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What is Tick-borne Relapsing Fever (TBRF)?
Relapsing fever (RF) is a zoonotic infection acquired from the bite of a soft tick (endemic or tick-borne RF) or human body louse (epidemic or louse-borne RF), resulting in an illness associated with recurrent episodes of fever. This disease results from infection with spirochetes (bacteria) of the genus Borrelia. RF was known in ancient times and ticks were identified as vectors here in the United States in 1915. We will abandon louse-borne RF (LBRF) at this point and only deal with its tick-borne cousin (TBRF).
How do people get TBRF?
The spirochetes and soft ticks associated with TBRF may be found throughout the world. Soft ticks dwell mainly in the mountains and foothills. Small rodents such as squirrels, chipmunks and mice serve as the natural carrier of infected ticks. As a consequence, soft ticks live in dark, cool places such as rodent nests, shaded woodpiles outside buildings, and indoors between walls or underneath flooring and above ceilings. These ticks may survive for 20 years without feeding and remain infectious up to 10 years following an infection. Infected ticks pass the spirochetes to the offspring.
In contrast to the patient hard tick, the soft tick actively seeks hosts to feed upon and will not hesitate to bite humans found during its search. Unlike hard ticks, which may remain attached for several days, soft ticks remain attached for only 5-20 minutes while feeding, frequently at night, and lack a painful bite. Most people never realize that they were bitten by soft ticks as opposed to hard ticks. Most cases occur during outdoor activities associated with camping in areas having rodent hideaways, especially old cabins and outbuildings. Infection may result from the bite or by contamination of the wound or skin by tick secretions.
What are the symptoms of TBRF?
Infected individuals develop a recurring febrile illness (fever) following an average incubation period of 7 days (range of 3-18 days) after a tick bite. The early signs of RF are often nonspecific and may resemble many other infectious and non-infectious diseases. Initial symptoms include abrupt onset of fever (104-105° F), chills, headache, and muscle ache. Abdominal pain, nausea and vomiting may occur during the course of the illness in addition to a rash. The initial bout of acute illness lasts 3 to 5 days and then abruptly disappears. A few days later, the fever and other symptoms return. With each recurrence the intensity of the illness decreases. This cyclic pattern may continue for several weeks or months without treatment. Jaundice occurs in 7% of patients with deaths recorded in 2%-5%.
Where do the most cases of TBRF occur in the United States?
TBRF is a seasonal disease, and is acquired in mountain forest habitats at altitudes from 3,000 to 9,000 feet in the United States during the summer and fall months when outdoor recreational pursuits are common, but cases may occur any time. The true incidence of TBRF in the United States is unknown as it has never been a nationally reportable disease.
Here in Oregon, 77 cases of TBRF were reported from 1954 through 1989 with 22 (29%) residing in Deschutes County. Cases were reported throughout the year with peak occurrence during the months of June and July. It is thought that the risk of infection from soft ticks exists largely in the eastern counties. One of two notable outbreaks in the Pacific Northwest in 1968 occurred in Oregon in Wheeler County. It involved 5 cases in 2 families, and was associated with sleeping with ticks in a log cabin. The other involved 11 cases among Boy Scouts staying in two rodent-infested log cabins near Spokane, Washington.
How is TBRF diagnosed?
A diagnosis of TBRF is based on a combination of clinical signs and symptoms and laboratory tests, including microscopic examination of blood films and cultures. Your doctor can usually diagnose TBRF by taking a blood sample and observing the spirochetes under a microscope. Spirochetes are most commonly seen in blood samples obtained during one of the episodes of fever.
What is the treatment for TBRF?
TBRF is easily treated with one to two weeks of antibiotics. Most individuals will lose their fever within 24 hours of antibiotic treatment and return to normal within a week. Long-term complications and death due to TBRF are extremely rare.
Can a person get TBRF more than once?
It is not known if immunity develops, nor how long it might remain following infection. Prior illness with TBRF should not deter persons from practicing good tick-preventive measures or visiting a physician if signs and symptoms consistent with TBRF occur, especially following a tick bite.
How can Tick-borne Relapsing Fever be prevented?
Limiting exposure to ticks reduces the likelihood of TBRF infection. In persons exposed to tick-infested habitats, prompt, careful inspection and removal of crawling or attached ticks is an important method of preventing disease. The most important action you can take is to educate yourself about where and how TBRF is likely to be acquired.
Be especially aware of the potential risks when visiting or camping in mountain forests. If you're planning to stay in a cabin:
- Check the sleeping areas for evidence of rodents—for example, holes in the floor or walls, shredded material from mattresses, and rodent feces on counters or in drawers and cupboards.
- Avoid sleeping on the floor or on a bed that touches the wall.
- If the dwelling has been unoccupied, change and wash all bedding before use.
Remember that a building does not have to be obviously rodent-infested to pose a risk of TBRF. Although most TBRF cases occur in older, rustic cabins, people have also been infected in clean, modern homes.
- Wear light-colored clothing to allow you to see ticks that are crawling on your clothing.
- Tuck your pants legs into your socks so that ticks cannot crawl up the inside of your pants legs.
- Apply repellants to discourage tick attachment. Repellents containing permethrin can be sprayed on boots and clothing, and will last for several days. Repellents containing DEET (n, n-diethyl-m-toluamide) can be applied to the skin, but will last only a few hours before reapplication is necessary. Use DEET with caution on children. Application of large amounts of DEET on children has been associated with adverse reactions.
- Conduct a body check upon return from potentially tick-infested areas by searching your entire body for ticks. Use a hand-held or full-length mirror to view all parts of your body. Remove any tick you find on your body.
- Parents should check their children for ticks, especially in the hair, when returning from potentially tick-infested areas. Additionally, ticks may be carried into the household on clothing and pets. Both should be examined carefully.
What is the best way to remove ticks?
To remove attached ticks, use the following procedure:
Folklore Remedies Don't Work!
- Use fine-tipped tweezers or shield your fingers with a tissue, paper towel, or rubber gloves. When possible, persons should avoid removing ticks with bare hands.
- Grasp the tick as close to the skin surface as possible and pull upward with steady, even pressure. Do not twist or jerk the tick; this may cause the mouthparts to break off and remain in the skin. (If this happens, remove mouthparts with tweezers. Consult your health care provider if infection occurs.)
- Do not squeeze, crush, or puncture the body of the tick because its fluids (saliva, body fluids, gut contents) may contain infectious organisms.
- After removing the tick, thoroughly disinfect the bite site and wash your hands with soap and water.
- Save the tick for identification in case you become ill. This may help your doctor make an accurate diagnosis. Place the tick in a plastic bag and put it in your freezer. Write the date of the bite on a piece of paper with a pencil and place it in the bag.
Folklore remedies, such as the use of petroleum jelly or hot matches, do little to encourage a tick to detach from skin. In fact, they may make matters worse by irritating the tick and stimulating it to release additional saliva or regurgitate gut contents, increasing the chances of transmitting the pathogen. These methods of tick removal should be avoided. A number of tick removal devices have been marketed, but none are better than a plain set of fine-tipped tweezers.
How can rodents and ticks be controlled?
Rodent control: Because rodents can pose a risk of other diseases such as plague and hantavirus pulmonary syndrome, household rodent control should be maintained at all times. In addition to eliminating the rodents currently in a residence, it is essential to take measures to prevent future reinfestation.
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Tick control: Direct control of ticks in an infested building is necessary for comprehensive prevention of TBRF. Eliminating rodents without tick control may actually increase the risk of people becoming infected, because hungry ticks will seek out other mammals, including you, upon which to feed if rodents are unavailable. Contact a licensed professional exterminator to discuss appropriate tick control measures for your dwelling.
- Thoroughly check the outside walls and foundation of the building for any openings through which rodents might enter. Ensure that external doors and windows close with a tight seal.
- Keep all food and garbage in tightly sealed containers. Promptly clean up any leftover or spilled food.
- Avoid feeding squirrels, chipmunks, and other rodents around dwellings.
- Eliminate wood piles in or near the house. Store firewood outside, away from walls. Stack wood on pallets or otherwise raised a few inches off the ground; this will discourage rodents from using these areas as nesting sites.