The world's scientific and social network for malaria professionals
8462 malaria professionals are enjoying the free benefits of MalariaWorld today

Can odour-baited mosquito traps help eliminate malaria?

July 15, 2010 - 12:35 -- Fredros Okumu

Current malaria control operations rely heavily on insecticide treated nets (ITNs) and indoor residual spraying (IRS), both of which are insecticide-based and target only mosquitoes that feed or rest inside houses. Although these methods are extremely powerful and have saved many lives, the protection that they confer is insufficient to eliminate malaria in the most endemic regions of Africa.

 

It has long been postulated that complementary methods to build upon these gains could include, among other options, novel technologies derived from synthetic human odors.

 

By reformulating an existing malaria transmission model to more accurately describe the feeding behavior of wild mosquitoes, we have now estimated the likely efficacy of odor-baited traps for malaria control in Africa and described a plausible target product-profile for developers to aim for.

 

Basically, to be effective, the traps should be very cheap to deploy, the baits should be at least as attractive as humans, and the geographic location of these traps should be optimized to capture the greatest possible proportions of mosquito populations, for example by placing them in just a small section of the village area, where approximately 80% of infective mosquitoes are likely to be found.

 

Because such traps attract mosquitoes from long distances, it is also important that they are positioned far from houses so as to minimize risk of excessive mosquito bites and increased exposure to mosquito-borne pathogens. Unlike ITNs which can be marketed as household consumer products, traps provide only communal benefits and would require a customized delivery mechanism to maximize its usefulness.

 

We expect that even if the target product profiles that we have outlined here were manageable cost-wise, vertical and presumably community-based delivery mechanisms would be necessary to supply and deploy the traps. We propose that where local governance and administrative systems are already strengthened, or where they can be supported by centralized national malaria control programmes, sustainable implementation of a traps-based strategy may possibly be achieved through participatory approaches similar to those applied for scaling up community-based sanitation technologies like Ventilated Improved Pit (VIP) latrines or water source protection among rural communities in developing countries.

 

Traps and delivery systems satisfying these criteria could dramatically reduce malaria transmission in endemic Africa, achieving protection as good as ITNs. Perhaps even greater impact, and possibly elimination of transmission, may be achieved if the traps are used to complement rather than replace ITNs.

 

For more information see:

Okumu FO, Govella NJ, Moore SJ, Chitnis N, Killeen GF (2010) Potential Benefits, Limitations and Target Product-Profiles of Odor-Baited Mosquito Traps for Malaria Control in Africa. PLoS ONE 5(7): e11573. doi:10.1371/journal.pone.0011573.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0011573

And

Okumu FO, Killeen GF, Ogoma S, Biswaro L, Smallegange RC, et al. (2010) Development and Field Evaluation of a Synthetic Mosquito Lure That Is More Attractive than Humans. PLoS ONE 5(1): e8951. doi:10.1371/journal.pone.0008951.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0008951

Average: 

Comments

Osvaldo Marinotti's picture
Submitted by Osvaldo Marinotti on

Fredros Okumu
Let me start agreeing with you that we need to devote more efforts to developing mosquito traps.
Would you please expand your thoughts about how to place the traps within a village to maximize their action? You wrote

"Basically, to be effective, the traps should be very cheap to deploy, the baits should be at least as attractive as humans, and the geographic location of these traps should be optimized to capture the greatest possible proportions of mosquito populations, for example by placing them in just a small section of the village area, where approximately 80% of infective mosquitoes are likely to be found."

Wouldn't this attract mosquitoes to the area with the most malaria infected people?

Osvaldo

Fredros Okumu's picture
Submitted by Fredros Okumu on

Dear Osvaldo,

Thank you for your question. These are the things I would do depending on the nature of existing circumstances

Firstly, where the community is small, tightly aggregated and surrounded by numerous and dispersed aquatic habitats (particularly where these are cryptic or unpredictably distributed) the best solution is probably to surround the perimeter of the settlement with traps

Secondly, where habitats are relatively few in number and easily identifiable, as may be the case in arid rural areas, surrounding the breeding sites may offer an even more effective strategy. Urban areas where major areas of mosquito proliferation are usually surrounded by human settlement, rather than vice versa represent a situation where these two strategies coalesce and are essentially equivalent.

It should therefore be possible, even without detailed maps of mosquito densities, to selectively position traps in ways that enhance their relative availabilities at least as well as the four-fold increase (indicative of the 80-20 statistical distribution).

In addition, if you were working with a specific trap with specific chracteristics, then you may need to fine tune this general positional strategy as per your scenario. for example if your traps are baited with long range lures such as the ones recently described in Ifakara (See Okumu et al 2010a PLoS ONE_Development and field evaluation of synthetic mosquito lures, and Okumu et al 2010 Parasites and Vectors_Attracting, trapping and killing disease transmitting mosquitoes using odour baited stations), then we suggest the following: 1) the traps must always be at leaast 10m from the nearest house, so as to avoid risk of mosquito bites to people (the further away the better), 2) the traps should be as near as possible to the larval breeding sites, so as to capture most of the mosquitoes where their populations are highest, 3) there should be more traps around areas where there are natural human aggregations, such as around evining markets etc. and then of course you want to keep your traps away from roads etc, and also in places where they will cause minimal disturbance to community members.

While we are very happy to share this info here, we imagine that it might also be interested to know that our group has ongoing work on geo-location models for such devices, and we would be willing to discuss even further. The just published modeling article (Okumu et al PLoS ONE_Potential Benefits, limitations and TPPs of traps) already provides an important basis as to how many traps you would need, what they should look like, how best to deliver them, how much they should cost and whether or not they would be appropriate in various epidemiological scenarios. It would be great if there wuld be some additional info on fine-scale positioning algorithmes describing how to actually implement this in a malaria endemic setting.

Otherwise thank you very much once again for your wonderful question.

Osvaldo Marinotti's picture
Submitted by Osvaldo Marinotti on

Fredros
Thank you for your detailed answer to my question.
I am considering the possibility of testing mosquito traps in Brazil. Will keep you informed of our plans.
Osvaldo