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Tick-Borne Diseases: What You Need to Know

If you spend time outdoors you need to be aware of the dangers posed by ticks. Multiple diseases are transmitted to humans by infected blacklegged ticks. Because these ticks are tiny—much smaller than an American dog tick or lone star tick—special precautions must be taken to avoid bites.

Basic tick facts

Everyone using the trails and grounds at Cary Institute of Ecosystem Studies should be aware that blacklegged ticks, formerly called deer ticks, are abundant on the site. They live in forests, brush, meadows, lawns, and gardens. Any time the temperature is above 0 degrees C (32 degrees F), ticks can be active.

During the larval stage, blacklegged ticks are about the size of the period at the end of this sentence—barely visible. Larvae molt into nymphs, which are about the size of a poppy seed. Most active from May to August, nymphs molt into adults in the fall. Adults are approximately two millimeters (0.08 inches).

A blacklegged tick
An adult blacklegged tick.

Reducing your chances of contracting a tick-borne illness

You can reduce your chances of contracting a tick-borne disease by taking basic precautions:

  • Dress for the outdoors. Ticks are easier to see on light-colored clothing. Wear long pants and sleeves to minimize exposed skin; tuck pants into socks to prevent ticks from crawling up your shoes and onto your bare legs. Wear closed shoes.
  • Use insect repellent. Repellent with no more than 33% DEET (N N-diethyl meta toluamide) may provide some protection. Spray repellent on your clothing, especially on your pant legs from knees to cuffs. Some people report irritation from DEET applied directly to skin. Clothing treated with Permethrin can also repel and kill ticks.
  • Stay on the trails. Ticks are more abundant in brush and leaf litter.
  • Check yourself for ticks. Ticks usually crawl upward and are commonly found on the scalp, behind knees, on the neck, in armpits, and in the groin area. They also seek areas, such as a waistband, where clothing is tight.
  • Remove attached ticks carefully using fine tweezers. Grasp ticks by the head (not the body) and gently pull them straight out. Avoid crushing the body or causing the tiny mouthparts to break off. Wash the wound site, apply antiseptic, and monitor the site for up to two weeks to detect signs of a rash. You may want to save the tick for later identification by your physician, should disease symptoms appear.
A trail on the Appalachian Trail
Staying on the trail when hiking is one precaution you can take to help reduce your chances of contracting a tick-borne disease. Photo: Ken Lund

Tick-borne diseases

Blacklegged ticks can carry organisms that cause the following diseases:

  • Lyme disease, caused by the bacterium Borrelia burgdorferi, was identified in Lyme, CT in 1975. The disease has quickly spread, with cases now reported in every state except Alaska. It is one of the fastest-growing infectious diseases in New York. Since the mid-1980s, scientists at Cary Institute have been researching the ecology of Lyme. Research has revealed intriguing links between the blacklegged tick, some of its hosts (white-tailed deer and white-footed mice), and acorn production in oak forests.
  • Human granulocytic anaplasmosis (HGA), formerly called human granulocytic ehrlichiosis (HGE), is caused by the bacterium Anaplasma phagocytophilum. Discovered in 1994, this disease seems to be rapidly emerging and expanding in Dutchess County and throughout the northeastern U.S. Cary Institute research indicates that in Dutchess County up to 42% of blacklegged ticks carry this disease-causing bacterium, and up to 28% of ticks carry both Lyme disease and HGA bacteria. Therefore, a single tick bite can cause a patient to be exposed to both diseases.
  • Human babesiosis, caused by a protozoan, is also transmitted by the blacklegged tick. Babesiosis appears to be widespread in New York, New England, New Jersey, and the Upper Midwest. Babesiosis is also emerging in Dutchess County.
  • Tick paralysis is transmitted by dog ticks in the eastern U.S. This rare illness is caused by a neurotoxin present in the tick’s salivary glands. While adults can be affected, victims are more frequently children under age seven. Domestic animals are also susceptible. Symptoms subside almost immediately after the tick is removed.
  • Rocky Mountain spotted fever is transmitted by American dog ticks and other tick species. Fewer than 50 cases are reported in New York each year.
  • Human monocytic ehrlichiosis is transmitted by the lone star tick, and appears to be expanding its range into the mid-Atlantic states and the northeast.

It’s important to know that tick-borne diseases are increasing across the US. Diseases carried by blacklegged ticks in Dutchess County are transmitted by similar tick species in different parts of the country.

In addition, you can have more than one disease at the same time! There have been instances of people coming down with multiple tick-borne diseases. This can occur when a person is bitten by a tick that is carrying multiple pathogens, or when a person has multiple tick bites. While the diseases can have similar symptoms, treatment often requires separate medication.

A white-footed mouse
The white-footed mouse is a primary carrier of the bacterium that causes Lyme disease, and a host to the blacklegged tick. Photo: Andy Reago and Chrissy McClarren

Disease symptoms and treatment

Lyme disease


A bull’s eye rash. Most people who contract Lyme disease exhibit a circular red rash at the site of the bite. The rash can appear roughly 3 to 30 days after the bite. Typically starting as a small red spot, the rash can expand to a diameter of 2.5 to 46 centimeters (1 to 18 inches). The rash may have a bright red border and a hard, often pale central area that is warm to the touch. Similar rashes may appear elsewhere on the body.

Early symptoms may resemble the flu: fatigue; headache; fever; chills; nausea; vomiting; diarrhea; sore throat; dry cough; stiff neck; chest, ear, or back pain; pain in muscles and joints; swollen lymph glands or spleen; dizziness; and sun sensitivity.

Later symptoms may include neurological problems such as Bell’s palsy, heart problems, and joint problems that can be confused with arthritis. some patients, the first and only indication of Lyme disease is arthritis, while in others it is neurological problems.


Treatment with an antibiotic—usually (but not limited to) amoxicillin, a penicillin derivative; doxycycline, a tetracycline; or Ceftin®—is most effective in the early stages, but later symptoms are also treatable.

Human granulocytic anaplasmosis (HGA)


Chills, high fever, headache (often severe), muscle aches, and fatigue. Nausea, vomiting, diarrhea, cough, and joint pain have also been reported. In fewer than 20 percent of cases, a rash may appear about one week after the onset of illness. Symptoms typically appear 7 to 11 days after being bitten by an infected tick, though they may emerge up to 21 days later. Anaplasmosis can be fatal.


Doxycycline and other tetracycline antibiotics are used to treat HGA when it is diagnosed early. HGA does not respond to amoxicillin.


Elderly individuals or those with weakened immune systems are most susceptible.


Most cases are asymptomatic; however, symptoms can include malaise, anorexia, fatigue, fever, drenching sweats, muscle pain, and headache. Hemolytic anemia, kidney failure, and dangerously low blood pressure are also possible. Babesiosis can be fatal.


Babesiosis is sometimes treated with atovaquone plus azithromycin or clindamycin plus quinine.

Scientist using seed basket to assess the acorn crop
Seed baskets are used to assess the acorn crop. Acorn production is linked to the health and abundance of white-footed mouse populations, which, in turn, help determine Lyme disease prevalence. Photo: Cary Institute