Changing the Carriers

By Cicely Krebill, Biology, 2019

Climate change and the concept of a “carbon footprint” has long been in the forefront of the public’s eye. A new focus, however, in the realm of climate change is now being brought to the table for discussion: the risk of vector-borne diseases coming to new regions in the United States. Vectors, like ticks and mosquitoes, carry diseases that are familiar to most people in the United States, like Lyme’s disease and West Nile Virus. They also carry diseases that are endemic in other parts of the world, like Dengue fever and Chikungunya. One of the reasons why the United States has not yet had to worry about diseases like Dengue fever is because the vectors generally remain in the climates that best suits them.

Although an influx of mosquitoes and ticks is usually just seen as a nuisance, what they are potentially bringing to the United States and exposing the population to is much more alarming. Dr. Mary Susan Potts-Santone, a professor in the College of Science, worries that, “Dengue fever is going to be a big issue in the U.S., and the Chikungunya virus as well. It’s because we’ve got this invasive Asian Tiger mosquito who is definitely going to spread with climate change. They are already thinking we’re going to see pandemics of it.” Both of these viruses lack preventative vaccines and treatment. As a result, they would pose a very real threat if brought to the U.S.

Part of the problem regarding climate change is that it affects the vector species’ survival and movement by affecting the species’ access to food resources as well as prevalence of its competitors and predators. The triatomine species, commonly known as “kissing bugs,” are the vectors that carry Chagas disease to humans when they bite and infect them. They are particularly sensitive to climate change. When the temperature increases, the bugs feed more to avoid dehydration, thus increasing the spread of the disease. Although there is an effective treatment for the disease, it is still potentially life threatening if not caught early on. Many people do not know that they have been infected because the disease is often asymptomatic and is only diagnosed when severe cardiac disorders or digestive alterations appear later in life and can lead to death.

Chagas disease currently affects between six and seven million people in Latin America, where the vector lives in cracks of homes. Because of the proximity of the vector’s natural habitat and the potential severity of an untreated infection, there was previous fear that this species would migrate up to the U.S., bringing Chagas disease with them. Recent findings, however, by military scientists in Texas suggest something different: the vector carrying the disease is already here. Similarly, the Center for Disease Control reports that the vector has been found as far north as New York. Few reports of new cases of Chagas disease have been made. This could be because the disease can be asymptomatic and therefore leading it to be under diagnosed. “It’s something that our physicians haven’t had to recognize and deal with that frequently. It’s not their first thought, but in fact we may be seeing more of it in the not so distant future,” Potts-Santone says.

Many of the diseases that have the potential to migrate to the U.S., including Chagas, Dengue fever, and the Chikungunya virus, are considered neglected tropical diseases — meaning that they cause substantial illness globally, affecting the world’s poorest people. Yet, they receive disproportionately less research and funding. Potts-Santone thinks this might change if these diseases migrate to the U.S.

Potts-Santone believes that if these diseases start to become endemic, the funding will change. One of the problems is that these diseases primarily affect people in poverty and immigrants with limited access to healthcare. This adds a lot of political pieces to the discussion, but Potts-Santone thinks, “They absolutely should be funding it.” Many researchers have echoed these sentiments as well, including a research group from the University of Texas-Pan American who believes that more funding should be contributed to understanding the movement of these vectors to better alert regions of risk.

Although the exact regional risks and predictions of which diseases are most likely to come in is still relatively unknown, Potts-Santone said the likelihood is that “if conditions get warmer and remain humid, some vectors that haven’t been here previously could now move into our areas, bringing in whatever they’ve got.”