Scientists scramble to forecast where and when the disease-carrying arthropods pose the most danger
Many factors, not all of them well understood by scientists, shape where and when disease-carrying tick species will thrive-and if they are likely to carry a pathogen at all.
Personal protections-such as long sleeves, tick repellents and regular checks of humans and companion animals-are the best defenses currently available against the ticks that carry these diseases.
Because some tick protections are annoying and difficult to maintain, says Richard Ostfeld, a disease ecologist at the Cary Institute of Ecosystem Studies, "You don't necessarily want to employ those methods all the time everywhere. But you might want to employ them where there's high risk." That's where a tick forecast would come in handy: a "Heat map" showing which areas can expect high numbers of disease-carrying ticks at a given time would allow residents and visitors to gear up when they have to but relax their vigilance when conditions are safer.
The influence of each of these factors varies according to what tick species are involved and can also change according to each species' preferred kinds of habitats, says Rebecca Eisen, a research biologist at the National Center for Emerging and Zoonotic Infectious Diseases.
If a tick feeds on an infected white-footed mouse, the tick has a 90 percent chance of picking up the bacterium that causes Lyme disease, says Felicia Keesing, a Bard College disease ecologist.
Scientists are working to perfect models that combine known tick factors and spit out something that resembles a weather forecast but for tick abundance.
In order to begin filling that gap, since 2018 the CDC has been publishing national tick surveillance data to pinpoint the current range of several medically important ticks.
"The resulting maps help us to identify areas where it looks like environmental conditions are suitable for the tick or pathogen to persist," Eisen adds, "But where we haven't yet found records of the tick or pathogen." Then they go looking for evidence of ticks and tick-borne illnesses in those locations.
Even without a forecast model, records of past tick activity can indicate potential disease hotspots of the future.
Still, unlike the maps that a weather forecast might use to show the areas at risk of heat or rain, these tick maps merely indicate where disease has already been found-not where it might already be spreading undetected.