Saturday, April 25, 2009

World Malaria Day

My standard answer to the question “What good are mosquitoes?” is “Ask a Plasmodium.” The quip is both flippant and profound. Plasmodium is the parasitic organism that causes malaria. It cannot complete its life cycle without the help of certain mosquitoes. We tend to collectively frame other living things by their relevance to ourselves only. Today, on World Malaria Day, I challenge you to think differently, and ask if deadly tropical diseases like malaria can be eradicated without rendering extinct either vectors or microbes.

Many parasitic diseases have driven human evolution over the eons. Sickle-cell disease is our unfortunate evolutionary answer to malaria, but who knows what future immune responses might be, and how they will become encoded in our genes?

Diseases can also have an impact on ecosystems. African sleeping sickness, caused by parasites called trypanosomes, and transmitted by the infamous tsetse flies, is a case in point. Wildlife is essentially immune to trypanosomyasis, but in livestock the parasite manifests itself as “ngana.” Avoiding the disease and its vectors is largely what has driven the nomadic lifestyle of certain indigenous tribes. Cattle are moved with the fluctuating “fly belt” to territory not occupied by tsetses. This seasonal migration has allowed livestock and grazing wildlife to co-exist on the savannah to a much greater degree than would be the case if ngana was eliminated. Subsaharan Africa would become, more or less, one big cattle ranch without the fear of flies and disease.

Our response to human mortality factors in general has left a long trail of unintended consequences, and we should be cognizant of the potential to repeat those mistakes. Please, by all means purchase a net or two to insure the safety of those in remote villages that risk nightly exposure to bites from malaria mosquitoes. Continue to contribute to organizations seeking to end poverty across the planet through improved housing, water quality, and education. We need to be both generous and cautious human beings.

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