Category Archives: Larvicide

Malaria News Today 2020-10-02/03

Recent news and abstracts include mosquito control using solar disruption of of larval habitats and plants that repel the insects around homes. The challenges of malaria related anemia in pregnancy is discussed. Malaria cases increase in Mali and Mozambique, but in the latter, deaths actually decrease. Malaria parasites have ways of making people more attractive to mosquito bites. Finally covid-19 has not disrupted malaria work as much as anticipated. Read more at the links in the sections below.

Improved Mosquito Control with Solar Power Machine that Causes Ripple Effect

Kristina Panos writes that mosquito haters of the world, rejoice! A few years ago we told you about the first version of this solar-powered mosquito repellent that works by disturbing the surface of standing water. Since then, the project has received worldwide attention, and [Pranav] is back with Solar Scare Mosquito version 2.0 in time for the the 2020 Hackaday Prize.

The idea’s still the same as before: let mosquitoes lay their eggs in the standing waters of tanks and swamps, then disturb the water with vibrations so the larvae on the surface can’t breathe. As smart as this simple idea is, version 2.0 is even smarter. It has a microphone that listens to the wing-beat frequencies of mosquitoes that like to hang around places like that. Inside there’s an Arduino MKR GSM to run the ripple-generating air pump, detect water from the sensor, and gather data from the microphone.

With a network of these devices all reporting data, [Pranav] envisions an early warning system for mosquito-borne epidemics that works by alerting the locals through their phones. Solar Scare Mosquito has come a long way since 2014.

Malaria cases spike in northern Mali

Malaria cases in northern Mali have spiked, according to medical workers, claiming 23 lives in the often lawless desert region last week alone. Mali’s ministry of health said this week that 59 people have died of malaria in the north since the start of the year, almost double the number of deaths over the same period last year.

Already struggling to curb coronavirus, the poor Sahel country is also fighting a brutal jihadist insurgency active in the north and centre of the country.

A powerful attractant: Malaria parasites lure blood-sucking mosquitoes

The malaria parasite’s gametocyte-stage has been demonstrated in the field to heavily manipulate the blood-seeking behaviour of vector mosquitoes through increasing the appeal of biting an infected host.

Plasmodium parasites, the causative agents of Malaria in humans and animals, are well known for manipulating both their human and mosquito hosts as a way of maximising the probability of interactions between them, thereby increasing the chance malaria parasites are transmitted from host to host. One way in which these devious parasites have been shown to increase the probability of host interaction is during their transmissible (gametocyte) stage.

This is achieved by inducing host red blood cells to produce volatile compounds that attract malarial vector species, such as mosquitos in the Anopheles family. The increase in production of volatile compounds, such as certain aldehydes and terpenes, by host red blood cells was shown back in 2017 to be specifically induced by a gametocyte-produced molecule called (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate, also known as HMBPP.

Malaria campaigns fight off Covid disruptions to deliver programmes

Almost all planned work against the disease has gone ahead this year, delivering nets, drugs and the world’s first malaria vaccine. More than 90% of anti-malaria campaigns planned this year across four continents are on track, despite disruptions caused by the coronavirus pandemic, according to new research.

The delivery of insecticide-treated nets and provision of antimalarial medicines in the majority of malaria-affected countries across Africa, Asia and the Americas were still going ahead, a high-level meeting organised by the RBM Partnership to End Malaria heard on Thursday.

Malaria associated with increased prevalence of anemia during pregnancy

Ken Downey Jr. and colleagues conducted a study in seven sub-Saharan African countries demonstrated an association between malaria and an increased prevalence of anemia among pregnant women, according to findings published in BMC Pregnancy and Childbirth.

“Pregnant women in sub-Saharan Africa suffer a double burden of malaria and HIV infections, and these infections interact with each other to cause anemia,” Ssentongo told Healio. “If not treated, the risk of the mother and the unborn baby dying is high. Multipronged strategies to prevent and treat malaria in HIV pregnant women are critical to ensure the survival of the mothers and their unborn babies.”Paddy Ssentongo, MD, MPH, a research assistant professor at Penn State University,

Mozambique: Malaria Cases Increase, Malaria Death Toll Declines

From January to August, 442 people in Mozambique are known to have died from malaria, according to Health Minister Armindo Tiago. Speaking at the launch of a National Home Spraying Campaign, Tiago said the malaria death toll, in the first eight months of the year, was significantly lower than that recorded in the same period in 2019, when 562 people died of the disease.

But although fewer people are dying of malaria, the number of malaria cases has actually increased – from 7.86 million cases in January-August 2019 to 8.36 million in the same months this year. The number of cases rose by 6.4 per cent, but the number of deaths fell by 21.4 per cent. Thus there is the drive to persuade families to change their behaviour.

The Plants That Keep Mosquitoes Away

Protect outdoor areas from mosquitoes and bugs to enjoy evenings outside. Including the following plants in a home garden can provide homeowners with some important weapons in the war against mosquitoes.

1. Citronella Plants: You may already be familiar with citronella plants, as they are known for emitting a strong smell that mosquitoes find objectionable. This group of plants contain citronellal, the active ingredient commonly found in mosquito repellents like citronella patio candles or sprays.

2. The Mint Family: Some members of the mint family have the power to repel mosquitoes, or at least take the sting out of their bites. Check Lemon Balm, Peppermint, Basil, Lavender, Sage, and Catnip.

3. Flowers: Believe it or not, ornamental plants can actually do double duty and function as mosquito repellents. Even better, these plants love sun and are drought resistant. Marigolds, and their relative, tarragoncontain pyrethrum, an ingredient found in many insect repellents. Verbena is a lemon-scented, easy-to-grow perennial. Citrosum is also named “the mosquito plant,” and is one of the best plants in the game for repelling mosquitoes.

The Weekly Tropical Health News 2019-07-13

In the past week more attention was drawn to the apparently never-ending year-long Ebola outbreak in the northeast of the Democratic Republic of the Congo. Regarding other diseases, there is new information on the RTS,S malaria vaccine, river prawns have been found to play a biological control role in schistosomiasis, and an update from the World Health Organization on essential medicines and diagnostics. New malaria vector control technologies are discussed.

Second Largest Ebola Outbreak One Year On

Ronald A. Klain and Daniel Lucey in the Washington Post observed raised concern that, “the disease has since crossed one border (into Uganda) and continues to spread. In the absence of a trajectory toward extinguishing the outbreak, the opposite path — severe escalation — remains possible. The risk of the disease moving into nearby Goma, Congo — a city of 1 million residents with an international airport.”

They added their voices to a growing number of experts who are watching this second biggest Ebola outbreak in history and note that, “As the case count approaches 2,500 with no end in sight, it is time for the WHO to declare the outbreak a public health emergency of international concern — a ‘PHEIC’ — to raise the level of global alarm and signal to nations, particularly the United States, that they must ramp up their response.” They call for three actions: 1) improved security for health workers in the region, 2) stepped up community engagement and 3) extended health care beyond Ebola treatment. The inability to adequately respond to malaria, diarrheal diseases and maternal health not only threated life directly, but also threated community trust, putting health workers’ lives at risk.

Olivia Acland, a freelance journalist based in DRC, reporting for the New Humanitarian describes the insecurity and the recent “wave of militia attacks in the Democratic Republic of Congo’s northeastern Ituri province has left hundreds dead and roughly 300,000 displaced in recent weeks, triggering a new humanitarian crisis in a region.” Specifically, “Ituri, a fertile region rich in gold deposits, has been an epicentre of conflict in Congo for decades. Between 1999 and 2003, around 60,000 people were killed here, as a power struggle between rebel groups escalated into ethnic violence,” related to traditional tensions between Hema cattle herders and Lendu farmers with roots in Belgian colonization.

Updates from the DRC Ministry of Health report on average 11 new Ebola cases per day in the past week. So far over 160,000 people have been vaccinated, and yet the spread continues. The Ministry also describes new protocol contains three vaccinations strategies that can be used depending on the environment in which confirmed cases are found including:

  • Classic Ring: The classic strategy of vaccinating contacts of confirmed cases and contact contacts.
  • Enlarged ring: It is also possible to vaccinate all inhabitants of houses within 5 meters around the outbreak of a confirmed case.
  • Geographical Ring: In an area where team safety can not be guaranteed, they can vaccinate an entire village or neighborhood.

Malaria Vaccines, Essential Drugs and New Vector Control Technologies

Halidou Tinto and colleagues enrolled two age groups of children in a 3-year extension of the RTS,S/AS01 vaccine efficacy trial: 1739 older children (aged 5–7 years) and 1345 younger children (aged 3–5 years). During extension, they reported 66 severe malaria cases. Overall they found that, “severe malaria incidence was low in all groups, with no evidence of rebound in RTS,S/AS01 recipients, despite an increased incidence of clinical malaria in older children who received RTS,S/AS01 compared with the comparator group in Nanoro. No safety signal was identified,” as seen in The Lancet.

WHO has updated the global guidance on medicines and diagnostic tests to address health challenges, prioritize highly effective therapeutics, and improve affordable access. Section 6.5.3 presents antimalarial medicines including curative treatment (14 medicines) for both vivax and falciparum and including tablets and injectables. Prophylaxis includes 6 medicines including those for IPTp and SMC. The latest guidance can be downloaded at WHO.

Paul Krezanoski reports on a new technology to monitor bednet use and tried it out in Ugandan households. As a result. “Remote bednet use monitors can provide novel insights into how bednets are used in practice, helping identify both households at risk of malaria due to poor adherence and also potentially novel targets for improving malaria prevention.

In another novel technological approach to vector control, Humphrey Mazigo and co-researchers tested malaria mosquito control in rice paddy farms using biolarvicide mixed with fertilizer in Tanzanian semi-field experiments. The intervention sections (with biolarvicide) had lowest mean mosquito larvae abundance compared to control block and did not affect the rice production/harvest.

Prawns to the Rescue in Senegal Fighting Schistosomiasis and Poverty

Anne Gulland reported how Christopher M. Hoover et al. discovered how prawns could be the key to fighting poverty and schistosomiasis, a debilitating tropical disease. They found that farming the African river prawn could fight the disease and improve the lives of local people, because the African river prawn is a ‘voracious’ predator of the freshwater snail, which is a carrier of schistosomiasis.

The researchers in Senegal said that, “market analysis in Senegal had shown there was significant interest among restaurant owners and farmers in introducing prawns to the diet.” The prawn could also for the basis of aquaculture in rice paddies and remove the threat of schistosomiasis from the rice workers.

—- Thank you for reading this week’s summary. These weekly abstractings have replaced our occasional mailings on tropical health issues due to fees introduced by those maintaining the listserve website. Also continue to check the Tropical Health Twitter feed, which you can see running on this page.

Zero Malaria Starts with Universal Coverage: Part 3 Innovations and New Interventions

Newer malaria interventions are coming on board, and whether these will be used of a large scale or targeted to certain epidemiological contexts remains to be seen. In each case, one will need to examine if in each context one can measure whether the intervention is universally accessible to and used by the intended population or subgroup.

After 30 years of research and testing, a malaria vaccine is ready to go through implementation testing in Malawi, Ghana and Kenya. This pilot of the vaccine, known as RTS,S, will be made available to children up to 2 years of age with the Malawi launching first during the week of World Malaria Day.

WHO explains that, “The malaria vaccine pilot aims to reach about 360,000 children per year across the three countries. Ministries of health will determine where the vaccine will be given; they will focus on areas with moderate-to-high malaria transmission, where the vaccine can have the greatest impact.” There will be a strong monitoring component to identify coverage levels as well as any implementation challenges and adverse effects that may only become visible in a larger scale intervention that the typical efficacy trials. Implementation is occurring in areas with a relatively strong existing malaria control effort, with an intent to learn how a vaccine can complement a total control package.

Mass Drug Administration (MDA, also known as preventive chemotherapy) has been a successful strategy for controlling and eliminating neglected tropical diseases with special reference to onchocerciasis, lymphatic filariasis, trachoma, soil transmitted helminths and schistosomiasis. MDA use in malaria has been limited due to a number of financial and logistical challenges, not the least of which is the need to achieve high coverage over several periods of distribution. This is why WHO recommends, “Use of MDA for the elimination of P. falciparum malaria can be considered in areas approaching interruption of transmission where there is good access to treatment, effective implementation of vector control and surveillance, and a minimal risk of re-introduction of infection.”

Another link with MDA for a different disease, onchocerciasis, has pointed to a potential new malaria intervention. Around ten years ago it was observed that after ivermectin treatment for onchocerciasis in Senegal survivorship of malaria vectors was reduced. Subsequently the potential effect of ivermectin has been intentionally researched with the outcome that, “Frequently repeated mass administrations of ivermectin during the malaria transmission season can reduce malaria episodes among children without significantly increasing harms in the populace.” Mathematical models for onchocerciasis control have predicted the need to achieve annual coverage targets below what could be called universal levels. Using ivermectin for mosquito control would require more frequent dosing and higher coverage.

Although not defined as ‘new’ it is important to include mention of additional vector interventions like larviciding and indoor residual spraying, as these present technical and coverage challenges. For example, larviciding interventions either chemical or biological, do not cover individuals. These focus on breeding sites in communities. This may require better use of the concept of geographical coverage as has been used in onchocerciasis control wherein the proportion of endemic villages reached is monitored.

For example, in Mali the NTD program aimed to achieve 80% program coverage of individuals eligible for preventive chemotherapy and 100% geographical coverage yearly. This means all villages should be reached. In reality, the program achieved 85% geographical coverage for lymphatic filariasis and over 90% for onchocerciasis.

In conclusion, we have seen that defining as well as achieving universal coverage of malaria interventions is a challenging prospect. For example, do we base our monitoring on households, villages, or populations? Do we have the funds and technical capacity to implement and sustain the level of coverage required to have an impact on malaria transmission and move toward elimination? Are we able to introduce new, complimentary and appropriate interventions as a country moves closer to elimination?

What do we know about larvicides?

In we read that, “Cuba has announced plans to build biolarvicide factories in Brazil and several African countries in a bid to tackle malaria and dengue fever.” The move is based on apparent successes of efforts such as those in Angola where the Director-general of Labiofam says that, “Angola, for instance, has reduced malaria incidence by 50 per cent, and some areas have seen a 70 per cent fall,” with similar results in Accra, Ghana.

WHO says that larviciding is “indicated only for vectors which tend to breed in permanent or semi-permanent water bodies that can be identified and treated, and where the density of the human population to be protected is sufficiently high to justify the treatment with relatively short cycles of all breeding places.” What actual documented evidence is there from Angola and elsewhere in Africa about the use and effectiveness of larviciding?

An article on the history of malaria control in Liberia reviews early efforts to use synthetic insecticides for indoor residual spraying and larviciding.  Unfortunately, “These projects encountered a spate of difficulties that foreshadowed the general retreat from malaria eradication efforts across tropical Africa by the mid-1960s.” What has changed now that we are in the days of rolling back malaria?

A newly published article on mosquito larval source management in areas experiencing flooding in The Gambia concluded that …

The intervention was associated with a reduction in habitats with late stage anopheline larvae and an 88% reduction in larval densities. The effect of the intervention on mosquito densities was not pronounced and was confounded by the distance of villages to the major breeding sites and year. There was no reduction in clinical malaria or anemia. Ground applications of non-residual larvicides with simple equipment are not effective in riverine areas with extensive flooding, where many habitats are poorly demarcated, highly mobile, and inaccessible on foot.

dscn7743sm.JPGA key approach to the use of larvicides may be integrated vector management, where there is not reliance on one control measure alone. In the Kenyan highlands researchers found that, “Vector control with microbial larvicides enhanced the malaria control achieved with ITNs alone. Anti-larval measures are a promising complement to ITN distribution in the economically important highland areas and similar transmission settings in Africa.”

Larviciding was found to have a positive effect in reducing childhood malaria in Tanzania where “larviciding reduced malaria prevalence and complemented existing protection provided by insecticide-treated nets. Larviciding may represent a useful option for integrated vector management in Africa, particularly in its rapidly growing urban centres.”

The two promising articles from Kenya and Tanzania would be strengthened if large scale operations like those described for Angola were better documented and published because as was seen in Liberia many years ago it was the basic operational issues that limited program effectiveness.

Devine and Killeen report in discuss some of the practical issues of larviciding in Malaria Journal and note that, “The effective operational implementation of these campaigns is difficult, time consuming, and expensive,” in part because of “The myriad and cryptic nature of aquatic habitats and the difficulty in identifying and targeting the most productive of these (which) makes maximizing that impact very challenging.”

Devine and Killeen recommend a “new auto-dissemination methodology” based on a “detailed characterization of oviposition behaviour and of the effective transfer distances between feeding, resting and aquatic resources.” Again, these are good ideas, but what of evaluation of current large scale approaches underway? In addition, as RTI suggests programs must establish “baseline information on the acute, intermediate, and chronic effects of chemicals used in malaria vector control on workers and the general population.”

The basic question remains – what can we learn about the right conditions for larvicide use as a major tool in integrated vector management for malaria? All partners in rolling back malaria have a responsibility for helping this learning process by documenting and publishing their experiences. Maybe the proceedings of the recent Labiofam Conference in Havana will be published soon.