
You Give Me Fever: Four "Other" Tickborne Illnesses
Tickborne Illnesses
Tickborne infections in the United States include bacteria, rickettsiae, viruses, and protozoa. The most common is Lyme disease, reviewed in an earlier Medscape slideshow, which is transmitted by Ixodes scapularis and Ixodes pacificus, both much smaller (1-3 mm) than Dermacentor andersoni (shown above).
Preventive measures are the same for all ticks: avoiding grassy wooded areas, particularly in the summer when ticks are active; wearing long-sleeved shirts and long pants; and applying insect repellents on clothing and exposed skin.
Knowledge of the epidemiology of tick-borne infections is perhaps the most important factor for early diagnosis and treatment because signs and symptoms other than fever are often subtle. This slide presentation will review four common infections clinicians will likely encounter in the United States and many other regions of the world.[1]
You Give Me Fever: Four "Other" Tickborne Illnesses
Rocky Mountain Spotted Fever (RMSF)
RMSF, one of the most common rickettsial infections,[1] is transmitted by the wood tick and, in some regions, by the dog tick and the Lone Star tick. It is often seen in the South Atlantic and South-Central United States. R rickettsii replicate within the endothelial lining and smooth muscle cells of blood vessels to produce a generalized vasculitis associated with a centrifugal petechial rash and fever.
Hyponatremia and thrombocytopenia are frequent laboratory features that alert the clinician to consider the diagnosis. The diagnosis is confirmed with serologic indirect immunofluorescence antibody (IFA) assays, which may not be positive until 10 days after the onset of symptoms, necessitating early empiric treatment based on fever and the characteristic rash. Doxycycline is the antibiotic of choice for all ages, and it is given until the patient has been afebrile and symptom free for 3 days.[2,3]
You Give Me Fever: Four "Other" Tickborne Illnesses
RMSF in a child
The above image is from an 8-year-old child living in Virginia who had a fever of 105° F for 7 days, and centrifugal maculopapular exanthema for 6 days, with chills, severe headache, photophobia, and sore throat. When petechiae and some purpura appeared on the feet and palms, a diagnosis of RMSF was suspected and then confirmed with an R rickettsii IFA of 1:8.
You Give Me Fever: Four "Other" Tickborne Illnesses
RMSF in an infant
This 8-month-old developed fever and a centrifugal petechial rash that began as a macular
rash on the wrists and ankles. A tick on the anterior fontanel was removed, and RMSF was confirmed.
You Give Me Fever: Four "Other" Tickborne Illnesses
Ehrlichiosis
Human monocytic ehrlichiosis ("ehrlichiosis)" is caused by the organism Ehrlichia chaffeensis. This acute, systemic, febrile illness clinically resembles RMSF, except only 60% of children and less than 30% of adults develop a rash, giving it the moniker of Rocky Mountain spotless fever.[4,5]
You Give Me Fever: Four "Other" Tickborne Illnesses
When the rash of ehrlichiosis is present, it is usually maculopapular and diffuse. Striking laboratory features are leukopenia, predominantly lymphopenia, and, occasionally, identification of the organism in blood.
Other closely related rickettsiae are anaplasmosis caused by Anaplasma phagocytophilum and ehrlichiosis caused by E ewingii and E muris eauclairensis. Symptoms of these conditions, similar to that caused by E chaffeensis, are quite nonspecific and include fever, headache, chills, malaise, and myalgia. The diagnoses are made by polymerase chain reaction (PCR) of whole blood. Treatment is doxycycline until the patients are afebrile and clinically improved for 3 days.[4,5]
You Give Me Fever: Four "Other" Tickborne Illnesses
Tularemia
There are six clinical presentations of tularemia caused by Francisella tularensis, as follows[6,7]:
- Glandular
- Ulceroglandular
- Oculoglandular, also called Parinaud's oculoglandular syndrome
- Oropharyngeal
- Typhoidal
- Pneumonic
You Give Me Fever: Four "Other" Tickborne Illnesses
The incubation period for tularemia is 3-4 days after the tick bite. General symptoms of tularemia are abrupt, with high fever, chills, headache, and myalgia. Painful adenitis is an early finding for the glandular presentations.[6,7]
You Give Me Fever: Four "Other" Tickborne Illnesses
Babesiosis
Babesia infection is usually asymptomatic or mildly symptomatic in the immunocompetent host, but it is life threatening in patients who are asplenic or immunocompromised and can be severe in the elderly. When symptomatic, it presents with fever, flu-like symptoms, and hemolytic anemia. Babesiosis is transmitted by ixodid ticks, most commonly the tiny (1-3 mm) I scapularis, commonly called a deer or black legged tick.[8]
You Give Me Fever: Four "Other" Tickborne Illnesses
The geographic distribution of babesiosis is mostly limited to the New England, Mid-Atlantic, upper Midwest, and Pacific West regions, and the disease is seen in travelers to these regions. Most blood banks now screen for Babesia organisms because they can be transmitted with blood transfusions. A diagnosis of babesiosis can readily be made by identification of the organism in blood smears.[8,9]
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