Safety of insecticide-treated mosquito nets for infants and their mothers: randomized controlled community trial in Burkina Faso

A taste of a toxin paradise: Xenorhabdus and Photorhabdus bacterial secondary metabolites against Aedes aegypti larvae and eggs

Aedes-transmitted arboviral infections such as Dengue, Yellow Fever, Zika and Chikungunya are increasing public health problems. Xenorhabdus and Photorhabdus bacteria are promising sources of effective compounds with important biological activities. This study investigated the effects of cell-free supernatants of X. szentirmaii, X. cabanillasii and P. kayaii against Ae. aegypti eggs and larvae and identified the bioactive larvicidal compound in X. szentirmaii using The EasyPACId method. Among the three tested bacterial species, X. cabanillasii exhibited the highest (96%) egg hatching inhibition and larvicidal activity (100% mortality), whereas P. kayaii was the least effective species in our study. EasyPACId method revealed that bioactive larvicidal compound in the bacterial supernatant was fabclavine. Fabclavines obtained from promoter exchange mutants of different bacterial species such as X. cabanillasii, X. budapestensis, X. indica, X. szentirmaii, X. hominckii and X. stockiae were effective against mosquito larvae. Results show that these bacterial metabolites have potential to be used in integrated pest management (IPM) programmes of mosquitoes.

Facilitators and barriers to integrated malaria prevention in Wakiso district, Uganda: A photovoice study

Malaria continues to cause significant morbidity and mortality globally, particularly in sub-Saharan Africa. Appropriate combinations of non-chemical and chemical methods of malaria vector control in the context of integrated vector management have been recommended by the World Health Organization. The aim of the study was to explore facilitators and barriers to using integrated malaria prevention in Wakiso district, Uganda. This qualitative study employed photovoice among 20 community members in Kasanje Town Council, Wakiso District. The photos taken by participants for 5 months using smartphones were discussed during monthly meetings with the researchers. The discussions were audio-recorded, and resulting data analysed using thematic analysis with the support of NVivo (2020) QSR International. Findings indicated that various conventional and non-conventional measures were being used for preventing malaria such as: insecticide treated nets; clearing overgrown vegetation; draining stagnant water; mosquito coils; smouldering of cow dung; spraying insecticides; plant repellents near houses; eating of prophylactic herbs; as well as closing doors and windows on houses early in the evening. Facilitators supporting the use of several malaria prevention methods holistically included: low cost and accessibility of some methods such as slashing overgrown vegetation; and support provided for certain methods such as receiving free mosquito nets from the government. Barriers to using several malaria prevention methods holistically included: inadequate knowledge of some methods such as housing improvement; allergic reactions to chemical-based methods such as insecticide treated nets; unaffordability of some methods such as insecticide sprays; and inaccessibility of certain methods such as body repellents. These barriers to integrated malaria prevention need to be addressed to achieve greater impact from the combination of methods in endemic communities.

Collateral Effects of Insecticide-Treated Nets on Human and Environmental Safety in an Epidemiological Model for Malaria with Human Risk Perception

Malaria remains a major health problem in many parts of the world, including Sub-Saharan Africa. Insecticide-treated nets, in combination with other control measures, have been effective in reducing malaria incidence over the past two decades. Nevertheless, there are concerns about improper handling and misuse of nets, producing possible health effects from intoxication and collateral environmental damage. The latter is caused, for instance, from artisanal fishing. We formulate a model of impulsive differential equations to describe the interplay between malaria dynamics, human intoxication, and ecosystem damage; affected by human awareness to these risks and levels of net usage. Our results show that an increase in mosquito net coverage reduces malaria prevalence and increases human intoxications. In addition, a high net coverage significantly reduces the risk perception to disease, naturally increases the awareness for intoxications from net handling, and scarcely increases the risk perception to collateral damage from net fishing. According to our model, campaigns aiming at reducing disease prevalence or intoxications are much more successful than those creating awareness to ecosystem damage. Furthermore, we can observe from our results that introducing closed fishing periods reduces environmental damage more significantly than strategies directed towards increasing the risk perception for net fishing.

Integrated malaria prevention in rural communities in Uganda: a qualitative feasibility study for a randomised controlled trial

Background

A randomised controlled trial (RCT) on integrated malaria prevention, which advocates the use of several malaria prevention methods holistically, has been proposed. However, before conducting an RCT, it is recommended that a feasibility study is carried out to provide information to support the main study, particularly for such a complex intervention. Therefore, a feasibility study for an RCT on integrated malaria prevention in Uganda was conducted.

Methods

The qualitative study carried out in Wakiso District employed focus group discussions (FGDs) and key informant interviews (KIIs) to explore community willingness to participate in the RCT as well as assess stakeholder perspectives on the future study. The participants of the FGDs were community members, while the key informants were selected from malaria stakeholders including Ministry of Health officials, health practitioners, local leaders, district health team members, and community health workers (CHWs). Thematic analysis was employed with the support of NVivo.

Results

A total of 12 FGDs and 19 KIIs were conducted. Five main themes emerged from the study: malaria prevention practices related to integrated malaria prevention; preferred malaria prevention methods in the integrated approach; potential challenges of integrated malaria prevention; perspectives on the proposed RCT; and sustainability of integrated malaria prevention. Despite a few methods being employed holistically in the community, insecticide-treated nets were the most widely used and preferred method for malaria prevention mainly because they were provided free by the government. The main challenges in the integrated approach were the high cost of some methods such as house screening, and concerns about the potential side effects of insecticide-based methods such as indoor residual spraying. Participants expressed high willingness to participate in the RCT to promote the use of multiple methods in their households and community. Involvement of CHWs during implementation was proposed as a sustainability strategy for the RCT interventions.

Conclusion

There was high willingness to participate in the proposed RCT on integrated malaria prevention. However, high cost and perceived negative health effects from some methods were identified as potential challenges. The type of methods to be included as well as sustainability mechanisms needs to be considered during the design of the RCT.

Anopheles metabolic proteins in malaria transmission, prevention and control: a review

The increasing resistance to currently available insecticides in the malaria vector, Anopheles mosquitoes, hampers their use as an effective vector control strategy for the prevention of malaria transmission. Therefore, there is need for new insecticides and/or alternative vector control strategies, the development of which relies on the identification of possible targets in Anopheles. Some known and promising targets for the prevention or control of malaria transmission exist among Anopheles metabolic proteins. This review aims to elucidate the current and potential contribution of Anopheles metabolic proteins to malaria transmission and control. Highlighted are the roles of metabolic proteins as insecticide targets, in blood digestion and immune response as well as their contribution to insecticide resistance and Plasmodium parasite development. Furthermore, strategies by which these metabolic proteins can be utilized for vector control are described. Inhibitors of Anopheles metabolic proteins that are designed based on target specificity can yield insecticides with no significant toxicity to non-target species. These metabolic modulators combined with each other or with synergists, sterilants, and transmission-blocking agents in a single product, can yield potent malaria intervention strategies. These combinations can provide multiple means of controlling the vector. Also, they can help to slow down the development of insecticide resistance. Moreover, some metabolic proteins can be modulated for mosquito population replacement or suppression strategies, which will significantly help to curb malaria transmission.

Asymptomatic malaria infection among pregnant women attending antenatal care in malaria endemic areas of North-Shoa, Ethiopia: a cross-sectional study

Background

The effort to reduce the burden of malaria should target transmission in the community by accurate identification of asymptomatic infections. In malaria-endemic areas, asymptomatic malaria infection is still associated with complications. Malaria during pregnancy is characterized by anaemia and placental malaria, leading to low birth weight and perinatal morbidity and mortality. This study aimed to provide reliable data on the burden of asymptomatic malaria among pregnant women in malaria endemic areas of North-Shoa, Ethiopia.

Methods

Cross-sectional study was carried out to assess the prevalence and predictors of asymptomatic malaria in pregnant women from November 2018 to January 2019. Multistage sampling technique was employed to include 263 study participants. Data were analysed using SPSS version 20.0 statistical software. In all comparisons, p-values ≤ 0.05 was considered as statistically significant.

Results

The prevalence of asymptomatic malaria infection was 5.7% (15/263) and 3.4% (9/263) by using microscopy and RDTs, respectively. Plasmodium falciparum was a dominant species 9 (3.4%) and Plasmodium vivax accounted for 6 (2.3%) of Plasmodium infections as detected by microscopy. Multivariate analysis showed that ITN usage and haemoglobin level had a statistically significant association with Plasmodium infection after adjusting other possible factors. Compared to those who were using ITN always, the odds of Plasmodium infection was 18.16 times higher (95% CI 1.84–179.07) in pregnant women who were not using ITN, and 5.19 times higher (95% CI 0.55–49.21) in pregnant women who were using ITN sometimes. Asymptomatic malaria infected pregnant women were 3.78 times (95% CI 0.98–14.58) more likely to be anaemic compared to non-infected pregnant women.

Conclusion

The present study showed asymptomatic malaria is prevalent in pregnant women and it has statistically significance association with the haemoglobin level of pregnant women. This indicates pregnant women have to be screened for asymptomatic malaria to avoid health consequences of malaria infection during pregnancy for the mother and fetus.

Transgenic Metarhizium pingshaense synergistically ameliorates pyrethroid-resistance in wild-caught, malaria-vector mosquitoes

Transgenic Metarhizium pingshaense expressing the spider neurotoxin Hybrid (Met-Hybrid) kill mosquitoes faster and at lower spore doses than wild-type strains. In this study, we demonstrate that this approach dovetails with the cornerstone of current malaria control: pyrethroid-insecticides, which are the cornerstone of current malaria control. We used World Health Organization (WHO) tubes, to compare the impact on insecticide resistance of Met-Hybrid with red fluorescent M. pingshaense (Met-RFP), used as a proxy for the wild-type fungus. Insecticides killed less than 20% of Anopheles coluzzii and Anopheles gambiae s.s. mosquitoes collected in a malaria endemic region of Burkina Faso where pyrethroid use is common. Seven days post-infection, mortality for insecticide-sensitive and resistant mosquitoes averaged 94% with Met-Hybrid and 64% with Met-RFP, with LT80 values of 5.32±0.199 days and 7.76±0.183 days, respectively. Eighty nine percent of insecticide-resistant mosquitoes exposed to permethrin five days post-infection with Met-Hybrid died within 24 hours: only 22% died from Met-Hybrid alone over this 24-hour period. Compared to Met-RFP, Met-Hybrid also significantly reduced flight capacity of mosquitoes 3 to 5 days post-infection. Based on WHOPES phase I laboratory susceptibility bioassays, transgenic Met-Hybrid provides effective biological control for adult African malaria vectors that may be used to synergistically manage insecticide resistance with current methods.

Assessment of human exposure to pesticides by hair analysis: The case of vegetable-producing areas in Burkina Faso

The present work assesses human exposure to pesticides in vegetable-producing areas in Burkina Faso, using hair as an indicator. The study design includes a comparison between operators who are occupationally exposed while working in the fields and a reference population (i.e. not occupationally exposed) to evaluate both occupational and indirect exposures. Hair samples from volunteers (n=101) were positive for 17 pesticides (38 analyzed). Acetamiprid, desethylatrazine, carbofuran, and deltamethrin were detected for the first time in field samples. With a maximum of 9 residues per sample, pesticide exposure was ubiquitous in both populations. Contamination by acetamiprid, cypermethrin, and lambda-cyhalothrin (used in vegetable production) prevailed in operator samples. For other pesticides, such as imidacloprid and deltamethrin, no significant difference was found. This indicates a potentially large environmental exposure (dietary intake or atmospheric contamination) or the prevalence of other contamination sources. The present findings are concerning, as detected levels are globally higher than those previously reported, and indicate exposure to endocrine disrupting chemicals and probable carcinogens. Hair was found to be a suitable matrix for biomonitoring human exposure to pesticides and assessing dominant factors (i.e. sex, age, and protective equipment) in subgroups, as well as identifying geographical contamination patterns.