Dissertation

My doctoral research at the Center for Sustainability and the Global Environment (SAGE) at the University of Wisconsin-Madison was on the ecology of Nipah virus in Bangladesh and malaria in the Brazilian Amazon.

Nipah virus (NiV) is a zoonotic disease that is harbored in fruit bats known as Indian flying foxes.  NiV was discovered in 1998 in Malaysia when the virus jumped from fruit bats into pigs and caused a country-wide epidemic.  The bats feeding in orchards surrounding pig farms dropped partially-eaten fruit into the pens, the pigs became ill after eating the infected fruit, and the movement of infected pigs to slaughterhouses facilitated the spread of the virus to pig farmers and pigs throughout the country.  The epidemic continued for several months until the government ordered the mass culling of over 1 million pigs, and the last human case occurred in May 1999.

There has not been another outbreak in Malaysia, but Nipah virus was first recognized in Bangladesh in 2001.  There have been seasonal outbreaks in Bangladesh almost every year since.  The transmission cycle in Bangladesh does not involve pigs.  Rather, in Bangladesh, there is a practice of tapping sap from date palm trees to drink.  When the fruit bats are foraging at night, they often help themselves to the sap as it is dripping from the tree into the collection pot, thereby infecting the sap.  People are infected when they drink the fresh, contaminated sap.

Date palm sap collector hanging a collection pot.
Date palm sap collector hanging a collection pot.

All the human Nipah cases in Bangladesh have been in the Northeast and central part of the country in an area known as the “Nipah Belt.”  We do not know why this is.  My research compared the roosting habitats of the fruit bats in villages where there have been outbreaks and villages with no reported outbreaks.  We found that although there is bat habitat available throughout Bangladesh, Nipah virus outbreaks have been concentrated in areas with high population density and a highly fragmented forest.

You can read the details of the study in the American Journal of Tropical Medicine and Hygiene and the Journal of Applied Ecology.  Information on the field work protocol and questionnaires can be found in the appendices of my dissertation.