Featured Research

from universities, journals, and other organizations

Climate Change May Alter Malaria Patterns

Date:
February 17, 2009
Source:
Penn State
Summary:
Temperature is an important factor in the spread of malaria and other mosquito-borne diseases, but researchers who look at average monthly or annual temperatures are not seeing the whole picture. Global climate change will affect daily temperature variations, which can have a more pronounced effect on parasite development, according to a Penn State entomologist.

Temperature is an important factor in the spread of malaria and other mosquito-borne diseases, but researchers who look at average monthly or annual temperatures are not seeing the whole picture. 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 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."


Story Source:

The above story is based on materials provided by Penn State. Note: Materials may be edited for content and length.


Cite This Page:

Penn State. "Climate Change May Alter Malaria Patterns." ScienceDaily. ScienceDaily, 17 February 2009. <www.sciencedaily.com/releases/2009/02/090214162631.htm>.
Penn State. (2009, February 17). Climate Change May Alter Malaria Patterns. ScienceDaily. Retrieved September 2, 2014 from www.sciencedaily.com/releases/2009/02/090214162631.htm
Penn State. "Climate Change May Alter Malaria Patterns." ScienceDaily. www.sciencedaily.com/releases/2009/02/090214162631.htm (accessed September 2, 2014).

Share This




More Health & Medicine News

Tuesday, September 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

Newsy (Sep. 2, 2014) The U.N. says the problem is two-fold — quarantine zones and travel restrictions are limiting the movement of both people and food. Video provided by Newsy
Powered by NewsLook.com
Get on Your Bike! London Cycling Popularity Soars Despite Danger

Get on Your Bike! London Cycling Popularity Soars Despite Danger

AFP (Sep. 1, 2014) Wedged between buses, lorries and cars, cycling in London isn't for the faint hearted. Nevertheless the number of people choosing to bike in the British capital has doubled over the past 15 years. Duration: 02:27 Video provided by AFP
Powered by NewsLook.com
Can You Train Your Brain To Eat Healthy?

Can You Train Your Brain To Eat Healthy?

Newsy (Sep. 1, 2014) New research says if you condition yourself to eat healthy foods, eventually you'll crave them instead of junk food. Video provided by Newsy
Powered by NewsLook.com
We've Got Mites Living In Our Faces And So Do You

We've Got Mites Living In Our Faces And So Do You

Newsy (Aug. 30, 2014) A new study suggests 100 percent of adult humans (those over 18 years of age) have Demodex mites living in their faces. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins