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Malaria and Architecture: Can house improvement play a role in reducing malaria?
A close look at some of the houses that were in use by poor peasants in Italy shortly after the discovery in 1897 that malaria is spread through the bite of a mosquito, is revealing. These were constructed out of local materials, clay, and grass thatch, indeed the type of house commonly found in rural parts of Africa today.
The Italian researchers Grassi and Celli started experiments in 1899 to demonstrate that making such houses mosquito-proof could have a major impact on the transmission of malaria. They sealed off any possible entry route for mosquitoes into local houses, and left other houses untouched. The 112 peasants that occupied the sealed houses were asked not to leave their house between dusk and dawn; a group of 415 other peasants continued to occupy houses that were not mosquito-proof and were allowed to venture outside during the evening and night. The results were amazing: between July and October of that year, during the peak transmission season, only 5 people in the ‘sealed-house group’ got malaria, whereas all of the 415 others got ill. Other trials followed and showed an overall 96% protective efficacy. This ‘mechanic prophylaxis’ as they called it, formed the basis for house improvement throughout the tropics, mainly of houses occupied by expatriates serving in the colonies. Equally, these findings led to the installment of screened porches still seen in many houses in the south of the USA, and were at least partially responsible for the eventual elimination for malaria there.
Very little in terms of house improvement as a means to interrupt transmission of malaria has been undertaken in Africa. Following a review by Steve Lindsay and colleagues in 2002, interest slowly gained momentum – more than a Century after the successes in Italy. Studies have since been undertaken in The Gambia and Kenya, and the latest results were recently published in the Lancet. Although these results were not overly impressive, there is much to be gained in house improvement as a means to reduce the mosquito and thus transmission burden.
What is clearly needed here is a better understanding of mosquito behaviour in and around the house. Besides, we need to know a lot more about possibilities to improve traditional houses but also indoor climatic conditions during the day and night. A better understanding of air flow in traditional houses may give possibilities to channel odours from occupants in such way that mosquitoes that respond to these can be trapped. Imagine turning houses into traps and it is likely that coverage does not have to reach the 80% that is desired with bednets in order to have effects at population level.
We start this forum to generate ideas within the MalariaWorld community for house improvement as a way to reduce transmission of malaria. We welcome ideas from around the world, and hope to draw on your collective ideas as a way to move forward with new plans to revive mechanical prophylaxis. Your views and ideas are very welcome.
I like the comments from the architect Jakob Knudsen. I have seldom stayed under a bednet, precisely because it is too hot.
That is an advantage of window screens. However they too, restrict air flow. The mosquito needs stable air with an established chemical gradient from our body odors, to find us. She doesn't search for us with a flashlight, she sniffs out our location. So better air circulation, provided by more screened windows, will reduce her success.
anophelines enter houses in Africa through eaves (porous areas between wall and roof). So the eaves should be plugged with paper or whatever. But more wall openings at low levels in sleeping areas - screened - will make it more comfortable for us to sleep, and more difficult for the nasty lady to find us.
Willy
I really agree with this idea. But from my thought, the proper management for this prevention by mosquito impregnated net use is more quite appropriate than screening especially for the poor endemic areas, (no money spend for the screening), but we had suggested the poor to frame the window and the door by using bamboo tree, applied with the fishing net (SWG, Standard wire gauze) (around 0.025 – 0.03 mm or 1.2-1.3 mm/mesh) it can protect them from the mosquito biting, anyhow the problem from the poor house, those making with wood, they have also exposed to the mosquito by the many holes of floor and wall?!? (some houses they have no wall). I thought that if it 's possible, they should settle their household with locate 2-3 kilometers from the vector breeding sites and also the wind direction. Therefore, the prevention of malaria infection could be managed through the improvement of household characteristics such as plugging the holes of a house and putting mosquito nets at doors and windows. Moving houses from nearby water bodies to safe areas would also reduce the incidence of malaria. However, in practical, the people's protection behavior who has been supported for free or low cost mosquito impregnated bednet, most of them do usually leave the net as the furniture (fold the net to the wall), they said it is too hot to use the net and feel uncomfortable and unbreath under the net.
Usa
Housing improvement can play a major role in reducing transmission. What is the plan then? As I will continue to emphasize, fine-grain interventions will be useful where consistently applied. For large-scale and intensive control and elimination, probably not.
Screen the windows. Hang a net. Hang curtains. Don't expect malaria to disappear.
I agree that more needs to be done in the peridomestic setting due to the inability to permanently hand out LLINs. I think one of the big issues not being addressed is the effect of microclimate effects on endophilic vectors. Although it is impossible to design a house in many settings that completely exclude vectors it would be worth determining which aspects of the microclimate are antagonistic to host-seeking vectors.
Dear Paul,
Thanks for these comments. Microclimate is not only an issue in terms of comfort (as Jakob explains in his comment), but also affects the resting positions of mosquitoes. I have been playing around with the idea for a long time to measure the precise temperature, humidity and light intensity of the resting position of malaria vectors. This could then be used to draw up the comfort zones of mosquitoes and compare that with our comfort zones.
Does anybody have such detailed indoor climate data?
Yes indeed, one of the tragedies of malaria control has been the neglect of some useful practices such as using architecture to contribute to reducing mosquito-man contact. Practices such as use of mosquito screens on windows at the time of construction helps to reduce number of mosquitoes going into homesteads. Certainly poor housing predisposes you to a higher risk of contracting malaria infection.
Dear Pascalina,
Let me raise a question on this. To what extent would you consider it feasible in Zambia to pass a law that any new house that is being built should have screening to prevent mosquitoes from entering? Curious to read your thoughts on this.
Kind regards, Bart
Laws may be passed and they may not be implemented or followed. The question should be the practical viability and the local economic impact that changes in housing structures will have. Without doubt the efficiency of a bed net is much higher but unlike bed-nets which can be manufactured in another country and then shipped to the target region, changing household structures would account to transforming the local economy. Modification of households would require local resources and manpower, thereby improving both the skill base of the community as well as foster new job base. However, the challenge remains to find ways to fuel such activity locally without much external support, as self-sustenance is vital in any environmental modification strategy.
It pains me to see that WHO keeps on proposing and promoting Integrated Vector Management but hasn't really focussed on anything other than ITNs and IRS as of date. Even research on basic efficiency of these environmental methods is lacking, let alone the econometric analysis.
The article recent article by Kirby et al. (2009) on the effect of house screening on exposure to malaria vectors and the comments on the same article by Gimnig and Schluster (2009) raise numerous possibilities and questions The ‘buy-in’ to such an intervention is likely to be culturally dependent. In The Gambia, according to Steve Lindsay, people are frightened of geckos touching them or falling into their food hence a ceiling should go down well.
The question ‘Who pays?’ is obviously the most important one. Free handouts of such things as mosquito nets will not go on forever, and they anyway lead to a culture of dependency. I believe that most people accept the quantitative transition from a low price to a sustainable one more than they do the qualitative one of ‘free’ to ‘pay’ (whatever the price). The question of who pays is linked to the efforts that people will go to improve their health. The mere presence of a good and practical idea is not enough for it to be widely taken up. The relative dearth of VIP latrines in many African countries argues against people rushing out to install ceilings or screen doors. The problem becomes one of information availability and marketing.
We developed a simple household based intervention ‘Protégé’ in Mozambique (netting over openings and a fold-down screen door) and worked it up into a kit. We made leaflets describing its benefits and sold it within our study village. We marketed it with an offer of free malaria treatment at our clinic for the household for a year following installation. (We had, of necessity, recently introduced charges for adults to pay for the medicines that we dispensed). The offer of free treatment was the only reason that people bought the intervention. In this part of the world doors are often ill-fitting and the screen-door was an important component of the intervention. Observation of the first 15 or so households that purchased it indicated, quite clearly, that our screen doors were a problem – they were designed to be rolled down at night and up in the morning. This was not happening. Like the Grand old Duke of York’s men they were either ‘up’ or ‘down’ – all of the time.
Thus, whilst our experience so far is that household intervention will be difficult our experience shows that the provision of a good local treatment centre is highly valued in areas such as the one I work in.
The way forward as far as I can see for interventions like ours, in Mozambique at least, is to design a malaria and mosquito unfriendly house and sell it to people about to build their own new house. Not to modify houses already built. The house itself would be made of locally available material (reed and palm thatch here but other material in other places) but with the interventions installed (at a price per metre square) at the time of building. Factors that would probably be included would be:
• Screen door (which means a proper door frame),
• Netting ceilings set up as mosquito traps with optimal opening size for ventilation and mosquito entry
• Impregnated wall material (essentially impregnated ‘wallpaper’ available in a variety of colours –and impregnated with a different insecticide to that used on the nets also in use),
• A system to remove odour from the house – such as by a chimney in the bedroom – might also be a possibility.
• Resting-traps in bedrooms
One might presume to install a VIP latrine if necessary. Such things as the direction of the door relative to the setting sun may also be a consideration as would be the elimination of alternative resting sites for mosquitoes within the house. A window box of repellent plants might be included, but most houses here don’t have windows since they are an additional expense and make the occupants more vulnerable to malefactors.
IIC has like Derek worked for some years with house screening and asked some years ago for Gates Foundation to support it's development from proven idea to real tool.
We started together with Millener from University if Michigan as in the old days in Italy, US and Israel with screening the windows and eves. The experience was that yuo really had to close every little hole to make this work, otherwise the mosquioes would find it and enter. So, it took days a nd it was not practically.
Then we used insecticide incorporated net (actually, Netprotect material) knitted in bands of about a meter and with some training, a staff of 2 people could put it up in one hour, most of that time was the window and door screens. The amount of material per house was the same as if we had installed 2,5 bednets, so this would also be the cost. The houses were with 3-4 chambers and 3 sleeping places, so the comparison is fair.
This worked very well without a perfect fit, so our experience is that insecticidal net material will work a lot better than just nets
As an architect I find that there is a fundamental problem in the way we are approaching the problems of keeping the mosquitoes away from the persons sleeping inside the house.
In 1973 Koenigsberger and co-workers introduced what they called the human comfort zone. They showed that high temperature and humidity can be made more comfortable through air movement. This is why we put up ceiling fans. This is also why we head for a shady place at the beach on a hot summer day – the breeze from the sea makes the high temperature acceptable. It all comes down to airflow.
The problem of both insecticide treated bednets (ITN) and full house screening of different kinds are that these interventions basically obstructs airflow and therefore makes the micro climate for the person resting in his bed unbearably hot and/or humid. It might have been hot all the time, but now he is suddenly outside the comfort zone. The result is obviously that people don’t comply with the interventions. They open the doors and windows, they don’t use the ITN or they choose to sleep outside on the front porch.
There is a need for a fundamental discussion of these issues. How do we make a well ventilated house where mosquitoes are kept away from the sleeping persons? Just screening without taking airflow into consideration is not an option.
There is also a need for baseline facts. As far as I know there is not a lot of controlled data on temperature, humidity and airflow at bed level as a consequence of different interventions.
This is very interest topic and certainly one of the possible intervention to rescue many from malaria. The challenge is going straight forward to the facts- house improvement.
With vivid example from the pictures posted which represent a high percentage of most homes of resource constrained communities in Africa, it will be of a short term, unreliable and poor allocation of funding to houses for the purpose of malaria control.
The reasons remains to be clear, that these house can easy fall/get broken apart especially during rainfall or in just wind.
I have been real thinking about this after observing that over 70% of houses in some high malarious regions acts as highest risk factor for continuous malaria transmission, despite the usage of bed net which dont protect he user all the time.
About airflow issue, it must be taken unto consideration, we are not looking forward of making a house as ''chicken hut'' in attempting to control mosquitoes rather than making a normal ventilated home for people to stay comfortably.
Taping from a community itself and formulating a community-research participatory project it is possible to exploit what is available at community level and be able to construct better, affordable, insects proof home, which will not only protect people from malaria, but also from other diseases associated with hygiene.
Knowing that the proportional of mosquitoes feeding on human while outside is very small, by amassing our well planned strategies on better housing by blocking mosquitoes entry,it possible to have significant reduction/elimination of malaria.
'' Let us put our efforts where we can see its fruits at community expenses for over a long term period ".