Current Situation of Malaria and Resistance of Main Vectors to WHO Recommended Insecticides in an Endemic Area, Southeastern Iran

Although malaria is endemic in some areas of southeastern Iran, following the successful national malaria elimination plan, the local transmission area has been shrunk. The main cases in Iran are due to Plasmodium vivax followed by P. falciparum. This study was aimed to determine the current situation of malaria in Kerman Province of Iran and evaluate the insecticide resistance of main vectors. The field study was conducted in 2019. Data of new malaria cases were obtained from the health centers for the period of 2009–2018. Susceptibility status of Anopheles stephensi and An. dthali was evaluated against dichlorodiphenyltrichloroethane, Dieldrin, Malathion, Bendiocarb, Deltamethrin, and Temephos at the diagnostic dose. A total of 522 malaria cases were recorded and divided into indigenous (33.14%) and imported (66.86%) categories. The highest incidence of the disease was reported from the southern areas of the province, where all indigenous cases occurred. Adults of An. stephensi were resistant to dichlorodiphenyltrichloroethane while its resistance to be confirmed to dieldrin, bendiocarb and deltamethrin. As An. dthali had less than 98% mortality against bendiocarb, the resistance status should be confirmed with more tests. Our findings showed both species had less than 98% mortality against bendiocarb and deltamethrin insecticides which are used in malaria vector control program in Iran. Due to the susceptibility of these vectors to temephos, larviciding can be advised for vector control in this area.

Detection of Knockdown-Resistance Mutations (V1016G and F1534C) in Dengue Vector from Urban Park, Surabaya, Indonesia

An urban park is potentially a source of vector-borne disease transmission due to it being a natural and artificial mosquito breeding habitats combined with people's continuous presence. Thus, this study aims to screen the occurrence of knockdown-resistance (kdr) mutant alleles (V1016G and F1534C) in mosquito populations collected from urban parks in Surabaya, Indonesia. Cross sectional study was conducted in July 2019. A total of 28 ovitraps were installed in seven urban parks, having four ovitraps installed in each park. In total, 1,662 eggs were collected, and only 187 emerged into adult mosquitoes, consisting of 97 Aedes (Stegomyia) aegypti and 90 Aedes (Stegomyia) albopictus. All-female adult mosquitoes (n=55) were tested using allele-specific polymerase chain reaction assay (AS-PCR) to detect voltage gated sodium channel (VGSC) gene mutations. This study found no mutations in Valine to Glysine mutation in point 1016 (V1016G) and Phenylalanine to Cysteine in point 1534 (F1534C) alleles in both two species. All of mosquito samples have wild type genotype of kdr alleles (V1016V and F1534F). Data were analysed using R Studio 1.4 Version by Genetics package. Results showed that the frequency of resistant alleles (G1016 and C1534) was zero, and the frequency of susceptible allele was 1 (V1016 and F1534). Insecticide bioassay could not be established due to the limited number of adult mosquitoes, so insecticide resistance status could not be determined. However, this study can be used as preliminary monitoring for the vector control program.

Contemporary Resistance Status of Anopheles Stephensi against Insecticides in District Dungarpur, Rajasthan, India

Pyrethroids are powerful insecticides used in the vector control program with impregnated mesh, and residual indoor sprays. However, resistance to insecticide reduces the effectiveness. The present susceptibility study carried out against theAnopheles Stephensi to monitor the sensitivity conditions of An. Stephensi vector, which raises the need to understand the state of vector resistance in the Dungarpur region of Rajasthan, India in order to better report vector-based interventions. The sensitivity study was carried out by the WHO standard method using recommended diagnostic doses of DDT, alpha-cypermethrin, permethrin, and deltamethrin. An. Stephensi showed resistance to DDT from the entire study while sensitive to alpha-cypermethrin, permethrin, and deltamethrin. The study looks at the selection and circulation of the appropriate insecticide’s molecule for a vector control program as insecticide need constant monitoring to develop effective vector control strategies such as improving insecticide by applying integrated biological and ecological methods.

The effect of some insecticides on the larvae of Aedes aegypti in Jeddah Governorate, Makah Province, Kingdom Saudi Arabia

Mosquitoes can act as vectors for many disease-causing viruses and parasites through carrying these organisms from person to person. The objective of this study was to evaluate the susceptibility of Aedes aegypti larvae to some insecticides in Jeddah Governorate. Mosquito larvae were collected from all the available breeding sites in Jeddah municipalities using standard larval collection kits. The diagnostic doses (LC50 and LC90) were calculated from the mortality and concentration data. The larvicides Pirimiphos methyl, Fenitrothion, Bifenthrin and Cypermethrin were tested against the larvae of Ae. aegypti mosquito. The results showed positive correlation between the concentrations under investigation and mortality% of the treated larvae. Cypermethrin gave strong effect against Ae. aegypti larvae (LD50 0.0015 ml/L) followed by Pirimiphos methyl (LD50 0.0020 ml/L), Bifenthrin (LD50 0.039 ml/L), and at last rank Fenitrothion (0.041 ml/L). The same trend was obtained in LD90s. Ae. aegypti in Jeddah was susceptible to Bifenthrin, Cypermethrin, Pirimiphos methyl and Fenitrothion. Further studies should be run to conduct an intensive and appropriate vector control program in Jeddah Governorate.

First Observations of Plasmodium Malariae and Its Evolution During the Parasitological Evaluation of the Long-term Village Scale Malaria Vector Control Program in the Balombo Area of Angola

Background: A long-term village scale vector control program was implemented in eight villages around the Balombo town (Benguela Province, Angola) to compare the efficacy of four methods of vector control inside houses including long-lasting deltamethrin insecticide treated nets (PermaNet© 2.0 model or P.2.0); association of P.2.0 and deltamethrin Insecticide Treated Plastic Sheeting (ITPS)-Zero Fly© model; deltamethrin ITPS-Wall Lining model alone; and 2 rounds of lambdacyhalothrin Inside Residual Spraying followed by installation of ITPS.Methods: Cross sectional parasitological surveys (CSS) were done every two months. Thick blood films (TBF) were microscopically examined at the Medical Department of the Angolese Sonamet company in Lobito and a sample of them were double-checked in Yaoundé. Plasmodium species determination, parasitaemia and gametocytes presence, and evolution in time were analyzed.Results: A total of 190 CSS was done between 2007 and 2011, Plasmodium spp. were observed in 5,431 of the 21,804 TBF done. Plasmodium malariae alone was observed in 22 TBF (0.4%) and mixed infections P. falciparum and P. malariae in 44 TBF (0.8%).Conclusion: The very low frequency of P. malariae could explain the fact it is usually not reported in classical point prevalence surveys. Our study confirms the presence of this species in Angola, which must be known due to its special clinical impact, quartan fever, kidney failure, chronicity, symptomless carriers, persistence for several years with long term recrudescence and reported cases of resistance to classical ACTs. The prevalence of P. malariae decreased after implementation of vector control methods.

Susceptibility Status of a Recently Introduced Population of Aedes albopictus to Insecticides Used by the Vector Control Program in Merida, Yucatan, Mexico

ABSTRACT In recent years, Aedes albopictus has become the most important invasive mosquito species worldwide. In 2018, Ae. albopictus was found in a suburban area of Merida, one of the cities with the highest number of arbovirus cases in Mexico in the last 10 years. As Ae. albopictus continues its range expansion, there is a need to monitor its susceptibility to existing insecticide classes, since countries like Mexico currently do not consider Ae. albopictus in its insecticide management programs. In order to determine its susceptibility to the insecticides usually applied by the vector control program in Mexico, the Centers for Disease Control and Prevention bottle bioassays were performed on individuals from established population of Ae. albopictus from Merida, Yucatan, Mexico. Results suggested that the population recently found in the suburban area of Merida is susceptible to permethrin, deltamethrin, chlorpyrifos, malathion, bendiocarb, and propoxur. Further studies of insecticide resistance using biochemical and molecular tools together with more knowledge of the biology and ecology of this species are necessary to generate specific and efficient control strategies in Mexico.

Monitoring and Mapping of Insecticide Resistance in Medically Important Mosquitoes (Diptera: Culicidae) in Iran (2000–2020): A Review

Background: Mosquitos due to their role in the transmission of different pathogens to humans are considered as an im­portant group in the phylum Arthropoda. According to the WHO and FAO guideline different groups of insecticide applied for controlling pests in both the agricultural and public health sectors. Methods: All the data published about resistant status of the mosquitoes Anopheles, Culex, Aedes and Culiseta species were searched on PubMed, Elsevier, Web of Science, Magiran and google scholar. The objectives of this study was to review the trend of resistance to insecticides during 2000–2020 in medically important mosquitoes in Iran. The criteria for resistant are followed according to WHO guideline. Results: The Results showed that there are widespread, multiple resistances in the country to different organochlorine, organophosphates, carbamate and pyrethroids insecticides in the mosquitoes. Conclusion: The effect of pesticide residues on the environment could be a cause for selection pressure on mosquitos and lead to insecticides resistance to them. Insecticides resistance is main challenge of the vector control program. Also result will provide a guideline for control of the mosquito-borne diseases in the country as well as the world.

Abundance and Seasonality of Aedes aegypti (Diptera: Culicidae) in Two Suburban Localities of South Mexico, With Implications for Wolbachia (Rickettsiales: Rickettsiaceae)-Carrying Male Releases for Population Suppression

We conducted a baseline characterization of the abundance and seasonality of Aedes aegypti (Linnaeus, 1762)—a vector of dengue, chikungunya, and Zika—in two suburban localities of Yucatan, Mexico, as the first step in the implementation of an integrated vector management (IVM) plan combining ‘traditional Aedes control’ (source reduction/truck-mounted ultra-low volume [ULV] spraying) and incompatible insect technique/sterile insect technique for population suppression in Yucatan, Mexico. Weekly entomological collections with ovitraps and BG-sentinel traps were performed in 1-ha quadrants of both localities for 1 yr. Three distinct periods/phases were identified, closely associated with precipitation: 1) a phase of low population abundance during the dry season (weekly average of Aedes eggs per ovitrap and adults per BG trap = 15.51 ± 0.71 and 10.07 ± 0.88, respectively); 2) a phase of population growth and greatest abundance of Aedes (49.03 ± 1.48 eggs and 25.69 ± 1.31 adults) during the rainy season; and finally 3) a phase of decline among populations (20.91 ± 0.97 eggs and 3.24 ± 0.21 adults) after the peak of the rainy season. Seasonal abundance and dynamics of Ae. aegypti populations suggest that it is feasible to develop and implement time-specific actions as part of an IVM approach incorporating integrating novel technologies (such as rear-and-release of Wolbachia-infected males) with classic (insecticide-based) approaches implemented routinely for vector control. In agreement with the local vector control program, we propose a pilot IVM strategy structured in a preparation phase, an attack phase with traditional vector control, and a suppression phase with inundative releases, which are described in this paper.

Insecticide Susceptibility Status of Aedes albopictus in Dengue Hotspot Areas in Malaysia

The vector control program has become challenging due to the resistance problem occurs in Aedes mosquitoes. Aedes albopictus (Skuse, 1894) is the most dominant species contributing as a vector of dengue, Chikungunya and Zika viruses in Malaysia. Knowledge of the current insecticide resistance of Ae. albopictus is essential for the success of vector control program. Here, we reported the susceptibility status of Ae. albopictus collected from the dengue hotspot areas in the Northern District of Penang Island, Malaysia on three common use insecticides in vector control program. Aedes albopictus was sampled from three localities at Flat Hamna, Kampung Sungai Gelugor and Kampung Tanjung Tokong in the Northern District of Penang Island, Malaysia. The adult bioassay results suggested the Flat Hamna strain (FH) was found to develop incipient resistance after 24h exposure towards all three insecticides tested; permethrin, deltamethrin and malathion (mortality 97-87%). With 1.93 fold of Resistance Ratio 50 (RR50) values, FH strains have the highest chances to develop resistance towards permethrin. Among all insecticides tested, malathion was contributed to significantly higher KdT50 in all Ae. albopictus strains as compared to VCRU reference strain (p<0.001). Thus suggesting malathion insecticide is the least effective insecticide in our vector control program. Our finding can be used as a baseline for insecticide resistance of Ae. albopictus to improve vector control across Malaysia. Permethrin and deltamethrin are still reliable to be used in the control program, nonetheless require continuous monitoring on their susceptibility towards Ae. albopictus.