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Skip to 0 minutes and 12 seconds Hi, everyone. Today I’m going to talk about the control of Zika through larval control. But before I do, I want to make it absolutely clear that actually, we’re not just talking about the control of Zika. We’re talking about the control of Aedes-transmitted infections, so that’s yellow fever, dengue, chikungunya, and whatever comes next after Zika. And this mosquito is spread throughout the tropics and exploits the urban environment extraordinarily well. And it’s spread throughout all the cities and towns in the tropics. Now, we know that vector control works, because it has been very successful in the past. In large parts of Latin America, in Brazil, Aedes aegypti was eliminated through larval control.

Skip to 1 minute and 3 seconds In those days, in the 1960s, it was brought about by spraying oils and later on by DDT, which enabled the mosquito to be eliminated. So larval control does work. Larval control is not just the responsibility of the health department. It’s everyone’s responsibility. And importantly, you’ve got to get the communities on board with you. So what are you going to do? Well, this mosquito breeds literally everywhere in small containers. It loves plastics that we litter the towns with. It breeds in water storage containers. It breeds in guttering. And it’s found in tyres in tyre dumps. So here’s a few practical examples of what to do.

Skip to 1 minute and 47 seconds Number one, you need to empty containers, both indoors and outdoors, which hold small amounts of water. And you need to scrub these out, because the eggs of Aedes aegypti are very resistant to drought and they can withstand drought conditions for many months. Add water again, the eggs will hatch, you get more larvae. So it’s not just emptying, but it’s often scrubbing out those water containers as well. Now, of course, there are some containers which you can’t do that with, so then you resort to spraying. So you could spray with an organophosphate like temephos, which is very safe. You can drink water after temephos has been sprayed in it. You can use a microbial like BTI, which is incredibly safe.

Skip to 2 minutes and 34 seconds So that’s an effective additional method for controlling larvae. Now, when you’re looking for larval breeding sites, don’t just look on the ground. Look up as well. You may get deposits of water in the guttering as well. So I know that in some control programmes, people walk around with bamboo poles with mirrors on the top of them looking to see whether there’s any water contained in the guttering. And if there is, that needs to be treated as well. The third thing you can do is cover the water storage jars with insecticide-treated netting. This is a very effective way of stopping adult mosquitoes dropping their eggs into water or if there are any larvae inside, to stopping them getting out.

Skip to 3 minutes and 21 seconds So three different ways to control larvae: empty containers, spray the containers, cover containers. So a lot of what I’ve talked about really is what we want to do to get the communities to reduce Aedes aegypti levels to the levels that don’t allow diseases to be transmitted. But in the long term, what we’re really interested in is building out Aedes aegypti from our cities and towns. We need to make our large tropical cities sustainable for people that live in them. And we’ve got to deal with Aedes aegypti. So it’s not just Zika. It’s all the potential viruses that this mosquito transmits.

Skip to 4 minutes and 4 seconds And we can do that in three ways: getting in piped water so you don’t have water storage jars. Secondly, improve refuse collection so you don’t get a plethora of containers spread littering the ground. And thirdly, housing has to be improved. And screening houses to keep the mosquitoes out can be an effective way of reducing this. So what I’m describing here is many different ways in which we can reduce the breeding sites of this mosquito, which will contribute to lowering the risk of infections transmitted by this mosquito.

Larval control

Methods to control the spread of Zika are also important for a number of other Aedes-transmitted infections. Larval control involves targeting of breeding sites in order to reduce the adult mosquito population, and has in the past proven very successful in Latin and South America.

In this video, Professor Steve Lindsay from Durham University discusses the importance of larval control and why it isn’t solely the responsibility of governments and health departments: it’s something everyone can do with simple vigilance and practical approaches.

Cast your mind back to Step 2.7 where we thought about the places larvae might potentially be present in and around our homes. How easy would it be to identify these breeding sites and treat them accordingly?

Please note that the audio for this step was captured remotely and its quality will not be of the same standard as a studio recording. If you experience problems with the audio please use the subtitles or transcript file.

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This video is from the free online course:

Preventing the Zika Virus: Understanding and Controlling the Aedes Mosquito

London School of Hygiene & Tropical Medicine

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