Also known as hard-tick relapsing fever, is caused by a spirochete bacterium related to the Lyme disease bacterium Borrelia burgdorferi, but it is in the relapsing fever group of spirochetes rather than in the Lyme disease or borreliosis group. It was originally found from a tick in Japan in 1991 and was found in Ixodes scapularis in Connecticut in 2001. Clinical cases of BMD in the US were not described until 2013. Borrelia miyamotoi has been found in 2% of I. scapularis ticks collected throughout its northern range from New England to the Mid-West. It has also been found in Ixodes pacificus in the western states.

Borrelia miyamotoi infection in ticks can be passed from an adult female tick to offspring through infected eggs. Thus, all stages (larva, nymph and adult) can transmit the infection to humans by tick bite. The time required for transmission of spirochetes by tick bite may be as soon as 24 hrs, with increasing probability of 75% after complete feeding.

Although not a mandatory reportable disease, more than 100 cases per year are estimated to occur. This is surely an underestimate considering its wide geographic distribution, prevalence in ticks, mode of transmission in ticks, and efficient transmission from tick to humans. BMD is considered to be an emerging disease by the CDC.

Symptoms of BMD include flu-like symptoms: fever, fatigue, sleepiness, chills, muscle and joint stiffness, aches and pains, and nausea. BMD does not cause the EM skin rash associated with Lyme disease. Like other relapsing fever diseases, symptoms may reappear after a period without symptoms. Infection in immunocompromised patients can be much more severe. In combination with generalized flu-like symptoms, immunocompromised patients often exhibit reduced cognition, disturbed gait, memory deficits, confusion, and other neurological deficiencies resulting from inflammation of the brain. Coinfection with B. burgdorferi is possible, but no cases have yet been reported.

Diagnosis of BMD can be difficult. There is currently no specific standardized diagnostic test approved by the FDA. Spirochetes can be visualized in peripheral blood or detected in blood by PCR. Despite its relationship to B. burdgorferi, it cannot be detected by standard antibody tests for Lyme disease. Except for an EM rash, the symptoms are similar to Lyme disease, but symptoms of Lyme disease do not relapse.

Treatment for BMD typically follows the guidelines used for Lyme disease. The antibiotics doxycycline, amoxycillin, and ceftriaxone have been successful in clearing infection. Thus, patients infected with B. miyamotoi, misdiagnosed as Lyme disease, would benefit from the same treatment.

Colloquially known as “rabbit fever,” is a bacterial infection caused by Francisella tularensis. Francisella tularensis is one of the most infectious pathogenic bacteria known; as few as 10 organisms can cause disease in humans, which is an exceedingly low infectious dose.

 While not only transmitted by ticks, F. tularensis can be transmitted by the wood tick (Dermacentor andersoni), the lone star tick (Amblyomma americanum), and the dog tick (Dermacentor variabilis). F. tularensis can also infect humans through multiple routes of exposure, including inhalation, ingestion, and direct skin contact, and other arthropod bites. The bacterium can also survive for weeks in the environment, especially in water and soil. This persistence facilitates its transmission through various means, such as contaminated water or aerosols. This versatility makes it a significant concern from both natural outbreaks and potential bioterrorism perspectives.

Tularemia can be found throughout the U.S., but it’s more common in the south-central, Pacific, and western regions. Outside of the U.S., it has been reported in various parts of the world, especially in the northern hemisphere. While not as prevalent as other zoonotic diseases, several hundred cases are reported annually in the US.. 270 cases of tularemia were reported in 2019.

Symptoms of tularemia depend on the route of infection, with the disease presenting in various forms. After a tick bite, the following forms of tularemia can present:

• Ulceroglandular Tularemia: This is the most common form of tularemia following a tick bite. Patients with this form often develop a skin ulcer at the site of the tick bite. The ulcer is accompanied by swelling of regional lymph nodes, usually those that are nearest to the site of the tick bite.
• Glandular Tularemia: Similar to ulceroglandular tularemia, this form involves swollen lymph nodes but without the presence of an ulcer. It’s less common than the ulceroglandular form but can also result from a tick bite.
• Oculoglandular Tularemia: Though more commonly associated with direct contamination of the eye (e.g., from handling infected animals and then touching the eye), it can occasionally present after a tick bite, especially if one touches the bite and then their eye. It’s characterized by eye inflammation, pain, and discharge, along with swollen lymph nodes.
• Typhoidal Tularemia: This is a more generalized form of the disease, presenting without localized symptoms. It can be a result of any route of infection, including tick bites. Patients might experience fever, fatigue, and other systemic symptoms without obvious ulcers or lymph node involvement. This form can be particularly severe and can sometimes be mistaken for other febrile illnesses.
• Pneumonic Tularemia: While this form is most often associated with inhalation of the bacterium, it can also arise secondarily from other forms of tularemia, potentially including those initiated by a tick bite. Pneumonic tularemia involves cough, chest pain, and difficulty breathing.

One other presentation of tularemia, oropharyngeal tularemia, can be acquired from consuming contaminated food or water. Symptoms impact the mouth, throat, and digestive system and include sore throat, lymphadenopathy, mouth ulcers, tonsillitis, pharyngitis, abdominal pain, diarrhea, vomiting, and fever.

With appropriate treatment, the mortality rate for tularemia is around 1%. However, certain forms, especially pneumonic and typhoidal, can have mortality rates up to 7% if untreated.

Tularemia’s diverse clinical presentation can make initial diagnosis challenging. However, a combination of clinical presentation, history of potential exposure (like tick bites or handling wildlife), and laboratory tests can confirm the diagnosis. Serologic tests, cultures, and PCR are commonly used, though biocontainment procedures must be implemented in handling patient samples due to the bacterium’s high infectivity.

The antibiotic streptomycin has traditionally been the drug of choice for treating tularemia, but gentamicin can also be effective. In mild cases or for patients allergic to aminoglycosides, the antibiotic doxycycline might be used.

Is an emerging tick-borne disease caused by the rickettsial bacterium Rickettsia parkeri, a relative of Rickettsia rickettsii, the bacterium that causes Rocky Mountain Spotted Fever. Rickettsia parkeri is a member of the spotted fever group of Rickettsia, a collection of bacteria that cause similar clinical symptoms but vary in disease severity and specific presentations.

Rickettsia parkeri is transmitted by the Gulf Coast tick, Amblyomma maculatum. Rickettsia parkeri infection is rare with only around 40 cases have been reported since the illness was defined in 2004. Historically, Rickettsia parkeri Rickettsiosis has been associated with the southeastern and south-central regions of the U.S., in line with the geographic range of the Gulf Coast tick. However, cases have now been reported in several states, expanding the known range of this disease.

Symptoms of R. parkeri infection typically appear within 2-10 days after a tick bite and often have overlap with other rickettsial spotted fevers, including fever, fatigue, headache, muscle aches, a distinctive skin rash. Lymphadenopathy (swollen lymph nodes) may also present near the site of the tick bite. In addition, an eschar (a dark, scab-like lesion resembling a sore or a pimple) can be found at the site of the tick bite, distinguishing R. parkeri rickettsiosis from some other rickettsial diseases, and is often the first symptom of infection.

Rickettsia parkeri Rickettsiosis is generally considered milder compared to other rickettsial diseases like Rocky Mountain spotted fever. No identified fatalities have been reported in the US to date, and many patients recover without complications. The antibiotic doxycycline is the recommended treatment for all age groups.

 Like other rickettsial spotted fevers, Rickettsia parkeri Rickettsiosis is diagnosed using a combination of clinical symptoms, history of tick exposure, and laboratory testing. Serologic tests can detect antibodies to R. parkeri, while PCR and culture can identify the bacterium in clinical samples. The presence of an eschar can be a helpful diagnostic clue, but not all patients will have this manifestation.

Is caused by infection by one of several different species of spirochete bacteria of the genus Borrelia. These constitute a group of bacteria that is distinct from the group of spirochetes that cause Lyme disease. In western and central North America the two species that cause infections of humans are Borrelia hermsii and Borrelia turicatae. Other species of Borrelia cause TBRF in South America, Africa, and Eurasia. Another RF agent is Borrelia recurrentis, which is transmitted by the human body louse and not by ticks. Louse-borne relapsing fever has caused large epidemics in the past in which there is spread between people via lice. Louse-borne relapsing fever continues to occur in parts of Africa but not elsewhere. (Borrelia miyamotoi is also a member of the RF group of species but is transmitted is transmitted by hard ticks of the genus Ixodes.)

These bacteria are transmitted to humans through the bite of soft ticks of the genus Ornithodoros. Soft ticks differ in two important ways from the more familiar “hard ticks” that can cause other tick borne illnesses in humans (e.g., the dog tick and the deer tick). First, unlike the more commonly known hard ticks, soft ticks tend to feed quickly, with feeding lasting less than half an hour. Soft ticks often bite hosts during the night and then retreat to their natural habitats, making them less noticeable. Second, soft ticks do not search for prey in tall grass or brush and they do not quest like hard-bodied ticks. Instead, they tend to live within nests in burrows, logs, rock piles, caves, or within walls and ceilings of cabins and houses, feeding as needed on the rodent or other mammal as it sleeps.

The unique feeding and nesting behavior of soft ticks dictates the risk of disease aquisition. Borrelia hermsii, spread by Ornithodoros hermsi ticks, is overall the most commonly reported cause of TBRF in the US. Infection with B. hermsii is commonly associated with rustic cabins where rodents, such as chipmunks, build nests within wall and ceiling spaces. Its distribution ranges from foothills to high elevations of mountainous regions of western North America. Borrelia turicatae, transmitted by Ornithodoros turicata, is typically found at lower elevations of more arid areas of western North America. B. turicatae acquisition is often associated with entry into or sleeping in caves that provide shelter for a variety of small and large mammals.

The incidence of TBRF in the U.S. is low, with 251 total cases reported between 2012-2021, occurring in 11 states, with median case prevalence of 24 reported cases of TBRF every year. Over 70% of cases occur in 3 states: California, Washington, and Colorado. But it is likely under-reported because of the non-specific nature of the presenting illness, lack of diagnostic capacity in most healthcare facilitiies, and empirical use of antibiotics of undifferentiated febrile illnesses by healthcare practitioners.

TBRF has a very distinctive clinical presentation, where patients experience two or more episodes of fever separated by intervals of apparent recovery. These recurrent episodes of fever typically last 2-7 days, separated by afebrile periods of 3-7 days. The first episode may be diagnosed as a viral illness and managed only with symptomatic treatment. Not uncommonly the diagnosis is made when the patient returns to emergency department or clinic with a return of the fever. Other nonspecific symptoms can also be present including headache, muscle and joint aches, chills, and nausea. The name “relapsing fever” derives from these cyclical fever episodes that can recur several times before illness resolves in untreated patients. The bacteria in each relapse are variants that are able to escape from the antibodies that first appear in response to the initial infection.

During each febrile period the temperature may reach 103-104 degrees F. and commonly is accompanied by shaking chills. The febrile period ends over a few to several hours and is accompanied by intense sweating as the body temperature declines. During this time the patient may also have marked fatigue and low blood pressure that calls for intravenous fluids and other support in the hospital. Some patients, especially those infected with B. turicatae, experience neurologic involvement, including facial muscle weakness (Bell’s palsy) or a type of meningitis.   

While TBRF can be debilitating during febrile periods, it’s generally not fatal, especially with timely treatment and if there is not underlying immune deficiency or malnutrition. The mortality rate is estimated to be less than 2% globally, and death due to TBRF is rare in the US. Many milder cases of TBRF may go unnoticed or misdiagnosed as an “acute viral illness”, and an individual’s immune system eventually clears infection after a few cycles of illness even without treatment.

Findings on physical exam vary depending on the severity of illness and when the patient seeks medical care. Regardless, there are no findings, such as a particular type of rash, specific for TBRF. There may be enlargement of the spleen.

Diagnosing TBRF involves a combination of clinical presentation, history of potential exposure, and laboratory testing. The spiral-shaped bacterium can often be seen in smears of blood taken at the time of the fever. The smears are processed with Wright or Giemsa staining as for routine differential counts of white cells by microscopy. Between febrile episodes, the bacteria cannot be seen in blood smears. PCR assays of the blood for RF species are available from some commercial reference laboratories. Tests of antibodies to RF Borrelia species are available from some laboratories but are only useful for retrospective confirmation of the diagnosis after the patient has recovered.

RF is treated with antibiotics. This is usually a penicillin or cephalosporin given intravenously or doxycycline, a tetracycline, given orally. An alternative to the tetracycline for pregnant women is erythromycin or related macrolide antibiotic. With any antibiotic treatment there commonly may be a temporary worsening of the clinical status within an hour or two of administration of the first dose. This includes a rise in temperature and a fall in blood pressure. This phenomenon is called a Jarisch-Herxheimer reaction, and it is in response to the death of many bacteria all at once. Recovered patients may experience some post-infection fatigue, but there is no evidence of persistent infections with a TBRF spirochete either after antibiotic therapy or a natural cure.

There is no vaccine to prevent TBRF. If there has been known exposure to RF, such as an overnight stay in a cabin where there has been another case, a single or a few doses of doxycycline can prevent infection.

Is one of a few tick-borne illnesses in the United States caused by a viral pathogen, specifically, the Colorado Tick Fever Virus (CTFV). CTF is quite rare, with only 59 cases reported between 2010 and 2019. CTFV is a virus in the Coltivirus genus, and is somewhat related to a similar tick-borne virus in Europe, Eyach virus, which can also cause illness in humans. CTFV is an RNA virus, which means that its genetic material is made of ribonucleic acid rather than deoxyribonucleic acid (DNA). CTFV was first isolated from human blood in 1944.

CTFV is transmitted to humans through the bite of the Rocky Mountain wood tick, Dermacentor andersoni, and cases of CTF are almost exclusively restricted to higher elevations (altitudes from 4,000 to 10,000 feet) in the Rocky Mountain region of the US. As of 2020, CTF is a locally notifiable disease in nine states: Arizona, Colorado, Idaho, Montana, New Mexico, Oregon, South Dakota, Utah, and Wyoming.

Symptoms of CTF typically appear between 1 and 14 days following an infected tick bite. Initial symptoms most commonly include fever, chills, headaches, muscle pain, and malaise. Less common symptoms can include pain behind the eyes, photophobia (light sensitivity), abdominal pain, hepatosplenomegaly, nausea and vomiting, sore throat, and rarely, a flat or pimply rash. CTFV often infects erythrocytes (red blood cells), which can lead to biphasic illness in about half of affected individuals. This means symptoms will often dissipate for a few days and then reappear again.

Most cases of CTF are mild, and illness is self-limiting. Affected individuals generally recover completely, although post-illness fatigue and weakness (post-infection sequelae) may persist for several weeks. In rare instances CTF can progress to more severe illness involving the central nervous system and lead to complications such as aseptic meningitis (presenting with stiff neck) and encephalitis (presenting with confusion). Death due to CTF is exceedingly rare.

Diagnosis is primarily based on clinical symptoms and a history of potential exposure to the vector tick in endemic areas. Laboratory tests, such as serology and PCR, can be used to confirm the diagnosis. Given the overlapping symptoms with other illnesses, differential diagnosis is crucial to rule out other tick-borne diseases or conditions that might present similarly.

There is no vaccine to prevent CTFV infection and there are no specific antiviral treatments available to cure infection. Treatment of illness is largely supportive, addressing the symptoms rather than the virus itself. This typically includes rest, fluids, and over-the-counter analgesic and antipyretic medications. In rare cases of severe CTF, some individuals may be hospitalized for intravenous fluids and medications.

Is a rare but emerging tick-borne infection caused by the Heartland virus (officially Heartland bandavirus) (HRTV). HRTV is a Phlebovirus in the Bunyavirus order, which are segmented genome RNA viruses. Distant relatives include the more commonly known Hantaviruses and Arenaviruses (Lassa virus, Junin virus). HRTV was first discovered in 2009 in Missouri by Dr. Scott Folk of Heartland Regional Medical Center.

HRTV is transmitted through the bite of infected Lone star ticks (Amblyomma americanum), which is also the vector capable of spreading Rocky Mountain Spotted Fever, Ehrlichiosis, Tularemia, southern tick-associated rash illness (STARI), and Bourbon Virus Disease.

Currently, HRTV is quite rare, but cases of the Heartland virus have been recognized in several states, including Missouri, Arkansas, Illinois, Indiana, and Oklahoma. It is likely the range of HRTV overlaps with the endemic range of the Lone star tick. As of November 2022, 60 cases of HVD have been reported.

Symptoms typically present between a few days to 2 weeks following a tick bite. Signs and symptoms are similar to several other tick-borne illnesses including ehrlichiosis and include fever and chills, fatigue, headache, muscle/joint pain, decreased appetite, nausea, and diarrhea. Some infected individuals may have low white blood cell counts (leukopenia) and low platelet count (thrombocytopenia). HVD can become quite severe, especially if immune cell function is impacted. While identified cases are rare to date, many have required hospitalization. Current reported mortality rate, based on the limited number of identified cases, is around 10%, but this is likely an overestimation as most unreported cases were likely mild. As such, it’s important to recognize that the true prevalence and mortality rate may differ as more cases are identified and studied.

The diagnostic process for the Heartland virus remains challenging. Given its recent emergence, standard diagnostic tests are not widely available. Typically, diagnosis hinges on a combination of clinical presentation, history of tick exposure, and specialized laboratory tests, often in collaboration with health departments or the CDC. Clinical criteria have recently been defined, which include: fever greater than 38 °C (or 100.4 °F). thrombocytopenia or platelet count lower than 150,000 per mm3, leukopenia or white blood cell count lower than 4,500 cells per mm3, and evidence of a recent infection with Heartland virus (detection of viral RNA in the blood or tissues by reverse transcription polymerase chain reaction, or by viral neutralization assays using convalescent serum from the patient).

There is no vaccine to prevent HRTV infection and there are no specific antiviral treatments available to cure infection. Treatment of illness is largely supportive, addressing the symptoms rather than the virus itself. This typically includes rest, fluids, and over-the-counter analgesic and antipyretic medications. In rare cases of severe HVD, some individuals may be hospitalized for intravenous fluids and medications.

Is a rare but emerging tick-borne infection caused by the Bourbon virus. BVD is a Thogtovirus in the Orthomyxovirus family, which are segmented genome RNA viruses. Bourbon virus was first identified in 2014 in a man in Bourbon County Missouri and isolated by CDC researchers from those patient blood samples.

Thogtoviruses almost never cause illness in humans. The case in 2014 was only the eighth human illness caused by a thogtovirus, and there have been only 5 cases of Bourbon virus reported to date.

The precise vector that can transmit Bourbon virus is still under investigation. However, based on the fact that other Thogtoviruses are transmitted through arthropod bites and the geography and epidemiology of the limited cases of Bourbon viruses in the United States, the leading candidate is the lone star tick (Amblyomma americanum).

Scientists are still learning about possible symptoms caused by this relatively new virus. Symptoms seem to appear about a week after a tick bite, and seem to include fever, fatigue, rash, headache, other body aches, nausea, and vomiting. They also had lower than normal counts of white blood cells (leukopenia) and lower than normal counts of platelets (thrombocytopenia).

Given the limited number of reported cases, determining a precise mortality rate for the Bourbon virus is challenging. However, it is known that the disease can be severe, with some cases being fatal, including the reference case in 2014. Since its discovery, only a handful of cases have been reported, making it a rare but concerning pathogen. Yet, underreporting or misdiagnosis could mean the actual prevalence is higher than currently recognized 

Diagnosing Bourbon virus is complex due to its similarity in presentation to other tick-borne diseases. Currently, there isn’t a widely available standard test for the virus. Diagnosis usually requires specialized laboratory techniques, often involving collaboration with specialized institutions or the CDC.

There are no vaccines or specific antivirals to treat Bourbon virus infection. Care is mainly supportive, focusing on treating symptoms and complications. Hospitalization may be necessary, especially in severe cases or for individuals with other underlying health conditions.

Is a recent emerging illness that the causative agent has not yet been identified. While its clinical presentation is reminiscent of Lyme disease, caused by the Borrelia burgdorferi bacterium, repeated studies have not conclusively linked this or any other specific pathogen to STARI.

 STARI is believed to be transmitted primarily through the bite of the lone star tick (Amblyomma americanum) due to current epidemiology and geographic range of cases. As the name suggests, STARI is primarily observed in the southeastern and south-central United States, which corresponds to the habitat range of the lone star tick. This includes states such as Missouri, Oklahoma, North Carolina, and parts of Texas, among others.

The symptoms typically manifest within a week of the tick bite and can vary in severity. They can include an expanding “bull’s-eye” Erythema migrans rash similar to that observed in Lyme disease, fatigue, fever, headache, muscle and joint pains, and lymphadenopathy (swollen lymph nodes). Other symptoms associated with Lyme such as asymmetrical arthritis, neurological symptoms, or other persistent symptoms.  

They are key clinical distinctions between STARI and Lyme disease. Patients diagnosed with STARI were more likely to recall a tick bite than were patients with Lyme disease and time interval between tick bite to skin rash was shorter among patients with STARI (6 days compared to an average interval of 2 weeks for Lyme). STARI patients were less likely to have other symptoms in addition to EM, it was less likely to present with multiple EM, and size of EM is smaller and more circular (6-10 cm). While causative agent has not yet been identified, antibiotic treatment with doxycycline has typically been used due to symptom similarity to Lyme. After antibiotic treatment, STARI patients recovered more rapidly than did Lyme disease patients.

STARI is typically not associated with long-term complications and is not known to be fatal. The precise prevalence is difficult to pin down, given the challenges in differentiating it from Lyme disease based on clinical presentation alone. However, it’s believed to be a relatively uncommon condition. Exact annual case numbers are not well-established due to the diagnostic ambiguities and potential underreporting.

Diagnosing STARI is challenging because of its clinical similarities to Lyme disease and the absence of a specific diagnostic test. Typically, diagnosis is made based on clinical presentation, history of tick bite, and exclusion of Lyme disease, especially in areas where Lyme is less prevalent. Laboratory tests currently cannot reliably distinguish STARI from Lyme disease.

Even though the exact causative agent of STARI remains unidentified, treatment with oral antibiotics, particularly doxycycline, has been shown to be effective in alleviating symptoms. It’s believed that early treatment can prevent potential complications or the progression of symptoms.

Is a condition that can be initiated by a tick bite, but is not caused by infection with a pathogen. It is the development of an allergy against a specific sugar found in mammals called alpha-galactosidase (galactose-α-1,3-galactose) or alpha-Gal, which humans don’t produce. The subsequent allergy is called alpha-Gal syndrome (AGS).

Ticks also don’t produce alpha-Gal, but non-human mammals that they feed on do. The primary vector associated with the development of AGS in the U.S. is the lone star tick (Amblyomma americanum). However, other tick species worldwide, such as the Australian paralysis tick and European castor bean tick, have also been implicated in the condition. 

The distribution of AGS correlates with the range of the responsible tick species. In the U.S., this primarily encompasses the southeastern and central states, where the lone star tick is prevalent. However, with other tick species implicated internationally, cases have also been reported in Europe, Australia, and parts of Asia.

 AGS can develop independently of a tick bite, but it is thought that exposure to alpha-Gal through tick saliva can trigger this. It is not a common allergy; currently it is estimated around 1% of the US population have IgE antibodies against alpha-Gal.

In the context of tick-bite associated AGS, it is hypothesized that alpha-Gal molecules from a previous blood meal a tick has taken can end up in the tick’s body and be transferred to a new animal once mixed with the tick saliva. In some humans, this sugar may be recognized as foreign, which triggers an immune response. This is the same process that occurs in the development of other food and environmental allergens.

Individuals with AGS may develop symptoms 2-6 hours following consumption of animal products that contain alpha-Gal. Symptoms are similar to other allergies, and can range from mild to severe and include urticaria (hives), itchy skin, swelling, often around the eyes, lips, or inside the mouth, abdominal pain or cramps, nausea or vomiting, diarrhea, runny or stuffy nose, asthmatic symptoms, and rarely, anaphylaxis, a severe allergic reaction that can be life-threatening.

Diagnosis of AGS involves a combination of patient history and specific blood tests that measure IgE antibodies against the alpha-gal molecule. The delayed onset of symptoms after eating red meat, combined with a history of tick bites, often provides clinical clues.

Management includes avoiding foods that contain this sugar. Fish, poultry, and produce do not contain alpha-Gal. Some medications and medical devices may be derived from animal products containing alpha-Gal so ingredient labels may be important for those with AGS.

There is no cure, but recommendations in the US include reducing risk of bites from the Lone Star tick, which has been linked to AGS. For inadvertent exposures or reactions, antihistamines can be used to treat mild symptoms. In cases of severe reactions, like anaphylaxis, injectable epinephrine is necessary, and individuals diagnosed with AGS are often prescribed an epinephrine auto-injector to carry with them. There is currently no cure for AGS, but some individuals have reported a reduction or resolution of their allergy over time, particularly if they avoid further tick bites.