Joy of Learning

Climate Change and Disease

Level: High School

Objectives: To help students understand the transmission of malaria, describe how climate affects the life cycle of vectors and think about possible methods to reduce the occurrence and spread of disease and improve treatment facilities for affected people.

Materials: Map of malaria distribution; atlas with weather (temperature, rainfall information in different regions of India); chart showing lifecycle of the mosquito

Procedure

1. Have students look at maps of present-day distribution of malaria in order to characterize the regions where malaria occurs. Specifically, they should consider the climate, such as average annual temperatures, average nighttime (low) temperatures, and precipitation. An atlas with maps of temperature and precipitation distribution is probably the easiest
   way to search for this information.
2. Ask students to identify the regions where malaria is currently present and also temperature and rainfall in these regions.
3. Ask students to observe the life-cycle of mosquitoes.
4. Next, guide a discussion by having students consider the following three perspectives:
   
   a. How does climate impact the vector directly?
   b. How does climate impact the vector’s (or intermediary host’s) habitat?
   c. How does climate impact the parasite?

Discuss with students ways to control malaria in regions where it is likely to spread and enhance treatment for affected persons. You may like to point out the importance of education and awareness among people about the disease itself, and the simple ways to control spread of mosquitoes.

Resources
• A color map showing model projections of changes in malaria distribution with a warming climate can   be found in the Epstein (August 2000) Scientific American article.
• < http://www.sciam.com/article.cfm?colID=1&articleID=0008C7B2-E060-1C73-9B81809EC588EF21 >
• Map illustrating the local consequences of global warming http://www.climatehotmap.org/
• Climate statistics can be found at http://www.weatherbase.com/

Adapted from the activity Exploring Climate Change Impacts in the booklet Global Warming: Early Warning Signs Curriculum Guide for High School Courses in Biology, Environmental Science, Geography, Earth Science and others focusing on the society environment interface developed by Union of Concerned Scientists: Citizens and Scientists for Environmental Solutions downloadable from
www.climatehotmap.org/curriculum/climate_change_guide.pdf

A useful keysheet titled ‘Climate Change Impacts on Human Health in India’ is downloadable from
http://www.defra.gov.uk/ENVIRONMENT/climatechange/internat/devcountry/pdf/india-climate-9-health.pdf

	Information for the Teacher Increasing temperatures will be accompanied by changes in rainfall and humidity, including a likely increase in the frequency of heavy precipitation events. Some areas will become drier because higher temperatures also increase evaporation. A vector-borne disease is one in which the disease-causing microorganism is transmitted from an infected individual to another individual by an arthropod (e.g. mosquito or tick) or some other agent. Other animals, wild and domesticated, sometimes serve as intermediary hosts. Key vector-borne diseases of concern include malaria, dengue fever, yellow fever and several forms of encephalitis. Climate constrains the range of many vector-borne diseases (VBDs). They are currently prevalent mainly in tropical and subtropical countries. Mosquitoes, for example, are limited to seasons and regions where temperatures stay above a certain minimum. The winter kills many eggs, larvae, and adults. Climate also influences the availability of suitable habitat and food supply for vectors. Weather affects the timing and intensity of disease outbreaks. Within their temperature range of tolerance, mosquitoes will reproduce more quickly and bite more in warmer conditions. Warmer temperatures also allow the parasites within mosquitoes to mature more quickly, increasing the chances that the mosquito will transfer the infection. Floods can trigger outbreaks by creating breeding grounds for insects. Droughts can reduce the number of predators that would normally limit vector populations. Several modeling studies have predicted that increasing temperatures will lead to the spread of malaria and other diseases into previously unaffected areas. Climate change may also affect the severity of the disease at a given location. Socioeconomic factors also affect the distribution of vector-borne diseases. A good public health infrastructure, including prompt treatment of cases to reduce the risk of spread of the disease, and mosquito-control measures help to limit disease transmission. Land-use by humans can change the availability of habitat for vectors.