Written by Nóra Lehotai.
World Mosquito Day has been celebrated on 20th August worldwide since 1897. That day, Sir Ronald Ross, a British doctor stationed in India, made the groundbreaking discovery which enabled the future of malaria research: malaria is transmitted from mosquitos to humans only by female mosquitos. He declared this day to be known as “World Mosquito Day” and for his scientific achievements, Ross received the Nobel Prize in Medicine in 1902.
"On World Mosquito Day, I reflect on these annoying flies” - says Claire Sayers, a postdoctoral researcher in Oliver Billker’s group. “While only female mosquitoes bite us to produce eggs, they also feed on nectar and act as pollinators. Mosquitoes have an ecological role, but some species are vectors for deadly diseases such as malaria. Mosquitoes are known as the world’s deadliest animal with over a million people dying from mosquito-borne diseases each year. The WHO estimated that 409,000 people died from malaria in 2019. I study the transmission stages of malaria parasites to better understand how they infect mosquitoes to spread the disease."
Pictures of mosquitos taken by Claire Sayers. All credits: Claire Sayers.
Claire explains what we see on the pictures above: “Pictured are Anopheles mosquitoes that were allowed to feed on mice infected with Plasmodium berghei, a rodent malaria model parasite. These parasites are genetically modified to express a green fluorescent protein (GFP), allowing us to select infected mosquitoes for our experiments. After ingestion of the blood meal, the parasites invade the mosquito midgut wall and develop into oocysts. After two weeks, you can see hundreds of green oocysts glowing through the mosquito’s abdomen under a fluorescence microscope. The parasites replicate within oocysts and eventually burst free and invade the mosquito salivary glands, ready to infect a new host when the mosquito takes another blood meal.”
Arjun Balakrishnan, senior research assistant in the Billker lab, shows the Plasmodium sporozoites infected mosquito salivary gland on this picture:
On the left side: fluorescent image, showing the GFP pattern of the malaria parasites. Right side: Light microscope image, showing the anatomy of the salivary gland. Pictures taken by Arjun Balakrishnan. All credits: Arjun Balakrishnan.
Arjun explains that “the time what the malaria parasites takes to develop in the mosquito from the point of ingestion, invasion of midgut and to enter the salivary gland to become infectious, is the so called extrinsic incubation period (EIP). We are trying to understand genetic and environmental factors that regulate the EIP during malaria infection in mosquitoes.”
Karsten Meier, a PhD student in Barbara Sixt’s group says:
"In my case, mosquitos keep me fit, because they force you to keep moving. As soon as you are too slow, they will get you! I heard mosquitos are an important food source for birds... But can't the birds eat them a bit faster then?" - concludes Karsten.
Editor’s note: Karsten is a very successful runner, member of the IFK Umeå long distance running team.
On the picture (from left to right): Stuart Wales, Karsten Meier, Claire Sayers and Arjun Balakrishnan. Pictures owned by the authors.
Stuart Wales, current mosquito caretaker at MIMS, reflects on World Mosquito Day :
“It has been beautiful few months in Umeå, but for me the summer of 2021 will always be associated with mosquitoes.
For the past few months, I have been maintaining the stock of mosquitoes used by the malaria research teams at MIMS, and whilst outside of work I am sure they have been more prevalent than ever. At times it feels like I have seen them, sensed them, had them around me even when I know they are not. A movement in the corner of my eye or that familiar high-pitched buzz. Somewhere nearby. I have even dreamt about mosquito larvae swimming around in bowls after a good few hours at work of trying to count them.
It surprises friends at home in the UK when I tell them about the mosquitoes here, it is not something that “Visit Sweden” talks much about. They are there, of course, in all of those stunning photographs and sweeping drone footage of forest and lakes, but just too small to see. Small, buzzy and bitey, they can ruin a mushroom picking trip to the forest and make you search the cupboards for that old half full bottle of repellant.
They’re generally not much more than an inconvenience here, but of course that is not the case everywhere. As a child in the 1970s, I lived for some years in Zambia and at one point my mother contracted malaria. She became quite unwell but had the privilege of being treated quickly and effectively, a privilege not extended then or now to many people in malaria zones around the world. Her experience gives me a personal reference for the importance of the research that I am involved with, taking place at MIMS and elsewhere.
This is what I will be thinking about in the insectary today on World Mosquito Day.”