Though they are one of America’s favourite game animals, white-tailed deer are basically walking bags of disease. From Lyme disease and chronic wasting disease to the bluetongue virus, deer just can’t catch a break, and now the news is even more bleak because, according to a new study, they also carry a native form of malaria. The good news is that humans are likely unaffected by it.
The research team, led by Ellen Martinsen from the Smithsonian’s Conservation Biology Institute, estimates that between 18 and 25 percent of white-tailed deer living along America’s East Coast are infected by Plasmodium odocoilei, a malaria parasite, which makes white-tailed deer the first and only mammal species in North or South America to carry a native form of the disease.
Martinsen discovered the parasite by chance while collecting mosquitos from the Smithsonian’s National Zoo, in hopes of finding a malaria parasite that might infect birds. After her initial discovery, a team of researchers from multiple universities helped analyse the parasite to verify her results.
After examining their findings, the team concluded that, even though much of the white-tailed deer population is infected, the parasites are "cryptic", meaning that deer only have small amounts of them inside their bodies. At this point, they have no idea if the disease is hurting the deer population or not - a question that will take more research to fully answer.
The real question is where did this form of malaria come from? According to Martinsen, an ancestor of the white-tailed deer likely travelled to North America from Eurasia about 4.2 to 5.7 million years ago. In doing so, this ancient deer probably brought a form of malaria with it.
From there, the parasite - like all living things - evolved into different species, and one of those species eventually became the version recently found in American deer. This means that the white-tailed deer population has, for all intents and purposes, always had this parasite living inside of them.
Though malaria is a vicious disease that plagues many parts of the world, the team fully believes that deer malaria doesn’t pose any sort of threat to humans. However, their discovery points out that sometimes parasites can live right in our backyard and we should keep an eye out for them, especially with Zika virus - another disease spread by mosquitos - causing wide-spread panic in South America.
The newly found parasite is also forcing researchers to rethink previously accepted theories about how malaria interacts with mammals, which basically opens the door for a bunch of new research and scary questions. For example, could this parasite already infect other hoofed animals in America, such as diary cows? We certainly hope not, but only time and research will tell.
Hopefully, the latest find will enable us to better understand one of the most widely spread disease currently in existence.
The study has been published in Science Advances.