While most people worry about tick bites after outdoor activities like camping, hiking and golf, the majority of bites happen close to home.
The federal Centers for Disease Control and Prevention and the National Institute of Allergy and Infectious Diseases are investigating an alarming rise in several different types of tick-borne infections including Lyme disease, Rocky Mountain spotted fever and ehrlichiosis. Not only are more diseases being spread by ticks, but more species of ticks are transmitting disease, including some, like brown dog ticks, not previously considered a danger to humans. The blood-sucking parasites are the leading carriers of disease in the U.S. and second only to mosquitoes worldwide.
The CDC is promoting "integrated tick management," which includes the use of landscaping to discourage ticks and recommending people treat yards in affected areas with pesticides. Studies by Kirby Stafford, chief entomologist at the Connecticut Agricultural Experiment Station, show that 82% of ticks on a property are within three yards of the lawn perimeter, particularly along woodlands, stone walls, and ornamental plantings.
Dr. Stafford's recommendations include making a barrier of wood chips made of cedar—a natural tick repellent—between wooded areas or stone walls and lawns heavily used by the family, keeping pets out of woods, and avoiding vegetation that attracts deer. As an alternative to chemical pesticides, Dr. Stafford is also working with the CDC to field-test the effectiveness of new organic repellent products that use such substances as rosemary oil, Alaskan cedar and garlic. Some are already on the market.
Often victims aren't aware they've been bitten. Most ticks are hard-backed and can be the size of a pinhead. They may not be noticed until they have embedded themselves in the skin, growing larger as they gorge themselves on blood. Disease can often be avoided if ticks are removed within 24 hours.
To combat the spread of ticks on animals, the CDC and the U.S. Department of Agriculture have been working with state and local officials to study applying insecticides directly to animals in the wild. For deer ticks, which carry three types of disease including Lyme, studies show that feeding stations armed with pesticide can sharply reduce ticks on deer. When the deer eat corn in the feeders, four paint rollers filled with pesticide brush against their ears, neck, head and shoulders. Bait boxes that apply pesticides to mice have also worked. In Arizona, the CDC has been fighting an outbreak of Rocky Mountain spotted fever spread by brown dog ticks by going door-to-door to place tick collars on dogs.
Behind the rise in ticks and the diseases they carry: More homes are being built near wooded areas and on land once used for farming that has reverted to secondary forests. The deer population around the country has exploded. Infectious disease experts also cite warming temperatures and increasing humidity.
"The more people study ticks, the more new pathogens are discovered," says Joseph Piesman, who oversees tick-borne diseases at the CDC.
While some tick-borne infections cause only mild illness that can be treated with antibiotics, others can require hospitalization and cause serious long-term health issues. There are few vaccines for tick-borne diseases.
Reported cases of Lyme, the most prevalent of tick-borne diseases, have risen sharply over the last decade, with 35,198 cases in 2008 compared with 13,000 cases in 2000. The CDC says because of under-reporting, the actual number of cases may be three times as high. Though still largely a problem in the Northeast and upper Midwest, Lyme is turning up all over the U.S. If not correctly diagnosed and treated, Lyme can cause chronic joint inflammation, neurological symptoms such as facial palsy, impaired memory and heart-rhythm irregularities.
Other tick-borne illnesses, though less widespread, are also on the rise. In 2008, there were 2,563 reported cases of Rocky Mountain spotted fever , compared with 579 in 1999. The fever can be quickly fatal unless treated with a powerful antibiotic. Last May, Wisconsin and Minnesota warned about a new species of the tick-borne bacteria ehrlichia, not previously found in North America, which can cause flu-like illness. The disease is transmitted by lone star ticks, which have spread to more states in recent years and are also linked to a new illness, called STARI, for southern tick-associated rash illness.
Tick-borne diseases often exhibit symptoms that look like something else. Without rapid or reliable tests for some diseases, it can be hard for doctors to suspect and diagnose, says David Davenport, an infectious disease specialist at the Michigan State University Center for Medical Studies. "These are rare diseases most physicians don't know much about, or they learned in medical school that the diseases only occur in certain areas," says Dr. Davenport. "But these patterns are rapidly changing and a whole lot of what we are trying to control is a moving target."
Connie Sargent, a nurse at Bronson Methodist Hospital in Kalamazoo, Mich., was admitted to the hospital as a patient last summer after she spiked a fever of 104, became sick to her stomach, and a red rash spread all over her body. Dr. Davenport diagnosed Rocky Mountain spotted fever.
Ms. Sargent did notice some bites, but wasn't sure if she got them gardening in her yard or while at her lake cottage in Traverse City. She was successfully treated with the antibiotic Doxycycline. It took her several weeks to recover. Now, she uses tick repellent when gardening, dons long sleeves and examines herself when she comes inside.
On Wild Horse Island in Montana's Flathead Lake, soft-backed ticks bite quietly in the night, typically inside cabins in wooded areas, leaving people infected with relapsing fever that can cause repeated illness over years. Scott MacDonald, whose family developed the island and sold part of it to the state as a park, was infected with relapsing fever along with several relativesin a 2002 outbreak. Everyone recovered after treatment, he says.
Tom Schwan, an expert in tick-borne diseases at the National Institute of Allergy and Infectious Diseases' Rocky Mountain Laboratories, who first identified the outbreak on the island, has helped property owners rid cabins of ticks with pesticides and remove rodents' nests that harbor ticks. He is now studying how animals and birds may be spreading the disease in Western states.