Global climate change will affect daily temperature variations, which can have a more pronounced effect on parasite development, according to a Penn State entomologist.
"We need higher resolution environmental and biological data to understand how climate change will affect the spread of the malaria parasite," says Matthew Thomas, professor of entomology. "We need to understand temperature from the point of view of the mosquito."
Female Anopheles mosquitoes spread malaria by biting infected humans and ingesting the malaria parasites along with the blood they need to reproduce other mosquitoes. In the mosquito's gut, the parasites are implanted in the gut wall where they develop into cyst-like structures and multiply. Once mature, the cysts burst releasing thousands of parasites, which migrate to the mosquito's salivary glands. The next time the mosquito bites a human, the parasites enter the human along with mosquito saliva. Except through blood transfusions, humans cannot directly spread malaria to other humans.
Temperature plays a key role in the development of malaria parasites in the mosquito. Adult female Anopheles mosquitoes can live up to eight weeks but most die within two or three weeks, so malaria parasites must complete their development before the last time a female feeds to infect humans. Scientists have known for a long time that temperature influences the speed at which malaria parasites develop in mosquitoes, but temperature's effects are more complicated than previously thought.
"A day in the tropics may vary from something like 65 degrees Fahrenheit at night to 86 degrees Fahrenheit in the day, even though the daily average may be 77 degrees Fahrenheit, " Thomas told attendees at the annual meeting of the American Association for the Advancement of Science today (Feb. 14) in Chicago. "Our research suggests this fluctuation matters because it alters the parasite incubation period in the mosquito, which is the most important factor in the spread of malaria. Small changes in incubation can lead to big changes in transmission."
The cooler the ambient temperature, the slower the malaria parasite develops. The warmer the ambient temperature, the faster the malaria parasite develops. If the incubation period takes longer than the life of the mosquito, the parasite will never infect a human. In some places, especially at higher elevations, malaria does not exist or is seasonal because, with cooler temperatures the mosquitoes die before the parasites are mature. While other factors such as how often a mosquito bites and the fertility of the mosquitoes remain important, the development of the parasite is the key to infection.
A daily mean temperature of 77 degrees Fahrenheit can indicate that the temperature was 77 degrees for 24 hours, or that it dipped to 59 degrees Fahrenheit and rose to 86 degrees Fahrenheit and still had a mean of 77 degrees Fahrenheit. Depending on how long the temperature stays cool and how long it is warm, the malaria parasite's time to maturity changes and the effects can be complex because fluctuation around cooler average temperatures has the opposite effect to fluctuation around warmer average temperatures.
"Daily temperature fluctuation can increase or decrease malaria risk, depending on background conditions," said Thomas.
Day-long fluctuations are not the only thing that influences the development of the malaria parasite. According to Thomas, during the first 12 hours of parasite development, temperature fluctuations can be fatal. Most mosquitoes bite to feed on blood in the evening or at night. If they bite in the early evening, the temperature will remain cool for at least 12 hours. Some mosquitoes may feed much closer to morning. If the morning feeders then face rapidly rising daytime temperatures reaching 88 to 90 degrees before 12 hours elapse, then the malaria parasite development can be stopped.
"If climate change increases the frequency of days when the temperature quickly exceeds the threshold temperature, then entire cohorts of mosquitoes could fail to develop the parasite," says Thomas.
In the developed world, the key to eradicating malaria, which once existed in parts of the U.S. and Europe, was an infrastructure that included good healthcare, mosquito control and habitat management. Future changes in temperature and rainfall are not likely to bring endemic malaria back to the U.S. or Europe. However, in parts of the world where these malaria preventing approaches do not exist, climate change may well lead to changes in malaria dynamics; whether this will be an increase in malaria or a decrease in malaria will depend not only on changes in mean conditions, but also changes in the daily temperature fluctuations.
The control of malaria depends on the environment of a small bodied, cold blooded insect -- the mosquito. A complete understanding of the temperature regime where they live as both larvae and adults is important to understand disease risk.
"Unfortunately, the areas where we need to get more sensitive temperature readings are also sometimes the most difficult places to obtain data," said Thomas. "But, this is the basic biology we need."
A'ndrea Elyse Messer | EurekAlert!
Collagen nanofibrils in mammalian tissues get stronger with exercise
14.12.2018 | University of Illinois College of Engineering
New discoveries predict ability to forecast dementia from single molecule
12.12.2018 | UT Southwestern Medical Center
The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.
Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...
What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...
A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.
The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...
A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.
Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...
Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...
12.12.2018 | Event News
10.12.2018 | Event News
06.12.2018 | Event News
14.12.2018 | Power and Electrical Engineering
14.12.2018 | Physics and Astronomy
14.12.2018 | Physics and Astronomy