From: imbibe@mindspring.com   
      
   Deforestation Brings Bat-Borne Virus Home to Roost   
   By Emily Anthes, Nov. 16, 2022, NY Times   
      
   In Sept. 1994, a mysterious interspecies outbreak erupted in Hendra, a suburb   
   of Brisbane, Australia. First, a pregnant mare fell ill and died. Soon, more   
   horses were sick, spiking fevers and expelling a foamy discharge from their   
   snouts. Two middle-aged    
   men — a stablehand and a horse trainer who had reportedly tried to hand-feed   
   the dying mare — developed flulike symptoms, too. Although the stablehand   
   recovered, the trainer ultimately died, as did more than a dozen horses.   
      
   Scientists eventually traced the outbreak to a virus carried by fruit bats,   
   also known as flying foxes. The bats shed the pathogen, which was named the   
   Hendra virus, in their feces and saliva, spreading it to horses, which can   
   then pass it on to humans.    
   In the years since, there have been dozens of additional outbreaks in horses,   
   and several more cases in humans.   
      
   A new study, based on 25 years of data from Australia, suggests that   
   environmental changes have been driving these spillovers by radically altering   
   the ecology of black flying foxes. Deforestation, coupled with climate-linked   
   food shortages, has driven    
   the bats into human-dominated habitats like farms, where food is readily   
   available but may be of poorer quality, scientists reported in Nature on   
   Wednesday.   
      
   In many of these new roost locations, the bats are not only in closer contact   
   with horses but may also shed higher levels of the virus, perhaps because of   
   nutritional stress, according to a second study conducted by many of the same   
   researchers and    
   published in Ecology Letters last month.   
      
   â€œWe’re transforming the planet in this way where we’re driving animals   
   to be really at the brink — at the edge of their capacity to cope,â€� said   
   Raina Plowright, an infectious disease ecologist at Cornell University and   
   senior author of both    
   studies. “And this is creating stresses that are also more likely to drive   
   pathogens into human populations.â€�   
      
   The idea that deforestation can increase the risk of disease spillover is not   
   a new one, and scientists have repeatedly documented connections between   
   forest fragmentation and outbreaks of diseases as varied as Ebola, malaria and   
   Lyme.   
      
   But the new research is an extraordinarily detailed case study, experts said,   
   unpacking precisely how environmental changes can drive disease risk — and   
   how and where experts might be able to intervene.   
      
   â€œIt’s just an enormously impressive undertaking,â€� said Dr. Aaron   
   Bernstein, the interim director of the Center for Climate, Health and the   
   Global Environment at the Harvard T.H. Chan School of Public Health, who was   
   not involved in the research. “   
   These scientists have essentially traced the dots across a bunch of the   
   factors that we know can drive emerging infections.â€�   
      
   He added, “I think it points to how critically important it is to focus on   
   prevention upstream to really prevent spillover.â€�   
      
   The new study is the result of a decade-long collaboration between Dr.   
   Plowright and Peggy Eby, a wildlife ecologist with an adjunct position at the   
   University of New South Wales who has spent 30 years studying the flying foxes   
   that live in a subtropical    
   region of Eastern Australia. They worked with an interdisciplinary group of   
   colleagues to analyze a wide range of ecological data — including on bat   
   roosts, bat fitness, climate, nectar shortages, habitat loss and viral   
   spillover into horses —    
   collected in the region between 1996 and 2020.   
      
   Historically, the local black flying foxes, which feed heavily on the nectar   
   of eucalyptus flowers, have lived in enormous nomadic groups, winging their   
   way through native forests in search of trees in bloom. Although the flowers   
   are abundant in summer,    
   during the winter and spring, the supply is much more limited. And every few   
   years, a fluctuation in the climate, such as a strong El Niño event, disrupts   
   winter or spring blooming, creating food shortages.   
      
   Typically, the bats have coped by splitting into smaller groups and setting up   
   temporary roosts near more readily available food sources, such as farms or   
   urban gardens. When the nectar shortages eased, the bats would find their way   
   back to the forest. †  
   œAs soon as the nectar started to flow again, they’d re-fuse into big   
   aggregations and start becoming nomadic and feed in native forests again,â€�   
   Dr. Plowright said.   
      
   This pattern held during the early years of the study period, from 1996 to   
   about 2002, the researchers reported. And during these years, there were no   
   Hendra spillovers detected in the region.   
      
   But around 2003, the pattern changed, the scientists found. When major food   
   shortages struck, new groups of bats would still splinter off from their   
   compatriots and set up shop near farms and cities. But now, the bats made   
   these new habitats permanent,    
   abandoning their nomadic forest lifestyles.   
      
   Between 2003-2020, the total number of roosts in the region tripled, while the   
   size of each bat group declined. In addition, the roosts grew closer together,   
   and the bats foraged in smaller areas.   
      
   The researchers theorized that this behavioral change stemmed from the fact   
   that the forests the bats had relied upon, especially for the scarce supply of   
   nectar in winter, were rapidly disappearing. In southeastern Queensland,   
   nearly one-third of the    
   bats’ winter foraging habitat disappeared between 1996 and 2018, they found.   
      
   â€œWe think what’s happened is that it doesn’t make any sense anymore for   
   these animals to maintain these big nomadic populations,â€� Dr. Plowright   
   said. “It’s too hard to find food.â€�   
      
   Instead, she said, the bats may find it easier to survive by settling near the   
   ready supply of lower-quality food that farms and gardens provide. “You   
   don’t have to spend a lot of energy to find it,â€� she said. “It’s   
   easier to eke out a living.    
   You live next door to McDonald’s.â€�   
      
   In their second study, Dr. Plowright, Dr. Eby and their colleagues reported   
   that bats living in these novel habitats also excreted more virus in winter   
   than those that remained in the forest, perhaps because they were not   
   well-nourished enough to    
   maintain a robust immune response. (Viral shedding also tended to be higher in   
   both bat populations after food shortages.)   
      
      
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