There are around 850 tick species, making them the second most important insect vectors of human disease after mosquitos. The first description of tick-borne disease dates back nearly 2500 years. In the early 18th century, European physicians observed patients displaying symptoms similar to those of Lyme disease as we recognize it today. Subsequent discoveries further enhanced our knowledge of diseases transmitted by ticks.
In the United States, ticks are the primary carriers of disease among insects. Whether you engage in outdoor pursuits or not, encountering ticks is almost inevitable. Additionally, pets can introduce ticks into households, affecting even those who do not spend time outdoors.
The global warming trend has extended the period during which ticks are present and the timeframe for potential exposure to them. Due to the rising temperatures, ticks are now being discovered at higher elevations.
After a tick starts feeding, its feeding organ (hypostome) penetrates the host's skin. The hypostome is equipped with numerous barbs that are directed backwards from the point of entry into the skin, aiding in the tick's attachment.
Various infectious agents are transmitted by ticks. Below are the main diseases in the United States that are transmitted by ticks.
Illnesses caused by Borrelia
In the United States, Lyme disease is the most significant illness caused by species of Borrelia.
Lyme Disease
In the 1970s, physicians from the Yale School of Medicine examined a group of arthritis cases in children living close to Old Lyme, Connecticut. Subsequent research revealed that this was a disease transmitted by arthropods, which, similar to any infection, improved with antibiotic treatment.
The surveillance of Lyme disease commenced in 1982 at the Centers for Disease Control and Prevention (CDC), with the disease being designated as reportable in 1991. By the year 2000, Lyme disease constituted over 90% of all cases of vector-borne diseases in the United States (2).
Lyme disease can affect anyone, with two peak age groups being children aged 5 to 14 and adults aged 50 to 59. This disease is a worldwide issue, having been identified on all continents (3,4).
Symptoms
There are various constitutional, skin, nerve, cardiac, and musculoskeletal symptoms associated with Lyme disease. The predominant symptoms include general muscle aches, headaches, fatigue, neck stiffness, and bone pain. These symptoms can be challenging to differentiate from common viral infections, potentially resulting in misdiagnosis.
The disease progresses through three stages. It typically starts with a localized infection accompanied by constitutional findings and symptoms, leading to the appearance of the characteristic red, round rash (stage 1). Within a few days, the spirochetes disseminate through the bloodstream and nerves, resulting in cardiac and joint abnormalities (stage 2). Ultimately, chronic infection of the joints, nerves, skin, or eyes can manifest months or even years later (stage 3).
Diagnosis
The CDC has established a surveillance case definition for Lyme disease. This requires exposure to ticks in an endemic area and a skin lesion that is larger than 5cm. By this definition, exposure requires outdoor activities in the past 30 days of the onset of skin lesion. An endemic area is considered one where there has been at least two confirmed cases of Lyme disease. Unfortunately this definition is used for reporting and not helpful in actual individual diagnosis.
Although there are various blood tests available, most of them show non-specific results. Culture is considered the most accurate method for diagnosis, but it can be challenging to acquire. An alternative approach is to perform a skin lesion biopsy.
Ultimately, an accurate clinical diagnosis of Lyme disease hinges on the patient's medical history, risk factors, and a physician with expertise in the condition.
Treatment
Although most symptoms of Lyme disease will get better on their own without treatment (3), using the right antibiotics can help speed up recovery at any stage of the illness.
The likelihood of severe complications in individuals with a known tick bite who do not receive treatment is minimal, as fewer than 5% of those bitten in areas where ticks are common end up getting infected. Additionally, the majority of individuals who notice a tick bite remove the tick before it has been attached for the 36-48 hours needed for the tick to transmit an infection.
Lastly, the typical rash develops in nearly 90% of those who get infected, making diagnosis easier.
Rickettsial Diseases
Out of these, three have the potential to spread diseases. These are Rocky Mountain spotted fever, Q fever, and ehrlichial infections. It is crucial to emphasize that coming into contact with crushed ticks or their fluids can transmit rickettsiae.
Rocky Mountain Spotted Fever
In 1896, the Snake River Valley area of Idaho was where this disease was initially identified. Dr. Howard Ricketts not only determined the epidemiology of the disease but also discovered that ticks were responsible for transmitting it. The causative organism was subsequently named Rickettsia rickettsii.
Symptoms
If a person with a history of tick exposure experiences a sudden onset of chills and fevers, it could be a sign of Rocky Mountain spotted fever. This disease typically causes a widespread rash with inflammation of blood vessels in around 90% of affected individuals. The rash commonly starts on the wrists, hands, ankles, and feet before spreading towards the center of the body.
At first, it starts as a small reddish lesion that turns into a larger, more prominent lesion that does not blanch. Eventually, the rash darkens to a red-black color.
While immunocompromised patients are unlikely to develop this rash, they are at a higher risk of mortality from this disease (6). Additional symptoms may range from mild headaches to encephalopathy, seizures, ataxia, and delirium. Gastrointestinal symptoms are also frequently observed.
Diagnosis
Early detection and prompt treatment greatly decrease the morbidity rate and almost completely eliminate the risk of death from this illness. As a result, some physicians may initiate treatment based on suspicion of Rocky Mountain spotted fever, even prior to a conclusive diagnosis. Serology serves as the confirmatory test, although it is not flawless.
Treatment
If individuals residing or spending time in regions where Rocky Mountain spotted fever is common experience symptoms like headache, fever, and muscle aches, it is advised to use antibiotics. Those who receive prompt antibiotic therapy are three times less likely to succumb to the illness (7).
Q Fever
Discovered in Australia in 1937, this zoonotic illness is present globally and impacts both wild and domestic animals. The typical method of transmission to humans is through aerosol dissemination of the pathogen Coxiella burnetii.
Thankfully, this occurrence is quite uncommon, with only around 10 cases being reported in the United States annually.
Symptoms
Flu-like symptoms such as fevers, headache, and muscle aches are the most frequently observed clinical manifestations.
Diagnosis
Q fever is diagnosed using serologic testing.
Treatment
The cornerstone of treatment is antibiotics, with the specific drug and duration of therapy determined by whether the disease is acute or chronic.
Ehrlichiosis
In the mid-1980s, Ehrlichiosis was identified in rural regions of Arkansas where numerous instances of a fever-causing illness with symptoms resembling those of Rocky Mountain spotted fever were reported (9).
Human monocytic ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE) are the two fundamental forms of ehrlichiosis that affect humans.
Human Monocytic Ehrlichiosis (HME)
While it has been reported in 46 states, this disease is mainly concentrated in the south central and southeastern regions of the United States. The primary transmission of the disease occurs between March and November.
Human Granulocytic Ehrlichiosis (HGE)
The disease is prevalent in the northern-central and northeastern regions of the United States.
Symptoms
From a clinical standpoint, HME and HGE exhibit striking similarities. Symptoms such as malaise, back pain, gastrointestinal issues, and fevers reaching up to 102 F (39 C) typically manifest within one to two weeks following exposure to a tick carrying the infection. A significant portion of infected individuals need to be hospitalized. It is important to note that this illness has the potential to be life-threatening.
Typically, individuals who are immunocompromised, aged over 60, and those who have not been administered suitable antibiotics within a week of symptom onset are at the highest risk of mortality (12).
Diagnosis
There are laboratory tests that can be done to verify the diagnosis.
Treatment
The main treatment approach relies on using the right antibiotic therapy.
Tick borne viral diseases
Colorado Tick Fever
Only adult ticks are typically capable of transmitting this tick-borne virus, which is the most common in the United States.
Symptoms
Similar to dengue fever, this illness presents with fevers reaching 104F (40C) for a few days, followed by a short period of relief before another fever episode of similar length. Severe complications are more likely to arise, particularly in children under the age of 10.
Diagnosis
Typically, this is diagnosed clinically, although a laboratory diagnosis is possible.
Treatment
The treatment is not specific and consists solely of providing support. Typically, recovery lasts for a few weeks, but the infection usually results in lifelong immunity.
Babesiosis
There are pleomorphic protozoan parasites, with over 70 species identified (13). They are transmitted through a tick bite.
Symptoms
Symptoms typically begin with a slow development of malaise, loss of appetite, and tiredness, progressing to fever, sweating, and muscle aches over the course of several days. The incubation period ranges from one to four weeks after being bitten by a tick, and the majority of individuals do not remember being bitten once symptoms appear. While most individuals with a healthy spleen recuperate without the need for specific treatment, prolonged fatigue and malaise are frequently experienced.
Diagnosis
Individuals with unexplained fevers living in or traveling to an endemic region during the midsummer months should be mindful of the possibility of having babesiosis, especially if there is a history of a tick bite. Diagnosis involves confirming the presence of the parasite through a blood smear.
Treatment
Individuals with mild symptoms typically get better on their own without the need for treatment. Antibiotic treatment may be necessary for those who are immunocompromised, lack a functioning spleen, or are elderly (15).
Prevention
In order to avoid tick-borne diseases, it is crucial to understand ticks and the diseases they can transmit. Wearing light-colored clothing can aid in spotting ticks more effectively.
DEET-based insect repellents are generally safe, efficient, and can be applied directly to the skin. For added protection, you may consider using a permethrin-based acaricidal spray such as Permanone on clothing, which will provide protection for approximately a month and endure several washes. It is crucial to avoid applying permethrin directly onto the skin.
It is important to regularly check your body when in an area infested with ticks. While certain tick-borne illnesses may necessitate the tick to remain attached to the skin for 24 to 48 hours, others can transmit diseases within just one hour.
It is not recommended to remove attached ticks using bare hands. Instead, fine tipped forceps can be utilized to carefully grasp the tick as close to the skin as feasible and slowly pull it out in a straight motion. While there are commercial kits available for this purpose, they are generally more expensive.
Using petroleum jelly, a lighted match or cigarette, alcohol, or fingernail polish does not help in removing the tick. On the contrary, these "home remedies" can lead to an increased release of tick saliva and other contents, raising the risk of disease transmission (16,17).
To effectively eliminate ticks, it is advisable to wash clothes in hot water and then dry them on high heat after being in areas where ticks are present. While this method usually works, there is still a chance that some ticks may survive. Therefore, it is recommended to dry clothing on high heat in the dryer for a minimum of one hour (18).
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Safe travels.
Please remember that medical information provided by us must be considered an educational service only. This blog should not be relied upon as medical judgement and does not replace your physician’s independent judgement. This is NOT medical advice. Please seek the advice of your physician.
References:
1- Hoogstraal H: Tick-borne Crimean-Congo hemorrhagic fever. In Steele JH (ed): CRC Handbook Series in Zoonoses, Section B: Viral Zoonoses, vol I. Boca Raton, Fla, CRC Press, 1981.
2- Herrington JE: Risk perceptions regarding ticks and Lyme disease: A national survey. Am J Prev Med 26:135–140, 2004.
3- Hudson BJ, Stewart M, Lennox VA, et al: Culture-positive Lyme borreliosis. Med J Aust 168:500–502, 1998.
4- Russell RC: Lyme disease in Australia-still to be proven! Emerg Infect Dis 1:29–31, 1995.
5- Salazar JS, Gerber MA, Goff CW: Long-term outcome of Lyme disease in children given early treatment. J Pediatr 122:591, 1993.
6- Walker DH, Mattern WD: Rickettsial vasculitis. Am Heart J 100:896, 1980.
7- Hattwick MA, Retailliau H, O'Brien RJ, et al: Fatal Rocky Mountain spotted fever. JAMA 240:1499–1503, 1978.
8- Dalton MJ, Clarke MJ, Holman RC, et al: National surveillance for Rocky Mountain spotted fever, 1981–1992: Epidemiologic summary and evaluation of risk factors for fatal outcome. Am J Trop Med Hyg 52:404–413, 1995.
9- Derrick EH: Q fever, a new fever entity: Clinical features, diagnosis and laboratory investigation. Med J Aust 2:281, 1937.
10- Fishbein DB, Sawyer LA, Holland CJ, et al: Unexplained febrile illnesses after exposure to ticks: Infection with an ehrlichia? JAMA 257:3100–3104, 1987.
11- Fishbein DB, Dawson JE, Robinson LE: Human ehrlichiosis in the United States, 1985 to 1990. Ann Intern Med 120:736, 1994.
12- Standaert SM, Yu T, Scott MA, et al: Primary isolation of Ehrlichia chaffeensis from patients with febrile illnesses: Clinical and molecular characteristics. J Infect Dis 181:1082–1088, 2000.
13- Ristic M, Healy GR: Babesiosis. In Steele JH (ed): CRC Handbook Series in Zoonoses, Section C: Parasitic Zoonoses, vol I. Boca Raton, Fla, CRC Press, 1981.
14- Ruebush [or as Reubush] TK 2nd, Cassaday PB, Marsh HJ, et al: Human babesiosis on Nantucket Island: Clinical features. Ann Intern Med 86:6–9, 1977.
15- Centers for Disease Control: Clindamycin and quinine treatment for Babesia microti infections. MMWR Morb Mortal Wkly Rep 32:65–66, 72, 1983.
16- Barker RW, Burris E, Sauer JR, Hair JA: Composition of tick oral secretions obtained by three different collection methods. J Med Entomol 10:198–201, 1973.
17- Needham GR: Evaluation of five popular methods for tick removal. Pediatrics 75:997,1985.
18- Carroll JF: A cautionary note: Survival of nymphs of two species of ticks (Acari: Ixodidae) among clothes laundered in an automatic washer. J Med Entomol 40:732– 736, 2003.
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