Tick-borne disease - a serious and growing threat in your own backyard.

In the northeastern United States, people are most likely to contract Lyme disease at home. Your odds of contracting the disease are directly related to the number of ticks existing on your own property that carry the disease-causing bacteria.

Lyme disease is not an illness to be taken lightly. It can be difficult to diagnose, and if it goes undiagnosed and untreated, it can result in serious, permanent damage to the victim's joints and heart. Animals can be affected, too. Dogs, cats, and horses are all subject to Lyme disease.

Lyme disease is the most frequently reported vector-borne illness in the United States, and the number of cases continues to rise. In the year 2002, state health departments received reports of 23,000 cases, and the total number of cases might actually be much larger. According to estimates by the Centers for Disease Control and Prevention, nine out of ten cases go undiagnosed and unreported.

How the disease is spread.

The deer tick is the culprit that infects people and animals with Lyme disease, so when most people think of the disease, they think of deer and deer ticks. This is only part of the story.

While deer serve as hosts to the deer tick, they do not play a role in spreading the disease. Even if deer are infected with Lyme disease, they cannot pass it on to anything or anyone -- including the deer tick. And, there can be deer ticks and Lyme disease present on your property even if you don't have deer.

The most important player in the spread of Lyme disease is the white-footed mouse. It is this rodent that primarily harbors the bacteria that cause Lyme disease. Ticks pick up the bacteria when they feed on the blood of infected mice.

Lyme disease and the deer tick lifecycle.

There are three stages in the life of a deer tick: larva, nymph, and adult.

While in the larval and nymphal stages, deer ticks pass the Lyme disease bacteria to and from the mice and other rodents they feed on. During the ticks' nymphal stage, they might also feed on humans and pets. As nymphs, the ticks are light in color and no bigger than pinheads so they can easily go undetected. This is when they are most likely to pass Lyme disease to humans.