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Below you’ll find an alphabetized list of useful terms for understanding tick-borne illness. This list is by no means comprehensive, but I’ll be updating it periodically–and taking suggestions in the comments!


Anaplasma phagocytophylum: a bacterium transmitted primarily by the black-legged tick (Ixodes scapularis) and the western black-legged tick (Ixodes pacificus) that causes Anaplasmosis (see below).

Anaplasmosis: a tickborne disease caused by the bacterium Anaplasma phagocytophilum. It was previously known as human granulocytic ehrlichiosis (HGE) and has more recently been called human granulocytic anaplasmosis (HGA). See Anaplasmosis fact sheet for more details.

arthralgia: a fancy medical term for joint pain. The origin is Greek (arthro- = joint; -algos = pain). Arthralgias may be a symptom of injury, infection, illness, or an allergic reaction. They are a common symptom with tick-borne infecious diseases (TBIDs) like Borrelia burgdorferi (Lyme Disease), Borrelia hermsii (TBRF), and Babesia.

Arthritis: inflammation of the joints. There are over 100 different types of Arthritis. According to the CDC, it is “the most common cause of disability in the United States, limiting the activities of nearly 21 million adults.”

assay: an investigative (analytic) procedure in laboratory medicine for qualitatively assessing or quantitatively measuring the presence or amount or the functional activity of a target entity (the analyte) which can be a drug or biochemical substance or a cell in an organism or organic sample. Read about labs and testing for Borrelia infections.

Atovaquone: see Mepron.

azithromycin: an antibiotic in the azalide subclass of macrolide antibiotics. It is often used to treat ear infections, strep throat, pneumonia, typhoid, and sinusitis. Some doctors use it to treat Lyme Disease, Babesiosis (in combination with Mepron), and Bartonella infections.


Babesiosis: caused by infection with bacteria in the genus Babesia (including Babesia microti, B. divergens, B. duncani (WA-1), and MO-1 (unnamed strain)), which are transmitted by  blacklegged ticks (or deer ticks, Ixodes scapularis) To read more about symptoms, diagnosis, and treatment, see the Babesiosis fact sheet.

Bartonella: a genus of Gram-negative bacteria that can be transmitted from the bites of ticks, fleas, sand flies, lice, and mosquitoes (and also cats, in the case of B. henselae). See below for species specifics.

Bartonella henselae: bacterium that causes cat-scratch disease (CSD). CSD can be contracted through scratches and bites from domesticated or feral cats. Symptoms include  fever; enlarged, tender lymph nodes that develop 1–2 weeks after exposure;  and a papule or pustule at the inoculation site. This infection can also cause endocarditis, bacillary angiomatosis, and peliosis hepatis. Both IgM and IgG antibody tests for B. henselae are available in the U.S.

Bartonella quintana: bacterium transmitted by the human body louse (Pediculus humanus) that causes trench fever. Symptoms of trench fever include fever, headache, a transient rash, and bone pain, mainly in the shins, neck, and back. Both IgM and IgG antibody tests for B. quintana are available in the U.S.

Bell’s palsy: This is a paralysis of the muscles in the face caused by damage to the seventh cranial nerve. It is often unilateral (only on one side), and it’s more commonly seen in patients with Borrelia burgdorferi. As you may know, one of the consequences of Borrelia infection is inflammation, and this inflammation can lead to loss of nerve function. You can read more about Bell’s palsy here. Patients with Borrelia infections may also have damage to the eighth cranial nerve (also known as the auditory vestibular nerve), which can result in tinnitus (ringing of the ears) and problems with balance. Read about other symptoms of tick-borne infections.

Borrelia burgdorferi: a species of spirochete bacteria that causes Lyme Disease. It is transmitted through the bite of the blacklegged tick (or deer tick, Ixodes scapularis) and the western blacklegged tick (Ixodes pacificus). To read more about B. burgdorferi, see the fact sheet.

Borrelia hermsii: a species of spirochete bacteria that can be transmitted through the bite of the soft-bodied tick Ornithodoros hermsi (from which the bacterium gets its name). Borrelia hermsii infection causes Tick-borne Relapsing Fever. To read more about TBRF, see the infection fact sheet.


Cat-scratch disease: see Bartonella henselae.

Ceftriaxone: (brand name Rocephin) a third-generation cephalosporin antibiotic with broad spectrum activity against Gram-positive and Gram-negative bacteria. It is often used for IV infusion therapy to treat Borrelia infections like Lyme Disease and Tick-borne Relapsing Fever. To read more about treatment with Ceftriaxone, see this post.

Choline: an essential nutrient classified as the newest member of the B Vitamin family. It can be found in many foods, including eggs, beef, chicken, brown rice, spinach, asparagus, and avocados. You can read more about choline here.

Clindamycin: a lincosamide antibiotic usually used to treat infections with anaerobic bacteria but can also be used to treat some protozoal diseases, such as malaria. It is used in combination with Quinine to treat Babesiosis.


Doxycycline: a member of the tetracycline antibiotics group, commonly used to treat a variety of infections, including Borrelia burgdorferi (Lyme Disease), Anaplasmosis, Ehrlichiosis, and Rocky Mountain spotted fever. Taking oral Doxycycline with food (especially dairy products like milk) may decrease its effectiveness. To read about prophylaxis with Doxycycline, see this post.


Ehrlichiosis: caused by infection with bacteria in the genus Ehrlichia (including Ehrlichia chaffeensis, Ehrlichia ewingii, and Ehrlichia Wisconsin HM543746), which are transmitted by lonestar ticks (Amblyomma americanum) and deer ticks (Ixodes scapularis). To read more about symptoms, diagnosis, and treatment, see the Ehrlichiosis fact sheet.

Erythema chronicum migrans: sometimes abbreviated erythema migrans (EM). A skin rash that resembles a bull’s-eye, common in Borrelia burgdorferi infection (Lyme Disease)–according to the CDC, 70-80% of patients have the rash. It may appear 3-30 days after a tick bite and gradually expand (up to 12 inches). It can appear on any part of the body (including one’s rear end) and is rarely itchy or painful. Read about other symptoms of tick-borne infections.


herx: see Herxheimer reaction

Herxheimer reaction: (a.k.a. Jarisch-Herxheimer reaction, herx, J-H R) Named after dermatologists Adolf Jarisch and Karl Herxheimer in the late nineteenth century, who discovered it while treating Syphilis patients with mercury. A Herxheimer reaction can occur when one is being treated for an infection with antibiotics. It’s thought to be caused by the endotoxins that are released as bacteria start to die off. Herx usually occur within 24 hours of the first dose of antibiotics, and are characterized by fever, chills, rigor (shaking), hypotension, headache, tachycardia, hyperventilation, vasodilation with flushing, myalgia (muscle pain), and exacerbation of skin lesions. To read more about herx, see my post: Arthralgias, myalgias, and herx–oh my!


IFA: see indirect fluorescent antibody test below.

IgG: abbreviation for immunoglobulin G; a type of antibody involved with secondary immune responses. The body usually starts producing IgG when it stops making IgM (see below). Patients may still produce IgG antibodies years after an infection. Western Blots and IFAs usually measure both IgG and IgM responses.

IgM: abbreviation for immunoglobulin M; this antibody is usually produced as a primary response to an acute (new) infection (in the first 3-5 days).

immunoglobulin: another word for “antibody”; Y-shaped proteins produced by B-cells that identify and attack antigens (foreign microbes) in the body. People who do not make enough immunoglobulin (due to B-cell deficiency) are called hypogammaglobulinemic, and may have more difficulty fighting infections. This condition is often treated with intravenous gammaglobulin (IVIG).

indirect fluorescent antibody test: (abbreviated IFA), can also be referred to as serologic (as in blood serum) testing. A blood test to detect antibodies to a certain microorganism. IFA tests are available for many tick-borne infections, including Borrelia hermsii, Anaplasma, Babesia, Rocky Mountain spotted fever, and Ehrlichia.


Lyme Disease: caused by infection with Borrelia burgdorferi bacteria or another closely-related Borrelia species (like B. afzelii or B. garinii). To read about symptoms, diagnosis, and treatment, visit the Lyme Disease fact sheet.


Mepron: the brand name for Atovaquone. It is an oral suspension used in combination with azithromycin (Zithromax) to treat Babesiosis (Babesia). (Atovaquone is also one of two components of the drug Malarone, which is used to treat and prevent Malaria.) Mepron is not usually recommended for treatment of children or pregnant women. It has a reputation for unpleasant side effects, including vomiting and rash. Read more about diagnosis and treatment for Babesiosis.

myalgia: a fancy medical term for muscle aches. Myalgias can be a symptom of infection with Borrelia burgdorferi (Lyme Disease), Borrelia hermsii (TBRF), Babesia, Ehrlichia, Anaplasma phagocytophilum, Rocky Mountain Spotted Fever, Toxoplasmosis, Malaria, or Influenza. They can also be a symptom of inflammatory diseases like Multiple Sclerosis. Read about other symptoms of tick-borne infections.


postural tachycardia: tachycardia (elevated pulse, over 100) when you stand up for 3 minutes after lying down for 3 minutes. According to my doctor, this has been a great predictor of whether a patient has an infection, and he puts every new patient though the “tilt test”: lie down three minutes, have your vitals taken, stand up 3 minutes, have your vitals taken. Often, the difference in lying and standing pulse will decrease over the course of treatment. Read about other symptoms of tick-borne infections.

prophylaxis: administering medication or performing a procedure to prevent–rather than treat or cure–a disease. To read about prophylaxis following tick bites, see this post.

PubMed: a public resource for biomedical literature maintained by the United States’ National Library of Medicine at the National Institutes of Health (NIH), available online at pubmed.gov.


Quinine: a drug used in combination with Clindamycin to treat Babesiosis.  


Rickettsia rickettsii: a bacterium transmitted by  the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni), brown dog tick (Rhipicephalus sanguineus), and the Cayenne tick (Amblyomma cajennense) that causes Rocky Mountain spotted fever (RMSF)–see below.

Relapsing Fever: See Tick-borne Relapsing Fever.

Rocephin: See Ceftriaxone.

Rocky Mountain spotted fever (RMSF): caused by infection with the bacterium Rickettsia rickettsii. Symptoms may include chills, confusion, fever, headache, muscle pain, and a spotted rash. Contrary to its name, RMSF is not only common near the Rocky Mountains, with many cases reported in the eastern U.S. as well. To read more, see the RMSF fact sheet.


tachycardia: a heart rate that exceeds the normal range (usually indicated by a pulse greater than 100). Some people with infections have tachycardia all the time, but many only have postural tachycardia

TBID: abbreviation for tick-borne infectious disease. Any infection (bacteria, viral) that can be transmitted via the bite of a tick. For more information about infections transmitted from ticks to humans, see Infection Fact Sheets.

Tick-borne Relapsing Fever: caused by infection with one of the relapsing fever Borrelia species, including Borrelia hermsii, Borrelia parkeri, Borrelia duttoni, and Borrelia miyamotoi. For information about symptoms and treatment, visit the TBRF fact sheet.

trench fever: see Bartonella quintana.


VBID: abbreviation for vector-borne infectious disease. A vector-borne infectious disease is any disease that is transmitted from one organism (the vector) to another. In tick-borne infections, ticks are the vectors.


Western Blot: a laboratory test used to detect IgM and IgG antibodies (in blood) to Borrelia burgdorferi, a bacterium that causes Lyme Disease. Read more about labs and testing for Borrelia infections.


Zithromax: see azithromycin.

Check back later for the rest of the alphabet.


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