In Finding out Sick Fish, Researchers Trace Historical past Of Fevers

Enlarge this imageIf they are in a position to swim to incredibly hot water, carp will survive an infection using a kind of herpes virus.Jean-Louis Wertz/University of Liegehide captiontoggle captionJean-Louis Wertz/University of LiegeIf they are ready to swim to very hot drinking water, carp will endure an infection using a variety of herpes virus.Jean-Louis Wertz/University of LiegeEach 12 months, fish farms produce a large amount of carp so much that in the event you set all that fish on a person facet of the scale, and all of the persons living in the U.S. over the other side, they’d rather a great deal harmony just about every other out by body weight. But for your earlier few of many years, carp have been suffering from a sort of herpes virus, referred to as Koi herpesvirus. Now, as researchers report this week inside the journal Mobile Host & Microbe, there’s a simple way to prevent fish from dying of the virus. And during their investigation, the researchers also found something intriguing about how fish and humans fight infection. The virus first appeared while in the 1990s, when carp around the world started dying. “The virus emerged from nowhere. We have no idea where it came from,” says Alain Vanderpla schen, an immunologist at the University of Liege in Belgium who studies carp. “A healthy fish is very proud, very fairly to look at,” he says. Infected fish, within the other hand, would lie at the bottom of the tank, their fins limp and bodies secreting a cloud of mucus.”You won’t eat these carp. They look really ugly,” says Vanderpla schen. The virus was killing off swaths of fish, delivering a big blow to the industry. So Vanderpla schen and colleagues set out to develop a vaccine. Within the proce s of that research, they noticed that ill fish would huddle around the aquarium heater, he says, “like they were trying to warm up a little bit.” Maybe, he thought, heat could help them fight infection. It’s been recognized for a while that fish (and other animals that can’t generate heat internally) could help their immune systems fight off an infection by moving to a warmer spot. The phenomenon is called “behavioral fever.” Vanderpla schen and his colleagues wondered if a certain temperature would allow the fish to vanquish the virus. So they built a tank with three chambers connected by tunnels. One chamber was 75 degrees Fahrenheit, the temperature that carp normally thrive in. Another was 82 degrees, and a third was almost 90 degrees a temperature considered way too scorching for carp to be happy. (The drinking water in a very hot tub, by comparison, tends to be about 100 degrees.) When the scientists dropped healthy fish while in the tank, the fish would explore the chambers and eventually settle from the coolest just one. But carp infected with the herpes virus would settle in the very hot compartment. “It’s really too warm, but they decide to go there,” says Vanderpla schen. “And they will stay there for a few days. And as soon as they reach this temperature, they completely control the viral infection.” All the infected fish that hung out in scorching drinking water fought off the an infection and survived. And all the infected fish that were kept in colder h2o died. If carp farms would just give fish an option to swim to warm h2o, says Vanderpla schen, they might not have to worry about losing a bunch of fish to the virus, or about vaccinating them to prevent that from happening. It’s a simple solution to a complicated problem. “But that’s just the beginning of the story,” says Vanderpla schen. Something else about the infected carp grabbed his attention. Usually, animals including humans will become feverish soon after getting infected. But the carp waited about five or six days after an infection before swimming to very hot water. That meant the virus had almost a week to replicate inside the fish, making them more and more ill as they days pa sed. Why, the researchers wondered, did it take them so long to start their fever behaviors? Maybe, they hypothesized, the virus was somehow controlling the fish, preventing it from swimming to warmer water. After four years of research, the experts have concluded that yes, the virus does control the behavior of infected fish. The virus, they found, secretes huge amounts of a certain protein, called ORF12, into the carp’s blood. And that protein scams the fish immune system, acting as a decoy receptor for another protein, TNF-alpha, that the body normally uses to alert the immune system that it’s time to mount an attack. It was intercepting those signal proteins before they could reach their destination to alert the immune armies.AnimalsHow A Clever Virus Kills A Very Hungry Caterpillar When the researchers created a version of the virus that was incapable of producing ORF12, the fish would swim to scorching water shortly after infection and get rid of the an infection quickly. So with just 1 gene, encoding for a single protein, the virus was capable to hold the fish back until the virus had multiplied. That’s interesting for a few of reasons. “On one particular hand, it’s interesting from a very practical point of view, from an aquaculture point of view,” says Maureen Purcell, a research microbiologist with USGS’s Western Fisheries Research Center. “Koi herpesvirus is actually a pretty serious virus,” she says, and the aquaculture industry is still looking for a silver bullet to fight it. (To the opposite end of the spectrum, the Australian government has considered releasing the virus on purpose to get rid of invasive species.) Purcell says men and women have looked into manipulating aquarium temperatures to help fight disease. “This is different. Here, they are showing that the animals can do this behaviorally themselves, not through human manipulation,” she says. “And then to show that the virus has figured this out and come up using a way to delay this behavior is really interesting. The virus is delaying [the fever] so that it can replicate and become established.” There are very few examples of viruses that can control the behavior of their hosts. There are a couple in insects, like a single virus that can make a caterpillar climb up to the top of a plant, where a bird can easily snatch it up. And then there’s rabies, which causes lesions while in the brain that induce the animal to become aggre sive, pa sing the virus through their saliva during bites. But that’s pretty a great deal it. “It’s a great paper because it shows to the very first time the mechanism by which a viral agent in fishes is able to actually use the machinery of the organism to prevent the development of the fever,” says Robert Dantzer, a psychobiologist at the University of Texas MD Anderson Cancer Center who studies the interaction between the brain and the immune system. The opposite interesting piece is that the same molecules control fevers in fish and in humans. People today didn’t know that the protein TNF-alpha signaled to a fish that it was time for a fever. It’s the same protein that sets off fever in humans. “The two mechanisms rely over the same set of initial molecules, which is really fascinating and unexpected,” says Vanderpla schen, because the ancestors of fish and humans split off from each other more than 400 million years ago. That means that fevers probably originated back when all animals had a fishlike inability to generate their own heat, says Vanderpla schen. “Fever is not something bad,” says Vanderpla schen. Instead, he says, it’s an ancient and beautiful survival mechanism.