How a Virus Creates Zombie Insects

Written by DNA Learning Center Blog

Photograph courtesy of the USDA Forest Service via Wikimedia Commons

Kelli Hoover and her research team from the Penn State have found out how a virus can change the behavior of a host organism. The result is destructive for the gypsy moth but excellent for the virus.

Gypsy moths are an invasive species. In its larval stage caterpillars damage roughly a million acres of forest in the U.S. each year by feeding on tree leaves. But the damage would be greater if it weren’t for a pathogen called baculovirus that infects these caterpillars and causes them effectively to engage in suicidal behavior.

Viruses can’t live on their own, so they infect other organisms to help them survive and reproduce. They therefore need to find ways to spread to new hosts to continue living.

Researchers have known for over 100 years that caterpillars can be infected by baculoviruses, especially species of monarch butterfly and gypsy moth. After infection the virus blocks molting, this is casting off a part of its body’s outer layer, and keeps the caterpillars in a constant devouring state. Normally male gypsy moth caterpillars molt five times during their lives, while females molt six times before they pupate, which means they are undergoing transformation, and subsequently emerge as moths. But infected caterpillars remain very hungry and constantly crave more food. By expanding the caterpillars’ feeding stage, the virus maximizes the amount of biomass (food and energy) available for viral replication.

Infected moths also change their climbing behavior to get more tree leaves. Gypsy moth caterpillars are active at night when they climb up trees to feed,  but during the day they hide in the soil or bark crevices to protect themselves from predators, such as birds and squirrels. Baculovirus-infected caterpillars climb to the treetops during the day to reach fresh food, then they remain there until they die because the virus uses most of the host tissue to reproduce. The virus is so successful in inducing this “tree top disease” that in the U.S. it has been sprayed on trees to help control gypsy moth outbreaks since the early 1970s.

The exact mechanism of this suicidal behavior has intrigued researchers for centuries until Kelly Hoover presented an elegant explanation in September 2011 in the journal Science. Her team found that the virus transforms caterpillars into hormonal slaves. The baculoviral gene egt encodes the enzyme EGT (UDP-glycosyltransferase) in the caterpillars, which inactivates the molting hormone, ecdysone (20E), once EGT levels become high enough. But when 20E is inactivated, the caterpillars remain in a constant feeding state in the treetops where the majority die, liquefy and rain down viral particles over the leaves for other hosts below. The new hosts ingest the viral particles and become infected, continuing the cycle.

The virus seems also to tell the caterpillars to travel to the top of the tree, a location that is optimal for its transmission to new hosts. Whereas the ‘tree top disease’ changes climbing behavior, older caterpillars infected with the virus are induced to die on the bark next to where other gypsy moth will come to pupate, meaning they have to pass over the dead and infectious cadavers, enabling the virus to easily pass to the next generation during egg larving. This is a wonderful example for host-virus co-evolution as the most important challenge for a virus is “outcompeting” other viruses and finding a stable reservoir for its own replication. So baculovirus is a clever virus that makes its host die in a place that effectively spreads itself to other hosts, providing a big advantage.

With this study, Hoover and her coworkers were one of the first to identify a single gene of a parasite responsible for manipulating the behavior of the host animal. This concept is known innature but the underlying mechanisms are not well understood. Many parasites control their hosts’ habits, including toxoplasmosis and rabies in mammals. The parasitic disease toxoplasmosis mostly infects cats, but if a mouse becomes infected with toxoplasmosis, they lose their innate fear of cats and become easier to catch for dinner. This benefits the infecting protozoa because it is more easily transmitted to its preferred host. Similarly, the rabies virus causes normally nocturnal or shy animals to appear during the day and to become far more aggressive than normal.

Since scientists now know precisely how baculovirus functions in gypsy moth, we can create modified virus-strains to act as weapons against outbreaks. The great advantage is that this virus is specific for gypsy moth larvae but is harmless to all other animals, insects and plants in the treatment zone. This is therefore a far better treatment than alternative pest control methods like spraying pesticides and deadly fungi.

Zombie bees found in S.F. Chronicle hives

A phorid fly laying eggs inside the abdomen of a honeybee. 

Written by Meredith May,  San Francisco Chronicle, August 9, 2012

Photo by Christopher Quock, San Francisco State University

The professor had warned us.

After several months of using a light lure to trap our Chronicle bees at night, researchers at San Francisco State University have found zombie bees in our hives.

In late July, a sample of our bees taken to the S.F. State lab proved to be infested with Apocephalus borealis, a small parasitic fly that lays its eggs inside the bee so its hatchlings devour the host from within.

The invasion causes the bee to have a neurological meltdown and exhibit strange behavior, such as flying at night toward light.

Eventually the bee dies, and the fly pupae emerge from the soft part of the bee's neck.

Which is exactly what happened after biology Professor John Hafernik and graduate research assistant Christopher Quock collected 18 bees from our rooftop apiary on their fourth visit.

Five days later, they spotted seven fly pupae that had emerged from one of our bees.

"I'm not surprised we found zombie bees, because we've found them in a majority of the hives we've looked at," Hafernik said.

The researchers have found zombie bees in 77 percent of the Bay Area hives they've checked, including colonies in Walnut Creek, Marin, Redwood City, on their own campus and now atop The San Francisco Chronicle. Apocephalus borealis has also been found in commercial hives in the Central Valley and in South Dakota.

San Francisco State just launched a citizen scientist website at www.zombeewatch.org to collect more data from backyard beekeepers.

What is unclear is whether honeybee colonies have been successfully living with the flies all along, or if this is a new threat that's growing.

Commonly known as the phorid fly, there are 4,000 species worldwide, but only a handful that attack honeybees, mostly found in Costa Rica, Mexico and Colombia. Apocephalus borealis are native to North America, first reported in Maine in 1924, and later Alaska and New Mexico - but those flies were attacking bumblebees and paper wasps.

So it was shocking when Hafernik and Quock discovered flies emerging from honeybees they collected at San Francisco State in late 2008, leading beekeepers to wonder if phorid flies are a major contributor to the annual 30 percent drop in the honeybee population known as colony collapse disorder.

To get closer to an answer, Hafernik and Quock are gluing glitter-size radio tags on campus bees to monitor the bees' comings and goings, with a laser beamed over the entrance to their laboratory hive.

The goal is to see whether parasitized bees are also leaving the hive during the day. They are trying to understand if bees are sacrificing themselves and saving the colony by abandoning it.

Right now, our Chronicle bees have what Hafernik describes as a "light infestation." But it could get worse.

In California, parasitism peaks in fall and early winter.

"There's nothing a beekeeper can do at this point until we know more about colony behavior and co-existence, or not, with the fly," Hafernik said.

Plants Vs Zombies... the official first-person shooter? Might actually be happening

Written by Justin Towell, GamesRadar.com, August 9, 2012

Plants vs Zombies is perhaps the ultimate tower defense game. But even though you're in direct control of arranging your garden, you never really get to shoot the seeds at the zombies yourself. Incredibly, there are signs that might be about to change - namely a combination of industry rumour and a job advert for a new PopCap team. We might be about to get Plants vs Zombies as a first-person shooter, apparently for consoles and allegedly in the style of Team Fortress 2. Say what?

According to Kotaku, an unnamed source close to EA in Canada has said that several former members of EA's Black Box studio is working on a Plants vs Zombies console title that's "in the vein of Team Fortress 2". The source says the idea still has to be submitted to PopCap for approval later this month, even though development on a prototype has already begun. If true, that means there probably exists some form of rudimentary PvZ FPS already, somewhere.

It's all backed up by the job advertisement which advertises a role in "an exciting new PopCap team in Burnaby". That's in Canada, geography fans. The advert lists among the requirements:

- Expert knowledge of the human anatomy, form and weight (that'll be zombies falling over and their heads rolling away, presumably).

- Experience animating a wide range of characters and creatures, both human and non-human forms (zombies and plants, then)

- Able to create animation and interpret from various reference material, including storyboards and video clips (make 3D models of the 2D artwork)

- Strong ability to express emotion and exaggerate movement through animation techniques (just like the exaggerated animation style of PvZ).

It's almost too obvious. It also states: "The Animator will be involved from idea and prototype creation and the directing of actors and stuntmen during motion capture sessions, to the final stage when animating and implementing the results into the game."

So presumably someone's going to have to pretend to be a zombie. And perhaps a Wall Nut.

We should imagine even Nicholas Cage would have a hard job doing that one.

We quite like the idea of the game... although if we're totally honest, we'd rather just have Plants Vs Zombies 2 and yet more evolutions of Team Fortress 2. Sorry. And also, we have to point out... wouldn't playing as the plants get boring? After all, they are by their very nature 'rooted to the spot'.

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Top 5 Zombie movies (and TV shows) EVER!

By Karen D'Souza, ContraCostaTimes.com, August 8, 2012

The zombie invasion has begun. The flesh-eating contagion has spread to every corner of our culture from video games and movies to television. Here's my list of the Top 5 Zombie movies, and TV shows, ever. Grrr! Argh!:

1. "The Walking Dead": AMC infected the small screen with the zombie virus in high style with this thoroughly addictive drama. Half soap opera, half adventure series, it's a great TV show that just happens to be about zombies.

2. "Zombieland": Zombies head to the amusement park in this snarky next-gen horror movie starring Emma Stone and Jesse Eisenberg. Best thing about Zombieland? No Facebook status updates!

3. "Shaun of the Dead": This British charmer marries horror and comedy in one of the funniest tributes to the George Romero canon ever.

4. "28 Days Later": Zombies move at warp speed in this terrifying thriller about a monkey disease that goes viral and wipes out the world's population.

5. "Night of the Living Dead": The uber zombie movie. Cinema maverick George Romero gave birth to the universe of flesh-eating monsters as a parable about race relations in America.

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Houston uses video to teach how to handle shooting (VIDEO)

 

By RAMIT PLUSHNICK-MASTI, Associated Press, August 1, 2012

HOUSTON (AP) - Ominous music plays as a man in dark clothing, sunglasses and a backpack walks toward people working in a high-rise building. The narrator's voice warns: "It may feel like just another day at the office, but occasionally life feels more like an action movie."

Moments later, the man opens fire on a security guard near an elevator.

It's the beginning of a nearly 6-minute video created by the City of Houston in an effort to teach residents what to do during a shooting. Local Homeland Security officials said they realized during training exercises that first responders knew how to react but citizens were far less knowledgeable.

The video emphasizes a short mantra _ run, hide, fight _ to help people remember their options. The video was made using $200,000 from a federal grant, and its release was expedited following last month's movie theater shooting in Aurora, Colo.

"As children we're all taught by the fire department to stop, drop and roll if you're on fire," said Richard Retz, who works for the Mayor's Office of Public Safety and Homeland Security and helped produce the video. "Unfortunately, with our society the way it is today, we felt that there had to be a new one."

Several countries and other U.S. cities have done educational campaigns on similar topics, including a long-running one in Israel that tells people what to do if they see an unattended package. Such campaigns can be effective because they bring incidents people see on television closer to home, said Danny Davis, director of a homeland security graduate program at Texas A&M University.

The overall advice in Houston's video was useful, he said, though whether a person should run or hide before attempting to fight back depends on the situation.

"You're not going to turn a civilian into a commando with a short video, but at the same time you can at least put in the back of their mind the possible options," Davis said. "I particularly like the idea that they had in there the idea of fighting. When it comes down to it, and it's about survival, you better consider fighting."

But the video's lack of information about using a weapon in self-defense was a "glaring shortcoming," he said, noting Texas' concealed weapons law. Davis suggested that the Colorado shooting, which killed 12 people, may have ended differently had someone in the theater been armed and fired back.

Houston officials considered including a segment in the video advising armed residents to use their guns if possible. But when they delved into the facts, they got a surprise: Despite Texas' more relaxed gun laws, only about 2.7 percent of state residents are legally armed, Retz said.

What level of training each of those gun owners has and how they would react "is an entirely different story," Retz said, adding that the city wanted to produce a video for the general population.

Following the three-day shooting rampage in Mumbai, India, that killed 166 people in 2008, Houston officials decided to use grants from the U.S. Department of Homeland Security to train first responders to deal with a similar incident. They quickly realized first responders were well-equipped to handle such a situation but citizens were not, Retz said.

Houston used money from a $3.6 million federal grant to research and produce the movie, said Dennis Storemski, director of the Mayor's Office of Public Safety and Homeland Security. Filming began in May and the DVDs arrived in mid-July, days before the Colorado shooting.

Initially, Houston officials planned to release the video in a well-coordinated safety campaign, as the city has done in the past for hurricane or flood preparedness. The shooting in Colorado, however, changed the thinking.

"The fact that the shooting was on everyone's mind, we felt that it was important to get it out there as quickly as possible," Retz said.

Since being posted on YouTube a week ago, the video has been viewed more than 220,000 times, and Retz's email has been flooded for requests to reuse the movie _ from agencies across the U.S. and as far away as England and Germany _ a response he called surprising. The city also plans to distribute it in a more organized safety campaign that would reach workplaces and possibly schools.

"Visual media or video is universal," Retz said. "We wanted something that was compelling, that would draw their attention, but it was short and to the point."

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