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Dermacentor andersoni (Rocky Mountain wood tick) is the major vector for Rocky Mountain spotted fever (RMSF) and Colorado tick fever. Image courtesy of Russell Steele, MD.

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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]

The geographic distribution of RMSF in the United States is shown. Image from the Centers for Disease Control and Prevention (CDC).

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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]

The feet of an 8-year-old child with RMSF are depicted. Image courtesy of Russell Steele, MD.

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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.

An 8-month-old with RMSF is shown. Image courtesy of Russell Steele, MD.

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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.

Human monocytic ehrlichiosis with a generalized erythematous macular rash that had petechial components on the wrists and hands is shown. Image courtesy of Russell Steele, MD.

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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]

A buffy coat of blood with morulae or mulberry-like clusters of organisms in mononuclear cells is demonstrated. Image courtesy of Russell Steele, MD.

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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]

A child with glandular tularemia with suboccipital and posterior cervical adenitis was treated with gentamicin for 10 days, followed by drainage of the residual abscess. Image courtesy of Russell Steele, MD.

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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
Oculoglandular tularemia is seen in an adult who was rabbit hunting out of season and cleaning rabbits without wearing goggles. Inguinal glandular tularemia in an infant is shown. Images courtesy of Russell Steele, MD.

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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]

The size of blacklegged ticks relative to a dime is demonstrated. Image from the CDC.

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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]

The map shows the geographic distribution of babesiosis in the United States. Inset: This peripheral smear contains a parasitized red blood cell with the characteristic Maltese Cross of Babesia microti (arrow), often misidentified as a malaria parasite. Images from the CDC.

You Give Me Fever: Four "Other" Tickborne Illnesses

Russell W. Steele, MD | September 20, 2021 | Contributor Information

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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