Primate-parasite network analyses show how germs jump from host to host

A juvenile bonobo leaps from a branch. The bonobo, a threatened species of great ape found in the Congo Basin, is the closest existing relative to humans, along with the chimpanzee.

By Carol Clark

An extensive review of research on wild primate social networks and parasites underscores the importance of super-spreaders, or central individuals that play an outsized role in transmission of a pathogen.

Trends in Parasitology published the review, the first comprehensive synthesis of environmental and theoretical studies of disease dynamics in wild primate species — most of which are now threatened with extinction.

“This review gives critical insights that are applicable not just to conservation, but to our understanding of emerging infectious diseases and human health,” says Thomas Gillespie, lead author of the review and a primate disease ecologist at Emory University. “We hope it helps jump-start a new way of approaching research into disease transmission – one that integrates ecology, behavior and evolution on a grand scale.”

About 60 percent of the more than 500 known primate species face an extinction threat and more than three-fourths of them are on the decline, due to loss of habitat, hunting and disease. Large chunks of the world’s forests are succumbing to agriculture, mining and logging, bringing people, primates, pets and livestock into closer proximity. That juxtaposition sets the stage for more pathogens to jump between humans and our closest relatives. More than 20 percent of wild primate species harbor parasites capable of spilling over into humans. HIV, Ebola, yellow fever and respiratory viruses are examples of viruses shared by humans and wild primates.

“How an emerging pathogen spreads through a species tends to be ‘a black box’ until it causes an outbreak among people,” Gillespie says. The Zika virus, for instance, was first identified in monkeys in Uganda in 1947 but was not widely studied until recently, after it started sweeping through human populations.

Wild chimpanzees in Uganda's Kibale National Park. Chimpanzees, another threatened species of great ape, share 96 percent of human DNA. (Photo by Julie Rushmore)

Traditional infectious disease models generally assume that all individuals within a population have an equal probability of receiving or giving an infection, but more powerful analytical tools are showing that is not the case.

“Especially during the last decade,” Gillespie says, “it’s become much clearer that, just as everything in natural systems is heterogeneous, so is disease transmission.”

The so-called 80-20 rule – 80 percent of disease transmission events in an epidemic are caused by 20 percent of individuals – is now a well-established phenomenon. What’s not yet as well-understood are all of the variations within a disease system, and how these variations can combine to make an individual a super-spreader.

“Primate-parasite networks are an ideal model system for studying these questions,” Gillespie says, “because primate species are so varied and they have sophisticated social structures. We also have behavioral data for many primates – detailing the hierarchical ranking of individuals, and whom those individuals are related to and whom they interact with – collected over decades of observational studies.”

Combining knowledge of behaviors by individual species with data on their parasites can help researchers sort out high-risk traits and identify super-spreaders that contribute to transmission in a predictable way. Such patterns can help researchers to develop targeted interventions.

The review cites the example of a vaccine under development for Ebola virus, which is designed to replicate and spread immunity from a few individuals to others in a population. Targeting the most central individuals in an ape group with such a vaccine may be an effective way to mitigate future Ebola-related ape die-offs and spillover events into human populations.

The review also lays out a vision for the next decade of research into pathogen transmission, one that integrates ecology, behavior and evolution for studies of wild primates, other wildlife and humans.

“In addition to looking at how sociality influences infection, this review highlights the need to understand more about the flip side of that question: How do pathogens affect behavior and shape sociality?” Gillespie says. “We want to get people thinking about questions like this, in parallel networks of species.”

Co-authors of the review include Julie Rushmore of Oregon State University and the University of Georgia, and Donal Bisanzio of the University of Oxford.

Related:
Experts warn of impending extinction of many of the world's primates
Zeroing in on super-spreaders, and other hidden patterns of epidemics

Brain scans of service-dog trainees help sort weaker recruits from the pack

Some of the service dog trainees that were involved in the study pose with an fMRI scanner. (Photo by Gregory Berns.)

By Carol Clark

Brain scans of canine candidates to assist people with disabilities can help predict which dogs will fail a rigorous service training program, a study by Emory University finds.

The journal Scientific Reports published the results of the study, involving 43 dogs who underwent service training at Canine Companions for Independence (CCI) in Santa Rosa, California.

“Data from functional magnetic resonance imaging (fMRI) provided a modest, but significant, improvement in the ability to identify dogs that were poor candidates,” says Emory neuroscientist Gregory Berns, who led the research. “What the brain imaging tells us is not just which dogs are more likely to fail, but why.”

All of the dogs in the study underwent a battery of behavioral tests showing that they had a calm temperament before being selected for training. Despite calm exteriors, however, some of the dogs showed higher activity in the amygdala – an area of the brain associated with excitability. These dogs were more likely to fail the training program.

“The brain scans may be like taking a dog’s mental temperature,” Berns says. “You could think of it as a medical test with a normal range for a service dog. And the heightened neural activity that we see in the amygdala of some dogs may be outside of that range, indicating an abnormal value for a successful service dog.”

The findings are important, he adds, since the cost of training a service dog ranges from $20,000 to $50,000. As many as 70 percent of the animals that start a six-to-nine-month training program have to be released for behavioral reasons.

“There are long waiting lists for service dogs, and the training is lengthy and expensive,” Berns says. “So the goal is to find more accurate ways to eliminate unsuitable dogs earlier in the process.

The study found that fMRI boosted the ability to identify dogs that would ultimately fail to 67 percent, up from about 47 percent without the use of fMRI.

“This type of approach is not going to be feasible for individual trainers and their dogs because of the expense of fMRI,” Berns says. “It would only be practical for organizations that train large numbers of dogs every year.”

CCI is a non-profit that breeds, raises and trains dogs to assist human partners. Its service dog program, designed for disabled people, provides dogs to do tasks such as turn on lights, pick up dropped keys, open a door and pull a manual wheelchair.

Golden retrievers, Labradors — or crosses between the two — are the usual CCI service dog breeds, due to their generally calm and affable natures. After the puppies are weaned, they are adopted by volunteer puppy raisers for 15 months, before returning to CCI to undergo behavioral tests. Those that pass begin training.

For the Scientific Reports paper, the researchers taught the dogs how to remain still while undergoing an fMRI at the start of the training program.

The Berns lab was the first to conduct fMRI experiments on awake, unrestrained dogs, as part of an ongoing project to understand canine cognition and inter-species communication. In an early experiment, dogs were trained to respond to hand signals. One signal meant the dog would receive a food treat, and another signal meant that the dog would not receive one. The caudate region of the brain, associated with rewards in humans, showed activation when the dogs saw the signal for the treat, but not for the non-treat signal.

The researchers adapted this experiment for the current study — the largest yet involving dogs undergoing fMRI. The dogs were taught hand signals for “treat” and “no treat,” but sometimes the signals were given by the dog’s trainer and other times by a stranger.

The results found that dogs with stronger activity in the caudate in response to the treat signal – regardless of who gave the signal – were slightly more likely to successfully complete the service dog training program. However, if a dog had relatively more activity in the amygdala in response to the treat signal – particularly if the signal was given by a stranger – that increased the likelihood that the dog would fail.

“The ideal service dog is one that is highly motivated, but also doesn’t get excessively excited or nervous,” Berns says. “The two neural regions that we focused on – the caudate and the amygdala – seem to distinguish those two traits. Our findings suggest that we may be able to pick up variations in these internal mental states before they get to the level of overt behaviors.”

Berns hopes that the technology may become more refined and have applications for a broader range of working dogs, such as those used to assist the military and police forces.

Co-authors of the study include Andrew Brooks and Mark Spivak from Dog Star Technologies in Sandy Springs, Georgia, and Kerinne Levy from CCI.

Related:
What is your dog thinking? Brain scans unleash canine secrets
Dogs process faces in specialized brain area, study reveals

Atlanta Science Festival celebrates 'frontiers of the unknown'

Participants in the Zombie Outbreak Game scoured Peavine Creek on the Emory campus in 2016 for clues to the cause of a mock epidemic. The popular game returns this year on Sunday, March 19.

By Carol Clark

Watch for an astronaut, zombies, a hovercraft and liquid nitrogen ice cream to pop up on the Emory campus during the Atlanta Science Festival, March 14 to March 25. Thousands of science enthusiasts, of all ages, are also expected to appear for the fourth annual event – which includes lab tours, talks, a planetarium show, movie screenings, science-themed dance and games and lots more interactive fun.

The festival blasts off at Emory this year with a talk by NASA astronaut Mark Kelly. Tickets are going fast in the countdown to the event, set for 7 pm on Tuesday, March 14 at Glenn Memorial United Methodist Church.

“Emory University is proud to be a founder and strong supporter of the Atlanta Science Festival, which is just one example of the university’s engagement with our city and region,” says Emory President Claire E. Sterk. “We welcome the local community to our campus for the launch of the 2017 festival and to hear astronaut Captain Mark Kelly. Captain Kelly is an inspiration to all of us who are seeking to push the frontiers of the unknown.”

Name the ASF mascot

The title of Kelly’s talk is “Endeavor to Succeed.” He will give an insider’s perspective on space travel and the year-long NASA experiment he is participating in with his twin brother, also an astronaut, on how space affects the human body.

The public is invited to enter a contest to name the festival's new astronaut mascot. Entries are due by Friday, March 10 at 5 pm, and the winner will receive four VIP tickets to Kelly's talk.

Following are highlights of other festival events set at Emory.

“STEM Gems: Giving Girls Role Models in STEM Careers,” brings together women leaders from business, academia, NASA and more for a panel discussion on Thursday, March 16. They will offer advice aimed at girls ages 10 and up, who are interested in careers involving science, technology engineering or math.

The “Zombie Outbreak Game” returns to campus this year, on Sunday, March 19, giving participants ages 12 and up a chance to investigate a mock zombie disease outbreak, using real-world tools employed by scientists at Emory and the Centers for Disease Control and Prevention. Actors from Out of Hand Theater will play the patients as participants don masks and gowns and follow a trail of clues through streams, woods and labs across campus.

A dance performance, “Creating a New Normal: Race, Identity, Health and Activism,” will explore the themes involved in working towards an AIDS free generation, on the afternoon of Monday, March 20. The performance will be followed by a conversation with scientists and public health researchers — hosted by the Emory Center for Ethics — on the past, present and future of viral diseases.

“Investigating Our Human Past,” the evening of Monday, March 20, will allow visitors to examine the Emory Anthropology Department’s cast collection of fossilized skulls of our ancestors. Scientists will be on hand to discuss recent advances in our understanding of how the human brain evolved.

The Mathematics and Computer Science Department will present “Unveiling the Internet,” geared for teens, on the evening of Thursday, March 23. Participants will meet in a computer lab to tinker with code and learn concepts like how Snapchat snaps move through space.

Physics Live! set for Friday, March 24

The ever-popular “Physics Live!” returns to the Emory Math and Science Center on Friday, March 24. Children will be entertained with giant soap bubbles, a hovercraft and liquid nitrogen ice cream, among other activities. This year, the physics fun will be joined by a “Chemistry Carnival” at the Atwood Science Center. Chemists will turn into midway barkers, awarding prizes to visitors who play games like Peptide Jenga and Bacterial Telepathy, based on ongoing research in Emory labs.

The Oxford Campus will host a “Critter Crawl” through Oxford Forest on Sunday, March 19, to learn about wildlife native to Georgia. And on Sunday, March 21, an event called “It’s About Time” will bring guests and local researchers together to share scientific and social concepts of time.

In addition to on-campus events, members of the Emory community will be featured in Atlanta Science Festival activities happening throughout metro Atlanta:

“Science and Spirituality” will explore the intersections of physics and faith, biology and belief. The panel of local scientists and theologians will include Arri Eisen, a biologist from Emory’s Center for Ethics. On Thursday, March 16 at First Christian Church of Decatur.

“The Science Behind Tremors, the Movie,” features Emory paleontologist Tony Martin who will provide a lively discussion about real animals that inspired giant fictional worms. On Sunday, March 19 at Fernbank Science Center.

A live show and podcast called “You’re the Expert” will bring together a panel of comedians and podcast host Chuck Bryant, who will good-naturedly grill Emory chemist Cora McBeth about her work. On Tuesday, March 21 at 7 Stages Theatre.

The Exploration Expo, the culminating event of the festival, will include scientists from Emory biology, chemistry, environmental sciences, the Emory Herbarium and the Emory Center for the Study of Human Health. They will be among the hosts of 100 booths offering science-themed activities for families during the culminating event of the festival, set for Centennial Park on Saturday, March 25.