Of plagues and people: Cornell biologist teaches unique course on how insects carry some of history's nastiest diseases

ITHACA, N.Y. -- A flea lands on a man's arm and bites it. He scratches. The scratching aids the passage of the bacteria carried by the flea into the man's bloodstream. His temperature soars, his lymph glands swell and quickly his heart, liver and spleen are destroyed. He goes into septic shock, then into coma and finally dies.

And that was just the bubonic plague.

Next week, Laura Harrington, Cornell University assistant professor of entomology, will begin teaching what she believes is a unique university course, "Plagues and People," (Entomology 210). The class is devoted to understanding how insects are vectors for some of humanity's nastiest afflictions.

"Many people blame rats for causing the plague, but it is the fleas that are the vectors. The rats are the reservoir, but the fleas spread the disease around. Certainly the plague has had a big impact on history," says Harrington. "I've always been fascinated by medical entomology. It's gory, but fascinating."

Harrington says the two-credit course will focus on the causes of human plagues, with special attention to history's great scourges, including malaria, dengue fever and typhus. She will explain the co-evolution of the pathogens, parasites and arthropod vectors and how changes in the environment can cultivate plagues.

Throughout the semester, students will study the origins of the Black Death, the name given to the 14th century bubonic plague that spread from China to western Asia before decimating Europe (the disease causes a painful swelling of the lymph glands, called buboes, and also skin spots that turn black). Students also will learn about the Barbary plague that threatened the Chinese immigrant population in San Francisco a century ago.

"I really want to convey the horror of these diseases," Harrington says. "The Barbary plague was a horrific scene. Through readings, students will learn what it was like to live in this period of time and what it was like to die from the plague."Harrington knows of what she speaks. As a student conducting mosquito research in Thailand, she contracted malaria. On another research expedition, she contracted dengue fever.

The class will learn about the origins of yellow fever and how mosquitoes spread it among 19th century workers building the Panama Canal. They will gain an understanding of the spread of Rift Valley fever, Venezuelan equine encephalitis as well as emerging plagues. In an open laboratory, students will examine mosquitoes, fleas, lice, ticks and slide-mounted pathogens, including malaria protozoa and plague bacilli, under the microscope. For final projects, the students will prepare an in-depth examination of a topic related to plagues, people and history. The course will be offered every other fall.

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