Forest Fragmentation Boosts Tick Populations and Diseases

WESTBROOK, Maine, May 24, 2012 /PRNewswire/ -- Experts agree that ticks and tick-borne diseases are on the rise, due in large part to increased forest fragmentation that creates pockets of disease in areas of modern development. According to the Centers for Disease Control and Prevention (CDC), tens of thousands of people are infected with tick-borne diseases annually, and dogs sometimes serve as disease sentinels.

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Forest fragmentation occurs when large woodlands are split into smaller, more isolated sections for such uses as building roads, shopping centers or housing developments. As people began moving away from urban centers to suburbia and closer to wildlife in the 1980s, human and pet interaction with ticks and tick hosts naturally escalated. Homes near wooded areas and in subdivisions with green space became more common, as suburban dwellers sought residences near such edge habitats.

"There are clearly more ticks in more places than ever before, and a big part of that equation is forest fragmentation. What exists now is a patchwork-quilt ecosystem—an unnatural mosaic of small, isolated zones of trees interspersed with crops or grassland," said Michael W. Dryden, DVM, MS, PhD, a distinguished professor of parasitology at the College of Veterinary Medicine at Kansas State University who studies the biology and control of ticks and fleas. "The 'grassland' can be someone's backyard, and tick hosts like deer, coyotes and turkeys move back and forth between the grassy areas and patches of forest."

The conditions created by forest fragmentation are conducive to the proliferation of ticks. Additional sunlight; increased food sources for deer, white-footed mice and other tick hosts; and fewer tick-host predators translate to more ticks, which are highly effective at carrying and transmitting dangerous, illness-causing bacteria to pets and humans.

Ticks in forest fragments survive largely on blood from deer or mice, since many other species that ticks feed off of cannot survive in fragmented environments. So, both the disease-carrying animals and infectious ticks are left to multiply.

"The white-footed mouse will infect the majority of ticks that bite it, and populations of white-tailed deer—which can survive in forest patches—are increasing," said Brian Allan, PhD, assistant professor of entomology at the University of Illinois at Urbana-Champaign and ecologist who studies forest fragmentation and increasing tick diseases. "When you consider that people today are in more frequent contact with forest patches, it's not surprising that tick-borne illnesses are rising."

Tick-borne ailments—including, but not limited to, Lyme disease—affect dogs, cats and people in every U.S. state. According to the CDC, which acknowledges its published surveillance data may under-represent the actual number of Lyme disease cases in the country by as much as tenfold, Lyme disease incidence is growing. More than 35,000 Americans contract the disease every year, a figure that climbed 70 percent from 2000 to 2010. Tick diseases increasingly affect pets, too. Between 2006 and 2010, nationwide studies show a 30-percent increase in the rate of dogs exposed to tick-transmitted diseases (Little and Bowman, 2006).

Though rare, some tick-borne diseases can be fatal in both pets and people. And, according to the CDC, laboratory results for tick-borne illness in people are often negative on the first sample and require a second test two to three weeks later to confirm infection. Further, children are more susceptible to infections because of their immature immune systems.

Pets—particularly dogs—can signal human risk for tick-borne illness. For example, CDC scientists last year published a study showing that people in areas with a higher-than-average number of dogs with Lyme disease are at greater risk of contracting the disease. While dogs cannot transmit Lyme disease to people, canine incidence indicates human risk.

Lyme disease is the most common vector-borne disease, but Dryden and other experts are aware of at least 15 emerging, lesser-known tick diseases. These include ehrlichiosis, anaplasmosis, babesiosis, rickettsiosis and STARI (southern tick-associated rash illness). The CDC reports that many of these under-the-radar tick-borne illnesses are spreading rapidly. The numbers of ehrlichiosis and anaplasmosis cases reported to the CDC increased more than 200 percent during the last decade; agency officials postulate this may be the result of ecological changes influencing tick populations and disease transmission.

"In order to protect their families and their animals, pet owners must first be aware that ticks are a risk everywhere," said Ruth MacPete, DVM, a San Diego-based veterinarian. "They should know what ticks look like, how to properly remove them as well as have their pets regularly screened for parasitic disease by a veterinarian, since infected dogs often exhibit no symptoms. Administering year-round preventives as directed by veterinarians can greatly reduce the risks that parasites pose."

People who want to learn more about how to protect their families and pets should consult their veterinarians and www.DogsAndTicks.com, a helpful website with information about tick-bite prevention and tick diseases – including how prevalent some of them are in their own neighborhoods. Since early diagnosis and treatment options are keys to longer and higher-quality lives for dogs, the online resource also teaches people how to recognize difficult-to-distinguish signs of infection, properly check for ticks and remove embedded ticks (hint: petroleum jelly, matches and nail polish are not involved).

The veterinarians and veterinary parasitologists who support and develop content for www.DogsAndTicks.com are committed to educating pet owners about the prevalence and risks of tick-borne diseases. The website does not endorse any individual product but serves as an informational source, with tools that include interactive prevalence maps for tick-borne diseases based on diagnostic screenings from across the country.

IDEXX Laboratories, Inc., is a global market leader in pet healthcare innovation, helping practicing veterinarians around the world advance medical care with a broad range of diagnostic products and services. IDEXX created www.DogsAndTicks.com as a resource for pet owners.

SOURCE DogsAndTicks.com