZ2 and TV) against Ph. papatasi. Methods: To perform the bioassay test, fungal suspensions were applied for every stage of the sand fly life cycle. The mortality rate, longevity, and number of eggs laid were determined. Also, the probability of fungal survival on the surface of rodent's body was assessed. Results: The longevity of infected adult sand flies with both isolates of B. bassiana was significantly lower (P< 0.05) in comparison to the negative control. The estimated Lethal concentration 50 (LC50) values for adult female and male sand flies treated with OZ2 isolate were 1.4×106 and 2.2×107 conidia/ml, respectively, while they were 6.8×106 and 2.3×108 conidia/ml for TV isolate, respectively. Both isolates of B. bassiana exhibited nonsignificant mortality rates in sand fly larvae and pupae and fecundity rate (P> 0.05). According to our findings for both isolates, the fungus continued to spread throughout the surface of the rodent's body for 144 hours after spraying. Conclusion: The current study demonstrated that both isolates of B. bassiana have considerable biological control capacity against adult sand flies.

Insecticide Resistance Status of Malaria Vectors in a Malarious Area, Southeast of Iran.

Background: Malaria continues to be the main vector-borne disease in Iran. The endemic foci of malaria are in Sistan and Baluchistan Province, the borderline of Iran and Pakistan. By the year 2020 the program of the country is malaria elimination. The main vector control is using insecticide as Indoor Residual Spraying. The aim of the study was to evaluate the susceptibility of main malaria vectors to different insecticides recommended by WHO. Methods: All the insecticides papers supported by WHO and evaluation of insecticide resistance of Anopheles stephensi, Anopheles culicifacies, Anopheles superpictus to different chemical groups of imagicides including DDT 4%, malathion 5%, propoxur 01.%, lambdacyhalothrin 0.05%, deltamethrin 0.025% and permethrin 0.75% were followed by the WHO guideline. Results: Results of the susceptibility test against different insecticides revealed that An. stephensi and An. culicifacies are resistant to DDT and susceptible to other insecticides. An. superpictus is susceptible to all groups of pesticides. Conclusion: Knowledge on insecticide resistance in target species is a basic requirement to guide insecticide use in malaria control programmes in local and global scales.

Baseline Susceptibility of Culiseta longiareolata (Diptera: Culicidae) to Different Imagicides, in Eastern Azerbaijan, Iran.

BACKGROUND: Culiseta longiareolata is an important vector for many human diseases such as brucellosis, avian influenza and West Nile encephalitis. It is likely an intermediate host of avian Plasmodium that can transmit Malta fever. The aim of this study was to determine the susceptibility level of Cs. longiareolata to different classes of imagicides which are recommended by World Health Organization . METHODS: Larval stages of the Cs. longiareolata were collected from their natural habitats in Marand County at East Azerbaijan Province, northwestern of Iran in 2017. Adult susceptibility test were carried out with using impregnated papers to insecticides including DDT 4%, Cyfluthrin 0.15%, Deltamethrin 0.05%, Propoxur 0.1% and Fenitrothion 1% by standard test kits. RESULTS: Results showed that Cs. longiareolata adult is more susceptible to pyrethroid and carbamate insecticides. Among tested insecticides, Cyfluthrin was the most toxic against Cs. longiareolata with LT50 value of 11.53 minutes and Fenitrothion had the least toxic effect (LT50: 63.39 min). CONCLUSIONS: This study provided a guideline for monitoring and evaluation of insecticide susceptibility tests against Cs. longiareolata mosquitoes for further decision making.

Chemical Composition and Repellent Activity of Achillea vermiculata and Satureja hortensis against Anopheles stephensi.

BACKGROUND: One of the best ways to control the malaria disease and to be protected human against Anopheles mosquito biting is the use of repellents. Throughout repellents, herbal ones may be an appropriate and safe source for protection. METHODS: Chemical constituents of Achillea vermiculata and Satoreja hortensis were determined by using gas chromatography-mass spectrometry. Efficacy and the protection time of these plants were assessed on Anopheles stephensi under the laboratory condition. RESULTS: The mean assessed protection time and efficacy for A. vermiculata was 2.16 and 3.16 hours respectively and the obtained ED50 and ED90 for this plant was 5.67 and 63 µl/cm(2) respectively. The figured for S. hortensis was 4.16 and 5 hours respectively. ED50 and ED90 for this plant were 5.63 and 45.75µl/cm(2) respectively. CONCLUSION: Results of investigation showed that S. hortensis plant has an acceptable protection time, therefore, this plant could be considered as a good herbal repellent against anopheles mosquitoes.