Geographic distribution of ticks and disease cases in the U.S.
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Ticks are small, parasitic arachnids that belong to the order Parasitiformes. They are ectoparasites, meaning they live on the outside of their host’s body, and they feed on the blood of mammals, birds, and sometimes reptiles and amphibians. Ticks are found worldwide, especially in warm, humid climates, and they are known for transmitting a variety of diseases to humans and animals.
Ticks have a fascinating life cycle that typically includes four stages: egg, larva, nymph, and adult. During each stage, ticks require a blood meal to progress to the next stage. Ticks can be active year-round, depending on the species and location, but they are most active during the warmer months.
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Species of Ticks
According to the Centers for Disease Control and Prevention in the United States, nine ticks most often attack humans. The most common and the most dangerous tick, in terms of the diseases it can transmit, is the black-legged tick (Ixodes scapularis).
Blacklegged Tick (Ixodes scapularis)
Blacklegged ticks, also known as deer ticks, are broadly spread over the eastern U.S. The highest risk of being bitten by these ticks is in the spring, summer, and fall, particularly in the Northeast, Upper Midwest, and Middle Atlantic regions. Adult ticks may be out hunting for a host any time winter temperatures are over freezing. They transmit Borrelia burgdorferi and B. mayonii (Lyme disease), Anaplasma phagocytophilum (anaplasmosis), B. miyamotoi disease (a form of relapsing fever), Ehrlichia muris eauclairensis (ehrlichiosis), Babesia microti (babesiosis), and Powassan virus (Powassan virus disease).
Lone Star Tick (Amblyomma americanum)
The lone star tick widely spread in the eastern and southern U.S. The highest risk of being attacked is in early spring through late fall. They transmit Ehrlichia chaffeensis and Ehrlichia ewingii (ehrlichiosis), Francisella tularensis (tularemia), Heartland virus (Heartland virus disease), Bourbon virus (Bourbon virus disease), and Southern tick-associated rash illness.
American Dog Tick (Dermacentor variabilis)
The dog tick is widely distributed east of the Rocky Mountains and in restricted areas on the Pacific Coast. The highest risk of being bitten happens during spring and summer. They transmit Francisella tularensis (tularemia) and Rickettsia rickettsii (Rocky Mountain spotted fever).
Brown Dog Tick (Rhipicephalus sanguineus)
The Brown Dog Tick is widely distributed globally. They transmit Rickettsia rickettsii (Rocky Mountain spotted fever).
Groundhog Tick (Ixodes cookei)
The Growndhog Tick is widely distributed everywhere the eastern half of the U.S. They transmit the Powassan virus (Powassan virus disease).
Gulf Coast Tick (Amblyomma maculatum)
The Gulf Coast Tick is widely distributed southeastern and Middle Atlantic U.S. states and southern Arizona. Transmits Rickettsia parkeri (spotted fever).
Rocky Mountain Wood Tick (Dermacentor andersoni).
The Rocky Mountain Wood Tick is widely spread Rocky Mountain states. Transmits Rickettsia rickettsii (Rocky Mountain spotted fever), Colorado tick fever virus (Colorado tick fever), and Francisella tularensis (tularemia).
Soft Tick (Ornithodoros spp.)
The Soft Tick is widely distributed everywhere the western half of the U.S., including Texas. Humans commonly come into contact with soft ticks in rustic cabins. The ticks attack at night while people are resting. Transmits Borrelia hermsii, Borrelia turicatae (tick-borne relapsing fever).
Western Blacklegged Tick (Ixodes pacificus)
The Western Blacklegged Ticks are widely distributed in the Pacific Coast states. They transmit Anaplasma phagocytophilum (anaplasmosis), Borrelia burgdorferi (Lyme disease), Borrelia miyamotoi (Borrelia miyamotoi disease).
Tick-borne Disease Cases in the U.S.
Tick-borne diseases are a significant health concern in the United States, with several different types of ticks capable of transmitting various diseases. Here are some of the most common tick-borne diseases in the United States.
Lyme disease: Transmitted primarily by the black-legged tick (also known as the deer tick), Lyme disease is caused by the bacterium Borrelia burgdorferi. Symptoms can include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. If left untreated, Lyme disease can spread to the joints, heart, and nervous system. Lyme disease is the most common tick-borne illness in the U.S. According to the CDC, about 476,000 people are diagnosed and treated each year for Lyme disease.
The map below shows distribution of ticks infected with Lyme disease in the United States.
Here is the map showing where Lyme Disease antibodies found in dogs are used to pinpoint areas where people may be more vulnerable to disease-carrying ticks, according to the 2017 Clemson study.
Rocky Mountain spotted fever (RMSF): RMSF is caused by the bacterium Rickettsia rickettsii and is transmitted by the American dog tick, the Rocky Mountain wood tick, and the brown dog tick. Symptoms include fever, headache, rash, and muscle aches. RMSF can be severe and potentially fatal if not treated early with antibiotics.
Ehrlichiosis: Ehrlichiosis is a bacterial illness transmitted to humans by the lone star tick. Symptoms can include fever, headache, fatigue, and muscle aches. Severe cases can lead to organ failure and death if not treated promptly with antibiotics.
Anaplasmosis: Anaplasmosis is caused by the bacterium Anaplasma phagocytophilum and is transmitted by the black-legged tick and the western black-legged tick. Symptoms can include fever, headache, muscle aches, and fatigue. Like other tick-borne diseases, anaplasmosis can be treated with antibiotics.
Babesiosis: Babesiosis is caused by microscopic parasites that infect red blood cells. It is transmitted by the black-legged tick and, less commonly, by blood transfusions. Symptoms can range from mild to severe and include fever, chills, sweats, and fatigue. Severe cases may require hospitalization and treatment with antiparasitic medications.
Powassan virus: Powassan virus is a rare but serious tick-borne disease transmitted by the black-legged tick and the groundhog tick. Symptoms can include fever, headache, vomiting, weakness, confusion, seizures, and memory loss. There is no specific treatment for Powassan virus, and severe cases may require hospitalization for supportive care.
Tularemia: Tularemia, also known as rabbit fever, is a rare infectious disease caused by the bacterium Francisella tularensis. It can be transmitted to humans through contact with infected animals, insect bites, contaminated food or water, or inhaling the bacteria. Symptoms include fever, skin ulcers, swollen lymph glands, and respiratory issues. Treatment with antibiotics is effective, and preventive measures include avoiding contact with wild animals and using insect repellent.
The map below, created by Buglord.com, shows confirmed cases of these diseases in the United States.
The Impact of Weathe and Climate Change on Tick Spread in the United States
Weather and climate change can significantly impact the spread of ticks in the United States. Warmer temperatures and changing precipitation patterns can alter the distribution and abundance of tick populations, leading to an increased risk of tick-borne diseases. Warmer winters can allow ticks to survive and reproduce more effectively, leading to larger populations. Changes in temperature and humidity can also affect the behavior of both ticks and their animal hosts, influencing the timing and duration of the tick season. Additionally, extreme weather events, such as hurricanes and floods, can disrupt tick populations and lead to the spread of ticks into new areas.
Climate change is expected to exacerbate these effects, potentially leading to an expansion of tick habitats into new regions. As temperatures warm, some tick species may expand their geographic range into areas where they were previously unable to survive. This could lead to the introduction of new tick-borne diseases to regions where they were not previously a concern.
The maps below created by globalchange.gov and washingtonpost.com display the modern and projected probability of establishing tick populations (Ixodes scapularis) that transmit Lyme disease. Predictions are presented for 2020, 2050, and 2080. The predicted extension of tick habitat covers much of the eastern half of the U.S. by 2080. For some regions around the Gulf Coast, the possibility of tick population establishment is projected to decline by 2080.
Preventing Tick Bites: Tips for a Safe Outdoor Experience
Ticks are commonly found in grassy, wooded areas, making outdoor activities like hiking, camping, and gardening prime opportunities for tick encounters. To reduce your risk of tick bites and tick-borne diseases, follow these preventive measures:
- Use insect repellent: Apply an EPA-registered insect repellent containing DEET, picaridin, or other effective ingredients to exposed skin and clothing.
- Wear protective clothing: Wear long sleeves, pants, and socks when outdoors, and tuck your pants into your socks to prevent ticks from crawling up your legs.
- Stay on marked trails: Avoid walking through tall grasses and brush where ticks are more likely to be found.
- Perform tick checks: After spending time outdoors, check your body, clothing, and gear for ticks. Pay special attention to areas like the armpits, groin, and scalp.
- Shower after outdoor activities: Showering within two hours of being outdoors can help wash away ticks that have not yet attached to your skin.
- Remove ticks safely: If you find a tick attached to your skin, use fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible and pull upward with steady, even pressure.
- Treat clothing and gear: Consider treating clothing and gear with permethrin, an insect repellent that can be applied to clothing and gear.
Taking these precautions can help protect you and your family from tick bites and the diseases they may carry. If you develop a fever, rash, or other symptoms after a tick bite, seek medical attention promptly.
Safely Removing Ticks: Essential Tips for Proper Tick Removal
Ticks can transmit a variety of diseases, so it’s crucial to remove them properly and promptly. Follow these steps to safely remove ticks:
- Use fine-tipped tweezers: Grasp the tick as close to the skin’s surface as possible.
- Pull upward with steady, even pressure: Avoid twisting or jerking, as this can cause the mouthparts to break off and remain in the skin.
- Clean the bite area: Use soap and water, rubbing alcohol, or an antiseptic to clean the area after removing the tick.
- Dispose of the tick properly: Place the tick in a sealed bag or container, or flush it down the toilet.
- Monitor for symptoms: Watch for signs of tick-borne illnesses, such as fever, rash, or flu-like symptoms, and seek medical attention if symptoms develop.
By following these steps, you can safely remove ticks and reduce the risk of tick-borne diseases.
Debunking Common Misconceptions About Ticks
Ticks are often misunderstood, leading to misconceptions about their behavior and the risks they pose. Here are some common misconceptions about ticks:
- Ticks jump or fly: Ticks do not have the ability to jump or fly. Instead, they wait on grass or shrubs and latch onto passing hosts.
- All ticks carry diseases: While many ticks can carry diseases, not all ticks are infected. The risk of disease transmission varies by region and tick species.
- Ticks only bite humans: Ticks feed on a variety of hosts, including mammals, birds, and reptiles. They can bite humans, pets, and wildlife.
- Ticks die in the winter: While ticks are less active in cold weather, they can survive winter temperatures by seeking shelter in leaf litter or other protected areas.
- Ticks are only found in rural areas: Ticks can be found in both rural and urban areas, including parks, yards, and wooded areas.
- Ticks can be removed with heat or petroleum jelly: Using heat or petroleum jelly to remove ticks can actually increase the risk of disease transmission. It’s best to use fine-tipped tweezers for safe removal.
Understanding the facts about ticks can help you take appropriate precautions to protect yourself and your family from tick bites and tick-borne diseases.
Want to know more about ticks? These books might pique your interest.
- Ticks: Dangerous Hitchhikers (Arachnid World)
- Preventing Lyme & Other Tick-Borne Diseases
- Winning the War on Ticks: Learn Proven Combat Methods for Preventing Tick Bites
