Young Explorer Cara Brook is in Madagascar studying the impact of human land development on biodiversity and how it could potentially spread infectious diseases that are transmitted from animals to people. Cara will focus on bubonic plague in small mammals and henipaviruses and lyssaviruses (two strains of viruses) in bats.
I sit hunched with my companions under a rocky outcrop, holding a silent vigil as the massive bats swirl against the night sky. The forests of eastern Madagascar stretch out before me towards the distant Indian Ocean, and the gray-black mist-net waves almost imperceptibly in the soft moonlight. We hold our breath as one of our quarry wheels towards its shadowy surface…
I write to you once again returned from an expedition sur terrain—two weeks of field training, spent netting and sampling Malagasy megabats with colleagues at the Institut Pasteur. For those of you not well-versed in bat biology, you should know that bats (mammalian order Chiroptera), are broken down into two very distinct and divergent suborders—Microchiroptera and Megachiroptera.
I am studying Megachiroptera, also known simply as megabats or flying foxes. These unique creatures are found only in the Old World and share many features more consistent with modern carnivores than what one traditionally thinks of as a bat. Their faces resemble that of a small dog—with canid-like dentition—and typically, they do not echolocate but instead use their large eyes and keen sense of smell to locate the fruits on which they feed. By contrast, most (though not all) microbats are insectivorous.
Megabats are noteworthy in disease ecology because of their recently discovered—and still not fully elucidated—roles as reservoirs for some of the world’s most dangerous emerging zoonotic viruses, including Nipah and Hendra henipaviruses and likely Ebola and Marburg filoviruses, as well.
Theories abound as to why and how these fascinating animals are able to host such virulent pathogens without falling susceptible to infection themselves—these creatures are uniquely gregarious, long-lived, and very ancient. Currently, bat immunology is a bit of a black box, and researchers like myself are working hard to try to understand what about the evolution and ecology of these animals has allowed them to peaceably coexist with so many of these viruses for millions of years.
Megabats of the genus Pteropus received widespread public attention in the 1990s for their role as reservoirs of Hendra and Nipah henipaviruses—which broke out in human communities in Australia and Malaysia respectively. Nipah—the inspiration for the popular 2011 film, Contagion—still results in periodic human outbreaks in Bangladesh. It was originally thought that henipaviruses were limited in range to the range of their Pteropus hosts—which live in Oceania, Asia, and Australia but not continental Africa.
However, recent studies have found that African clades of flying fox—specifically Eidolon helvum—can play host to Hendra and Nipah-like henipaviruses, as well. Forever the biogeographic melting pot, Madagascar is home to three endemic species of megabat, including one of Asian (Pteropus) and one of African (Eidolon) descent.
In addition to my studies on rodent-borne Leptospirosis, my work on metapopulation dynamics of disease seeks to explore the impact of habitat perturbation on contact rates and viral sharing between Malagasy Pteropus rufus and Eidolon dupreanum. I’ve got five years ahead of me to nail it all down, but for the moment, I’m just learning how to catch these animals and draw their blood…
Malagasy megabats are protected species but still widely hunted as bushmeat across the island, and we find ourselves navigating the underground black market for information on where to find Pteropus and Eidolon roost sites—and for expert hunter advice on how to catch them. The Malagasy word for bat is ramanavy, but these ramanavy ngeza—big bats—are known colloquially as fanihy, and people all over Madagascar assure me that they are matavy—fatty—and matsiro—delicious—when consumed as laoka, the traditional side-dish that accompanies rice.
I probably don’t need to tell you that it is a fairly terrible idea to eat an Old World Fruit Bat that could be the reservoir for the next emerging henipavirus, but that does not seem to stop the Malagasy, and indeed, the locals hardly believe us when we explain that we are live-trapping, blood-sampling, and releasing these animals. We have to knock on doors in Lakato, the site of our Eidolon sampling in the Moramanga region of eastern Madagascar, and bring the villagers out of their houses to watch as we release our thumb-banded flying foxes. Even still, they turn our pillowcase containment bags inside out, searching for the bat we must have secreted away to keep for dinner.
“Wow,” I say aloud to Christian. “What kind of vazaha do they think we are, anyway? You’d have to pay me a lot to make me want to eat a bat…”
But megabat is a delectable to most everyone else in Madagascar, and you can find it on the menu in some of the more remote hotelys in coastal regions like Morondava, Mahajanga, and Vaingandrano. Wandering the beaches of Morondava, I also discover that the Malagasy sell and consume palm juice in abundance—and Pteropus rufus likes to roost in palm trees.
In Bangladesh, Nipah outbreaks tend to follow the routes of young bicycle salesmen vending fruits and juices from Pteropus roost palms, and I cannot help but wonder if Madagascar is the next henipavirus disaster-waiting-to-happen. In addition, GuanoMad, a large Malagasy corporation, collects flying fox excrement and redistributes it as fertilizer all across the island…What viruses, I wonder, are lurking in its midst?
It’s a fascinating, thrilling, detective sort of field work, and I feel my heart skip wildly as another Eidolon dupreanum dives into our mist-net. As with much of my work in Madagascar, this project is daunting in its difficulty—it took an eight hour car ride and a five hour hike, with liquid nitrogen and centrifuge in tow, to get to the Lakato roost site.
And then there was rain, and more parasys burrowing in my feet, and it has been days since I slept and weeks since I showered, but I would not trade it for the world. It is adventure and discovery and science rolled into one, and as my flying fox friend cocks its head and blinks at me personably in my gloved hand, I cannot help but smile and feel that perhaps—finally—I have found my research calling.