EcoSeed

By Jhoanna Frances S. Valdez

Shifting drought, rainfall, gradually warming weather and other effects of climate change have allowed disease carrying insects such as mosquitoes to thrive.

Climate change may make it difficult for world governments to control the spread of diseases, especially the insect-borne ones, the World Health Organization said.

In a bulletin, W.H.O. climate change head Diarmid Campbell-Lendrum said the presence of warmer temperatures in the earth's atmosphere - climate models project the average surface temperature will rise by 1.1 degrees Celsius to 6.4 degrees Celsius over the 21st century - will make diseases like malaria and the West Nile virus harder to control as the climate can actually help disease-carrying insects thrive.

"Climate change is not going to invent any new diseases; it's going to make controlling existing diseases harder. We've been describing the links between climate change and health for quite a long time," he said.

Mr. Campbell-Lendrum said the erratic incidences of rainfall, humidity, temperature, coupled with a wetter weather will help boost the number of mosquitoes, as mosquitoes' survival decreases under dry conditions.

He added that shifting drought and rainfall and a gradually warming weather has made mountains more welcoming to mosquitoes.

According to him, the projected rise in sea level associated with climate change is likely to eliminate breeding habitats for salt-marsh mosquitoes. On the other hand, inland intrusion of salt water may turn former fresh water habitats into salt-marsh areas which could support vector and host species displaced from former salt-marsh habitat.

The W.H.O. estimates that global increase in malaria may be associated with a combination of deforestation, water development projects, and agricultural practices in poor countries.

"The West Nile pathogen - the warmer the temperature, the faster it moves from the blood to being transmitted. It usually takes a while for the virus to get into the mosquito's salivary glands. The biting rate also gets faster. So those things are all going to give you more transmission," said Marm Kilpatrick, an assistant professor in ecology and evolutionary biology at the University of California, Santa Cruz in an article in Scientific America.

The West Nile virus originated in Africa and emerged in North America in 1999, making it a relatively recent disease.

"It's possible that W.N.V. transmission is modulated primarily by rainfall and temperature, and if so, climatic conditions in 2002 and 2003 were especially suitable. If WNV transmission is regulated by climate, then severe epidemics could recur, especially if they are facilitated by climate change," Mr. Kilpatrick said.

"The same questions we're wondering about West Nile apply to malaria and dengue," said Mr. Kilpatrick.

According to the U.S. Center for Disease Control and Prevention, dengue fever is one of the world's most common disease, with one-third of the world living in endemic areas and afflicting 900 million people worldwide.

Mr. Campbell-Lendrum said the disease risks are inequitable, as greenhouse gases that cause climate change originate mainly from developed countries, but the health risks are concentrated in the poorest nations, which have contributed least to the problem.

Also, forecasts of infectious diseases' responses to climate change are complicated by the difficulties associated with predicting how ecosystems will respond to changes in climate, she said.

The W.H.O. advises world governments to increase global disease surveillance, continue epidemiological research into associations between climatic factors and infectious diseases, and improve public health training, emergency response, and prevention and control programs.

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