Deer Tick Season Is Early, Thanks to Global Warming. Here Is What You Need To Know

March 15, 2023
Picture of deer tick

The deer tick can transmit Lyme disease. Its hallmark is a bull’s eye-patterned rash that can be warm to the touch and spread up to 12 inches across.

Winter weather has been wonky in the United States this year.

Record snowfall has stunned Californians. Destructive storms have raced across the country, bringing tornados, flash floods and bracing winds to parts of the South and Midwest.

In the Northeast, warmer winters are creating a different kind of disruption. Health experts say global warming is having another, destructive effect: Deer tick season has become a year-round event.

In Virginia, deer ticks have been making an early appearance as well, before their typical spring debut. With ticks come the threat of disease for humans and animals.

Dr. Christopher Holstege is the University of Virginia’s chief of the Division of Medical Toxicology. Throughout his 30-year medical career, he has seen many patients present with tick-borne disease, including Lyme disease, ehrlichiosis, Rocky Mountain spotted fever and Southern tick-associated rash illness.

“One of my six children developed stage 2 Lyme disease and developed symptoms that included general malaise, fever, dizziness, headache, muscle aches and joint pain that especially affected his knees,” he said.

UVA Today reached out to Holstege to learn more about how warmer weather is affecting deer tick season, what it means and how people can protect themselves.

Q. What is happening right now with global warming and deer ticks as you understand it in the Northeast, and in Virginia in particular?

A. Tick exposure can occur year-round, but ticks are most active during warmer months, normally from April to September. As global temperatures rise, tick activity will be less hindered due to fewer cold days. 

Portrait of Dr. Christopher Holstege
Dr. Christopher Holstege is chief of UVA Health’s Division of Medical Toxicology. (Photo by Sanjay Suchak, University Communications)

Q. Can you describe the life cycle of deer ticks in Virginia?

A. The life cycle of the deer tick, also known as the blacklegged tick, or Ixodes scapularis, is generally two to three years. During this time, they go through four life stages: egg, larva, nymph and adult. After the egg hatches, the larva and then nymph must find a blood meal to develop to the next life stage.

Larval and nymphal ticks can become infected with Lyme disease bacteria when feeding on an infected wildlife host, which is usually a rodent. Nymphs or adult females can then spread the bacteria during their next blood meal.

Deer are important sources of blood for ticks and are important to tick survival and movement to new areas. However, deer are not infected with Lyme disease bacteria and do not infect ticks.

Q. Do deer ticks transmit Lyme disease with a single bite?

A. In most cases, a tick must be attached for 36 to 48 hours or more before the Lyme disease bacterium can be transmitted. If you remove a tick quickly (within 24 hours), individuals can greatly reduce the chances of getting Lyme disease. In areas of the Eastern United States where Lyme disease cases are common, people may be bitten by deer ticks carrying bacteria from spring through the fall. From April through July, nymphs are actively looking for hosts in the environment, and in early spring and fall seasons, adults are most active.

Nymphal ticks pose a particularly high risk due to their abundance and small size – about the size of a poppy seed – which makes them difficult to spot. Lyme disease patients are often not even aware of a tick bite before getting sick. Adult female ticks also can transmit the bacteria, but because of their larger size – about the size of sesame seed – they are more likely to be noticed and removed from people before transmission of the bacteria can occur.

Q. Has the deer population in Virginia grown or lessened, and how is that affecting deer ticks this season?

A. Beginning in the 1940s, work was done to protect Virginia’s deer herd and it subsequently grew as a result of protective game laws, deer stocking and habitat restoration. Today, deer management objectives have changed to control and stabilize populations over much of Virginia.

Current computer reconstruction models provide a pre-hunt season population estimate of 850,000 to 1 million deer in Virginia. According to the Virginia Department of Wildlife Resources, most of Virginia’s deer herds are managed through regulated hunting at moderate to low population densities, in fair to good physical condition, and below the biological carrying capacity of the habitat.

Q. Is there a particular deer species in Virginia most responsible for helping to spread deer ticks?

A. White-tailed deer serve as the primary host for the adult deer tick, the vector for Lyme disease, human babesiosis and human granulocytic anaplasmosis. The number of resident-reported cases of Lyme disease per 100 households was strongly correlated to deer density in the community.

Q. What are the dangers deer ticks pose to humans and animals?

A. There are a number of tick-borne pathogens that can be passed to humans by the bite of infected ticks. Ticks can be infected with bacteria, viruses or parasites. The most common tick-borne diseases in the United States include Lyme disease, babesiosis, ehrlichiosis, Rocky Mountain spotted fever, anaplasmosis, Southern tick-associated rash illness, tick-borne relapsing fever and tularemia. Other tick-borne diseases in the United States include Colorado tick fever, Powassan encephalitis, and Q fever.

Ticks are capable of causing many diseases in other animals, including our pets. Many of the same diseases that infect humans can infect our pets also. 

Q. Are there other types of ticks in the state people should be aware of, and what dangers do they pose?

A. The Centers for Disease Control and Prevention maintains an excellent resource of which ticks transmit which human diseases. In Virginia, deer ticks can also cause anaplasmosis, which brings headache, chills and muscle aches. Rocky Mountain spotted fever is transmitted by the American dog tick. The lone star tick can transmit Southern tick-associated rash illness, whose ring-like rash can be confused with Lyme disease. The lone star tick can also transmit alpha-gal syndrome, a serious and potentially life-threatening allergic reaction with symptoms that occur after people eat red meat.

Q. What are the symptoms of Lyme disease and what should people do if they think they have it?

A. The hallmark of early localized Lyme disease is a bull’s-eye-patterned rash that can be warm to the touch and spread up to 12 inches across. It typically appears seven to 14 days after tick detachment.

Patients can also experience fever and aches and pains. The rash is typically described as a macular, erythematous, round or oval skin lesion that expands gradually over a period of days to reach a diameter of 5 to 20 centimeters (2 to 8 inches). The rash is generally not painful or itchy, but it may be warm to the touch. Approximately 70% to 80% of patients with Lyme disease will present with a rash, and it is the most valuable sign for the clinical practitioner. In the appropriate clinical situation, the rash is the only sign of Lyme disease that is sufficiently distinct to allow clinical diagnosis in the absence of laboratory confirmation.

‘Inside UVA’ A Podcast Hosted by Jim Ryan
‘Inside UVA’ A Podcast Hosted by Jim Ryan

Q. What happens if Lyme disease is not caught in its early stages?

A. Lyme disease may progress to a later stage and usually develops three to 12 weeks after the initial infection. Features may include general weakness; fever; neurological features, including dizziness and headache; muscle pain; and cardiac symptoms like chest pain, palpitations and shortness of breath. The knee, ankle and wrist joint are often involved. These symptoms may last 12 to 20 weeks, but recurrence is rare. Bell’s palsy is seen in about 5% of patients. Encephalopathy may rarely occur and present with deficits in concentration, cognition, memory loss and changes in personality that may include extreme irritability and depression.

Q. What are the best ways to prevent exposure to ticks for humans and pets?

A. Know where to expect ticks. They live in grassy, brushy or wooded areas and can attach and be transmitted to humans from pets. Many people get ticks in their own yard or neighborhood. When on trails, walk in the middle.

Treat clothing and gear with products containing 0.5% permethrin. Use Environmental Protection Agency-registered insect repellent containing DEET, picaridin, IR3535, Oil of Lemon Eucalyptus, para-menthane-diol or 2-undecanone.

Check yourself and clothing for ticks after being outside. Ticks may be carried into the house on clothing. Any ticks that are found should be removed. Tumble dry clothes in a dryer on high heat for 10 minutes to kill ticks on dry clothing after you come indoors. If the clothes require washing first, hot water is recommended. And don’t forget the check your pets for ticks, too.

Q. Why isn’t there a Frontline-type of product for humans?

A. Frontline is made from Fipronil. There hasn’t been significant research into its impact on human health and it isn’t a part of any product intended for human use. There is no similar product for humans.

Media Contact

Jane Kelly

University News Senior Associate Office of University Communications