Chester County has the highest number of dogs in the Greater Philadelphia region that have tested positive for Lyme disease, writes Tom Avril for the Philadelphia Inquirer.

A new study published in the journal Plos One examined the results of millions of tests for Lyme disease done on canines nationwide during their annual visits to the veterinarian.

The findings showed that over the last five years, a growing number of canines tested positive in North Dakota and West Virginia, where more human cases of the disease are also showing up.

Some states, such as Pennsylvania, that already have a well-established presence of the disease in humans also showed a significantly higher number of positive tests in dogs. In Greater Philadelphia, Chester County topped the list last year with 2,484 positive findings out of 14,290 dogs tested, or 17.4 percent.

Nationwide, the national average is just 6.4 percent.

According to the study’s authors, these numbers could determine where the next human outbreak of the disease will occur. This would help local public health officials know when to start educating the public on preventive steps. These include staying on the path and wearing long pants when taking walks in nature, using insect repellent, and always checking for ticks.

Read more about the findings in the Philadelphia Inquirer here.