THE role of the mosquito in spreading the Zika virus led to it being described last week as the most dangerous animal in the world, carrying diseases that kill around a million people every year.

But this is only part of the story.

Dr Heather Ferguson, a Reader in the Institute of Biodiversity, Animal Health and Comparative Medicine at the University of Glasgow, points out that there are many thousands of different species of mosquito - including 30 in the UK alone - and that only a "relatively small proportion of them have any role in disease transmission."

She told the Sunday Herald: "There are lots of mosquitoes that have positive impacts: birds, spider and bats can eat them, and they can have a useful role in ecosystems. It's not mosquitoes per se that are the enemy, but there are certain species that have adapted to spread diseases."

Science writer David Quammen, quoted on the BBC website, believes that mosquitoes have limited the destructive impact of humanity on nature: "Mosquitoes make tropical rainforests, for humans, virtually uninhabitable." Rainforests, crucial to our ecosystem, are under serious threat from man-made destruction. "Nothing has done more to delay this catastrophe over the past 10,000 years, than the mosquito."

• How many species of mosquito are capable of spreading disease?

It's hard to be precise, says Dr Ferguson. "Some of them might be very rare species that might not have been studied very extensively but there are many others that we do know about, because they transmit malaria and diseases like dengue fever and other viruses."

• Is there any reason why some species carry diseases and others don't?

"That's a good question," Dr Ferguson said. "There is no simple answer. Part of it has to do with the ecology. Some of the main species, including the one responsible for the Zika virus, and malaria, are ones that are really specialised to feed on the blood of humans, and live in and around human homes. This makes them very efficient at transmitting diseases between humans because they live in such close contact with them. But even this is not enough - a mosquito needs to be physiologically susceptible to the pathogen, whether it be a virus or malaria parasite, before it can play a role in transmission. There are mosquito species that bite people often but don't spread diseases because pathogens can't survive in them."

• How much of a role does the environment have to play?

"An extremely important one. Many mosquito species thrive in moist, warm conditions, although even for this there are exceptions. Mosquitoes are found in every continent except Antarctica, you can even find mosquitoes in the Arctic."

This may surprise some people, but the Arctic's thick swarms of mosquitoes are an annual menace. A report in National Geographic last September quoted Lauren Culler, a postdoctoral researcher who studies insects in Greenland for Dartmouth College’s Institute of Arctic Studies: “There aren’t a lot of animals for them to eat in the Arctic, so when they finally find one, they are ferocious. They are relentless. They do not stop. They just keep going after you.”

Adds Dr Ferguson: "A lot of mosquitoes, particularly the disease-carrying ones, such as Aedes aegypti, which transmit Zika and dengue, and the Anopheles, which transmit malaria, do well in warm temperatures. These mosquitoes lay their eggs in small pools of water, including small household containers or puddles in muddy fields. Thus you get big mosquito populations under conditions where temperatures are high and aquatic breeding habitats are available".

• How close are we (if at all) to eradicating disease-carrying mosquitoes?

"There are a number of ways in which you can try to control or eliminate disease-carrying mosquitoes, with the most effective strategy depending on what mosquito you are dealing with," said Dr Ferguson. "Insecticide-treated nets have been really successful for controlling malaria in Africa, because the mosquitoes that carry it bite inside houses and at night. This approach would not work for Zika or Dengue because the Aedes aegypti mosquitoes that transmit the disease bite during the day, and often outside. So unless you were literally wearing a bed-net while you were out and about, this approach wouldn't work.

"Numerous options are being considered when it comes to controlling Aedes aegypti, and one of the most novel approaches is based on the development of a genetically-modified strain of the Aedes aegypti mosquito carried out by the UK company, Oxitec. Their approach is based on releasing male Aedes aegypti (which don't bite) that have been genetically-modified to be sterile. On release, they will mate with wild females and also cause them to be sterile.

"The idea is that if you release enough of these GM males through time, the mosquito population will eventually crash because they are producing no offspring. This approach is not in wide use, but promising results have been obtained from a few small pilot studies in south America."

* Is climate change a factor in mosquitoes and disease?

Some reports on climate change have claimed that rising temperatures could lead to malaria-carrying

mosquitoes in the UK. Dr Ferguson acknowledges that there is growing concern that climate change could bring about an increased risk of vector-borne disease but adds: "The impacts of climate change on mosquito-borne disease are likely to be complex and hard to generalize. For example, it could mean that we get new diseases spreading into areas they weren't before, but it could be that mosquitoes disappear from other areas because conditions will become too dry for them."

DR Ferguson's main focus is on the mosquitoes that transmit malaria in Africa and south-east Asia. She herself lived in Tanzania for three years and contracted malaria on several occasions.

Asked what it is that keeps her so devoted to her work, she says: "I'm an ecologist. I'm passionate about using that knowledge to improve public health, especially in the poorest parts of the world, such as Africa. All of these diseases, whether we're talking about Zika, malaria or dengue, are all diseases of poverty. Mosquitoes thrive where poverty thrives; in places where there is poor health infrastructure, inadequate drainage, and low-quality houses. I want to be part of the fight to improve global health, and feel that as an ecologist I can contribute to this by studying mosquitoes."

She added: "The kind of problems we are seeing right now are ultimately to do with poverty combined with environmental change, I believe. Many of the solutions for these diseases are already in our hands: good health systems, careful surveillance, and mosquito control combined with effective diagnosis and treatment. Unfortunately treatments are not yet available for diseases like Zika and Dengue, but could be forthcoming with more research.

"But we need political will, commitment and investment to find the kind of solutions that could work here."

Like many, she has publicly welcomed the renewed global commitment to cut deaths from Malaria by 90% in the next 15 years thanks partly to a landmark £3 billion funding commitment announced by Chancellor George Osborne and Bill Gates, co-chair of the Bill & Melinda Gates Foundation.

"That was fantastic news," she said. "The will is there, but we need to keep building on it."