Tropical Health Matters

News and abstracts provide more on the surge of malaria in Mali. COVID-19 complicates malaria elimination in Southeast Asia. Peace Corps health care for volunteers in Comoros is questioned. Malaria risk in Ecuador is investigated. Risk maps are used/not used in three Sub-Saharan countries. The potential of microbiological control is considered. More information on each topic is available in the links provided.

Health workers raise alarm over surge in malaria cases, deaths in Mali

More details emerge on malaria in northern Mali. Medical workers in Mali raised an alarm over a surge in malaria cases which has seen at least 23 people killed by the disease in just the past one week. About 13,000 malaria cases were reported in the north by medical workers between September 21 and 27, representing an 88 percent increase in cases from the previous week. 59 people have died of malaria in the nation’s northern region since the beginning of the year, according to the ministry, which confirmed the deaths of the 23 people over the aforementioned September period.

Will COVID-19 hamper ASEAN’s fight to eliminate malaria?

Although progress elsewhere in the world has been slow, in the Asia-Pacific, deaths due to the mosquito-borne disease have dropped by 70% and cases have dropped by 22%. Within ASEAN, those figures—according to the Asia Pacific Leaders Malaria Alliance (APLMA)—are 92% and 67% respectively. The battle to eliminate malaria is continually evolving with different species of disease-carrying mosquitoes and parasites presenting new challenges. In 2008, a new strain of malaria that proved resistant to the anti-malarial drug artemisinin, nicknamed “super malaria”, emerged in Cambodia. It spread through the Greater Mekong region into Laos, Thailand and Vietnam and by 2017, it had developed resistance to another drug, piperaquine.

In response, scientists and researchers focused their resources on areas where the new strain was present and were making headway towards eliminating it. COVID-19 could threaten that progress. “We have enough evidence from the Ebola epidemic to suggest how progress on malaria elimination could be derailed and we are seeing some clear warnings now,” APLMA/APMEN commented. Historically, malaria cases have risen in countries where healthcare is interrupted due to conflict, disaster and war.

Peace Corps faces questions over death of volunteer from Inverness

By Sheryl Gay Stolberg of the New York Times reported that the Peace Corps, which suspended all operations for the first time in its history as the novel coronavirus raced around the globe, is facing renewed questions about the quality of its medical care — in particular, after the death of a 24-year-old volunteer from undiagnosed malaria — as it prepares to send volunteers back into the field.

An investigation by the Peace Corps inspector general documented a string of problems with Heiderman’s care. Her doctor had “limited training in tropical medicine,” the investigation found, and failed to test for malaria, which would have revealed that Heiderman had been infected by the deadliest malaria parasite. The Peace Corps was also using outdated 2006 guidelines for malaria, which did not reflect the current standard of care.

Anopheline and human drivers of malaria risk in northern coastal Ecuador

Understanding local anopheline vector species and their bionomic traits, as well as related human factors, can help combat gaps in protection. In San José de Chamanga, Esmeraldas, at the Ecuadorian Pacific coast, anopheline mosquitoes were sampled by both human landing collections (HLCs) and indoor-resting aspirations (IAs) and identified using both morphological and molecular methods.

Among 222 anopheline specimens captured, based on molecular analysis. The exophagic feeding of anopheline vectors in San Jose de Chamanga, when analysed in conjunction with human behaviour, indicates a clear gap in protection even with high LLIN coverage. The lack of indoor-resting anophelines suggests that indoor residual spraying (IRS) may have limited effect. The presence of asymptomatic infections implies the presence of a human reservoir that may maintain transmission.

How useful are malaria risk maps at the country level?

This study examined the perceptions of decision-makers in Kenya, Malawi and the Democratic Republic of Congo. Declining malaria prevalence and pressure on external funding have increased the need for efficiency in malaria control in sub-Saharan Africa (SSA). Modelled Plasmodium falciparum parasite rate (PfPR) maps are increasingly becoming available and provide information on the epidemiological situation of countries. However, how these maps are understood or used for national malaria planning is rarely explored. In this study, the practices and perceptions of national decision-makers on the utility of malaria risk maps, showing prevalence of parasitaemia or incidence of illness, was investigated.

Three different types of maps were used to show malaria epidemiological strata: malaria prevalence using a PfPR modelled map (Kenya); malaria incidence using routine health system data (Malawi); and malaria prevalence using data from the most recent Demographic and Health Survey (DRC). In Kenya the map was used to target preventative interventions, including long-lasting insecticide-treated nets (LLINs) and intermittent preventive treatment in pregnancy (IPTp), whilst in Malawi and DRC the maps were used to target in-door residual spraying (IRS) and LLINs distributions in schools. Maps were also used for operational planning, supply quantification, financial justification and advocacy. Findings from the interviews suggested that decision-makers lacked trust in the modelled PfPR maps when based on only a few empirical data points (Malawi and DRC). Despite the availability of national level modelled PfPR maps in all three countries, they were only used in one country.

Infection of highly insecticide-resistant malaria vector Anopheles coluzzii with entomopathogenic bacteria

This study found that Chromobacterium violaceum reduces its survival, blood feeding propensity and fecundity of mosquitoes in Burkina Faso. The study was motivated by the concern that malaria eradication will not be achieved without the introduction of novel control tools. Microbiological control might be able to make a greater contribution to vector control in the future. The interactions between bacteria and mosquito make mosquito microbiota really promising from a disease control perspective.
Methods

To assess entomopathogenic effects of C. violaceum infection on mosquitoes, three different types of bioassays were performed in laboratory. These bioassays aimed to evaluate the impact of C. violaceum infection on mosquito survival, blood feeding and fecundity, respectively. During bioassays mosquitoes were infected through the well-established system of cotton ball soaked with 6% glucose containing C. violaceum.

The data showed important properties of Burkina Faso C. violaceum strains, which are highly virulent against insecticide-resistant An. coluzzii, and reduce both mosquito blood feeding and fecundity propensities. However, additional studies as the sequencing of C. violaceum genome and the potential toxins secreted will provide useful information render it a potential candidate for the biological control strategies of malaria and other disease vectors.

 

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