Those nasty ticks are again lingering on bushes, grass, trees and other inviting areas where your pets like to hang out.

And if they catch a ride on your pet into your house, they also may bring Lyme disease, a bacterial infection spread by the bite of an infected tick.

Although not every tick carries the Lyme bacteria, caution must be exercised, especially in tick-infested areas. Maine health officials say Lyme disease cases have increased over the last five years in Maine and occur in all 16 counties.

Human cases of Lyme disease have increased dramatically, from 245 reported in 2005 to 970 reported in 2009.

David Bronder, a veterinarian at the Kennebec Valley Animal Clinic in Farmingdale, said more people are calling his clinic and asking questions about ticks, which indicates they’re finding them on pets earlier this year.

“Today we tested eight dogs and we had three positives (for Lyme disease),” Bronder said Tuesday. “That’s quite high. But now we’re starting to see it. Some were infected right after the snow melted, while others were exposed last fall.”

Bronder said ticks have two peak seasons: spring and late fall. “Midsummer is not as bad, generally,” he said.

Bronder said pet owners have three lines of defense against ticks.

• The first is observation: People should check their pets when they come into the house, especially if they were in contact with tall grass or brush. Bronder said 85 percent of the time, you will succeed in finding one.

“Ticks drop on them from shrubbery and grass,” he said. “Once on, they crawl up to higher areas and typically attach to the head, neck area and armpit. You should also check the groin.”

• The second defense is chemical treatment.

“There are four or five on the market that do a good job,” Bronder said. If a product doesn’t work, he said, it’s probably because it was not properly applied. The pesticide must come in contact with an animal’s skin for it to be absorbed.

In heavily infested tick areas, “you may want to reapply it in 25 to 27 days instead of 30 days,” he said.

“There are a couple of new tick collars that do seem to have good repellents that last anywhere from three to six months. But you have to put them on ahead of tick season and replace them at the appropriate time,” Bronder said.

He said over-the-counter tick-prevention products, which are less expensive, are not as successful as some of the products that veterinarians carry.

Products are priced according to a pet’s weight and doses. For example, a four-pack of K9 Advantix for a 30-pound dog costs about $68, while a three-pack of Frontline for the same size dog sells for $56.

• The third line of defense is easy, Bronder said: Vaccinate your pet.

“It will give good protection if administered properly and ahead of the season, as opposed to when pets have already been exposed,” he said.

But pet owners need to be aware of the dangers with using pesticide products on pets.

In 2008, the Environmental Protection Agency logged some 600 pet deaths and about 44,000 reports of harmful reactions, including skin irritation, vomiting and seizures in pets.

In April 2009, the EPA issued an advisory warning users of certain types of flea and tick products to take precautions. The advisory applied to nearly 70 spot-on products, including popular Frontline and Advantage products, that contain registered pesticides.

A spot-on product is one that generally comes in tubes or vials and is directly applied to specific areas of the pet’s body to control fleas and ticks, such as in between the shoulders or in a stripe along the back.

The EPA said people need to carefully follow label directions and monitor their pets for any signs of an adverse reaction after application, particularly when using these products for the first time.

Maine health officials last week issued a Lyme disease advisory.

Stephen Sears, state epidemiologist, said that although Lyme disease was first reported in Maine 27 years ago, it is now the second most commonly reported disease in the state.

Sears said the four best ways for pet owners to prevent infection are:

• Wear protective clothing.

• Use insect repellent.

• Perform daily tick checks.

• Use caution in tick habitats.

The most common early symptom of Lyme disease is an expanding red rash at the site of the tick bite three to 32 days after being bitten. Fever, joint and muscle pain may also occur.

The Maine Veterinary Medical Association forwarded an email warning the public about ticks to its 400 members at the request of State Veterinarian Don Hoenig and the Maine Center for Disease Control and Prevention.

The email said “ticks have been active for several months in Maine, in some areas since February or early March, and we expect the number of Lyme disease cases to continue to increase throughout the summer.”