Tropical Health Matters

Abstracts and news look at mosquito control measures including screening eaves and indoor residual spraying from Malaria Journal. Mosquito-associated bacteria, fungi, and even viruses represent untapped tools. Finally one can buy and wear a face mask and help eliminate malaria. Click the links to get more information

Evaluating effectiveness of screening house eaves

… a potential intervention for reducing indoor vector densities and malaria prevalence in Nyabondo, western Kenya. Mosquito-proofing of houses using wire mesh screens is gaining greater recognition as a practical intervention for reducing exposure to malaria transmitting mosquitoes. Screening potentially protects all persons sleeping inside the house against transmission of mosquito-borne diseases indoors. The study assessed the effectiveness of house eaves screening in reducing indoor vector densities and malaria prevalence in Nyabondo, western Kenya. 160 houses were selected for the study, with half of them randomly chosen for eaves screening with fibre-glass coated wire mesh (experimental group) and the other half left without screening (control group).

At all the three parasitological follow-up survey points, house screening significantly reduced the malaria prevalence by 100% (p?<?0.001), 63.6% (p?=?0.026), and 100% (p?<?0.001) in the 1st, 2nd and 3rd follow-up surveys respectively. The study demonstrated that house eave screening has potential to reduce indoor vector densities and malaria prevalence in high transmission areas.

Rapid reduction of malaria transmission following the introduction of indoor residual spraying

… in previously unsprayed districts: an observational analysis of Mopti Region, Mali, in 2017. The National Malaria Control Programme (NMCP) of Mali has had recent success decreasing malaria transmission using 3rd generation indoor residual spraying (IRS) products in areas with pyrethroid resistance, primarily in Ségou and Koulikoro Regions. In 2015, national survey data showed that Mopti Region had the highest under 5-year-old (u5) malaria prevalence at 54%—nearly twice the national average—despite having high access to long-lasting insecticidal nets (LLINs) and seasonal malaria chemoprevention (SMC). Accordingly, in 2016 the NMCP and other stakeholders shifted IRS activities from Ségou to Mopti. A set of retrospective, eco-observational time-series analyses were performed using monthly incidence rates of rapid diagnostic test (RDT)-confirmed malaria cases reported in the District Health Information System 2 (DHIS2) from January 2016 until February 2018.

At HFs in communities of Mopti where IRS was introduced in 2017, peak incidence fell by an average of 42% (CI95 31–63%) between these years, a significantly greater decrease (p?=?0.040) almost double what was seen in the comparator HFCAs. The opposite effect was observed in Ségou Region, where peak incidence at those HFs where IRS was withdrawn after the 2016 campaign increased by an average of 106% (CI95 63–150%) from year to year, also a significant difference-in-differences compared to the comparator no-IRS HFs (p?<?0.0001).

Annual IRS campaigns continue to make dramatic contributions to the seasonal reduction of malaria transmission in communities across central Mali, where IRS campaigns were timed in advance of peak seasonal transmission and utilized a micro-encapsulated product with an active ingredient that was of a different class than the one found on the LLINs used throughout the region and to which local malaria vectors were shown to be susceptible. Strategies to help mitigate the resurgence of malaria cases that can be expected should be prioritized whenever the suspension of IRS activities in a particular region is considered.

COVID-19 Mask Raises Money for Malaria Elimination

Goodbye Malaria was founded by African entrepreneurs who truly believe African creativity is the key to solving Africa’s biggest problems. “From saving lives to saving livelihoods – the birth of the Goodbye Malaria mask.”  Mask initiative helps to raise funds support on-the-ground malaria elimination in Southern Africa. it empowers local crafters to create stylish merchandise using Goodbye Malaria’s iconic shwe shwe fabric. Goodbye Malaria co-founder Kim Lazarus said: “We have never asked the public for donations, instead, offering consumers an opportunity to support malaria elimination efforts through their purchase of our merchandise.” (see photo above)

Prospects and Pitfalls: Next-Generation Tools to Control Mosquito-Transmitted Disease

Annual Review of Microbiology reports that Mosquito-transmitted diseases, including malaria and dengue, are a major threat to human health around the globe, affecting millions each year. A diverse array of next-generation tools has been designed to eliminate mosquito populations or to replace them with mosquitoes that are less capable of transmitting key pathogens. Many of these new approaches have been built on recent advances in CRISPR/Cas9-based genome editing. These initiatives have driven the development of pathogen-resistant lines, new genetics-based sexing methods, and new methods of driving desirable genetic traits into mosquito populations.

Many other emerging tools involve microorganisms, including two strategies involving Wolbachia that are achieving great success in the field. At the same time, other mosquito-associated bacteria, fungi, and even viruses represent untapped sources of new mosquitocidal or antipathogen compounds. Although there are still hurdles to be overcome, the prospect that such approaches will reduce the impact of these diseases is highly encouraging.

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