Tick-Borne Disease

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tickIn the United States, ticks are responsible for more human disease than any other insect. Tick-borne diseases are also known as zoonotic diseases. A zoonotic disease is an infectious disease that can be transmitted between animals and humans. Ticks are very effective transmitters of disease because most ticks take blood from a large variety of small and large mammals, reptiles and even birds. In general, ticks must ingest a blood meal before they can molt and move to the next stage in their life cycle. Ticks become infected with a disease-causing agent by feeding on infected mammals or birds. For example, a tick can pick up Lyme disease from a field mouse, and later in its life transmit bacteria to a deer, dog or human.

At least six different human tick-borne diseases have been reported in Missouri: Rocky Mountain spotted fever, ehrlichiosis, tularemia, Q-fever, Lyme or a lyme-like disease and the southern tick-associated rash illness.

Tick-borne diseases are a type of emerging disease, many of them first recognized in the last 30 years. Human case numbers per year for tick-borne diseases are generally on the rise. This upward trend is due to better recognition and disease reporting, but is also a reflection of changes in the environment that fosters increased exposure and transmission to humans. Fortunately, not all ticks are infected, so a tick bite does not necessarily mean you will get a disease. More importantly, the Missouri Department of Health and Senior Services (DHSS) wants people to know that when they take precautions, they can reduce their chance of being bitten.

Tick-borne Disease Prevention

Understanding a little about tick behavior can give some clues on how to avoid being bitten. For example, one tried-and-true prevention measure is to walk in the center of trails to avoid overhanging brush and tall grass. This is effective because of the way some ticks seek a host, which is called "questing." A questing tick will perch itself, front legs extended, on the stems of grass, low brush or on the edges of leaves on the ground. Using this ambush strategy, the tick waits until a suitable host brushes against the vegetation. Ticks do not jump, fall or fly and are generally found within three feet of the ground.

Carbon dioxide, which is exhaled while breathing, as well as heat and movement serve as stimuli for tick questing behavior. Using an insect repellent that contains DEET on your skin protects you because it interferes with ticks' ability to locate you. Another repellant called permethrin, which is used on clothing, actually kills ticks (as well as mosquitoes and chiggers). Permethrin products are designed to bind with fabric and persist through launderings when used according to label directions.

Once on a host, the tick seeks a place to attach and take a blood meal. Ticks attach on people in many places, but are most frequently found around the head, neck, underarms, and groin. Light-colored clothing helps you spot ticks more easily and tucking or even taping your pant legs into your socks helps slow them down in their quest for your skin. Prompt, careful inspection and removal of ticks is an important method of preventing disease.

If you find an attached tick, it should be removed promptly. The longer it is attached the greater the risk of infection. There are many "old wives tales" about how to remove a tick. However, to reduce the chance of disease transmission correctly using tweezers or commercial tick removal tools is preferred. The key to using tweezers correctly is to position the tips of tweezers around the area where the tick's mouthparts enter the skin. Then use a slow, steady motion when pulling the tick a way from the skin. After removing the tick, disinfect the skin with soap and water, or other available disinfectants.

DHSS has prepared a fact sheet for each of the most common tick-borne diseases in Missouri:

Rocky Mountain spotted fever
Ehrlichiosis
Tularemia
Q-Fever
Lyme/Lyme-like disease

If you want information on how to be careful and still enjoy the outdoors, check out the DHSS checklist of tick-bite prevention techniques and download or order a copy of the new DHSS Check, Check, Check for Ticks poster.

Signs and Symptoms of Tick-borne Disease

The signs and symptoms of tick-borne disease vary among individuals and differ according to the infecting agent. In general, a person should consider consulting a health care provider whenever he or she experiences a sudden high fever, severe headache, muscle or joint aches, nausea, vomiting or diarrhea. If these symptoms occur following a tick bite, or even after exposure to a tick habitat, the health care provider should be informed of this fact. Another possible sign of tick-borne disease is a rash or pus-filled wound that appears at the site of a tick bite, or a spreading rash that follows a tick bite or exposure to tick habitat.

Reporting Tick-borne Disease

Most tick-borne diseases, such as Rocky Mountain spotted fever, ehrlichiosis, tularemia, Q- fever and Lyme or a lyme-like disease are reportable in Missouri. Reporting helps DHSS monitor disease trends, track unusual occurrences or clusters of diseases and identify possible risk factors associated with diseases. If you want to know more about reporting diseases and conditions in Missouri, the DHSS Reportable Disease List and the Communicable Disease Investigation Reference Manual are available on the DHSS website.