Field efficacy of expanded polystyrene and shredded waste polystyrene beads for mosquito control in artificial pools and field trials, Islamic Republic of Iran

Situation of insecticide resistance in malaria vectors in the World Health Organization of Eastern Mediterranean region 1990-2020

Malaria is the most important mosquito-borne disease, which is transmitted by Anopheles species. According to the recent report of World Health Organization, there were an estimated 229 million malaria cases in 2019 in 87 malaria endemic countries. There are several vector control method specially using pesticides. The aim of this study was to collect all the data about insecticide resistant of malaria vectors in the Eastern Mediterranean region countries. In this study, all the published papers related to insecticide resistance of malaria vectors in the region were collected and resistant status of vectors in the countries was mapped. Resistance to different insecticide classes such as pyrethroids, organophosphate, organochlorine and carbamates were evaluated using World Health Organization guidelines. Results showed a wide variety of susceptibility/resistance status to these chemicals according to the location, historical context of pesticide used, genetic background of vectors, age and abdominal conditions of adults may play a role in the susceptibility status of these species to different insecticides. The results of this study is providing a guideline for countries to manage their vector control activities against insecticide resistance of malaria vectors and provide novel approaches such as male sterility, using Wolbachia, using new insecticide with new mode of action.

Investigation of LAMP Technique in Diagnosis Type of Plasmodium Species in Anopheles Mosquitoes :A Fast and Practical Technique to Detect Malaria Pathogens in the Field

Background

Malaria is one of the main parasitic diseases and a major health issue in some countries. This study aims to determine the rate and type of infections of Anopheles mosquitoes with malaria parasites using the molecular LAMP method in the Southeastern Iran.

Methods

In this study, 400 Anopheles mosquitoes were collected by the Zahedan Medical Insecticide Center in Nikshahr City, a high-risk area of malaria transmission in Sistan-Baluchestan Province. The mosquitoes were caught manually (by hand) in domestic (humans and animals), natural, and artificial outdoor places (Shelter pits). After DNA extraction, the LAMP method was used, which was compared with Multiplex Nested-PCR as a standard method.

Results

Out of 400 samples collected from Nikshahr City, 6 samples (1.5%) were infected with Plasmodium vivax. No Plasmodium falciparum or a mix (Plasmodium vivax and Plasmodium falciparum) was detected in this study.

Conclusions

The results of this study indicate that in places with transmission of both species, i.e. Plasmodium vivax and Plasmodium falciparum, detection of malaria parasites by the LAMP method could be very useful in spotting infections in the field. Thus, molecular epidemiological studies could be conducted annually to monitor malaria in endemic regions. The results of this research show that contamination with mosquito malaria vectors is increasing in Nikshahr City, and it seems that more studies will be required to eliminate malaria until 2026.

Spatial Modelling of Malaria in South of Iran in Line with the Implementation of the Malaria Elimination Program: A Bayesian Poisson-Gamma Random Field Model

Background:

Malaria is the third most important infectious disease in the world. WHO propose programs for controlling and elimination of the disease. Malaria elimination program has begun in first phase in Iran from 2010. Climate factors play an important role in transmission and occurrence of malaria infection. The main goal is to investigate the spatial distribution of incidence of malaria during April 2011 to March 2018 in Hormozgan Province and its association with climate covariates.

Methods:

The data included 882 confirmed cases gathered from CDC in Hormozgan University of Medical Sciences. A Poisson-Gamma Random field model with Bayesian approach was used for modeling the data and produces the smoothed standardized incidence rate (SIR).

Results:

The SIR for malaria ranged from 0 (Abu Musa and Haji Abad districts) to 280.57 (Bandar–e-Jask). Based on model, temperature (RR= 2.29; 95% credible interval: (1.92–2.78)) and humidity (RR= 1.04; 95% credible interval: (1.03–1.06)) had positive effect on malaria incidence, but rainfall (RR= 0.92; 95% credible interval: (0.90–0.95)) had negative impact. Also, smoothed map represent hot spots in the east of the province and in Qeshm Island.

Conclusion:

Based on the analysis of the study results, it was found that the ecological conditions of the region (temperature, humidity and rainfall) and population displacement play an important role in the incidence of malaria. Therefore, the malaria surveillance system should continue to be active in the region, focusing on high-risk areas of malaria.

Ecology of Malaria Vectors in an Endemic Area, Southeast of Iran

Background:

Malaria has long been regarded as one of the most important public health issues in Iran. Although the country is now in the elimination phase, some endemic foci of malaria are still present in the southeastern areas of the country. In some endemic foci, there are no data on the malaria vectors. To fill this gap, the present study was designed to provide basic entomological data on malaria vectors in the southeastern areas of Iran.

Methods:

Adult and larval stages of Anopheles mosquitoes were collected by using different catch methods. Resistance of the main malaria vector in the study area to selected insecticides was evaluated using diagnostic doses advised by the World Health Organization in 2013–2014.

Results:

A total of 3288 larvae and 1055 adult Anopheles mosquitoes were collected, and identified as: Anopheles stephensi (32.1%), Anopheles culicifacies s.l. (23.4%), Anopheles dthali (23.2%), Anopheles superpictus s.l. (12.7%), and Anopheles fluviatilis s.l. (8.6%). Anopheles stephensi was the most predominant mosquito species collected indoors at the study area, with two peaks of activity in May and November. This species was found to be resistant to DDT 4%, tolerant to malathion 5% and susceptible to other tested insecticides.

Conclusion:

All the five malaria vectors endemic to the south of Iran were collected and identified in the study area. Our findings on the ecology and resting/feeding habitats of these malaria vectors provide information useful for planning vector control program in this malarious area.

Influence of Aquatain™, a monomolecular surface film on surface tension for controlling the filarial vector Culex pipiens (Diptera: Culicidae)

Surface tension is a phenomenon in the liquid media and plays an important part in the development and survival of aquatic animals. Influence of Aquatain™ monomolecular film on surface tension was determined against mosquito larvae and pupae at different temperatures (10, 15, 20, 25, 30 and 35 °C) and Aquatain™ doses (0.5, 1.0 and 2.0 ml/m²). In the laboratory, Aquatain™ showed larvicidal and pupicidal effects against the filarial vector Culex pipiens. Higher mortality was observed in late and more weighted instars/stages than young ones as well as in the pupal stage. The pupal mortality reached 76.2%, 86% and 93.3% after 12 h post-treatment at 0.5, 1.0 and 2.0 ml/m², respectively, and it was completely eliminated (100%) within 24 h compared to 15.1%, 26.9% and 38.2% for 1^st larval instar, respectively. Also, results showed at 0.5 ml/m² with temperature range: 10, 15, 20, 25, 30 and 35 °C, the mortality reached 4.0, 6.7, 10.8, 17.3, 22.7, 29.3% and 32, 44, 54, 72, 84, 97.3% for 1^st and 4^th larval instar, respectively, where the surface tension (γ) was 65.6, 62.4, 58.0, 57.0, 54.2 and, 49.6 dyn/cm, while the Aquatain™ was more effective on mosquito larvae and pupae at high doses with the temperature range. On the other hand, without Aquatain™ dose, the mortality value ranged between 0.0 - 1.2%, and the surface tension (γ) was 74.5 dyne/cm, which is considered as an accidental death. Aquatain™ was effective against all aquatic phases of mosquitoes, especially against the last and weighted ones. Not only was the efficacy of Aquatain™ increased by increasing the dose, but it also increased with the increased temperature of the environment. This efficiency of Aquatain™ is due to its ability to reduce the surface tension of the water medium, preventing different stages of mosquitoes from reaching the surface for breathing thereby leading to suffocation and death. Therefore, we recommended Aquatain™ in programmes for mosquito control and other aquatic insects as a safe, cost-effective control agent.

Malaria situation in a clear area of Iran: an approach for the better understanding of the health service providers' readiness and challenges for malaria elimination in clear areas

Background

Malaria mortality and morbidity have decreased in recent years. Malaria elimination (ME) and effective efforts to achieve ME is one of the most important priorities for health systems in countries in the elimination phase. In very low transmission areas, the ME programme is faced with serious challenges. This study aimed to assess the trend while getting a better understanding of Health Service Providers’ (HSPs) readiness and challenges for ME in a clear area of Iran.

Methods

This study was performed in two phases. At first, the malaria trend in East Azerbaijan Province, was surveyed from 2001 to 2018; afterward, it was compared with the national situation for a better understanding of the second phase of the study. Data were collected from the Ministry of Health’s protocol and the health centre of the province. In the second phase, malaria control programme experts, health system researchers, and health managers’ opinions were collected via in-depth interviews. They were asked regarding HSPs readiness and appropriate Malaria Case Management (MCM) in a clear area and possible challenges.

Results

A total of 135 and 154,560 cases were reported in the last 18 years in East Azerbaijan Province and Iran, respectively. The incidence rate decreased in East Azerbaijan Province from 0.4/10,000 in 2001 to zero in 2018. Furthermore, no indigenous transmission was reported for 14 years. Also, for the first time, there was no indigenous transmission in Iran in 2018. The main elicited themes of HSPs readiness through in-depth interviews were: appropriate MCM, holistic and role-playing studies for assessment of HSPs performance, system mobilization, improving identification and diagnosis of suspected cases in the first line. Similarly, the main possible challenges were found to be decreasing health system sensitivity, malaria re-introduction, and withdrawing febrile suspected cases from the surveillance chain.

Conclusion

Health systems in eliminating phase should be aware that the absence of malaria cases reported does not necessarily mean that malaria is eliminated; in order to obtain valid data and to determine whether it is eliminated, holistic and role-playing studies are required. Increasing system sensitivity and mobilization are deemed important to achieve ME.

The role of midgut symbiotic bacteria in resistance of Anopheles stephensi (Diptera: Culicidae) to organophosphate insecticides

In the current study, the effects of the presence of symbiotic bacteria on the activity of the enzymes involved in An. stephensi resistance to temephos are evaluated for the first time. Four different strains (I. susceptible strain, II. resistant strain, III. resistant strain + antibiotic, and IV. resistant strain + bacteria) were considered in order to determine the possible effects of the symbiotic bacteria on their hosts' resistance to temephos. The median values of all enzymes of susceptible strain were compared with those of other resistant strains. The results of this study indicated a direct relationship between the presence of bacteria in the symbiotic organs of An. stephensi and resistance to temephos. The profile of enzymatic activities in the resistant strain changed to a susceptible status after adding antibiotic. The resistance of An. stephensi to temephos could be completely broken artificially by removing their bacterial symbionts in a resistant population.

Monitoring of Plasmodium infection in humans and potential vectors of malaria in a newly emerged focus in southern Iran

Despite control programs, which aim to eliminate malaria from Iran by 2025, transmission of malaria has not been removed from the country. This study aimed to monitor malaria from asymptomatic parasitaemia and clinical cases from about one year of active case surveillance and potential vectors of malaria in the newly emerged focus of Mamasani and Rostam, southern Iran during 2014-2015. Samples were collected and their DNAs were extracted for Polymerase Chain Reaction (PCR) assay using specific primers for detection of Plasmodium species. The Annual Parasite Incidence rate (API) was three cases per 1,000 population from 2,000 individuals in three villages. Parasites species were detected in 9 out of the 4,000 blood smear samples among which, 6 cases were indigenous and had no history of travels to endemic areas of malaria. Also, the prevalence rate of asymptomatic parasites was about 0.3%. Overall, 1073 Anopheles spp. were caught from 9 villages. Totally, 512 female samples were checked by PCR, which indicated that none of them was infected with Plasmodium. Despite new malaria local transmission in humans in Mamasani and Rostam districts, no infection with Plasmodium was observed in Anopheles species. Because of neighboring of the studied area to the re-emerged focus in Fars province (Kazerun) and important endemic foci of malaria in other southern provinces, such as Hormozgan and Kerman, monitoring of the vectors and reservoir hosts of Plasmodium species would be unavoidable. Application of molecular methods, such as PCR, can simplify access to the highest level of accuracy in malaria researches.