Scientists are developing a biological control method for malaria that uses larvae-eating fish to control mosquito populations in rain-fed pools.
Tanzania's Tropical Pesticide Research Institute (TPRI) is collaborating with the US-based Poseidon Science Foundation to investigate the best way to mass-produce and disseminate the fish embryos for eventual use in areas where malaria is endemic.
If successful the initiative will be used alongside insecticide-treated mosquito nets, pesticides and artemisinin drugs.
Using fish to control malaria is not a new idea, but the method has previously been restricted to permanent bodies of water. But in many high-risk areas malaria is seasonal, coming with the rains that create pools in which the larvae of malaria-carrying mosquitoes grow.
The Tanzanian fish species Nothobranchius guentheri is an annual species; the adults die off yearly, leaving their embryos in a state of suspended animation when the water recedes. The embryos hatch when the rainy season begins and feed on the mosquito larvae, which hatch around the same time.
The fish embryos can survive in pools as small as depressions made by elephants' feet.
"Once established in a particular depression, the fish will continue to come back year after year to feed on the mosquito larvae," says Shandala Msangi, the lead investigator of the programme at TPRI.
"This initiative to explore native annual fish populations as natural predators is part of [a] trend to explore indigenous technologies and resources," he adds.
Eliningaya John Kweka, senior scientific officer in medical entomology in TPRI's mosquito section says Tanzanian communities have a good understanding of the benefits of participating in mosquito control. "Therefore, we expect to have very good exciting results in this study in reducing malaria spread in Tanzania."
Storn Kabuluzi, controller of preventative health services and the former manager of malaria control in Malawi, says the method would be difficult and expensive to implement as cases of malaria are widespread.
According to Kweka, the major challenge is gaining significant, long-term support to carry out systematic studies and sustain a long-term programme. The Poseidon Science Foundation is supporting this initial programme and will need a consortium of participating organisations and countries to make this concept a reality, he says.
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I have been waiting for such a development for close to 40 years. It is about time that fishes are employed to reduce mosquitos. It is soo easy! However I do not belive that the right fishes are chosen. The species mentioned are already well established in places, where water is standing for considerable length of time. "Bondes" were rice is planted for example. In places, were water is standing for shorter time and than drying hard for the rest of the year, this fishes can not establish themselfes!
The real fish is a tiny fish with a max. length of about 30 milimetre. I have them since 40 years in a small pond in my garden. They need no food, no care and multiply, that rats look like beginners. I don't know the proper name as they have many. They are called: Million fishes - mosquito fishes - Gruppies - Minows - etc.
I put them in all water bodies in the garden like: Water tanks and rain water drums. No mosquito can breed, as all larva is eaten by the fishes. As simple as that.
My proposal: In each town and each district, a pond should be established. If need be like mine, built with concrete and made water tight so as not to loose water. It should be about 50 cm deep and filled with 20 cm earth, then water lilies planted in. Finished. The water will stay clear and maintain itself. However, at least half of the pool should be covered with Gras or Makuti on a frame, so as not to heat up the water too much. The pond could be about 2 x 2 or 2 x 3 metre. When the rains come, somebody is sent by bicycle with a bucket of water and fishes and puts a few in every rain pond. Within a short time the fishes will have multiplied to hundrets or thousands, depending of the size of the rain pond. A plan should be establisherd, were every rainy season water is standing.
It is as simple as that !!! It is unfortunate, that up to now I was not able to have anybody interestet and I have tried hard. May be the seed has now fallen onto fertile soil. I hope so.
For info: In Saudi Arabia they have eradicated Malaria 50 years ago with this tiny fishes, by puting them into the irigation channels. In the USA they are now putting them into the swimming pools of repossessed houses were rain water is standing, so mosquitos can not breed.