Due to climate change, tick season is starting early and is slowly becoming a year-round phenomenon.
Winter weather has been unpredictable in the United States this year. Record snowfall has taken Californians by surprise. Devastating storms have swept across the country, bringing tornadoes, floods and gale-force winds to parts of the South and Midwest. In the Northeast, the warmer winter is causing a different kind of disruption. In Virginia, ticks have appeared early, even before spring. According to health experts, global warming has another devastating effect: tick season has become a year-round occurrence, and with ticks comes the risk of disease for both humans and animals.
Dr Christopher Holstege is head of the Department of Medical Toxicology at the University of Virginia. During his 30-year medical career, he has treated numerous patients with tick-borne diseases, including Lyme disease, ehrlichiosis, Rocky Mountain spotted fever and the rash-causing disease transmitted by southern ticks. “One of my six children developed Lyme disease, and the symptoms included general malaise, fever, dizziness, headache, muscle pain and joint pain, which particularly affected his knees,” he said. UVA Today spoke to Holstege to find out more about how warmer weather is affecting tick season, what this means, and how people can protect themselves.
What is happening now with global warming and ticks in the North-East, and particularly in Virginia?
Exposure to ticks can occur all year round, but ticks are most active during the warmer months, generally from April to September. As global temperatures rise, tick activity will be less hampered by fewer cold days.
Could you describe the life cycle of the Virginia deer tick?
The life cycle of the deer tick, also known as the black-legged tick or Ixodes scapularis, is usually two to three years. During this time, it goes through four life stages: egg, larva, nymph and adult. Once the egg hatches, the larva and then the nymph must find a blood source to develop into the next life stage. Larvae and nymphs can become infected with the Lyme disease bacterium when they feed on an infected wild host, usually a rodent. Nymphs or adult females can transmit the bacteria during their next blood meal. Deer are an important source of blood for ticks and are crucial for their survival and migration into new areas. However, deer are not infected with the Lyme disease bacterium and do not infect ticks.
Can deer ticks transmit Lyme disease with a single bite?
In the eastern parts of the United States, where Lyme disease is common, people can be bitten by bacteria-carrying ticks from spring to autumn. From April to July, nymphs actively seek hosts in the environment, whilst adult ticks are most active in early spring and autumn. Nymph ticks pose a particularly high risk, as their large numbers and small size – about the size of a poppy seed – make them difficult to spot. People with Lyme disease are often unaware of a tick bite before they fall ill. Adult female ticks are also capable of transmitting the bacteria, but because of their larger size – about the size of a sesame seed – they are more likely to be spotted and removed from people.
What dangers do deer ticks pose to humans and animals?
There are numerous tick-borne pathogens that can be transmitted to humans through the bite of an infected tick. Ticks can be infected with bacteria, viruses or parasites. In the United States, the most common tick-borne diseases 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 can cause a number of diseases in other animals, including our pets. Many diseases that infect humans can also infect our pets.
Are there other tick species in the state that people should be aware of, and what risks do they pose?
The Centres for Disease Control and Prevention maintain an excellent resource on which ticks transmit which human diseases. In Virginia, deer ticks can also cause anaplasmosis, which is associated with headaches, chills and muscle aches. Rocky Mountain spotted fever is transmitted by the American dog tick. The lone star tick can spread southern tick-associated rash illness, whose ring-shaped rashes can be mistaken for Lyme disease. The lone star tick can also transmit alpha-gal syndrome, a severe and potentially life-threatening allergic reaction whose symptoms appear after eating red meat.
What are the symptoms of Lyme disease, and what should people do if they think they have contracted it?
Early, localised Lyme disease is characterised by a rosette-patterned rash, which may feel warm to the touch and can spread to a width of up to 30 centimetres. It typically appears 7–14 days after the tick has detached. Patients may also experience fever and pain. The rash is typically described as a maculopapular, erythematous, round or oval skin lesion that gradually spreads over several days and reaches a diameter of 5–20 centimetres. The rash is usually not painful or itchy, but may feel warm to the touch.
What happens if Lyme disease is not detected in its early stages?
Lyme disease can also develop in later stages, usually 3–12 weeks after the initial infection. Symptoms may include general weakness; fever; neurological symptoms, including dizziness and headache; muscle pain; and cardiac symptoms, such as chest pain, palpitations and shortness of breath. The knee, ankle and wrist joints are often affected. Bell’s palsy occurs in approximately 5% of patients. Rarely, brain damage may occur, involving impaired concentration, cognition, memory loss and personality changes, which may include extreme irritability and depression.
What are the best ways to reduce exposure to ticks for humans and pets?
It is worth knowing where to expect ticks. Ticks live in grassy, bushy or wooded areas and can attach themselves to humans from pets and be transmitted. Many people pick up ticks in their own gardens or in their neighbourhood. When walking on paths, walk in the middle. Treat clothing and equipment with products containing 0.5% permethrin. Use insect repellents registered by the Environmental Protection Agency that contain DEET, picaridin, IR3535, lemon eucalyptus oil, para-menthane-diol or 2-undecanone. Check yourself and your clothing for ticks after spending time outdoors. Ticks can enter the house on your clothing. Any ticks found must be removed. Dry clothes in the tumble dryer on a high heat setting for 10 minutes to kill any ticks that may have entered the house on dry clothes. If clothes need to be washed first, hot water is recommended. And don’t forget to check your pets for ticks too.
Source: University of Virginia
(C) Lyme Borreliosis Foundation
