Bug bites are an unpleasant part of outdoor summer activities but are often little more than an annoyance. Some bugs, though, can pose true health threats with their bothersome behavior. Under the right circumstances, few bugs are as poisonous as ticks, which can cause paralysis, Lyme disease and Rocky Mountain spotted fever to their hosts, whether humans and animal.
Joel Hutcheson, a Colorado State University assistant professor in pest management, is developing a new DNA test that would help physicians determine when a tick bite is serious.
Hutcheson embarks on no small task; there are 83 species of ticks in the United States and more than 800 in the world. The different species and populations within each species of tick are difficult – but important when investigating a tick bite – to identify.
That’s because whether or not a tick bite is poisonous depends upon several factors. Not all ticks are infected with and transmit diseases, some tick species transmit disease more efficiently than others, and geographic areas where ticks are found indicate whether or not certain species and populations of ticks may be carrying disease pathogens and may effectively transmit them. Because researchers know with some detail which species and populations of ticks are better at transmitting diseases and are likely to be carriers within a geographical area, correctly identifying a tick would make trouble-shooting and proactively treating a tick bite much easier for physicians.
Hutcheson, who was recently awarded a $250,000 two-year research grant from the National Institutes of Health, is developing a test that would identify harmful ticks by their DNA, helping physicians trace the risks associated with that tick’s species and location.
"The most common way to tell one species of tick from another is by looking at their mouthparts, located on the tick where you expect to see their head," said Hutcheson. "But, unless an attached tick is carefully removed, its mouthparts stay inside the host, making identification even more difficult. Even when the complete body of a tick is available, imagine sorting through several different tick species to determine which one bit you and the risk is poses.
"Lyme disease, for example, is not known to be carried by ticks in Colorado," said Hutcheson. "But it obviously is a risk to people bitten by black-legged ticks along the east coast where many of the ticks are infected with the disease agent and may transmit it to their hosts. On the other hand, in Colorado, Colorado tick fever or tick paralysis are risks from certain Rocky Mountain wood ticks that remain attached for a long period of time and contain and transmit a toxin or viral agent to their host. Putting a DNA test into the hands of physicians to help them identify the level of risk associated with a tick bite would be invaluable."
Identifying the genus and species of ticks becomes particularly important because the symptoms of a toxic tick bite can be difficult to diagnose. For example, the symptoms of Lyme disease – joint and body aches, fever, headache, fatigue – are similar to the flu. A telltale bull’s eye mark – called an erythema – around the tick bite is an easy visual clue of Lyme disease, but only about 60 percent of people who are infected develop the mark. Lyme disease can be reversed if caught soon enough, but if the disease persists without proper treatment, it may become a long-term and debilitating ailment. The slow paralysis caused by the Rocky Mountain wood tick is often mysterious and difficult to diagnose unless an attached tick is found and removed. Once the tick is removed, the symptoms quickly reverse; if the tick remains attached, the ascending paralysis can be fatal.
Hutcheson’s DNA test would be conducted after crushing the suspect tick that has attached to a host, looking at the DNA to show a specific DNA blueprint. The test would be a quick way for health professionals to look for DNA markers in ticks. By evaluating the ticks’ easily-identified DNA markers, they could determine if the tick was a health threat based on its specific identification.
Hutcheson also researches the abilities of genetic strains of ticks within a species to transmit disease. "A tick’s ability to transmit disease is genetic," said Hutcheson. "The same species of tick can differ genetically, so by testing and examining the ability of specific genetic strains, we can look with even more detail at the probability of infection in someone who has played host to a tick. We also can use genetics to find ticks that are related, which helps to pin-point where a tick was picked up by a host, helping to assess the individual’s level of risk for certain diseases."
Hutcheson added that DNA research on ticks also can begin to identify opportunities to biologically control ticks, reducing the risks of people and animals getting bitten.
Ticks have to already be infected with Lyme disease agent and other pathogens that cause illness before passing them on through their saliva. They pick up those diseases when feeding on animals that are infected, usually mice.
What’s the proper way to remove a tick?
Once a tick has become firmly attached to its host, removal can be difficult. Removing a tick should be done with great care to prevent additional health problems. For example, the mouthparts of a tick are barbed; they sometimes remain in the skin after a tick is removed and can be a source of infection. Do not heat the tick or squeeze its body to remove it. These methods cause the tick to expel blood back into the host, increasing the odds of the tick transmitting a disease.
The recommended procedure to remove a tick is a three-step process:
- Grasp the tick with blunt tweezers as close to the host’s skin as possible. If tweezers are not available and the tick must be grasped by hand, cover fingers with tissue or thin plastic to prevent against the transmission of disease pathogens.
- Pull the tick out of the host slowly and steadily, straight back from the host’s skin. Try not to crush the tick as it is being pulled free.
- After the tick is removed, treat its feeding site on the host with a disinfectant.
(For more information about ticks and tick-borne diseases, view the Colorado State University Cooperative Extension fact sheet on Ticks and Tick-borne illness at www.agnews.colostate.edu and search for "ticks").
What’s the best way to avoid ticks?
- Avoid areas where ticks are likely to be found. Like people, ticks are most active in the spring and early summer and are more abundant where their host animals commonly travel. This includes brushy areas along the edges of fields and woodlands or commonly traveled paths through grassy areas and shrubby areas.
- Wear protective clothing such as long pants and long-sleeved shirts which exclude ticks and help keep them from attaching to the skin. Ticks are usually acquired while brushing against low vegetation, so pull socks over the bottom of pant legs or wear pants with a closure at the bottom, such as a toggle or elastic. Wearing light-colored clothing can make it easier to see ticks that have been picked up.
- Check for ticks after outdoor activity. Ticks take several hours to settle and begin feeding on a host. For example, the Rocky Mountain wood tick takes 12 to 24 hours to start feeding. A thorough "tick check" can be an effective alternative to repellents.
- Few tick repellents are effective, but are an option. Permethrin (Permanone) is a relatively new tick product that should be applied only to clothing. It can rapidly kill ticks that come into contact with it. By far the most common tick repellent is DEET, the active ingredient in most insect repellents such as Cutters and Off! DEET (N, N-diethyl-metatoluamide) is most effective against ticks when it is applied to pants and other areas of the lower body that are more likely to come into contact with ticks. If DEET is used, precautions are urged:
- Do not use high concentration formulations (above 30 percent DEET) on children.
- Apply the repellent to clothing, not the skin.
- Do not apply DEET to hands or other areas of the body that might come into contact with the mouth.
- Do not apply DEET to wounds or irritated skin.
- After using DEET, wash or bathe treated areas, particularly on children.
(For more information about ticks and tick-borne diseases, view the Colorado State University Cooperative Extension fact sheet on Ticks and Tick-borne illness at www.agnews.colostate.edu and search for "ticks.")