Segment 1

VOICEOVER

One of the best ways to protect the most vulnerable people from malaria is a bed net. They're highly effective because malaria-carrying mosquitoes usually bite at night. But mosquitoes are adapting to survive. Their behavior is changing.

DR. HILARY RANSON [Liverpool School of Tropical Medicine, UK]

Bed nets work very well at tackling mosquitoes that feed indoors at night, but as more and more people use bed nets, the mosquitoes start biting earlier and biting outside. So attacking the larva or the immature stage of the mosquitoes is a good complement to using bed nets.

VOICEOVER

It's not just mosquitoes that are adapting. Africans are moving to cities in large numbers. So identifying and disrupting mosquito breeding sites makes sense.

DR. HILARY RANSON

In an urban setting, it's easier to identify those bodies of water where the mosquitoes lay their eggs, and to target those. In rural areas, they're just too numerous and dispersed, but in a city, it's feasible to identify the major breeding sites, and apply insecticide to kill the immature mosquitoes.

VOICEOVER

A pilot study in Dar es Salaam, Tanzania, led by Dr. Nicodem Govella, is testing how effective larvicide is in reducing malaria in a large city.

DR. NICODEM GOVELLA [Ifakara Health Institute, Tanzania]

We target the larvae because the egg doesn't eat anything, the pupa doesn't eat anything and the adult mosquito targets our blood. The larvae ingest this larvicide, they get poisoned, and then die.

VOICEOVER

The only way to find out if the mosquito larvae are being killed is to see if the number of adults has fallen.

DR. NICODEM GOVELLA

This is not a safari tent, but a technology for monitoring mosquito densities.

VOICEOVER

These six funnel-shaped entrances tilt upwards. Mosquitoes can enter easily, but getting out is much harder.

DR. NICODEM GOVELLA

In order for the trap to work, you need bait, and the bait we use is the human being. Okay, so a person is supposed to sleep inside here and act as an attractant to mosquitoes. A person sleep until the morning, when he wake up and starts emptying all the mosquitoes trapped in the chambers.

VOICEOVER

The results show that in the six wards of Dar es Salaam where larviciding took place, the density of adult mosquitoes fell by 57 percent. So it appears to be effective, but it's not cheap.

DR. HILARY RANSON

It's very labor intensive to identify all the breeding sites and to apply insecticides. One of the projects that we're involved with in Dar es Salaam is to try and see whether it's necessary to apply the insecticide to every breeding site, or whether you can have again more or less the same level of control by just targeting the most productive sites.