Squirrel Tick
Ixodes marxi
All life stages (larvae, nymphs, and adults) can bite humans. Squirrel ticks are typically found in wooded areas, forests, and places where squirrels are common, such as hardwood and mixed forests, parks, and suburban woodlands.
Common in wooded areas, forests, and places where squirrels are common
Primarily feeds on tree squirrels, but can also feed on other mammals and birds
Can transmit disease-causing pathogens such as Borrelia burgdorferi (Lyme disease) and Powassan virus
Identification & Key Features
Identification & Key Features Squirrel ticks are plain or inornate hard ticks, meaning they lack the conspicuous white or silvery markings seen on species such as American dog ticks and Gulf Coast ticks.
Adult females are generally tan to reddish tan with a darker scutum, while adult males tend to be reddish tan and somewhat smaller.
Adult Female
Typical features include:
- 8 legs
- Tan to reddish-tan body
- Darker, inornate scutum
- Scutum covering only the front portion of the back
- Mouthparts projecting forward and visible from above
- No eyes
- No festoons
- Anal groove positioned in front of the anus
- Abdomen capable of expanding considerably during feeding
Because the female’s scutum covers only the front portion of the back, the abdomen behind it can expand substantially during a blood meal.
Adult Male
Adult males:
- Have 8 legs
- Are generally reddish tan
- Tend to be somewhat smaller than adult females
- Have an inornate appearance
- Have a scutum covering essentially the entire dorsal surface
- Lack eyes
- Lack festoons
- Have an anal groove positioned in front of the anus
Because the male’s scutum covers essentially the entire dorsal surface, males do not become dramatically engorged like adult females.
Nymph
Nymphs:
- Have 8 legs
- Are much smaller than adults
- Have a partial, inornate scutum
- Lack eyes
- Lack festoons
- Feed primarily on animal hosts
- Can occasionally bite people
- Can be difficult to distinguish from other immature Ixodes ticks
Larva
Larvae:
- Have 6 legs
- Are extremely small
- Feed primarily on small mammal hosts
- Drop from the host after feeding
- Later molt into eight-legged nymphs
Other Identification Features
As a member of the genus Ixodes, the squirrel tick has important identification characteristics including:
- Inornate scutum
- No eyes
- No festoons
- Mouthparts visible from above
- Anal groove curving in front of the anus
These characteristics help distinguish Ixodes ticks from several other common tick genera.
However, distinguishing Ixodes marxi from other small Ixodes species can be difficult.
Using a magnifier can help make the tick’s scutum, mouthparts, legs, body shape, and other identification features easier to see.
Reliable species-level identification may require microscopic examination by someone trained in tick identification.
Distinguishing It From Similar Ticks
The squirrel tick can be confused with:
Groundhog Tick / Woodchuck Tick
Ixodes cookei
and
Blacklegged Tick / Deer Tick
Ixodes scapularis
All three:
- Are hard ticks
- Have an inornate scutum
- Lack eyes
- Lack festoons
- Have an anal groove positioned in front of the anus
- Occur in overlapping parts of eastern North America
Ecology and host association can provide useful clues.
Squirrel Tick — Ixodes marxi
- Strongly associated with squirrels
- Frequently found in squirrel nests
- Can occur in buildings occupied by squirrels
- Rarely bites people
Groundhog Tick — Ixodes cookei
- Strongly associated with groundhogs and other medium-sized mammals
- Frequently occurs in burrows and dens
- Rarely bites people
Blacklegged Tick — Ixodes scapularis
- Commonly occurs in wooded, brushy, and leaf-litter environments
- Uses a wide variety of hosts
- Nymphs and adult females commonly bite people
Because coloration varies and closely related Ixodes species can look similar, species identification should not be based on color or habitat alone.
Geographic Distribution & Habitat
Geographic Distribution & Habitat The squirrel tick occurs broadly across eastern North America, including much of the eastern United States and parts of Canada. It is particularly associated with the northeastern United States and eastern Canada.
Because squirrel ticks spend much of their lives closely associated with host nests rather than openly questing on vegetation, they may be encountered less frequently during routine tick surveillance than more openly host-seeking species.
Common Habitats
The squirrel tick is primarily nest-associated, or nidicolous.
Typical locations include:
- Squirrel nests
- Tree cavities used by squirrels
- Nesting areas inside buildings
- Attics
- Seasonal camps
- Cabins
- Sheds
- Abandoned or rarely occupied buildings
- Other protected locations where squirrels establish nests
Human Exposure in Buildings
Although squirrel ticks rarely bite people, unusual human exposure can occur when squirrels occupy buildings.
People may encounter squirrel ticks in:
- Seasonal cabins
- Camps
- Attics
- Sheds
- Other structures containing active or abandoned squirrel nests
This nest-associated behavior helps explain why human exposure is usually uncommon but can occasionally involve multiple ticks or multiple bites when an infested structure becomes occupied.
Life Cycle & Seasonal Activity
Life Cycle & Seasonal Activity The squirrel tick has four developmental stages:
Egg → Larva → Nymph → Adult
Like other hard ticks, larvae and nymphs take blood meals before molting to the next developmental stage. Adult females take a blood meal before producing eggs.
Larvae
Larvae:
- Have 6 legs
- Feed primarily on small mammals
- Remain closely associated with host nests
- Drop from the host after feeding
- Later molt into nymphs
Nymphs
Nymphs:
- Have 8 legs
- Feed primarily on squirrels and other mammalian hosts
- Can occasionally bite humans
- Drop from the host after feeding
- Later molt into adults
Adults
Adults:
- Have 8 legs
- Are strongly associated with squirrels
- Can also occur on other mammals
- Rarely bite humans
Adult females can take a substantial blood meal. After feeding and reproduction, the female drops from the host and lays eggs.
Common Hosts
As its common name suggests, squirrels are the principal hosts of Ixodes marxi.
Reported hosts include:
- Red squirrels
- Gray squirrels
- Flying squirrels
- Chipmunks
- Other rodents
- Rabbits
- Raccoons
- Foxes
- Other small- to medium-sized mammals
- Humans, rarely
The strong association between I. marxi and squirrels is particularly important in the natural ecology of Powassan virus Lineage 1.
Seasonal Activity
The seasonal activity of Ixodes marxi is less well characterized than that of common human-biting ticks such as Ixodes scapularis.
This is partly because squirrel ticks spend much of their lives in or near host nests and are encountered less frequently by people and routine surveillance programs.
Activity and exposure may be influenced by:
- Squirrel nesting activity
- Host availability
- Geographic location
- Temperature
- Life stage
- Building occupancy
Squirrel ticks may be encountered at different times of year depending on host and nesting activity. Human exposure is uncommon but can occur when squirrels establish nests in or around buildings, including when people enter seasonal structures that were occupied by wildlife.
Diseases & Health Risks
Diseases & Health Risks The principal established human-health concern associated with the squirrel tick is:
Powassan Virus Disease
Cause: Powassan virus
CDC identifies three Ixodes tick species capable of spreading Powassan virus in the United States:
- Ixodes cookei — Groundhog Tick
- Ixodes marxi — Squirrel Tick
- Ixodes scapularis — Blacklegged Tick
An important distinction is that:
Squirrel ticks rarely bite people, while blacklegged ticks bite people much more frequently.
Powassan Virus Lineage 1
Powassan virus has two closely related genetic lineages:
Lineage 1 — Powassan virus
and
Lineage 2 — Deer tick virus
The squirrel tick is particularly associated with the natural transmission cycle of Powassan virus Lineage 1.
A well-described ecological relationship involves:
Squirrel Tick — Ixodes marxi
↕
Squirrels
↕
Powassan Virus Lineage 1
Ixodes marxi is therefore considered an important enzootic vector involved in maintaining Powassan virus Lineage 1 in wildlife transmission cycles.
By comparison, Powassan virus Lineage 2, also called deer tick virus, is primarily associated with:
Ixodes scapularis — Blacklegged Tick
and small-mammal wildlife transmission cycles.
Both Powassan virus lineages can cause human disease.
Human Risk
Although the squirrel tick is a recognized Powassan virus vector, it is not a frequent human-biting tick.
Its primary ecological role involves maintaining Powassan virus within tick and wildlife transmission cycles.
Nevertheless:
An infected squirrel tick can transmit Powassan virus if it bites a person.
Human exposure from this tick is therefore uncommon but potentially medically important.
Possible Symptoms of Powassan Virus Disease
Many people infected with Powassan virus do not develop symptoms.
When symptoms occur, they generally begin approximately:
1 week to 1 month after the bite of an infected tick.
Initial Symptoms
Symptoms can include:
- Fever
- Headache
- Vomiting
- Weakness
Severe Neurologic Disease
Powassan virus can cause serious central nervous system infection, including:
Encephalitis
Inflammation of the brain
and
Meningitis
Inflammation of the membranes surrounding the brain and spinal cord
Symptoms of severe illness may include:
- Confusion
- Loss of coordination
- Difficulty speaking
- Seizures
Severity
Among people who develop severe Powassan virus disease:
- Approximately 1 in 10 die
- Approximately half of survivors experience long-term health problems
Long-term problems can include:
- Recurring headaches
- Loss of muscle mass or strength
- Memory problems
- Other neurologic complications
Treatment
There is currently:
- No specific antiviral treatment for Powassan virus disease
- No vaccine available to prevent Powassan virus disease
Treatment is supportive.
People with severe illness may require hospitalization for:
- Respiratory or airway support
- Hydration
- Seizure management
- Monitoring and management of brain swelling
- Other supportive medical care
Important Lyme Disease Clarification
The squirrel tick should not be presented as an established vector of Lyme disease.
The recognized U.S. vectors of Lyme disease are:
- Ixodes scapularis — Blacklegged Tick
- Ixodes pacificus — Western Blacklegged Tick
For a U.S.-focused educational page:
Powassan virus—not Lyme disease—is the established human disease association that should be emphasized for Ixodes marxi.
The squirrel tick should also not be listed as a recognized human vector of anaplasmosis, babesiosis, ehrlichiosis, or hard tick relapsing fever in current U.S. public-health guidance.
Important to Know
Finding a squirrel tick does not automatically mean that it carries Powassan virus or that infection occurred.
Risk depends on factors including:
- Whether the tick was infected
- Whether it attached and fed
- Geographic location
- Local Powassan virus activity
- Wildlife and tick transmission cycles
Powassan virus disease remains uncommon, although reported U.S. cases have increased in recent years. Most reported U.S. cases occur in the Northeast and Great Lakes regions.
Bite Prevention & Protection
Bite Prevention & Protection Because squirrel ticks are strongly associated with squirrel nests and structures occupied by squirrels, prevention should address both routine tick precautions and wildlife-associated exposure.
Around Buildings
To reduce exposure:
- Prevent squirrels from nesting in attics, cabins, seasonal buildings, sheds, and other structures when practical.
- Inspect seasonal buildings for evidence of squirrel activity before occupying them.
- Avoid unnecessary handling of squirrel nesting material.
- Seal appropriate entry points after confirming animals are no longer inside.
- Consider professional wildlife or pest-control assistance for significant infestations.
When Outdoors
To reduce tick bites generally:
- Avoid direct contact with dense brush and vegetation when practical.
- Use an EPA-registered insect repellent according to label directions.
- Treat clothing and outdoor gear with products containing 0.5% permethrin, or wear commercially pretreated clothing.
- Wear long pants, long sleeves, socks, and closed shoes when practical.
After Outdoor Activity
Perform a thorough tick check.
Pay particular attention to:
- In and around the hair
- In and around the ears
- Under the arms
- Around the waist
- Inside the belly button
- Behind the knees
- Between the legs
Also inspect:
- Children
- Pets
- Clothing
- Backpacks
- Outdoor equipment
Showering within two hours after coming indoors may help remove unattached ticks and provides a good opportunity to perform a complete body check.
Protect Pets
Pets may encounter squirrel ticks if they investigate:
- Squirrel nests
- Tree cavities
- Attics
- Sheds
- Seasonal structures
- Areas heavily used by squirrels
Check pets regularly and consult a veterinarian about appropriate tick-prevention products.
If You Find an Attached Tick
Remove the tick as soon as possible.
Do not wait for a healthcare appointment before removing an attached tick.
How to Remove a Tick
- Use clean fine-tipped tweezers.
- Grasp the tick as close to the skin’s surface as possible.
- Pull the tick away from the skin with steady, even pressure.
- Do not twist or jerk the tick.
- If mouthparts remain and can be removed easily with tweezers, remove them. If they cannot be removed easily, leave them alone and allow the skin to heal.
- Dispose of the tick safely.
- Thoroughly clean the bite area and your hands.
- Check the rest of your body for additional ticks.
Do not attempt to make the tick detach using:
- Petroleum jelly
- Nail polish
- Heat
- Other substances or chemicals
These methods should not replace prompt mechanical removal.
Tick Testing
CDC generally does not recommend commercial testing of removed ticks to guide medical treatment decisions.
A positive result does not prove that infection was transmitted.
A negative result can provide false reassurance.
After Removal
Monitor for concerning symptoms during the following days and weeks.
Contact a healthcare provider if you develop symptoms such as:
- Fever
- Headache
- Vomiting
- Weakness
- Confusion
- Difficulty speaking
- Loss of coordination
- Seizures
- Other unusual neurologic symptoms
Because Powassan virus can cause serious neurologic disease, confusion, seizures, major coordination problems, difficulty speaking, or other sudden neurologic symptoms require prompt medical evaluation.
Tell the healthcare provider:
- That a tick bite occurred
- When it occurred
Where the likely exposure occurred
Identification Gallery
Identification Gallery Adult Female
- Tan to reddish-tan body
- Dark, plain scutum covering the front portion of the back
- 8 legs
Adult Male
- Reddish-tan body
- Usually smaller than the female
- Scutum covers nearly the entire back
- 8 legs
Engorged Female
- Enlarged body after feeding
- Small dark scutum remains visible near the front
- Show beside an unfed female for comparison
Nymph
- Very small body
- 8 legs
- Partial scutum
- Show size comparison with an adult
- Use a verified Ixodes marxi nymph when possible
Larva
- Extremely small
- 6 legs
- Show size comparison with a nymph
Male vs. Female
Female: Tan to reddish-tan with a dark scutum covering only the front portion of the back.
Male: Reddish-tan and generally smaller, with the scutum covering nearly the entire back.
Life Stages
Egg → 6-legged Larva → 8-legged Nymph → Adult
Similar Species
Compare with:
Squirrel Tick (Ixodes marxi)
Groundhog Tick (Ixodes cookei)
Blacklegged Tick (Ixodes scapularis)
These ticks can look similar. Color alone should not be used for species identification. Identification may also depend on body features, mouthparts, scutum shape, life stage, location, host, and microscopic examination.
