What does the graph tell me?
- Tick-related emergency room visits are most common in the spring, when blacklegged tick nymphs are abundant, and fall, when adult female blacklegged ticks look for one more meal before winter arrives. Few ticks are out searching for meals in December, January and February, so tick-related emergency department visits are low during those times.
- Spring tick activity is associated with increased cases of Lyme disease and anaplasmosis, and Vermonters continue to be at risk for anaplasmosis during the fall months.
How was this graph built?
The Health Department collaborates with hospitals across the state to collect data on recent emergency room (and some urgent care) visits. Information like the date of the visit, reason for the visit, and diagnosis are analyzed to detect public health events and monitor trends in disease activity.
What do all the bars and lines mean?
The graph shows the weekly percentage of emergency department visits for tick-related issues. The purple line represents the average percentage of visits due to tick-related issues at that time of year (based on 2004-2021 data). The green dotted line represents the highest percentage of tick-related visits that has been recorded at that time of year. The blue bars show the percentage of visits due to tick-related issues in the current year.
What Should I Do?
Protect, Check, Remove and Watch. Visit our Prevent Tick Bites & Tickborne Diseases webpage to learn how to prevent and respond to tick bites.
Types of Ticks in Vermont
Fifteen different species of tick have been identified in Vermont. Get the full list of tick species. Of these 15 species, six are known to bite humans and can transmit diseases. However, over 99% of all tickborne diseases reported to the Vermont Department of Health are caused by only one tick: the blacklegged tick.
Tick Pathogen Surveillance
Ticks are collected in the spring and fall in locations around the state, then identified by species, life stage, and sex. Blacklegged ticks are then tested for four tickborne pathogens that cause human illness in Vermont. The information is compiled into annual reports.

Name: Blacklegged tick (Ixodes scapularis)
Distribution: throughout Vermont
Habitat: wooded areas and fields with tall grass and brush
Hosts: white-footed mouse, deer mouse, chipmunks, shrews, white-tailed deer
Transmits: the pathogens that cause Lyme disease, anaplasmosis, babesiosis, Powassan virus disease, and Borrelia miyamotoi disease
Active: In Vermont, blacklegged tick peak activity typically occurs in May and June when nymphal ticks are looking for a host. Tick activity increases again in October and November when adult female ticks are looking for another host before winter. Although blacklegged tick activity typically follows this pattern, these ticks may be encountered any time of year when temperatures are above freezing.
How common are disease-carrying blacklegged ticks in Vermont?
In 2018, the Vermont Department of Health initiated a project in collaboration with the Vermont Agency of Agriculture to understand the prevalence and geographic distribution of disease-carrying blacklegged ticks. Over 1,500 ticks were collected from 48 sites around the state in 2020; human-feeding nymphs and adult female ("host seeking") ticks were tested for four pathogens.
PAthogen | Percentage of ticks that tested positive |
---|---|
Borrelia burgdorferi | 59% |
Anaplasma phagocytophilum | 11% |
Babesia microti | 6% |
Borrelia miyamotoi | 1% |
Blacklegged ticks can carry more than one pathogen at the same time. The most common combinations were the pathogens that cause Lyme disease and anaplasmosis (8%) and the pathogens that cause Lyme disease and babesiosis (5%).

Name: American dog tick (Dermacentor variabilis)
Distribution: throughout Vermont
Habitat: mostly in grassy fields and other areas with little tree cover
Hosts: small rodents and medium-sized wild mammals, domestic cats, dogs and humans
Transmits: the bacteria that causes tularemia and Rocky Mountain spotted fever (human cases in Vermont are extremely rare)
Active: April through September

Name: Brown dog tick (Rhipicephalus sanguineus)
Distribution: throughout Vermont
Habitat: wherever humans and dogs live including indoors, unlike other tick species
Hosts: mostly dogs
Transmits: the bacteria that causes Rocky Mountain spotted fever in the Southwestern United States (no evidence of transmission in Vermont)
Active: throughout the year

Name: Lone star tick (Ambylomma americanum)
Distribution: this tick is not considered established, or able to complete its entire life cycle, in Vermont
The Health Department works with other state agencies to search for the lone star tick in Vermont and support people with information to protect themselves.
Habitat: woodlands with plenty of undergrowth and areas with tall, shaded grass
Hosts: squirrels, raccoons, deer, cattle, some bird species, cats, dogs and humans
Transmits: the pathogens that cause ehrlichiosis and tularemia (human cases in Vermont are extremely rare). Alpha-gal syndrome (AGS).
Active: April through September. While most ticks wait in grass or brush to grab on to people or animals who pass by (questing), lone star ticks also actively track down a host by following the trail of air the host breathes out.
Name: Squirrel tick (Ixodes marxi)
Distribution: throughout Vermont
Habitat: the nests of their hosts
Hosts: mostly squirrels, but also other medium-sized mammals; rarely bite humans
Transmits: Powassan virus (extremely rare in Vermont)
Active: generally, in warmer months
Name: Woodchuck tick (Ixodes cookei)
Distribution: throughout Vermont
Habitat: the burrow of their host animal; rarely on vegetation
Hosts: woodchucks, foxes, skunks, weasels, porcupines, small mammals, some bird species, raccoons, cats, dogs; rarely bite humans
Transmits: Powassan virus (extremely rare in Vermont)
Active: generally, in the summer months
Use the tick tracker
Spot a tick? Share information about where and what kind of ticks you found.