![]() ![]() Why is a widespread bird virus absent from the DNA of any birds, but present in the DNA of three mammals that are separated by the Indian Ocean? And how does it move from mammals to birds (or vice versa) anyway? Retroviruses shouldn’t be able to do that. The only hits came from the narrow-striped mongoose (another Madagascan mammal), and the short-beaked echidna-a spiny, egg-laying mammal from Australia. ![]() Niewiadomska and Gifford screened the genomes of other animals for similar fossilised viruses, but they couldn’t find any in birds. It stunts their growth, weakens their immune system, and occasionally causes cancer. REV and its relatives infect a wide range of poultry, including chickens, ducks and geese. But its closest relative turned out to be a bird virus known as reticuloendotheliosis virus (REV), which was first isolated from a turkey in 1957. ![]() Finding another one in the ring-tailed mongoose wasn’t odd. Niewiadomska and Gifford specialise in studying these fossilised viruses, and they’ve found more than anyone ever expected. An incredible 8 percent of your genome consists of these “endogenous retroviruses” or ERVs. These sequences sometimes get passed down the generations and turn into genetic “fossils”-remnants of ancient infections that are now permanent parts of their hosts. Many viruses-the retroviruses, in particular-have a habit of inserting their genes into the genomes of their hosts. A few years ago, virus hunters Anna Maria Niewiadomska and Robert Gifford were scanning the mongoose’s DNA when they noticed the complete genome of an ancient virus. It has a sinuous, rusty body and a fuzzy tail with black and red stripes. The ring-tailed mongoose, a native of Madagascar, looks like a cross between a ferret and a red panda. ![]()
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