Wiping out mosquitoes from countries ravaged by malaria would not have a negative impact on any other native species, scientists have suggested.
Researchers found that locally eliminating one species of mosquito could drastically cut cases of malaria without drastically affecting the diet of any other animal.
In 2016, there were around 216 million malaria cases worldwide, resulting in an estimated 445,000 deaths, mostly of children under five years old.
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Wiping out mosquitoes from countries ravaged by malaria does not have a negative impact on other native species, scientists have revealed (stock image)
In sub-Saharan Africa, where the majority of malaria cases occur, only a handful of the hundreds of native mosquito species can carry malaria.
An international team of researchers, led by experts at the Imperial College London, are hoping to suppress the ability to spread malaria in one of these species – Anopheles gambiae – using genetic engineering in the near future.
Before doing this, researchers wanted to assess the impact of suppressing Anopheles gambiae (also known as An. gambiae) would have on the ecosystem and species around it.
In their latest report, published in Medical and Veterinary Entomology, researchers reviewed previous studies into the species to see how it fits into the ecosystem.
The team published their findings under the name, Target Malaria.
They found that while some animals do eat An. gambiae, these animals also eat other species of mosquito and other insects.
As a result, their survival does not depend on An. gambiae.
‘As adults, An. gambiae mosquitoes are small, hard to catch, most mobile at night and not very juicy, so they are not a rewarding prey for both insect and vertebrate predators,’ said lead author Dr Tilly Collins.
Researchers found that although many do eat them – sometimes accidentally – there is no evidence that the mosquitoes are a vital part of the diet of any other animal.
‘There is one curious jumping spider known as ‘the vampire spider’ that lives in homes around the shores of Lake Victoria and does have a fondness for female blood-fed mosquitoes,’ Dr Collins said.
‘Resting blood-fed females are easy and more nutritious prey as they digest their blood meal, but this spider will readily eat other available mosquito species as opportunity arises.’
In 2016, there were around 216 million malaria cases and an estimated 445,000 deaths, mostly of children under five years old (stock image)
WHAT IS MALARIA?
– Malaria is an infection of the liver and red blood cells caused by parasites
– The parasites are spread through the bite of certain mosquitoes
– Contracted in tropical and subtropical areas of Asia, Africa, Central and South America, the Pacific Islands and parts of the Middle East
– Approximately 500 cases of malaria are diagnosed in Australia each year
– Almost all cases are in people who didn’t take anti-malarial medications
– Symptoms include sudden fever, chills, headache, sweating, nausea, vomiting and pain in joints and muscles
– Can include seizures, confusion, kidney failure, breathing difficulty and coma
– Pregnant women, young children and people visiting overseas are most at risk
Source: NSW Health
The team also looked at mosquito larval habitats.
The female mosquitoes tend to lay their eggs in small, temporary ponds and puddles out of sight from larger predators.
When forced to lay their eggs in larger ponds, predators are known to feed on the unborn mosquitoes. However, these animals also eat a number of other species.
As well as what eats An. gambiae, the team also reviewed what competes with them.
If a species is removed from an ecosystem, it can mean that a competitor species – one that uses a similar food resource, for example – grows much larger in numbers to fill the void.
This can create chaos in the careful equilibrium of an ecosystem.
Upsetting that balance can become a problem if the competing species carries its own dangers, for example, if it carries a different human disease, like yellow fever.
The team found that other species of mosquito are most likely to compensate for fewer An. gambiae.
To validate and improve their findings, the Target Malaria project is launching a four-year study led by the University of Ghana and the University of Oxford that will study An. gambiae in the local environment in Ghana.
WHY DO MOSQUITOES BITE SOME PEOPLE AND NOT OTHERS?
Around 20 per cent of people are more prone to mosquito bites.
And while scientists are yet to find a cure, they do have some ideas as to why the insects attack some of us more than others.
Certain blood types are more attractive to taste buds of mosquitoes.
Research has shown that people who have Type O blood – the most common blood type – tend to get bitten twice as much as those with Type A. People with Type B blood get bitten somewhere in the middle.
Exercise and metabolism
Working up a sweat during exercise can also make a person more susceptible to a mosquitoes bite.
Strenuous exercise causes higher body temperatures and a buildup of lactic acid, which emit yummy signals to the insects.
A cold glass of beer makes you sweat and your body release ethanol, which may be why mosquitoes like to land on beer drinkers.
Levels of bacteria on the human skin can entice mosquitoes to bite, particularly where bacteria clusters like on the ankles and feet.
Having different types of bacteria on the skin, however, tends to turn the insects off.
Mosquitoes use even the faintest of human body odours when searching for potential victims.
It’s been known for some time that female mosquitoes use specific sensors around their mouths to detect carbon dioxide being exhaled from humans and animals.
But a few years ago, researchers from the University of California Riverside discovered the blood-sucking insects also use these same sensors to detect body odours – especially the smell of feet.