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

Bioassays for the evaluation of the attractiveness of attractive targeted sugar bait (ATSB) against Anopheles mosquitoes in controlled semi-field systems

BACKGROUND

Sugar feeding is an essential aspect of mosquito biology that may be exploited for mosquito control by adding insecticides to sugar attractants, so-called 'attractive targeted sugar baits' (ATSBs). To optimize their effectiveness, ATSB products need to be maximally attractive at both short and long range and induce high levels of feeding. This study aimed to assess the attractiveness and feeding success of Anopheles mosquitoes exposed to attractive sugar baits (ASBs).

METHOD

Experiments were conducted in 2 × 5 × 2-m cages constructed within the semi-field systems (SFS) at Ifakara Health Institute, Bagamoyo, Tanzania. Male and female Anopheles gambiae s.s. and An. funestus s.s. mosquitoes were exposed to either 20% sucrose or different ASB station prototypes produced by Westham Co. in either (1) no-choice experiments or (2) choice experiments. Mosquitoes were exposed overnight and assessed for intrinsic or relative olfactory attraction using fluorescent powder markers dusted over the ASB stations and 20% sucrose and for feeding using uranine incorporated within the bait station and food dye in 20% sucrose controls.

RESULTS

Both male and female An. gambiae and An. funestus mosquitoes were attracted to the ASBs, with no significant difference between the sexes for each of the experiments conducted. Older mosquitoes (3-5 days) were more attracted to the ASBs (OR = 8.3, [95% CI 6.6-10.5] P < 0.001) than younger mosquitoes (0-1 day). Similarly, older mosquitoes responded more to 20% sucrose (OR = 4.6, [3.7-5.8], P < 0.001) than newly emerged Anopheles. Of the four prototypes tested, the latest iteration, ASB prototype v1.2.1, showed the highest intrinsic attraction of both Anopheles species, attracting 91.2% [95% CI 87.9-94.5%]. Relative to ATSB v1.1.1, the latest prototype, v.1.2.1, had higher attraction (OR = 1.19 [95% CI 1.07-1.33], P < 0.001) and higher feeding success (OR = 1.71 [95% CI 1.33-2.18], P < 0.001).

CONCLUSIONS

Data from these experiments support using ASBs v1.2.1, deployed in large-scale epidemiological trials, as it is the most attractive and shows the highest feeding success of the Westham prototypes tested. The findings indicate that future bioassays to evaluate ATSBs should use mosquitoes of both sexes, aged 3-5 days, include multiple species in the same cage or chamber, and utilize both non-choice and choice tests with a standard comparator.

Utilization of insecticide-treated bed nets and associated factors among households in Pawie District, Benshangul Gumuz, Northwest Ethiopia

INTRODUCTION

Insecticide-treated bed nets are often used as a physical barrier to prevent infection of malaria. In Sub-Saharan Africa, one of the most important ways of reducing the malaria burden is the utilization of insecticide-treated bed nets. However, there is no sufficient information on the utilization of insecticide-treated bed nets and their associated factors in Ethiopia.

OBJECTIVES

This study aimed to assess the utilization of insecticide-treated bed nets and associated factors among households in Pawie District, Benshangul Gumuz, North West Ethiopia.

METHODS

A community-based cross-sectional study was conducted in the Pawie district to identify factors influencing the use of insecticide-treated nets (ITNs). Diverse household groups were engaged, and data were collected using a structured questionnaire and observational checklists by trained interviewers. The data were entered into Epi-Data version 3.1 and analyzed using SPSS version 23. Advanced statistical methods, including binary and multi-variable logistic regression, were employed to examine the factors associated with ITN utilization.

RESULTS

From the total of 633 respondents, more than two third, 438 (69.2% with 95% CI: 65.2%, 72.5%) had utilized insecticide-treated bed nets during the early morning of the interview. Approximately 297 respondents (67.8%) successfully hung their insecticide-treated nets (ITNs) properly during the early morning of observation. In this study, 406 respondents (64.1%, 95% CI: 60.5, 68.1) showed a solid understanding of insecticide-treated nets (ITNs) utilization. Key predictors for the utilization of insecticide-treated bed nets (ITNs) included age (AOR = 1.86, 95% CI: 1.11, 3.13, p = 0.019), educational status (AOR = 0.45, 95% CI: 0.26, 0.77, p = 0.008), knowledge level (AOR = 2.64, 95% CI: 1.89, 3.81, p < 0.001), and family size (AOR = 1.89, 95% CI: 1.31, 2.74, p = 0.001). All of these variables were found to be statistically significant for the utilization of insecticide-treated bed net.

CONCLUSIONS

Utilization of the insecticide-treated bed nets (ITNs) remains low in the study area. To address this, it is crucial to raise public awareness and improve utilization of the insecticide-treated bed nets (ITNs) to decrease malaria transmission in the district. Ongoing health education initiatives, including demonstrations on the proper way to hang bed nets, will be essential in fostering better practices and improving community health outcomes.

Exploring the genetic progression of MDR1 in Plasmodium falciparum: A decade of multi-regional genetic analysis (2014-2024)

Background

The genetic progression of the MDR1 gene in Plasmodium falciparum, a key factor in drug resistance, presents significant challenges for malaria control. This study aims to elucidate the genetic diversity and evolutionary dynamics of P. falciparum, particularly focusing on the MDR1 gene across multi-regional populations. To analyze the genetic diversity of P. falciparum MDR1 gene across various multi-regional populations between 2014 and 2024, assessing allelic richness, genetic distances, and evolutionary patterns.

Methods

We conducted an extensive genetic analysis using methods such as Analysis of Molecular Variance (AMOVA), pairwise population matrices of Nei unbiased genetic distance and identity, PhiPT and Phi'PT values, and Principal Coordinates Analysis (PCoA). The study covered diverse P. falciparum populations from India, Nigeria, Ethiopia, Honduras, China, and Cameroon.

Findings

Our findings reveal significant genetic heterogeneity in the MDR1 gene. Populations like India: Odisha (2014) exhibited high allelic richness, indicating diverse drug resistance profiles. Notable genetic divergence was observed, especially between India (2016) and Nigeria (2020), suggesting different evolutionary trajectories in drug resistance. The PCoA analysis highlighted the multi-dimensional genetic variation, reflecting the complex interplay of factors influencing drug resistance in P. falciparum.

Interpretation

The comprehensive analysis of P. falciparum's MDR1 gene provides crucial insights into the multi-regional patterns of drug resistance. This knowledge is essential for developing effective malaria control measures and adapting treatment strategies to the evolving genetic diversity of the parasite.

Ace-1 Target Site Status and Metabolic Detoxification Associated with Bendiocarb Resistance in the Field Populations of Main Malaria Vector, Anopheles stephensi in Iran

Background

Anopheles stephensi is the main vector of malaria in Iran. This study aimed to determine the susceptibility of An. stephensi from the south of Iran to bendiocarb and to investigate biochemical and molecular resistance mechanisms in this species.

Methods

Wild An. stephensi were collected from Hormozgan Province and reared to the adult stage. The susceptibility test was conducted according to the WHO protocols using bendiocarb impregnated papers supplied by WHO. Also, field An. Stephensi specimens were collected from south of Kerman and Sistan and Baluchistan Provinces. To determine the G119S mutation in the acetylcholinesterase (Ace1) gene, PCR-RFLP using AluI restriction enzyme and PCR direct-sequencing were performed for the three field populations and compared with the available GenBank data. Also, biochemical assays were performed to measure alpha and beta esterases, insensitive acetylcholinesterase, and oxidases in the strains.

Results

The bioassay tests showed that the An. stephensi field strain was resistant to bendiocarb (mortality rate 89%). Ace1 gene analysis revealed no G119S in the three field populations. Blast search of sequences revealed 98-99% identity with the Ace1 gene from Pakistan and India respectively. Also, the results of biochemical tests revealed the high activity of non-sensitive acetylcholinesterase, alpha and beta-esterase in the resistant strain compared to the susceptible strain. No G119S was detected in this study additionally the enhanced enzyme activity of esterases and acetylcholinesterase suggesting that resistance was metabolic.

Conclusion

The use of alternative malaria control methods and the implementation of resistance management strategies are suggested in the study area.

Nanoemulsion and nanogel containing Artemisia dracunculus essential oil; larvicidal effect and antibacterial activity

Objective

Microbial infections and mosquito-borne diseases such as malaria, with 627 k deaths in 2020, are still major public health challenges.

Results

This study prepared nanoemulsion and nanogel containing Artemisia dracunculus essential oil. ATR-FTIR analysis (Attenuated Total Reflection-Fourier Transform InfraRed) confirmed the successful loading of the essential oil in nanoemulsion and nanogel. LC50 values (Lethal Concentration 50%) of nanogel and nanoemulsion against Anopheles stephensi larvae were obtained as 6.68 (2–19 µg/mL) and 13.53 (7–25 µg/mL). Besides, the growth of Staphylococcus aureus after treatment with 5000 μg/mL nanogel and nanoemulsion was reduced by ~ 70%. However, about 20% growth of Pseudomonas aeruginosa was reduced at this dose. Considering the proper efficacy of the nanogel as a larvicide and proper antibacterial effect against S. aureus, it could be considered for further investigations against other mosquitoes’ larvae and gram-positive bacteria.