Dr Nina Stanczyk works on mosquito control at the London School of Hygiene and Tropical Medicine, researching the development of new attractants and repellents. Nina and other researchers from the London School will be talking more about the insects that they work with at the Secret Insects of Bloomsbury walking tours this month, part of our Who’s the Pest?series.
Most people have been bitten by a mosquito at some point, and even if it’s just a nuisance for us in the UK, we’re very aware of the millions of people in other countries affected by the diseases that mosquitoes carry – such as malaria or West Nile virus. One of the best ways of preventing transmission of these diseases is to stop people being bitten. There are lots of possible ways to do this, including controlling the population with insecticides or preventing biting at night by using a bednet, but I look at manipulating mosquito behaviour. How? I look at what makes the mosquito respond in a certain way and see if I can use that against it.
I’m particularly interested in mosquitoes’ sense of smell. Mosquitoes use our odour to track us down from a distance and bite us. If we can isolate the chemicals in our smell that they find attractive, we may be able to make lures and traps for monitoring the population. If we isolate chemicals they find repellent, we can look at developing new repellents for people to use as personal protection.
At the moment I’m trying to find out whether mosquitoes infected with malaria react differently to people than uninfected mosquitoes do – are they more able to track you down and bite you? Do they sense different chemicals we could make a trap with?
An average day for me might be:
(1) Check on my mosquitoes, Anopheles gambiae, and collect females (only female mosquitoes bite) for experiments. Malaria-infected mosquitoes are kept safely in a maximum containment laboratory, isolated behind interlocking doors, mesh screens, incubators, doubled-sealed containers, and a healthy dose of paranoia. At the London School of Hygiene and Tropical Medicine, we have brilliant facilities for properly containing and dealing with diseases.
In order to infect a mosquito, we rear a mosquito adult to around five days old and give them a blood meal (artificially) with the infective stage of malaria in it.
(2) Culture the malaria. We can’t get malaria-infected blood from the source (i.e. humans) because they would have been treated before the malaria is transmissible to mosquitoes, so we grow it in flasks. These require a lot of care, with hours of staring down microscopes to check the parasites are still there and to see whether they are ready to infect a mosquito with.
(3) Do my experiments! I carry out behavioural experiments to compare the infected and uninfected mosquitoes. These could be flying mosquitoes down a wind tunnel to see which smell they prefer – which has to be done in the dark, as these are night feeders – or putting a sock on a cage (mosquitoes love human foot odour) to see how many mosquitoes try to bite it. I also look at the responses of the mosquito antennae to different odours, hooking the antennae up to a circuit to see if a signal is sent to the brain in response to specific chemicals. This is a brilliant way of identifying new semiochemicals (chemicals that affect the insect’s behaviour).
Once we know more about the response of infected mosquitoes to specific chemicals, we hope to develop an odour for traps that will target mosquitoes carrying the malaria parasites. This will prevent them being able to bite people and transmit the disease. Currently, around 1 million people a year die of malaria worldwide, with millions more affected, and any progress we can make towards reducing the spread of the disease is incredibly important.