Significance

Ticks are becoming an increasingly important public health issue— why? They are responsible for the transmission of a variety of pathogens that cause disease in humans and animals. In fact, in the U.S., tick-borne diseases have more than doubled in the last decade, accounting for 77% of all vector-borne diseases, of which 82% correspond to Lyme disease (Rosenberg et al. 2018). Moreover, with environmental factors such as habitat fragmentation and climate change, the geographic range of various ticks and the pathogens they carry is expected to increase. With the expanding distribution of ticks (especially the deer tick), knowing how many of these ticks are actually infected with pathogens that can affect humans is critical. A 2018 study in Minnesota collected 1240 host-seeking Ixodes scapularis nymphs and screened them for 7 human pathogens. They found that 25.24% were positive for Borrelia burgdorferi, 6.29% were positive for Anaplasma phagocytophilum, 4.68% were positive for Babesia microti, 0.49% were positive for Powassan virus, and 7.26% tested positive for multiple pathogens (Johnson et al. 2018).

Deer Ticks (Blacklegged ticks)

Deer ticks (Ixodes scapularis) are widely distributed across the eastern United States, and were first recognized in Wisconsin in 1968. They have a two-year life cycle. The tick eggs are laid in the spring, and hatch as larvae in the summer. Larvae feed on mice, birds, and other small animals. Larvae can become infected with bacteria or other types of microorganisms while feeding on these animals. Once a tick becomes infected, it remains infected for the rest of its life and can transmit the bacteria to other hosts, including humans, while feeding at a later life stage. Deer ticks are capable of transmitting Lyme disease, anaplasmosis, babesiosis, ehrlichiosis, and Powassan virus.

Humans are more likely to be bitten by nymphs rather than adult ticks. Nymphs are immature ticks that are about 2mm in size and are most active in spring and summer. Ticks can attach to any part of the human body, but are most likely to be found in hard-to-see areas, such as the scalp or armpits. In order for humans to become infected by the bacteria, the tick must remain attached for 24-48 hours.

Deer ticks are reservoir hosts for tick-borne diseases. Reservoir hosts are organisms that pathogens (like bacteria) depend on for survival, reproduction, and development. Reservoir hosts do not develop disease as a result of carrying the pathogen because killing or harming the host would also harm the pathogen.

Lone Star Ticks

Lone star ticks (Amblyomma americanum) are widely distributed in the southeastern and eastern United States. They are not typically found in Wisconsin, but they are capable of transmitting ehrlichiosis in other parts of the Midwest. Lone star ticks were given their name because the adult female is distinguished by a white dot or “lone star” on her back.

American Dog Ticks

American dog ticks (Dermacentor variabilis) are widely distributed across the eastern United States, including all of the North, South, and Midwest regions. In Wisconsin, they are sometimes referred to as wood ticks. They are capable of transmitting Rocky Mountain Spotted Fever and tularemia.

Brown Dog Ticks

Brown dog ticks (Rhipicephalus sanguineus) have a worldwide distribution. Dogs are the primary host for the brown dog tick in each of its life stages, but the tick may also bite humans or other mammals. This tick is more common in southern states and very rarely encountered in Wisconsin. They are capable of transmitting Rocky Mountain Spotted Fever, canine ehrlichiosis, and canine babesiosis to dogs.

Proper Tick removal

1. Use fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible.

2. Pull upward with steady, even pressure. Do not twist or jerk the tick— this can cause mouth-parts to break off and remain in the skin. If this happens, remove the mouth-parts with tweezers. If you are unable to remove the mouth easily with tweezers, leave it alone and allow the skin to heal.

3. After removing the tick, clean the bite area and your hands with rubbing alcohol or soap and water.

4. Never crush a tick with your fingers. To dispose of a live tick, put it in alcohol, place it in a sealed bag/container, wrap it tightly in tape, or flush it down the toilet.

5. Avoid remedies such as painting the tick with nail polish or petroleum jelly, or using heat to make the tick detach from the skin. These methods will NOT remove the tick!

Prevention strategies

On people

• Avoid contact with ticks. Ticks live in wooded or brushy areas with high grass and leaf litter. Be sure to avoid these areas and walk in the center of cleared trails.

• Wear protective clothing (socks, long sleeves, long pants)

• Treat clothing and gear with products containing 0.5% permethrin

• Use insect repellents containing DEET

• Bathe or shower after being outdoors

• Check your clothing for ticks. Place clothing in a hot dryer for 10 minutes to kill any attached ticks. Examine gear and pets for ticks as well!

• Check your body for ticks. Ticks often attach in hard-to-see areas, such as:

  • Under the arms

  • In and around the ears

  • Inside belly button

  • Back of the knees

  • In and around the hair

  • Between the legs

  • Around the waist

On Pets

Ticks that attach to pets can attach to humans later. Dogs are especially susceptible to tick bites and tick-borne diseases, so it’s important to use a tick preventative product on your dog. Check your pets for ticks daily, especially after they spend time outdoors, and if you find a tick on your pet, remove it immediately.

In the Yard

• Apply pesticides to yards to reduce the number of ticks

• Remove leaf litter and clear tall grasses and brush around homes and at edges of lawns

• Place a 3-ft wide barrier of wood chips or gravel between lawns and wooded areas to restrict tick migration into recreational areas

• Mow the lawn frequently

• Stack wood neatly and in a dry area (to discourage rodents)

• Keep playground equipment, decks, and patios away from yard edges and trees

• Discourage unwelcome animals from entering your yard by constructing fences. Discourage tick-infested deer by removing plants that attract deer.

• Remove old furniture, mattresses, or trash from the yard that may give ticks a place to hide

Sources

CDC 2018 (“Tickborne Diseases of the United States”): https://www.cdc.gov/ticks/geographic_distribution.html

Rosenberg et al. 2018 (“Vital Signs: Trends in Reported Vectorborne Disease Cases — United States and Territories, 2004–2016”): https://www.cdc.gov/mmwr/volumes/67/wr/mm6717e1.htm

Johnson et al. 2018 (“Prevalence and distribution of seven human pathogens in host-seeking Ixodes scapularis (Acari: Ixodidae) nymphs in Minnesota, USA”): https://www.sciencedirect.com/science/article/pii/S1877959X18301821?via%3Dihub

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