When scientist Ellen Martinsen was collecting mosquitoes two years ago at the Smithsonian’s National Zoo, she was attempting to find some that might potentially harbor a type of malaria that might infect birds, an avian form of the disease. Instead, she discovered a previously unknown DNA profile that existed in the parasites in some of the mosquitoes, which she later identified as carrying two lineages of malaria that do not appear to cause harm to humans, but lives in white-tailed deer, according to Smithsonian magazine.
Martinsen eventually found two “lineages,” or types of maria that infect white-tailed deer, though the parasites that cause both have only been found in an estimated 25 percent of the population of the mammals along the East Coast of the U.S. The malaria has not been detected in other types of deer so far, like mule deer and blacktail deer, and it has not been discovered in elk or pronghorn sheep. Other types of deer, like brocket deer and reindeer, as well as moose, have not yet been tested.
The name of the malaria parasite that Martinsen found in the white-tailed deer is Plasmodium odocoilei, according to the Eurasia Review. It is the first-ever known type of malaria parasite known to live in any species of deer. It is also the first-known type of malaria discovered to live in any mammal in North or South America, other than humans.
Though an article in Science mentions that “a 1967 report of what appears to be the same parasite in single specimen of white-tailed deer in Texas,” scientists had largely discounted that malaria was actually found in white-tailed deer until Martinsen’s discovery.
White-tailed deer are the most-closely studied species of wildlife in North America, but nobody had previously known that the deer can carry a type of malaria. Probably some of the very first white-tailed deer in the U.S. who traveled across the Bering Land Bridge became infected by the parasites, which might be native to the Americas. Martinsen and her colleagues think that is the case, with Martinsen stating, “We think malaria is native to the Americas, that it’s been here for millions of years.”
Martinsen led a study on the two lineages of malaria she had discovered in white-tailed deer, along with scientists from the University of Georgia, the Smithsonian Conservation Biology Institute,the National Park Service, the American Museum of Natural History, and also the malaria expert and biologist Joseph Schall from the University of Wisconsin-Milwaukee–and UVM. As Martinsen noted, “It’s a parasite that has been hidden in the most iconic game animal in the United States. I just stumbled across it.”
According to Martinsen, the two lineages of malaria that she and the other scientists wrote about in the study that was published this past week in the journal Science Advances split from each other probably around “2.3 to 6 million years ago,” according to the Eurasia Review.
Martinsen’s discovery that malaria infects approximately a fourth of the population of white-tailed deer in the U.S. came as a complete surprise to her, as she was looking for mosquitoes that transmitted an avian type of malaria. It was not the first time anyone had discovered an infectious disease in zoo animals before anyone knew that it existed. Another example of a disease that was first discovered in animals at a zoo is the West Nile virus.
By John Samuels