Category Archives: Integrated Vector Management

What do we know about larvicides?

In SciDec.net 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.

Malaria – tis the season

In many parts of the tropical world malaria is seasonal, depending in large part upon rains.  If taken into account, seasonality can allow malaria program managers to plan better to serve different areas of their countries.  There are areas where a dry season or colder weather may appear to put a stop to transmission completely, but often minimal transmission manages to take place.

When we know that some areas have more intense malaria transmission during certain times of year, we can ensure that our interventions are in place well in advance of major rains.  Knowledge of seasonality can guide vector control efforts and help plan for increased stocks of medicines and diagnostic tests in clinics, for example.  Several examples of the need for such preparations have been in the news this weekend.

Malaria’s Day in Court

In India the Kolkata Municipal Corporation is apparently under legal investigation for inadequate supplies of malaria medicines in clinics in Bhowanipore, which is a malaria-prone area.  In a bid to find out what he needed to do, a medical officer unknowingly broke protocol and visited the judge hearing the case to get advice on how better to serve the people of the area.

Fortunately he was not reprimanded for his efforts to get ahead of impending malaria outbreaks.

Awaiting the Storm

gustav-hanna-ike-and-josephine-20080902.jpgAdding to Haiti’s existing medical chaos and suffering is the season of increasing rains.  People are still living in makeshift tents that given no protection when it comes to mosquitoes and malaria.

The Boston Globe reports that, “Some rain typically falls every month in Haiti, meteorologists say, but heavy downpours could begin as early as this month.”  As seen in the satellite photo from NOAA, Haiti was in the path of several major hurricanes and tropical storms in 2008 – so rains from these storms kill people directly through flooding, and those who survive can expect to be threatened with malaria.

ngamonthsrisk.jpgInterfaith Preparation

Nigeria accounts for at least one-fourth of the malaria deaths in Africa, according to AFP.  A major national net distribution is underway, which will hopefully make major inroads before the heavy rains start.

Planning is the key – we must understand the malaria transmission patterns in our countries and plan to get the material and human resources in place in a timely manner so that they will be effective in bringing down malaria morbidity and mortality.

Ghana’s private sector support against malaria

Last week we highlighted the global role of the private sector in malaria control. Today we share some specific country level examples from Ghana.

malaria-cases-sm.jpgFor the past few years AngloGold Ashanti has been operating a successful pilot indoor residual spray (IRS) program in Obuasi District.  The project reported downward trends in hospital attendance and admission due to malaria which were attributed to the twice yearly spraying efforts.  Some pilot larviciding was also included.

Based on these efforts US President’s Malaria Initiative working with the National Malaria Control Program and partners began planning to initiate IRS in five northern districts. “PMI expanded IRS from five to six districts, protecting over 708,000 residents,” and is now planning collaboration with Ghana’s Global Fund grant recipients to expand further.

Now Now AngloGold Ashanti is ready “to extend its anti-malaria control to 40 districts in the Upper East and West, Ashanti, Western and Northern regions of Ghana, come January 2010,” as a recipient of Global Fund support from Ghana’s Round 8 Malaria Grant.

Another private partner in Ghana is the Zoomlion Waste Management Company. The Ghanaian Chronicle reports that, “The Volta Region office of Zoomlion Waste Management Company Limited has intensified its efforts to spray gutters, toilets and refuse disposal sites in the districts, as a step to destroying the breeding grounds and resting places of mosquitoes, to curb the menace of malaria.”

While such spraying may be more likely to kill culex species of malaria more than the malaria-bearing anopheles, the effort does show how the private sector can play a direct role.

Another mining company, Newmont, while not providing direct services, does offer health education to “help all those in affected areas prevent the spread of this terrible yet preventable disease,” on its website.

The telecoms giant, “MTN Ghana, a leading telecom company in Ghana, has announced that since its entrance into the Ghanaian telecom market, the company has invested about $2 million in socio-economic development projects in the areas of health and education.” More specifically, as part of its malaria fund and awareness raising efforts leading up to the Football World Cup of 2010, MTN is including Ghana in its target countries.

These examples are not meant to be exhaustive, but to show the different roles the private sector can play at the country level ranging from direct control activities to raising awareness and educating people to protect themselves.  For long term benefit, all such efforts need to be coordinated, like the IRS project, with the National Malaria Control Program and its RBM Partners.

Learn your vectors

An editorial marking World Malaria Day in Nigeria’s Daily Trust exhorted readers as follows: “If only we can learn to clean our gutters, fumigate our drainage channels, evacuate our rubbish heaps and take other simple and sensible steps to eradicate or reduce the vector that causes malaria, we will not have cause to embark on the yearly ritual of lamenting about how we suffer so much from this public health challenge.”

While mosquitoes may breed in discarded cans and tires in rubbish heaps or in gutters in out cities, the likely culprits are Aedes species, which carry yellow and dengue fevers, and Culex species, which carry filariasis and a variety of viral diseases. Eliminating such breeding sites will certainly go a long way to promoting public health, but may not elimnate the breeding of the Anopheles species of mosquitoes that carry malaria.

For Anopheles mosquitoes the US Centers for Disease Control and Prevention states that, “The larvae occur in a wide range of habitats but most species prefer clean, unpolluted water. Larvae of Anopheles mosquitoes have been found in fresh- or salt-water marshes, mangrove swamps, rice fields, grassy ditches, the edges of streams and rivers, and small, temporary rain pools.”  In contrast a study from Cameroon identified the following breeding sites for Aedes, many of which could be found in a refuse heap.:

Used tire, Plastic container, Can and broken bottle, Plastic cup, 200-L barrel, Abandoned car part, Cement washtub, Flowerpot, Tree hole, Cow horn, Cocoa pod, Enameled plate and Snail shell

slide1.JPGThe Press is an important Advocate in the fight to eliminate malaria, but it’s role is only as good as it’s access to scientifically sound information, which these days can be obtained on internet sites like those of WHO, RBM and CDC, but just as easily – a phone call to a local expert in the Ministry of Health or a local University.

Insecticide Treated Cows

Some malaria carrying mosquitoes are also attracted to cattle that may be sleeping outside the door of a dwelling. Studies have even shown that “cattle treated with pyrethroid in the control of malaria and reduction of vector density.” While we have seen malaria advocates calling for every house to have insecticide treated nets, we have yet to hear from the proponents of an ITCs (insecticide treated cows) for every home.

fulani-child1a.jpgActually there are a number of ways to fool a mosquito – not just on April 1st – and as the research mentioned above points out, the field of integrated vector management is wide.  There may be a number of issues to explore that are appropriate – culturally and technologically – for communities to control their mosquito populations. These need to be explored and promoted for long term sustainability of malaria control efforts.

In the meantime there are donor organizations that provide families in developing countries with cows and other livestock, just maybe not insecticide treated ones.  Maybe this is an opportunity for better integration of agriculture and malaria control.

Malaria and World Water Day

Greetings on World Water Day, which interestingly is taking place just about one month before World Malaria Day. The theme for the upcoming World Malaria Day focuses on malaria’s lack of respect for borders, and the challenge of guaranteeing and preserving safe water supplies also cuts across national boundaries.

dscn8553.JPGThe connection between water and the breeding of malaria carrying mosquitoes is well known. In a most simple example, one can visualize many of the newly installed borehole wells around Africa that were installed without adequate community involvement. in very little time, these become poorly maintained and spill off water collects into puddles ideal for anopheles mosquitoes.

One can also recall numerous agricultural projects that create mosquito breeding grounds through irrigation canals or simply land clearing that allows rain water to collects. When floods come, which has been very common in southeast Africa recently, communities lose access to safe water while ironically being surrounded by expanses of rivers that overflowed their banks, creating breeding opportunities for mosquitoes.

The ultimate lesson is that both programs, safe water and malaria control, cannot be solved in a vertical way. There needs to be collaboration and a broader development approach that addresses underlying

Oil on (Mosquito) Troubled Waters

The use of petroleum products (PPs) such as kerosene, gasoline and engine oil to control mosquito breeding and malaria dates back to early in the last century. Generally today there is not much emphasis on larviciding measures in major control programs, let alone the use of PPs.

Therefore it was interesting to read an article by Djouaka et al. documenting the continued application of petroleum products to standing water in several villages in Benin Republic. The practice appears to have been handed down from parents to children. The authors then tested various products and found that, “The relatively high efficacy of kerosene, engine oil and waste oil is likely to be due to their elevated persistency in breeding sites after treatment.”

ofiki-in-dry-season-sm.jpgBeales and Gilles in the Fourth Edition of Essential Malariology devote two pages to explaining the use of “petroleum oils” on standing water surfaces and how these can be highly toxic to larvae and pupae. They also address the drawbacks including cost, problems of vegetation, debris and wind and of course environmental contamination. No examples of actual use in current malaria control programs are given.

To buttress this lack of emphasis on PPs, the recent article by van den Berg and Takken did not include these products in their “framework for decision-making in integrated vector management.” Even a 1982 WHO manual on environmental management of mosquitoes only gives a historical perspective of PPs: “The earliest chemical control of mosquitoes was directed against the larval stage. By the end of the last (19th) century the first larviciding technique was developed. Crude kerosene and distilled petroleum oils were applied to mosquito breeding sites.”

A hint that PPs were not totally forgotten was found in a WHO 2005 Darfur Weekly Report of August 14-20, where, in the flood-affected Ardamata IDP camp, “Larval control … is accomplished by spreading used engine oil on mosquito breeding places.”

Finally in 2002 Yapabandara and Curtis reported testing various methods to control mosquito breeding in gem puts in Sri Lanka using polystyrene beads, temephos, used engine oil and filling pits with soil as well as two concentrations of pyriproxyfen. The latter chemical proved most effective and convenient needing only two applications annually while engine oil required 12 annual applications. PPs ultimately do not appear to have much to recommend them.

So let us return to the persistence of PP use in Benin communities, which occurs, Djouaka et al. surmise, because these measures are available, cheap and convenient. The ‘history’ lesson here is not a desire to return to the use of PPs, but the need for cheap and convenient malaria control measures that communities can manage for themselves.

Environmental Management of Malaria

A recent WHO publication, Preventing Disease through Health Environments, addresses environmental factors responsible for malaria spread and control. Malaria contributed 10% to the environmental burden of disease for children aged 0-14 years worldwide. Specifically, “An estimated 42% of the global malaria burden, or half a million deaths annually, could be prevented by environmental management.” According to the document, There are three main approaches to the environmental management of malaria:

  • Modify the environment. This approach aims to permanently change land, water or vegetation conditions, so as to reduce vector habitats.
  • Manipulate the environment. This approach temporarily produces unfavourable conditions for vector propagation and therefore needs to be repeated.
  • Modify or manipulate human habitation or behaviour. This approach aims to reduce contact between humans and vectors

Although some elements of individual and household behavior are involved in environmental control, it would be be an exercise in victim blaming to assume that individuals and households can take the main responsibility for taking environment measures. Water supply, drainage, road construction, river and stream control and other environmental measures are the responsibility of institutions and governments. Unfortunately such infrastructural improvements are costly, and one does not see them addressed in major malaria control programs like GFATM and PMI.

safe-and-reliable-water-for-the-community.jpgThe World Bank has noted that, “Malaria affects millions in the East Asia and Pacific (EAP) region and impedes economic development, particularly affecting the rural poor. In the early 1900s malaria was controlled in many parts of the region using environmental management (EM) for vector control. EM is where the environment is modified or manipulated to reduce malaria transmission by attacking local vector mosquitoes and requires an understanding of the ecology of these species. Today malaria control is based on drugs and insecticides…” Because of questions of sustainability and resistance, the possibility of a return to environmental management is raised.

The World Bank’s Malaria Booster Program document does consider some elements of environmental management, but many of these fall more in line with integrated vector control measures in country examples like IRS, larviciding, and larvivorous fish. Some mention is made of filling spots of standing water. The larger infrastructural issues are not addressed. This is not to say that wider World Bank projects don’t address such issues, but what is needed is a more integrated approach that the malaria control potential of infrastructural projects is assessed and planned. Other development partners need to join in this effort.