Attracting dangerous animals to save lives
You are lying in your bed. You hear a hint of the whine first, growing increasingly high-pitched and closer to your ear. Smack! I got it! Oh no, it’s already had a bite, now it’s going to itch. Why can’t they leave me alone?
Yes, why is your blood so irresistible to the female mosquito? Because she needs it to reproduce. The carbon dioxide you exhale triggers their blood-sucking behaviour, because the protein in your blood is what the mosquito needs to develop their eggs that will hatch into new mosquitoes. But blood is not all the mosquito eats. Its daily diet consists of other things, such as nectar and – cow urine.
Yellow fever mosquito, Aedes aegypti. Photo: Rickard Ignell
The battle against malaria rages on
In some parts of the world, a mosquito bite can be a death sentence, especially for children under the age of five, and particularly in the tropical and subtropical parts of Africa. Malaria parasites have plagued humans for thousands of years, but they can be defeated. In Skåne, where SLU’s Alnarp campus is located, malaria was eradicated in the 1930s.
Rickard Ignell, Professor at the Department of Plant Protection Biology. Photo: Johan Persson
‘If we can successfully reduce the number of mosquitoes carrying the pathogens, we can break the transmission of the disease,’ says Professor Rickard Ignell. ‘That was what happened in Sweden in the 1930s and in other parts of the world where malaria no longer exists. But in the tropics, the problem persists.’
Synthetic cow urine saved lives
The village of Magge in Ethiopia, 2019. Professor Rickard Ignell and his team of researchers prepare fifty mosquito traps containing the scent of synthetic cow urine. This was developed following several years of research in partnership with Addis Ababa University. The goal of this field research is to use this scent to attract and trap the infected mosquitoes in order to reduce the number of malaria cases in the village.
During the field study, a malaria epidemic breaks out in the part of Ethiopia where the village of Magge is located. But malaria cases do not increase in Magge. In fact, the incidence of the disease decreased by 60–70% during the field test. The research yielded excellent results – it helped save lives.
Doctoral student Yared Debebe installs mosquito traps with synthetic odour of bovine urine in the village of Magge in southern Ethiopia. To the right, Habte Tekie, our co-worker at Addis Ababa University. Photo: Rickard Ignell
‘We had a discussion with the village leaders and informed the local community associations of the purpose of the study,’ Ignell explains. ‘Getting them to agree wasn’t difficult, nor was it hard to get them to approve setting up solar panels. Not only did the panels allow us to charge the batteries for the traps, they also provided the villagers with electricity, for the first time ever, for lighting and to charge their mobile phones.’
Hillary Kirwa is in the process of identifying which plants malaria mosquitoes have sucked nectar from in the wild. His project is partly carried out in Burkina Faso, where the mosquitoes come from and which he is currently working on.
Photo: Johan Persson
Through an interdisciplinary analysis of mosquitoes' olfactory system, which includes molecular, genetic, neurophysiological, and chemical studies as well as behavioral studies, we are working to increase our understanding of why mosquitoes behave as they do and thereby identify new methods to combat them.
Photo: Mårten Svensson
To evaluate the synthetic fragrances we develop, they need to be tested in artificial natural environments, such as these experimental huts for mosquitoes in 'Mosquito City' in Ifakara, Tanzania.
Photo: Rickard Ignell
Sukritha Nalikaramal preforms behavioural studies in the laboratory to investigate how Yellow fever mosquitoes are reacting to floral scents in a future changed climate.
Photo: Johan Persson
The world-leading research on how mosquitoes’ and other insects’ behaviour is affected by odours and why, has been ongoing at SLU’s Chemical Ecology Unit for many years. The research on mosquitoes’ relationship to bovine urine is one of several fields that have been investigated.
The researchers have found out which chemical substances in the urine attract the mosquitoes and why. The traps in Ethiopia now contain chemical substances that to mosquitoes (and humans) smell like fresh cow urine, but the synthetic odour lasts for at least a month.
‘Compared with other scents currently used to attract mosquitoes that are searching for blood,’ Ignell says, ‘we do not need access to carbon dioxide, which is impossible to obtain in the African countryside. We are working to design simple traps that can be used to combat malaria cost-effectively here and in other parts of the world.’
Malaria mosquitoes are attracted to the scent because they drink fresh cow urine for energy; they utilise the nitrogen compounds in the urine to build muscles, live longer and have the strength to fly long distances. One of the advantages of attracting mosquitoes with this particular odour is that it attracts all mosquitoes, male and female, those who want to suck blood, those who have just sucked blood and those about to lay eggs. Laboratory studies have found that female mosquitos who first suck blood and then drink urine before laying their eggs produce more eggs and stronger offspring.
To ensure that we have constant access to mosquitoes for laboratory experiments, we feed them with blood. Photo: Rickard Ignell
Research about mosquitoes’ adaptation to a new climate
What is the next step in our knowledge development about mosquitoes? One example: SLU Alnarp is conducting experiments as part of its collaboration with the Max Planck Center on Next Generation Insect Chemical Ecology, nGICE.
Mosquitoes are placed in a climate chamber with a simulated potential future climate, with a higher temperature and carbon dioxide content. One of the effects the researchers have seen is that the insects become more stressed, leaving them more eager to drink blood.
Fully grown yellow fever mosquitoes in cultivation at the Swedish University of Agricultural Sciences in Alnarp. Photo: Johanna Grundström
Rohan Menon is identifying the two biotypes of the northern house mosquito, Culex pipiens – pipiens and molestus, as part of his work in nGICE. The biotypes themselves are not dangerous to humans, but hybrids between them can spread the West Nile virus from birds to humans. Photo: Johan Persson
Story:
Ida Andersson, Communications Officer, e-mail
Unit for Collaboration and Development
Press / research contact:
Rickard Ignell, Professor, e-mail
Department of Plant Protection Biology
Production:
SLU Division of Communication, e-mail
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