Category Archives: Environment

The Weekly Tropical Health News 2019-07-06: Eliminating Malaria in Low Transmission Settings

This week started with articles that drew attention to the challenges of malaria in low transmission areas and with low density infections. Malaria Journal has provided several insightful articles toward this end.

Being an island has certainly helped Zanzibar make progress toward malaria elimination as witness the fact that malaria prevalence has remained below 1% for the past decade. Not only does Zanzibar still face threats of infection from the mainland, it may also experience an upsurge locally if residual transmission and the role of human behavior and community actions are not well understood. April Monroe et al. conducted in-depth interviews with community members and local leaders across six sites on Unguja, Zanzibar as well as semi-structured community observations of night-time activities and special events to learn more.

While there was high reported ITN use, there were also times when people were exposed t mosquitoes while being outdoors during biting times. This could be around the house, or at special night events like such as weddings, funerals, and religious ceremonies. Men spent more time outdoors than women. Clearly appropriate interventions and needed and should be promoted in culturally appropriate ways in order to further reduce and eventually eliminate transmission.

Angela Early and colleagues presented findings on a diagnostic process of deep sequencing for understanding the dynamics and complexity of Plasmodium infections, but stress that knowing the lower limit of detection is challenging. They present “a new amplicon analysis tool, the Parallel Amplicon Sequencing Error Correction (PASEC) pipeline, is used to evaluate the performance of amplicon sequencing on low-density Plasmodium DNA samples.”

The authors learned that, “four state-of-the-art tools resolved known haplotype mixtures with similar sensitivity and precision.” They also cautioned that, “Samples with very low parasitemia and very low read count have higher false positive rates and call for read count thresholds that are higher than current default recommendations.” Better understanding of the genetic mix of plasmodium infections as countries move toward low transmission and elimination is crucial for selecting appropriate interventions and evaluating their outcomes.

Hannah Edwards and co-researchers examined conditions for malaria transmission along the Thailand-Myanmar border in areas approaching malaria elimination. While prevalence may be less than 1%, residual transmission still occurs. Transmission occurs not only around residences but in the forests where people work. The researchers therefore looked at the behavior of both humans and insects. Overall, they found that, “Community members frequently stayed overnight at subsistence farm huts or in the forest. Entomological collections showed higher biting rates of primary vectors in forested farm hut sites and in a more forested village setting compared to a village with clustered housing and better infrastructure.”

While mosquitoes preferred to bite inside huts, their threat was magnified by those who did not use long lasting insecticide-treated nets (LLINs). While out in the farms and forests, people tended to wake early and increase their likelihood of being bitten. The authors discuss the challenges of dual residences in terms of LLIN ownership and even concerning the potential access to indoor residual spraying. The definition for universal net coverage needs to expand from one net per two people to include adequate nets wherever people are located.

The Amazonian area of Brazil is another area working toward malaria elimination, in particular, Plasmodium vivax. Felipe Leão Gomes Murta et al. also looked at the human side of the equation and identified misperceptions by both community members and health workers that could inhibit elimination efforts. They found, “many myths regarding malaria transmission and treatment that may hinder the sensitization of the population of this region in relation to the use of current control tools and elimination strategies, such as mass drug administration (MDA),” and LLINs.

Problematic perceptions included mention by both groups that the use of insecticide-treated nets, may cause skin irritations and allergies. Both community members and health professionals said malaria is “an impossible disease to eliminate because it is intrinsically associated with forest landscapes.” They concluded that such perceptions can be a barrier to control and elimination.

Efforts to eliminate malaria from low transmission settings are an essential to the overall global goals. These four articles tell us that close attention to and better understanding of humans, parasites and mosquitoes is still needed to achieve these goals.

Earth Day, Climate, Environment and Malaria

The Earth Day website notes that, “Our planet is currently losing over 15 billion trees each year—that’s 56 acres of forest every minute. We’re working hard to reverse that trend by supporting global reforestation projects. Earth Day Network’s Reforestation Campaign benefits local communities, increases habitat for species, and combats climate change.”

This habitat change if often conducive to the spread of malaria in areas and among populations that may not have been affected before. Specifically, “More risks associated with El Niño are: flooding and landslides in the Americas, drought in Southeast Asia and Australia, scrambled fisheries, and malaria, cholera, and dengue outbreaks.”

Terry Devitt reported that the incidence of malaria jumps when Amazon forests are cut, establishing a firm link between environmental change and human disease. The report, which combines detailed information on the incidence of malaria in 54 Brazilian health districts and high-resolution satellite imagery of the extent of logging in the Amazon forest, shows that clearing tropical forest landscapes boosts the incidence of malaria by nearly 50 percent (according to Olson and colleagues).

Moyes et al. Predicted the geographical distributions of the macaque hosts and mosquito vectors of Plasmodium knowlesi malaria in forested and non-forested areas of Southeast Asia.  When urbanization and deforestation bring people into habitats they never lived in, zoonotic transmission of malaria results. Fornace et al. similarly observed that, “Marked spatial heterogeneity in P. knowlesi incidence was observed, and village-level numbers of P. knowlesi cases were positively associated with forest cover and historical forest loss in surrounding areas. These results suggest the likelihood that deforestation and associated environmental changes are key drivers in P. knowlesi transmission in these areas” of Malaysia.

Back to Brazil, de Alvarenga  and co-researchers reported in the transmission of Plasmodium simian malaria in the Brazilian Atlantic forest as a natural infection of capuchin monkeys (Cebinae subfamily). Because of human movement into forest areas, cases among people have now been documented.

The zoonotic transmission of malaria to humans due to changes in climate, environment and habitat pose another unwanted challenge to global efforts to eliminate malaria. On Earth Day it is imperative for malaria control and elimination workers to collaborate closely with colleagues in environmental health and protection.

World Mosquito Day Is Not Just About Malaria

World Mosquito Day Block the BiteOur colleagues at Roll Back Malaria remind is that 20 August is marked annually as World Mosquito Day since doctor Sir Ronald Ross first identified female Anopheles mosquitoes as the vector that transmits malaria between humans. This year, 2015 is the 118th annual observance.

It may seem obvious to state, but while malaria is carried by mosquitoes, not all types of mosquitoes carry malaria. And more specifically our control measures for combating the anopheles mosquitoes that carry malaria are not specifically aimed at aedes or culex. This has not stopped public health workers in the field, and health worker trainees in the classroom from broadcasting messages to the public implying that the control and destruction of any mosquito will prevent malaria.

In terms of health communication, if we convince people that any mosquito carries malaria, but institute measures like long lasting insecticide-treated nets and indoor residual spraying aimed at anopheles mosquitoes, we may lose some credibility as people will still see other types of mosquitoes flying about. And then when people develop another febrile illness from bites of those other mosquitoes, they may not differentiate illness types, but say our interventions do not work.

Old poster on malaria-mosquito presentionThe conflation of all mosquitoes with malaria is seen clearly in the image at the right from a common malaria poster. The dirty gutters may contain culex larvae; the cans and bottles may contain aedes larvae. Obviously none of these mosquito species is good for human health, so can we achieve clarity in health communication about mosquito-borne disease on World Mosquito Day and thereafter?

We often forget that people in the community are quite observant of their environment; sometimes more so the the public health inspectors who try to teach them about ways of preventing malaria by reducing mosquito breeding. Villagers deal with mosquitoes on a daily basis and can distinguish the coloring and posture of the different species.

Instead of telling people what to do, it would be more helpful for public health workers to engage in dialogue with people to learn what they know about different types of mosquitoes and different forms of febrile illness. Maybe by learning first from the people, health workers can then become better teachers about integrated vector management.

PS – maybe we can also educate the mass media to stop putting pictures of Aedes aegypti on their malaria stories!

Beyond Garki baseline results released, highlighting changes in malaria environment

Ilya Jones shares with us the latest update on Malaria Consortium’s Beyond Garki project that seeks to understand changes in malaria epidemiology and recommend effective strategies to improve control efforts ……

201506110316-malariometric-bannerOver the last 15 years, increased global investment in fighting malaria has contributed substantially to reduction in the prevalence of the disease in endemic countries around the world. With the development of new technologies and innovative approaches to disease control, there is more hope than ever that malaria will be eliminated in places where it used to be a major public health threat.

However, sustaining momentum requires a deep understanding of the changes in the frequency of the disease, determinants of transmission and impact of interventions in a changing environment. Understanding these changes is essential in order to tailor health interventions to be as effective as possible.

Malaria Consortium’s Beyond Garki project, funded by the UK government through the Programme Partnership Arrangement (PPA), seeks to understand changes in malaria epidemiology and recommend strategies to improve malaria control efforts. The project is named after the efforts of the World Health Organization and the government of Nigeria to study the epidemiology and control of malaria in Garki, Nigeria between 1969 and 1976. Beyond Garki began in Uganda and Ethiopia in 2012, with four survey rounds conducted to date. Additional studies were also carried out in Cambodia, and more studies are planned in Nigeria. Each survey tracks changes in malaria epidemiology over time and will ideally inform strategic decisions on the use of interventions.

The baseline results have been made available and will serve as a point of comparison for data obtained from subsequent survey rounds, which will be released in the autumn. However the results of the baseline survey are interesting in their own right. Some of the highlights are listed below:

  • Low to moderate malaria transmission intensity was observed in all sites. In Ethiopia, P. vivax was found to be a predominant malaria species, probably due to decline in transmission over recent years.
  • High coverage of insecticide treated nets (ITNs)was observed in three of four sites but it is still not at an ideal level.
  • ITN use rates among household members that had access were generally quite high. The studyNet use and infection also showed there is willingness to buy nets, at least in the Uganda sites.
  • In Uganda, a major vector of malaria, A. gambiae s.s., has developed resistance against pyrethroids.
  • Most human-vector contact still occurs indoors. However, there is a tendency of early biting of A. funestus s.l. in one of the sites in Uganda. More information is needed to determine the biting and resting habits of vector species in both countries.
  • The rate of malaria diagnosis using microscopy and rapid diagnostic tests (RDTs) has been strengthened in all sites. RDTs have been found to effectively predict negative malaria results, indicating that service providers should pay attention to other causes of fever when RDT negative results are reported for patients.
  • The level of use of intermittent preventive treatment of pregnant women (IPTp) needs to be strengthened in Uganda.

beyond garkiTo learn more about the project, the methods used to collect data, the findings and the recommendations, check out the dedicated microsite for Beyond Garki here, or read the baseline report here.

Malaria and the Rains of Africa

The World Health Organization is guiding countries across the Sahel of Africa to begin piloting ‘seasonal malaria chemoprevention” or SMC. We recently featured this in the May 2013 issue of Africa Health. WHO explains that “Seasonal malaria chemoprevention is defined as the intermittent administration of full treatment courses of an antimalarial medicine to children during the malaria season in areas of highly seasonal transmission.” This is an outgrowth of several years of research into intermittent preventive treatment for infants (IPTi) and children.

dscn8811a.jpgMalaria program managers wanted a more focused application of IPTi where it would be likely to make a major impact on disease control. Researchers found that areas meeting malaria seasonality definition of 60% of annual incidence within 4 consecutive months were observed more frequently in the Sahel and sub-Sahel than in other parts of Africa, and thus could provide an ideal focus for intervention.

What makes transmission more intense in those four months is the rainy season.  Ironically we have recently seen a more intense rainy season in the Sahel with serious flooding. IRIN reports that, “The African Centre of Meteorological Applications for Development (ACMAD) in a seasonal weather outlook says near-average or above-average rainfall is likely over the western Sahel, which stretches across Mauritania, Senegal and western and central Niger. These regions are ‘expected to be the area with the highest risk of above average number of extreme precipitating events that may lead to flash floods’.”

What does this flooding mean for SMC?  While breeding mosquitoes obviously need the pools that rainwater creates, too much rain may have an opposite effect with flash floods washing out breeding sites (let alone homes and possessions). When flooding results in larger and longer collections of standing water, mosquito breeding may be enhanced, but this will make logistical support for training, supervision, and drug supplies extremely difficult in the region.

dscn8824a.jpgThe Sahel is one of the areas in Africa where we might hope for some early progress toward malaria elimination. With global climate changes affecting the region we can only wonder whether the weather will cooperate and allow timely implementation of new interventions.  As IRIN implies – contingency planning is extremely important.

Malaria Control and Earth Day: are they compatible?

Clearly no one wants to argue against efforts to curb a deadly disease. The question is whether the approaches to doing so have any negative consequences that can be easily ameliorated.

dscn7103-sm.jpgVector control gets the most attention. One concern is the plastic bagging in which long-lasting insecticide treated nets are packaged. Rwanda, which has outlawed commercial use of plastic bags for shopping, is taking the LLIN packaging seriously.  The photo shows net packaging that has been removed at a health center and stored for later incineration. Clients take their nets home in paper bags and are encouraged to hang them immediately.

Another net concern is disposal of old, used, damaged nets. LLINs do not have under ‘normal’ conditions the 5-year lifespan originally hoped. Plans for proper disposal are not fully developed in most settings, but the massive distribution of nets to achieve universal coverage from about 2009-12 are about to need replacement. It is possible that some of the net misuse reported in the media is actually repurposing of old nets. More information from communities and local health authorities is needed.

Insecticides for indoor residual spraying usually are the first thought that comes to mind concerning environmental impact of malaria control. While arguments primarily focus on DDT, it is important to note that WHO has approved over a dozen different insecticides for IRS.  The problem is not so much the use of chemicals for actual IRS, but the misuse outside approved spraying programs for farms and fish kills. At present IRS is a highly geographically focused activity in most countries, and control of the activities seems to be working for the large part, but even the process of preparing for and cleaning up after a spraying exercise can results in spills and contamination. Guidelines exist, but are they followed?

dscn3829sm.jpgThen we get to the issue of medical waste from rapid diagnostic tests.  Some health centers sharps and waste boxes for short term disposal and as pictured here in Burkina Faso, have incinerators tor final disposal.  Community health worker use of RDTs is usually accompanied by sharps and disposal boxes that can be returned to health centers.  All of this needs careful monitoring.

One must even think about packaging of artemisinin-based combination therapy medicines which are prepackaged by age group. These packets are small and are sent home with patients and care-givers. The paper may be burned or composted, but there are also plastic blisters in the packet. This may not account for much on an individual family basis, but on the community level it may be substantial.

dscn3738-safety-box-sm.jpgReaders may think of other environmental concerns from their own experiences and share success stories for environmental management accompanying malaria control in their countries.  So, as noted, we will not stop malaria control efforts on Earth Day, but at least we can be more conscious of the materials used, whether they can naturally decompose in the environment and thus make some contribution to a healthier planet.

Malaria Related Presentations at APHA Conference 2012 San Francisco

aphabanner-75.gifThe APHA schedule search turned up 31 presentations, panels and posters related to malaria. If you are attending the American Public Health Assocation 140th annual meeting, take advantage of these.

1.    Barriers to practicing healthy behaviors for malaria prevention and child nutrition in Zambia: A qualitative study 263984 Barriers to practicing healthy behaviors for malaria prevention and child nutrition in Zambia: A qualitative study Wednesday, October 31, 2012 Lovemore Mwanza , Research, Monitoring, and Evaluation …

2.    Prevalence of Malaria in Pregnancy as Rwanda Moves towards Malaria Elimination
265783 Prevalence of Malaria in Pregnancy as Rwanda Moves towards Malaria Elimination Tuesday, October 30, 2012 : 3:00 PM – 3:15 PM Corine Karema …

3.    Malaria diagnosis: Perspectives from caregivers and health staff, Makarfi, Nigeria 261566 Malaria diagnosis: Perspectives from caregivers and health staff, Makarfi, Nigeria Tuesday, October 30, 2012 : 8:35 AM – 8:50 AM Olufemi …

4.    Impact of climate and land use influencing the spatial and temporal distribution of malaria risk in the Amazon 261531 Impact of climate and land use influencing the spatial and temporal distribution of malaria risk in the Amazon Tuesday, October 30, 2012 Beth J. Feingold, PhD, MESc, MPH , Department of Earth and Planetary …

4c_sm_apha_20128.gif5.    Measuring Malaria Advocacy Outcomes 270759 Measuring MalariaAdvocacy Outcomes Monday, October 29, 2012 : 11:30 AM – 11:45 AM Marc Boulay, PhD , Center for Communication Programs, …

6.    How can we Accelerate Programming for Malaria in Pregnancy? 274603 How can we Accelerate Programming for Malaria in Pregnancy? Monday, October 29, 2012 : 11:30 AM – 11:50 AM William R. Brieger, MPH, CHES, DrPH , Jhpiego, …

7.    Improper maternity wear, mean providers, and vomiting: Barriers to timely IPTp uptake for malaria prevention during pregnancy in rural Zambia 266032 Improper maternity wear, mean providers, and vomiting: Barriers to timely IPTp uptake for malaria prevention during pregnancy in rural Zambia Tuesday, October 30, 2012 : 3:15 PM – 3:30 PM Hilary Schwandt, PhD, MHS …

8.    How local government health workers in Nigeria manage suspected malaria cases 265691 How local government health workers in Nigeria manage suspected malaria cases Tuesday, October 30, 2012 : 2:45 PM – 3:00 PM Bright Orji, MPH , Nigeria, Jhpiego, Baltimore, MD William …

9.    Challenges of implementing intermittent preventive treatment in Zambia for malaria prevention in pregnancy 263075 Challenges of implementing intermittent preventive treatment in Zambia for malaria prevention in pregnancy Tuesday, October 30, 2012 : 2:30 PM – 2:45 PM Peter Mumba, MD, MSc , Zambia Integrated …

10.    Contemporary Issues in Malaria in Pregnancy: Why worry now? 274600 Contemporary Issues in Malaria in Pregnancy: Why worry now? Monday, October 29, 2012 : 10:30 AM – 10:50 AM Mary Nell Wegner, EdM, MPH …

11.    Community-based Interventions for Malaria in Pregnancy: Findings from Mozambique 274602 Community-based Interventions forMalaria in Pregnancy: Findings from Mozambique Monday, October 29, 2012 : 11:10 AM – 11:30 AM Leonardo Chavane, MD, MPH , …

12.    Spatial access to malaria treatment in Kenya and its impact on health seeking behavior: A GIS based study 270764 Spatial access to malaria treatment in Kenya and its impact on health seeking behavior: A GIS based study Monday, October 29, 2012 Brittany Goettsch, …

13.    Challenges of Addressing Malaria in Pregnancy through Antenatal Care Services: A Nigerian perspective 274601 Challenges of Addressing Malaria in Pregnancy through Antenatal Care Services: A Nigerian perspective Monday, October 29, 2012 : 10:50 AM – 11:10 AM Oladosu …

14.    Invited Panel: Malaria in Pregnancy: An urgent yet solvable problem uniting the maternal health and malaria communities in Africa 3150.0 Invited Panel: Malaria in Pregnancy: An urgent yet solvable problem uniting the maternal health andmalaria communities in Africa Monday, October 29, 2012: …

15.    Malaria & Vector-Borne Diseases 4320.0 Malaria & Vector-Borne Diseases Tuesday, October 30, 2012: 2:30 PM – 4:00 PM Oral Moderator: Pablo Aguilar, MD MHSc 2:30pm Challenges of implementing …

16.    Poster Session: Nutrition … 2012: 8:30 AM – 9:30 AM Poster Organizer: Mike S. Bailey, MA / Co-Chair Board 1 Barriers to practicing healthy behaviors for malaria prevention and child nutrition in Zambia: A qualitative study Lovemore Mwanza, Rikki Welch, MA, John Manda, Samantha Herrera, Ana Claudia …

17.    *Poster Session*: Emerging issues in environmental public health … MCP and Devon Payne-Sturges, DrPH Board 4 Impact of climate and land use influencing the spatial and temporal distribution of malaria risk in the Amazon Beth J. Feingold, PhD, MESc, MPH, Benjamin Zaitchik, PhD, Victoria Shelus, BSc and William Kuang-Yao Pan, …

18.    Innovation in Technology: Public Health Models Posters 2 … practices serving underserved communities Kristina Vasileva, MPH, Mandy Smith Ryan, PhD and Mariceli Comellas, MA Board 10 Spatial access to malaria treatment in Kenya and its impact on health seeking behavior: A GIS based study Brittany Goettsch, MPH Candiate See individual …

19.    Infectious Disease Epidemiology 2 … AM – 10:00 AM Oral This session will provide new findings in the area of infectious disease epidemiology including the areas of malaria, TB, and influenza. Session Objectives: Assess the adequacy of zip code tabulation areas as a proxy for census tracts when …

20.    Advocacy & Global Health … Kovach, MPH, A. Elisabeth Sommerfelt, MD, MS, Alice Nkoroi, MS, Robert Mwadime, PhD and Ferdousi Begum, MBBS, MS 11:30am Measuring Malaria Advocacy Outcomes Marc Boulay, PhD, Claudia Vondrasek, MPH, Matt Lynch, PhD and Sarah Dalglish, MPH See individual abstracts for presenting …

21.    Seeing the obscured: A social epidemiological assessment of malaria’s reemergence in deforested regions 269174 Seeing the obscured: A social epidemiological assessment of malaria’s reemergence in deforested regions Tuesday, October 30, 2012 Beth Phillips, MPH , Mel and Enid Zuckerman College of Public Health, …

22.    Factors associated with completion of Intermittent Preventative Therapy (IPT) among pregnant women in Malawi … Sciences for Health, Arlington, VA Allison Zakaliya , Baylor Children’s Foundation, Baylor Children’s Foundation, Lilongwe, Malawi Misheck Luhanga , National Malaria Control Program, Ministry of Health, Lilongwe, Malawi Johnes Moyenda , Mpemba Health center, Ministry of Health, Blantyre, Malawi Doreen Ali…

23.    Designing a translational epidemiologic study: Chloroquine and breast cancer chemoprevention in Returned Peace Corps Volunteers … present the design of a novel translational epidemiologic approach to confirm preclinical data on the chemopreventive potential of a well-characterized anti-malarial drug. BACKGROUND: Exposure to chloroquine, an off-patent anti-malarial drug with a 60-year history of use by millions, reduces the incidence…

24.    Exploratory assessment of alternative use of bed nets within the Arisi zone in Ethiopia: Findings from household interviews and observations … Thaddeus Pennas, MS , C-Change, FHI360, Washington, DC Background: Distribution of long lasting insecticide-treated nets (LLINs) is one of four malariaprevention interventions being scaled up in sub-Saharan Africa. Correct and consistent use of LLINs by households is central to the …

25.    Young and vulnerable: Comparing delivery care, domestic violence, and child undernutrition between adolescent girls and women in Bangladesh … and Asia on topics related to evidence-based advocacy to improve nutrition, reduce maternal mortality, increase newborn survival, and decrease the malariaburden; written on child health and nutrition; and domestic violence against women. Carried out the data assessment and analyses. Have …

26.    Determinants of insecticide treated bednet (ITN) use by households in Nigeria … tying ITN to nails on the wall, and frequent washing of the ITN. The number of times a child had malaria in past 6 months, where child slept at night, and use of other malaria control measures were also associated with …

27.    Measuring the competencies and skills of midwives in an accelerated training program in Zambia … 25% felt they were not competent to treat patients with pneumonia while only 2% felt incompetent to manage patients with malaria; neither were statistically associated with duration of service (X2=61539;2=3.163, p=0.075; X2=61539;2=0.002, p=0.962 respectively). Conclusions: The assessment showed that the certified …

28.    Community Health Workers and Prevention: How to measure effectiveness of preventive community health programs centered on CHW … effectiveness of their preventive messages and adapt them for maximum results. With an effective tool to measure the effectiveness of malaria and HIV prevention and messages on hand washing and adequate nutrition, CHW receive immediate feedback on the challenges their communities …

29.    Improving access to preventive healthcare in Haiti: A community based approach … under five years of age, prevention messages delivered through skits, micronutrient supplementation, mosquito nets to pregnant women to help preventMalaria in Pregnancy, and blood pressure checks for all. Preliminary data have shown increased uptake of services and better maternal and …

30.    Mobile technology-based approach for facilitating health data collection, sharing, analysis and use in Uganda … of health centers through UHIN including monthly HMIS reports, disease surveillance data, and specific reports related to HIV/AIDS, TB, and malaria. Rural hospitals use UHIN for capturing data on electronic daily registers such as PMTCT, in-patient, lab, HIV counseling, and ART …

31.    Climate change and blood safety … transmission of dengue fever occurred in France in 2010. Other infectious agents are of concern such as Hanta virus, leishmaniasis, malaria, tick-borne encephalitis and their relationship to climate change and blood safety will be discussed. These insights call for changes in …

What to Do with Old Insecticide-Treated Nets?

Recently Matt Lynch of the Johns Hopkins Center for Communications Programs and the USAID NetWorks Project was asked about the challenges of disposing old ITNs. His response has been shared on Malaria Update, but we thought readers on Malaria Matters, who are not Update subscribers, could also learn from Matt’s Ideas. Matt urges that each country and community needs to find its own economic and ecological solutions as seen below.

I would urge a careful look at all the options (including leaving the nets in the households) before leaping into actions which may end up with worse consequences than no action at all.

Much that I have heard on this topic begins with the assumption that nets must be collected – this is not necessarily true, and no one has been able to adequately describe to me exactly what the problem of leaving the used nets for households to re-purpose might be.  They are, on the other hand, very ready to describe the massive costs associated with collecting the nets, and the problems which will follow from concentrating enough old nets in one spot to actually have insecticide and plastic concentrations which do become quantifiable problems.

As far as I can tell from asking the manufacturers, most pyrethroids decay when exposed to UV light, and are broken down by soil bacteria.  This is why pyrethroids are so popular in agriculture – they don’t persist in the environment.  They are apparently quite toxic to fish, so that’s worth exploring in the island environments.  Dumping them into the sea is probably not a great idea.

commob-pics-068sm.jpgIn Africa, one frequently sees old, holed nets being used to cover plants, chicken coops, or to screen windows.  Such uses, as far as I can tell, do no harm and probably some good (who knows, the residual insecticide may help control chicken mites?).  In addition, they provide an opportunity for the UV light and soil bacteria to begin breaking down the insecticides.

One might expect polyethylene nets to pose more of a problem in terms of solid waste, but I have not seen any reports of drains being blocked by old bednets (plastic bags, frequently!).  Polyester nets are even more difficult to imagine as a serious solid waste problem – after all, there were millions of pretty toxic-looking polyester leisure suits sold in Africa through the 1980’s and no one seems concerned about their disposal…

So, I don’t mean to trivialize the issue;  I think we need a clear description of precisely what the problem is with letting households dispose of their worn-out nets through their usual practices.  There may well be harmful disposal practices that need to be addressed, but I do think we need a clear description of the problem before we rush into complicated, expensive and potentially hazardous “solutions”.   I personally doubt the optimal solution will be to collect the nets.

Modeling Malaria – getting a handle on vectors

Models represent reality but the closer they come to reality, they better they are at helping us plan.  A session at the American Society of Tropical Medicine and Hygiene yesterday addressed the modeling process for vector control.

VECNet is developing the capacity to take data from multiple sources to tailor vector populations and behavior to local situations. Such models need to consider vector bionomics/population variables, weather/climate/environment, and effectiveness of deployed vector control strategies.

a-stephensi-map-project-2.jpgModelers encourage us to think beyond existing malaria control strategies and consider a varierty of mosquitoe behaviors beyond direct feeding on humans and immediate resting thereafter. Such understandings can lead us to ask whether new interventions could be directed at other vector bevahiors such as …

  • laying eggs (oviposition)
  • feeding on sugars
  • seeking hosts
  • mating
  • resting generally

In short, we were challenged to look at aspects of vector biology that have been ignored or unknown in the past.

nga_gambiae_ss-sm.pngThe MAP project out of Oxford is also beginning detailed mapping of vectors by region and utlimately my country.  Globally there are 41 dominant vector species, so the work ahead is immense, but some mapping has started with three in a program called Risk Mapper.

The session also included product impact estimation. This should help program planners decide on hypothetical outcomes of investments in different existing interventions and even consider possible outcomes were new interventions developed to address the other aspects of mosquito behavior outlined above – e.g. traps, repellents.

The modeling process requires a lot of data that needs to be updated as control interventions proceed. Such data requires a strong corps of entomologists and health information systems staff that many countries lack.  Hopefully modeling efforts will also include these elements of human resource development.

Malaria Transmission: are we out of the woods?

Human activity is leading to deforestation in central Africa and bringing hunters and people in closer contact with our primate cousins and their collection of pathogens.  The Global Viral Forecasting Initiative is carefully studying these contacts between humans and other vertebrates in an effort to identify possible new viral epidemics. In the process they have also made observations about the origins of human malaria and the potential for transmission of primate plasmodium infections to people.

While transmission of malaria species between humans and other primates has been documented in South America and Africa, Southeast Asia has received the most attention.  In fact, the question is being raised as to whether P. knowlesi is becoming the fifth human malaria parasite. If new infections as well as new species are arising from the primate world, this has grave implications for efforts to eliminate malaria worldwide.

A recent study from Vietnam found that, “showed P. knowlesi infections in 32 (26%) persons with malaria (n = 125) and in 31 (43%) sporozoite-positive An. dirus mosquitoes (n = 73). The authors observed and warned that …

P. knowlesi–co-infected patients were largely asymptomatic and were concentrated among ethnic minority families who commonly spend nights in the forest. P. knowlesi carriers were significantly younger than those infected with other malaria parasite species. These results imply that even if human malaria could be eliminated, forests that harbor An. dirus mosquitoes and macaque monkeys will remain a reservoir for the zoonotic transmission of P. knowlesi.

In another study researchers confirmed P. knowlesi in humans in Cambodia. This is worrisome especially since Cambodia is one of the locations where resistance to artemisinin-based medicines is rising.

gametocytes-of-p-knowlesi-in-a-giemsa-stained-thin-blood-smear-from-a-patient-that-traveled-to-the-philippines.jpgLikewise, researchers in Malaysia reported that, “P. knowlesi is a major cause of severe and fatal malaria in Sabah. Artemisinin derivatives rapidly clear parasitemia and are efficacious in treating uncomplicated and severe knowlesi malaria.”  Gametocytes of P. knowlesi in a Giemsa-stained thin blood smear from a patient that traveled to the Philippines can be seen in the attached photo from CDC.

Simian reservoirs of malaria throughout Southeast Asia pose a major challenge for control efforts.  Tackling this problem in the forest habitats where people come into contact with monkeys will be daunting – we are not out of the woods yet for malaria elimination.