They're tiny, unwanted visitors and you rarely feel them bite. But the numbers of disease carrying ticks are on the rise and health professionals want you be to be warned.

The heat is on! It means more picnics and hikes, but also more bugs. And this summer is poised to be an especially bad tick season.

"This is supposed to be one of the worst years on record," said Nockamixon State Park Assistant Park Manager Jennifer Park.

For that she says you can blame acorns and mice.

"2010 was a really great year for acorns, which feeds the carrier for the ticks which is the white footed mouse."

The bumper crop of acorns lead to a surge in the mice the ticks normally cling to. This year the acorn crop returned to normal killing off the mice, and leaving the little blood suckers looking for something else to snack on. Us!

"The ticks you want to worry about are very small, like the size of a period in a sentence or the size of a pinhead," explained Park. "They're very tiny."

The bite form a deer tick can lead to Lyme Disease.

According to the CDC, Lyme Disease is one of the most rapidly emerging infectious diseases in North America. And the Lehigh Valley has some of the highest infection rates on the country.

In-fact Pennsylvania and New Jersey had more than 9,500 confirmed cases of Lyme Disease in 2009. That's nearly 32% of the nationwide total.

"Lyme Disease is actually a bacteria that's carried by the tick," said Park. "When they bite you the bacteria is injected into your skin and it can cause fever like symptoms and you'll get a rash."

The rash looks like a red bulls eye. You can also experience limping and painful joints or a decrease in appetite, vomiting and diarrhea.

But there are ways you can protect yourself this summer.

"Definitely want to wear long pants and long sleeved shirts," warned Park. "Wear darker colors because they like the lighter colors, don't be walking in the tall grasses like these or in the forest."

And make sure to do a tick check numerous times throughout the day.