In an event coordinated with the St. Mary’s County Health Department, St. Mary’s County of Maryland (SMCM) hosted an event titled “Changing Threats: Impact of Climate and Environmental Change on Tick-Borne Disease” on Oct. 22. The event was introduced by Dr. Meena Brewster, an adjunct professor of environmental studies, who is also the St. Mary’s County Health Officer. The speaker was Robyn Nadolny, PhD, who is a biologist and program coordinator at the Tick-Borne Disease Laboratory for the Army Public Health Center.
The Tick-Borne Disease Laboratory runs a program called the Human Test Tick Kit Program (HTTKP) which tests ticks collected from Department of Defense personnel, including all branches of the military. Once a tick has been collected, it is sent to the Tick-Borne Disease Laboratory where they test the tick for possible diseases. The results of the test are then reported back to the tick-bite victim.
Using this information the Tick-Borne Disease Laboratory is able to track tick-borne disease across the United States based on the reports they’ve received. From the HTTKP, the laboratory has seen that the population of lone star ticks has increased dramatically in the last 20 years in Fort Meade, MD. Maryland is in the top 20 percent of states with tick disease cases.
Ticks are responsible for at least a dozen human pathogens in the U.S., including Lyme disease, Rocky Mountain spotted fever and red meat allergy. Ticks find hosts in animals that they latch onto and feed off of, falling of the host when they’ve had enough blood. If the host a tick feeds on has a pathogen, the tick will ingest that pathogen. Ticks with pathogens can then infect hosts with the pathogen as well. When ticks latch onto humans, ticks are able to pass on the pathogens if they’ve been infected with one.
States in the Northeast, Midatlantic and Upper Midwest have the majority of ticks and tick-borne disease cases, but in recent years ticks have been expanding their territory across the U.S. Climate change means warmer areas in the U.S., so the hosts ticks live on also expand their territories, so the ticks are able to move farther than before. Climate change also means shorter winters kill off fewer ticks, increasing their populations and also increasing tick-borne diseases.
The shorter winter also means that the nymph ticks and adult ticks feed on hosts at the same time, which infects more of the nymph population because infected adult ticks will pass on diseases to nymphs. In turn, more nymphs are infected with tick-borne diseases and as they grow the adult population will carry more disease. Ticks are also able to survive extreme weather conditions, as they are able to adapt to climate differences.
The spread of tick territory also affects animal populations, as ticks host on many different animals such as deer, mice, birds and lizards. In a 2018 New York Times article titled “47,000 Ticks on a Moose, and That’s Just Average. Blame Climate Change,” scientists tagged moose calves in order to count the tick populations on them. Moose calves often die from the large number of ticks on their bodies, the article stated that they can die from “anemia, which develops when many ticks drain a moose’s blood.”
Dr. Nadolny suggests checking your body for ticks each time you return from spending time outdoors in places that may have ticks. There are other resources to that track tick activity in the U.S. such as TickEncounter and the Centers for Disease Control and Prevention has more information about tick-borne diseases and the areas they are most common.