It’s tick season again, North America. When the weather warms up and people move outside, the chances of encountering one of these bloodsucking arthropods increase. In fact, tick problems today appear to be worse than they were 50-60 years ago, experts told Live Science.
It pays to be cautious; Ticks cause at least 50,000 cases of the disease in the United States each year, and these are just the diseases that are diagnosed and reported to the Centers for Disease Control and Prevention (CDC).
In fact, the actual onset rates of tick-borne diseases are likely to be much, much higher. For instance, an estimate of 2021 suggests that 476,000 Americans are treated for Lyme disease alone every year. (This may overestimate the actual number of Lyme infections, according to the CDC, because people are sometimes treated for Lyme as a precaution after being bitten by a tick.)
While there is no single national surveillance system that catches all cases of tick-borne diseases, the risk clearly varies from state to state. In the northeast, where deer ticks (Ixodes scapular) thrive, Lyme is a concern. In the southeast, where dog ticks (Dermacentor variabilis) tend to reside, spotted fevers dominate, including spotted fever of the Rocky Mountains with the somewhat misleading name.
Related: 9 out of 10 ticks in this Pennsylvania park carried a potentially fatal neurological virus
Dating ticks on the rise
Ticks are effective disease propagators because they can feed on multiple host animals and because they remain attached to their hosts for several days, leaving ample time for pathogen transmission, said Jerome Goddard, professor of medical entomology at Mississippi State University.
Growing deer populations are a major reason tick encounters are on the rise, Goddard told Live Science. Ticks find food by ambushing passing animals, she said, and if the ticks don’t find a host, they die. When more deer are present, more ticks survive, which means that the deer and tick populations are intimately linked. The development of rural areas, bringing people closer to closer contact with ticks, also plays a role, According to the Center for Disease Control and Prevention. In the end, climate change can alter the range of ticks and tick pathogens in ways that are not yet fully understood, also potentially increasing the likelihood of people interacting with ticks.
According to the CDC Tick Bite Data TrackerMay and June are the peak months for tick bites that send people to the emergency room. During these months, the Northeast sees the highest number of tick-related emergency room visits per 100,000 people, followed by the Midwest and then the Southeast.
Lyme disease, which is caused by the bacterium Borrelia burgdorferi and transmitted by deer ticks, most commonly afflicts people in the Northeast and Midwest, as does anaplasmosis, another bacterial disease spread by deer ticks. People in the central Atlantic and southeast are most at risk for spotted fever, including Rocky Mountain spotted fever, caused by the bacterium Rickettsia Rickettsia.
Ehrlichiosis, a bacterial infection spread by both deer ticks and the lone star tick (American ambliomma), is most commonly reported in the mid Atlantic, southern, and Arkansas, Missouri, Oklahoma, and Kansas.
Typically, these tick-borne bacterial infections present with symptoms such as fever, headache, rash, and chills. They are all treatable with antibiotics if caught early, but missed infections can be fatal. Infections can also cause long-term problems. For example, a subset of people who contract ehrlichiosis later develop an allergy to red meat, Live Science previously reported.
These bacterial diseases have long been a consequence of tick bites. More recently, however, doctors and scientists have identified a number of viral diseases that also transmit ticks. These include Heartland and Bourbon viruses, which have been reported primarily from the South and Midwest. These viruses can cause fever, fatigue, headache, diarrhea, joint pain, and sometimes reduced platelet and white blood cell counts. There are no treatments for these viruses. Most people recover, but some patients have died. More serious is the Powassan virus, spread more often by ticks in the northeastern and Great Lakes regions, which is capable of infecting the brain and membranes around the spinal cord.
Fighting tick-borne diseases
With tick-borne disease a growing problem, researchers are looking for ways to combat. At SUNY Upstate Medical University in Syracuse, New York, microbiologist and immunologist Saravanan Thangamani and his team are working to develop vaccines for emerging tick-borne viruses, most notably the Powassan virus. These viruses are transmitted immediately when a tick bites, Thangamani told Live Science, so vaccines are needed that prevent the viruses from replicating in the human body and spreading beyond the skin.
Bacterial diseases are another story. In most cases, the bacteria that cause these diseases take 24 to 36 hours after the initial bite to spread. Instead of trying to develop vaccines for every single disease, Thangamani and other scientists are looking for vaccines that target the ticks themselves.
An effective tick vaccine would work by targeting a cocktail of proteins found in ticks’ saliva. Ticks inject a dynamic blend of these proteins during the days they feed to numb the skin and evade the host immune system. Animal trials led by Yale University researchers showed that an the tick vaccine can interfere with the feeding of ticks and get them to leave their host quickly, as previously reported by Live Science.
“I feel that in the next three or five years we should have good candidates” for vaccines, Thangamani said.
Meanwhile, the best defense is a good offense. To avoid tick bites in the first place, dress appropriately when in tick-rich areas, Goddard advised. Tucking your pants into your rubber boots – or at least your socks – can keep ticks at bay.
“If you wear boots, leather boots, that go up to your ankles and your trouser legs flap in the breeze, that’s an interstate highway up to your trouser legs,” Goddard said.
Treating your clothes with a spray containing the permethrin insecticide will kill ticks on contact. (Insect sprays containing DEET also help, Goddard said, but not as effectively.) Finally, checking your body for ticks after outdoor activities is key, Goddard said. If you find a tick attached, remove it immediately with tweezers by grabbing it close to the skin and pulling it straight up.
Mark the tick bites on a calendar so that if you get sick in the next few weeks, you can tell your doctor you were bitten and the date of the bite, Goddard said. There are some paid services that will test ticks for disease, as well as a limited number of state health departments and research organizations that will do the same for free. One of these organizations, NYticks.org, is run by Thangamani’s laboratory. Researchers have tested nearly 20,000 ticks, mostly from the state of New York, and have a real-time state data dashboard that shows which pathogens are present in which counties.
“The real-time presentation of the data is what is truly unique and very, very powerful,” said Thangamani.
Originally published in Live Science