The Quest for a ‘Tick Map’

Predicting where the ticks are likely to be concentrated is the ideal public health strategy to slow down the spread of tick-borne illnesses. Researchers are trying to come up with an accurate way of predicting where dangerous ticks might be. It would be great if a program could be used to anticipate danger areas.

It is always a good idea to be aware of tick-borne illness. Hikers can take extra precautions if they know that the woods they are passing through are likely to have dangerous ticks. Health care providers can look out for symptoms of tick-borne illnesses. During the danger season, local officials can tell citizens how to care for themselves outside. Accurate predictions are hard to make. Many factors, not all of them well understood by scientists, affect where and when disease-carrying tick species will thrive.

People are diagnosed with and treated for tick-borne diseases every year. Estimates from the U.S. Centers for Disease Control and Prevention show that the annual figure is nearly half a million. As tick species expand their ranges, that number is expected to increase. The best defense against the ticks that carry these diseases are personal protections. It's not enough to simply tell people that risk exists, it's important to put such measures in place.

"You don't necessarily want to use those methods all the time everywhere because they are difficult to maintain." You may want to use them where there is high risk. 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 better. Knowing where and when you are at risk is one of the benefits of personal protective measures.

The risk level increases and decreases with the number of ticks. An abundance of suitable animal hosts, warm winters, humid summers and habitats with lots of vegetation but low plant diversity are some of the things that scientists know can make these numbers increase. Cold winters, hot and dry summers, and tiny fungi that live in soil and attack bugs are some of the things that lower the tick population.

According to Rebecca Eisen, a research Biologist at the National Center for Emerging and Zoonotic Infectious Diseases, the influence of each of these factors varies depending on what tick species are involved and what habitat they prefer. In grassy areas, American dog ticks, which spread diseases, thrive. Deer ticks are more likely to live in forested areas.

The effects of environmental factors on tick numbers can be stronger than first thought. The Cary Institute studied fields in New York State for decades and found a correlation between oak trees and deer tick populations. During strong acorn years, the white-footed mouse's population shot up, and its furry bodies are a great source of blood for the ticks.

Other factors can affect the spread of tick-borne disease, but not necessarily on the tick population. White-footed mice have been shown to be carriers of a number of ailments that can be passed onto humans. If a white-footed mouse is bitten by a tick, the tick will pick up the bacterium that causes the disease. They have collaborated a lot. The chance of the same tick feeding on another person is only about 3%. What is that? It's a good question. She doesn't know why the disease leaves animal reservoirs and transfers to humans. It happens, we know that.

There are a lot of unanswered questions. Although researchers have a general sense of the meteorological conditions that may promote tick abundance, some specific factors are still poorly understood. Floods, heat waves, and cold snaps can kill ticks early in their life cycle, which can cause the population to boom. There is a big unknown.

Combine all these factors into a single model and there are other problems. Scientists are trying to perfect models that combine known tick factors and spit out something that resembles a weather forecast but for tick abundance The Cary Institute's long-term tick data can be used to train a type of probability model called a Bayesian network. The weather conditions and previous populations of host animals are some of the variables fed to the model by the lab. The researchers looked at how well the program predicted what would happen. Models are updated based on how predictions fit with actual data. He says that this project and others like it are still in their infancy.

The Cary Institute has tick records that are long and detailed, but they only cover a small part of upstate New York. Most places in the United States don't have that kind of information. Since the beginning of the year, the CDC has been publishing national tick data to identify the current range of several medically important ticks. There are seven key tick-borne illnesses. This information can be used by CDC researchers as well as scientists. The kind of background fundamental info that we should have is what it is.

The CDC has begun to develop its own models to predict where ticks are likely to be found and where they're likely to spread infections. She says that they use statistical models to come up with a good habitat for the tick. The models help the government agency allocate its limited resources and avoid new locations where ticks are likely to be found. Climate and vegetation data are used. The maps help us to identify areas where environmental conditions are suitable for the tick or pathogen to persist, but where we haven't found records of the tick or pathogen. They look for evidence of ticks and tick-borne illnesses in those places.

Most researchers who work on this issue acknowledge that a true forecast of where the ticks are likely to be is out of reach. A better understanding of how ticks interact with host species, both human and non human, and how the arthropods act as conduits for disease is part of the puzzle.

If a forecast model is not in place, the records of past tick activity can be used to identify disease hot spots. The CDC has collaborated with other organizations and individuals to create maps that show where tick-borne disease is on the rise. These tick maps only show where the disease has been found, not where it might be spreading.