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Tick-borne pathogens can be passed to humans by the bite of infected ticks. Ticks can be infected with bacteria, viruses, or parasites. Some of the most common tick-borne diseases in the United States include: Lyme disease, babesiosis, ehrlichiosis, Rocky Mountain Spotted Fever, anaplasmosis, Southern Tick-Associated Rash Illness, Tick-Borne Relapsing Fever, and tularemia.
Lyme disease is the most commonly reported tick-borne disease in the United States. In 2010, more than 22,500 confirmed and 7,500 probable cases of Lyme disease were reported to the Centers for Disease Control and Prevention (CDC).
Workers who are working outside are highly prone to tick-borne diseases if they work at sites with ticks. Worksites with woods, bushes, high grass, or leaf litter are likely to have more ticks. Outdoor workers in most regions of the United States should be more careful to protect themselves in the spring, summer, and fall when ticks are most active. Ticks may be active all year in some regions with warmer weather.
Ticks are abundant in woodlands all across Europe from early spring to late autumn. They used to live by sucking blood from animals and occasionally bite humans. Ticks themselves do not cause disease but if a tick is infected with a virus or bacterium, then that pathogen can be transmitted through the tick’s bite and cause disease in humans. Tick-borne encephalitis (TBE) is a common tick-borne disease in Europe (along with Lyme borreliosis).
An Overview Of Tick Bites
Ticks are hematophagous species that strictly feed on blood; thus, their survival is entirely dependent upon their ability to feed on hosts. Although wild animals are the primary hosts for ticks, humans can also experience tick bites when they visit a tick’s habitat.
Once a tick finds a humid and warm spot on the skin of an animal or human, the inset will pierce the epidermis with their chelicerates, which share a similar appearance to sharp blades, and settle into the skin with their hypostome. Thereafter, the tick will secrete a thick and cement-like substance that firmly retains its position on the skin to prevent it from dropping off.
The tick saliva itself exerts various pharmacological activities in the host including coagulation and pain inhibition, all the while inhibiting local immune responses in the host against the tick bite. Although tick saliva itself can cause an allergic reaction to arise at the bite site, various pathogens such as bacteria, viruses, and parasites can also be passed onto the host and induce a tick-borne disease.
Causes Of Tick-Borne Disease
The disease is caused by bacteria that is spread to humans by tick bites. The ticks that carry the spirochete are:
- Black-legged deer tick (northeastern, mid-Atlantic, and North-Central U.S.)
- Western black-legged tick (Pacific coastal U.S.)
Symptoms Of Tick-Borne Disease
The most common symptoms of tickborne diseases are:
- Fever and/or chills: Patients can experience fever at varying degrees and time of onset.
- Aches and pains: Tickborne disease symptoms include headache, fatigue, and muscle aches. With Lyme disease you may also experience joint pain. The severity and time of onset of these symptoms can depend on the disease and the patient’s personal tolerance level.
- Rash: Lyme disease, Rocky Mountain spotted fever, tularemia and ehrlichiosis can result in distinctive rashes.
- In Lyme disease the rash may appear within 3-30 days, typically before the onset of fever. The Lyme disease rash is the first sign of infection and is usually a circular rash called erythema migrans. This rash occurs in approximately 70-80% of infected persons and begins at the site of the tick bite.
- The rash seen with Rocky Mountain spotted fever varies from person to person in appearance, location and time of onset. About 10% of people with Rocky Mountain spotted fever never develop a rash. Most often, the rash begins 2-5 days after onset of fever as small, flat, pink, non-itchy (macules) on the wrists, forearms, and ankles and spreads to the trunk. The red to purple, spotted (petechial) rash is usually not seen until the sixth day or later after onset of symptoms and occurs in 35-60% of patients.
- In the most common form of tularemia, a skin ulcer appears at the site where the organism entered the body. The ulcer is accompanied by swelling of regional lymph glands, usually in the armpit or groin.
- Ehrlichiosis can cause a rash in about 30% of patients, and up to 60% in children. The appearance of the rash ranges from macular to maculopapular to petechial and may appear after the onset of fever.
Prevention Of Tick-Borne Disease
- Avoid tick-infested areas, particularly in May, June, and July.
- Wear shoes, long pants tucked into socks or pant legs, and long sleeves when outside in areas where there are deer ticks.
- Use insect repellent with 20%-30% DEET around your ankles, other areas of bare skin, and clothes.
- Check for ticks, especially around the armpits, groin, scalp, belt line, neck and head after being in areas where there may be ticks.
- Remove deer ticks on your skin as soon as you see them.
Diseases Transmitted by Ticks
- Lyme Disease – caused by Borrelia burgdorferi, is a potentially serious bacterial infection affecting both humans and animals. It is the most common tickborne disease reported in Minnesota and in the United States.
- Anaplasmosis – Also known as human granulocytic ehrlichiosis (HGE) is a bacterial disease that was first recognized in Minnesota in the early 1990s. It is transmitted to people by blacklegged ticks (deer ticks), the same ticks that transmit Lyme disease.
- Babesiosis – Babesiosis is a protozoan infection that occurs infrequently in Minnesota. Up to 20 percent of patients diagnosed with Babesiosis also have Lyme disease.
- Ehrlichiosis – caused by Ehrlichia chaffeensis is found throughout much of south-eastern and south-central United States
- Powassan – Powassan virus is a tickborne flavivirus that has been reported in patients from the Upper Midwest and Northeastern states.
- Borrelia miyamotoi – It is distantly related to the bacteria that cause Lyme disease. Small numbers of human cases have been reported to date from the Upper Midwest and Northeastern states.
- Rocky Mountain Spotted Fever(RMSF) – Rocky Mountain spotted fever is extremely rare in Minnesota, but isolated cases have been reported within the state. This disease is transmitted by the American dog tick.
- Tularemia – It is a potentially serious illness that occurs naturally in the United States. It is caused by the bacterium Francisella tularensis and can be transmitted by American dog ticks as well biting flies or infected animals. Human cases of tularemia are rarely reported in Minnesota.
Tick – Borne Disease – Risk Factors
- Spending time in wooded or grassy areas. In the United States, deer ticks are found mostly in the heavily wooded areas of the Northeast and Midwest. Children who spend a lot of time outdoors in these regions are especially at risk. Adults with outdoor jobs also are at increased risk.
- Having exposed skin. Ticks attach easily to bare flesh. If you’re in an area where ticks are common, protect yourself and your children by wearing long sleeves and long pants. Don’t allow your pets to wander in tall weeds and grasses.
- Not removing ticks promptly or properly. Bacteria from a tick bite can enter your bloodstream if the tick stays attached to your skin for 36 to 48 hours or longer. If you remove a tick within two days, your risk of getting Lyme disease is low.
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