By chance, she had discovered a malaria parasite, Plasmodium odocoilei--that infects white-tailed deer.  North America’s most popular game species, the white-tailed deer, harbors a secret: low levels of a malaria parasite that have only now been detected thanks to advanced DNA technology. "It's a parasite that has been hidden in the most iconic game animal in the United States. (Scientists had largely discounted the significance of a 1967 report of what appears to be the same parasite in single specimen of white-tailed deer in Texas.) But now Martinsen and her colleagues have discovered that the deer malaria is widespread--though it's "cryptic" she says, because the parasites occur in very low levels in many of the infected deer. Combined with sensitive molecular PCR techniques to understand the genetics, the team confirmed a high prevalence of the disease--between eighteen and twenty-five percent--in sites ranging from New York to West Virginia to Louisiana. The new research suggests that these malaria parasites have a long evolutionary history in the New World, dating back to the ancestors of white-tailed deer that made their way to the continent across the Bering Land Bridge 2.3 million to 6 million years ago Other as-yet-to-be discovered malaria parasites of mammals may be “hidden in plain sight,” the researchers write. Ellen Martinsen completed her undergraduate and doctoral training at UVM in Joe Schall's lab and went on to do her postdoctoral research at the Smithonian Conservation Biology Institute's Center for Conservation Genetics.
– Talk about a surprise: Two years ago, scientists researching avian malaria happened to learn that two strains of the parasite are infecting white-tailed deer—possibly 25% of those living on the East Coast, Smithsonian reports. Until then, no endemic malaria had been seen in North or South American mammals. "You never know what you're going to find when you're out in nature—and you look," says lead study author Ellen Martinsen, per a press release. "It's a parasite that has been hidden in the most iconic game animal in the United States. I just stumbled across it." Her team was screening mosquitoes for avian malaria at the Smithsonian's National Zoo in Washington, DC, when they stumbled across some surprise DNA and found that the insect had fed on white-tailed deer. Researchers then screened more than 300 white-tailed deer and found the parasite in 41 of them, in roughly half the states studied, Science reports. None were in the west, but it was common in the east, particularly in West Virginia and Virginia. Seems the two malaria species pose little risk to deer or to people: Though humans haven't been tested for the strains yet, co-author Robert Fleischer says "if it’s getting into humans, which it probably is, it probably isn’t able to reproduce. ... This is not Zika virus." The deer's ancestors may have brought the parasite into North America by way of the Beringia land bridge millions of years ago, researchers say. So how is it no one noticed malaria before in the much-studied deer? "This story suggests there is still much we don’t know about the natural world," says a biologist not involved in the study. (Meanwhile, Lyme disease is spreading across US counties.)