Cara Brook is a Disease Ecologist studying in the Andrew Dobson Lab at Princeton. She currently studies the great bats of Madagascar—flying foxes—and the diseases they carry that could spill over onto humans. She has just arrived back in Madagascar for another epic journey of both biology and self-deepening.
It is the eve of Independence Day in Antananarivo, Madagascar, and I find myself back on the far side of the world. I’ve left the heat of an American East Coast summer for the short, crisp days of Malagasy midwinter, and I’m not planning to see be home again until the holidays, which seem a lifetime away. It can’t help but feel daunting at times to be away from the U.S. for so long, but when I look out my window at the flickering lamps and fireworks that light up the inky dark streets of Tana on this special eve, I am reminded of why I choose to work in this foreign place. The exoticism and mystery of Madagascar takes my breath away—it’s astonishing that I was in Princeton, New Jersey a mere 48 hours prior. This time, I return to the Eighth Continent with so much more than a backpack full of traps and nets and a righteous fervor to make a difference in the world. In fact, I can hardly remember the girl who made this voyage so naively just over a year ago to embark on her first field season as a PhD student. This time, I travel fresh from my doctoral qualifying exams with a real plan and vision for the work—and adventures—ahead.
In case you’ve forgotten, as it’s been awhile since my last writing, I’m a PhD candidate in Andy Dobson’s lab at Princeton University, and members of our research group identify under the title “Disease Ecologist.” Ecology is the science of organisms and their interactions, so a disease ecologist studies the organisms—parasites, hosts, and vectors—responsible for disease and analyzes how those organisms interact with one another and with their surrounding environments. Our group works on both animal and human diseases, and I specialize in something in-between; zoonotic diseases, which pass from wildlife to human populations.
Specifically, I focus on bat-borne pathogens. I study the viruses, bacteria, and protozoans that infect Old World fruit bats, a special clade of giant bats (also called “flying foxes”), which exist only in Africa, Asia, and Australia. I work in Madagascar because the island hosts a unique assemblage of endemic fruit bats of both Asian and African lineages (three species—Pteropus rufus, Eidolon dupreanum, and Rousettus madagascariensis—found nowhere else in the world), some of which occasionally co-roost with insectivorous bats. These fruit bats are widely hunted and eaten as bushmeat in Madagascar, meaning that opportunities for zoonotic exchange of pathogens between bats and humans abound. Bat-to-human zoonotic emergence of several particularly virulent viruses (chiefly SARS coronavirus, Ebola and Marburg filoviruses, and Hendra and Nipah henipaviruses) has received much attention from the media in recent years. I study how bats are able to host these otherwise virulent pathogens without experiencing ostensible disease and also investigate the factors that motivate pathogen spillover from bats to human communities.
New research suggests that novel pathways encoded in bat mitochondrial DNA enable mediation of oxidative stress incurred while flying and might have had heretofore underappreciated consequences for bat immune systems, making them uniquely fit to host microparasitic infections, like viruses and bacteria. In the upcoming months in Madagascar, I’ll be exploring the extent to which bats share their pathogens between different species in large communally-roosting populations—and ask whether these cross-species transmission events play a role in how pathogens persist in the ecosystem. I’ll also examine the impacts of hunting on the lifespan of fruit bats and address whether this host longevity affects the life cycle and virulence of the pathogens these bats support.
I’ve learned loads in the past six months at Princeton, and I’ll be learning loads in a completely different sense in the upcoming six months in Madagascar. As ever, it’s hard to take my leave from friends and family home in America, but I am excited for the months ahead with friends and family in what is fast becoming my second home in Madagascar. I’m a different, deeper person in Madagascar, and it is to commune with that person that I seek out my field site.
“Why so long?” my colleagues ask at Princeton, when I tell them I am leaving for the rest of the year. Because it takes that long to delve deeply into my research and myself.
“Let us go,” wrote John Steinbeck, “into the Sea of Cortez, realizing that we become forever a part of it; that our rubber boots slogging through a flat of eelgrass, that the rocks we turn over in a tide pool, make us truly and permanently a factor in the ecology of the region. We shall take something away from it, but we shall leave something too.”
Yes, Madagascar—let us go.