Tuesday, July 24, 2007

Vacation is over...

Back to business... I'm now at the Gordon Research Conference for Microbial Population Biology. It's a small, fun meeting held every other year at Proctor Academy in Andover, NH. This year the talks have been decidedly hit or miss. The phrase, "Never judge a talk by its title" comes to mind. Some highly anticipated (to me anyway) talks have fallen signficantly short of the mark, while others, less obviously interesting, have thoroughly surprised. My favorite talk to date has been a presentation by Gary Schoolnik on "Chitin-induced natural transformation and the evolution of Vibrio cholerae in aquatic habitats."

Previously I was aware of cholera as a disease cycling between aquatic reservoirs and human hosts, where cholera numbers were amplified in the gut and transmitted through fecal contamination of drinking water etc. Schoolnik described how far back the causal chain of cholera outbreaks can be extended from the human host. Once cholera leaves the gut, it enters the aquatic habitat where it colonizes the chitinous exoskeletons of small aquatic crustaceans called copepods. Copepod numbers are largely regulated by their primary foodsource, algae. More algae, more copepods, more cholera.

Schoolnik elucidated how global climate change, deforestation and agricultural intensification have impacted cholera outbreaks. Seasonally cholera is associated with monsoons in India. It is suspected that global climate change is increasing the severity of monsoons, which in conjunction with deforestation, is leading to increased runoff in the Ganges watershed. In this runoff are increasing levels of fertilizers because of agricultural intensification and increasing levels of human wastes due to surging human population numbers. The nutrient and waste laden runoff is causing greater algal blooms and higher copepod densities leading to increased incidence of cholera in the drinking water and larger cholera outbreaks. Luckily the situation is can be partially remedied by providing clean drinking water, which can be as simple as filtering river water thru a sari. The whole story epitomized for me the fragile web of interactions that we disturb at our own peril.

The photo is of a cholera-carrying copepod taken by Rita Colwell and Anwarul Huq.

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