Featured Research

from universities, journals, and other organizations

Daily Temperature Shifts May Alter Malaria Patterns

Date:
August 5, 2009
Source:
Penn State
Summary:
Daytime temperature fluctuations greatly alter the incubation period of malaria parasites in mosquitoes, and alter transmission rates of the disease. Consideration of these fluctuations reveals a more accurate picture of climate change's impact on malaria.

Daytime temperature fluctuations greatly alter the incubation period of malaria parasites in mosquitoes and alter transmission rates of the disease. Consideration of these fluctuations reveals a more accurate picture of climate change's impact on malaria.

Related Articles


"Most studies use average monthly temperatures to study the impact of climate change on the global malaria burden," said Matthew Thomas, professor of entomology, Penn State. "But mosquitoes and the malaria parasites developing within them do not experience average temperatures; they are exposed to temperatures that fluctuate throughout the day."

According to Thomas, the key to understanding the transmission of malaria lies in the time parasites take to incubate within a mosquito. In areas of high malaria transmission, the parasites take between 10 to 14 days to mature and become infectious. But almost 90 percent of female mosquitoes -- which transmit the disease -- die within 12 days. So even a tiny increase or decrease in the parasites' incubation period can greatly alter the number of mosquitoes available to transmit malaria.

Thomas and his Penn State colleagues Krijn Paaijmans, post-doctoral fellow, and Andrew Read, professor of biology and entomology, used a thermodynamic model to estimate the growth of malaria parasites during 30-minute intervals while temperatures fluctuated.

They found that under warmer conditions the daily temperature fluctuation effectively slows down the parasites' growth, while under cooler conditions the parasites grow more quickly because at least for part of the day they experience a warm temperature.

"We measure how parasite growth rates accumulate over 24 hours and subsequently over days," explained Thomas, whose team's findings appear today (Aug 3) in the Proceedings of the National Academy of Sciences. "And if you add up the effects from parts of the day being very cool and parts of the day being very warm, you get a different outcome than if you simply use the mean monthly temperature."

The Penn State researchers' model suggests that in cooler areas with average monthly temperatures below 68 degrees Fahrenheit, a fluctuation of plus or minus 45 degrees Fahrenheit reduces the parasites' incubation period, making them infectious nearly two weeks earlier. For areas with mean temperatures above 77 degrees Fahrenheit, a similar fluctuation greatly increases their incubation period and thereby reduces their infectious potential.

"This is important because if we base our estimates of malaria transmission intensity on mean monthly temperatures alone then we are going to be wrong," said Thomas. "Most studies are probably overestimating transmission intensity under warmer conditions and underestimating the transmission intensity under cooler conditions."

To test their model Thomas and his colleagues looked up average monthly temperatures and change in daytime temperatures for 1987 through 2005 during the main malaria transmission season at Kericho, a site in the Kenyan Highlands.

Current malaria transmission models predict that for average monthly temperatures between 59 degrees Fahrenheit and 69 degrees Fahrenheit during Kericho's malaria season, the incubation time for malaria parasites is never less than three weeks and frequently exceed a number of months. However, because about 10 to 20 percent of mosquitoes die off each day and the oldest live for about 56 days, such lengthy incubation periods for the parasites make malaria transmission at Kericho possible only during six of the 17 years.

However, malaria epidemics have been reported from the Kenyan Highlands in all 17 years.

When researchers accounted for daytime temperature fluctuation, their model correctly predicted it would shorten the parasites' incubation period to below 56 days, making malaria transmission possible during all 17 years.

"In order to explain the frequency of malaria epidemics at Kericho, you need to invoke the effects of daytime temperature fluctuation," said Thomas. "You cannot simply explain it with coarser measures of monthly mean temperature."

The Penn State researcher added that the inclusion of daytime temperature fluctuations could be the key to accurately interpreting the potential impacts of climate change on the dynamics of diseases such as malaria.

"There is potential for climate change to increase or decrease the intrinsic risk of malaria, but predicting what will happen where and when requires we consider changes in temperature variation, and not just mean conditions, coupled with a more detailed understanding of mosquito ecology."

PA Department of Health Tobacco Settlement Funds supported this work.


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. "Daily Temperature Shifts May Alter Malaria Patterns." ScienceDaily. ScienceDaily, 5 August 2009. <www.sciencedaily.com/releases/2009/08/090803185826.htm>.
Penn State. (2009, August 5). Daily Temperature Shifts May Alter Malaria Patterns. ScienceDaily. Retrieved November 26, 2014 from www.sciencedaily.com/releases/2009/08/090803185826.htm
Penn State. "Daily Temperature Shifts May Alter Malaria Patterns." ScienceDaily. www.sciencedaily.com/releases/2009/08/090803185826.htm (accessed November 26, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Wednesday, November 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Pet Dogs to Be Used in Anti-Ageing Trial

Pet Dogs to Be Used in Anti-Ageing Trial

Reuters - Innovations Video Online (Nov. 26, 2014) Researchers in the United States are preparing to discover whether a drug commonly used in human organ transplants can extend the lifespan and health quality of pet dogs. Video provided by Reuters
Powered by NewsLook.com
Today's Prostheses Are More Capable Than Ever

Today's Prostheses Are More Capable Than Ever

Newsy (Nov. 26, 2014) Advances in prosthetics are making replacement body parts stronger and more lifelike than they’ve ever been. Video provided by Newsy
Powered by NewsLook.com
From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

Newsy (Nov. 25, 2014) The US FDA is announcing new calorie rules on Tuesday that will require everywhere from theaters to vending machines to include calorie counts. Video provided by Newsy
Powered by NewsLook.com
Daily Serving Of Yogurt Could Reduce Risk Of Type 2 Diabetes

Daily Serving Of Yogurt Could Reduce Risk Of Type 2 Diabetes

Newsy (Nov. 25, 2014) Need another reason to eat yogurt every day? Researchers now say it could reduce a person's risk of developing type 2 diabetes. 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:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

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