Questions and Answers

• What other some other tick-borne spotted fevers?
• What are the symptoms of Rickettsia parkeri and other U.S. tickborne spotted fevers?
• What are some examples of imported tick-borne spotted fevers?
• How are other tick-borne spotted fevers diagnosed and treated?
• How can other tick-borne spotted fevers be prevented?

 

What are some other U.S.-associated tickborne spotted fevers?

In addition to Rickettsia rickettsia, the agent of Rocky Mountain spotted fever, there are other similar agents transmitted by ticks that have been shown to cause human infections. In the United States, these include Rickettsia parkeri, which is transmitted by Amblyomma maculatum and causes a maculatum infection (a relatively mild, eschar-associated illness). There are also other genetically similar Rickettsia that are thought to cause occasional human illness, including one called 364D (Rickettsia phillipi, proposed).  Because these agents appear to exhibit serologic cross-reactivity with available tests for R. rickettsii, it is likely that some human illnesses currently being attributed to RMSF are actually caused by these distinct rickettsial species, and more research is needed to determine their prevalence and geographic distribution.

What are the symptoms of Rickettsia parkeri and other U.S. tickborne spotted fevers?

The symptoms of ehrlichiosis may resemble symptoms of various other infectious and non-infectious diseases. The initial signs and symptoms generally include:

• fever
• headache
• fatigue
• muscle aches

Other signs and symptoms may include:

• occasionally rash
• distinctive eschar that develops at the site of tick bite
• thrombocytopenia
• elevated liver enzymes

What are some examples of imported tickborne spotted fevers?

Internationally, there are numerous examples of Rickettsia species associated with human infection. These include:

Table 1. Tickborne rickettsiae known to cause disease in humans and clinical symptoms of the rickettsial diseases

Disease	Species	Geographic Distribution	Clinical Symptoms
Rickettsiosis	Rickettsia aeschlimannii	South Africa, Morocco, Mediterranean littoral	Fever, eschar, maculopapular rash
African tick- bite fever	Rickettsia africae	Sub-Saharan Africa, West Indies	Fever, eschar(s)
Queensland tick typhus	Rickettsia australis	Australia, Tasmania	Fever, eschar, regional adenopathy, rash on extremities
Mediterranean spotted fever or Boutonneuse fever	Rickettsia conorii‡	Southern Europe, southern and western Asia, Africa, India	Fever, eschar, regional adenopathy, maculopapular rash on extremities
Far eastern spotted fever	Rickettsia heilongjiangensis	Far East of Russia, Northern China, Eastern Asia	Fever, eschar,  maculopapular rash, lymphadenopathy, enlarged lymph nodes
Aneruptive fever	Rickettsia helvetica	Central and northern Europe, Asia	Fever, headache, myalgia
Flinders Island spotted fever, Thai tick typhus	Rickettsia honei	Australia, Thailand	Mild spotted fever, eschar and adenopathy are rare
Japanese spotted fever	Rickettsia japonica	Japan	Fever, eschar(s), regional adenopathy, rash on extremities
Australian spotted fever	Rickettsia marmionii	Australia	Fever, eschar, maculopapular or vesicular rash, adenopathy
Mediterranean spotted fever–like disease	Rickettsia massiliae	France, Greece, Spain, Portugal, Switzerland, Sicily, Central Africa and Mali	Fever, maculopapular rash, necrotic eschar
Rocky Mountain spotted fever, febre maculosa, Sao Paulo exanthematic typhus, Minas Gerais exanthematic typhus, Brazillian spotted fever	Rickettsia rickettsii	North, Central  and South America	Fever, headache, abdominal pain, maculopapular rash progressing into papular or petechial rash (generally originating on extremities)
North Asian tick typhus, Siberian tick typhus	Rickettisa sibirica	Russia, China, Mongolia	Fever, eschar(s), regional adenopathy, maculopapular rash
Lymphangitis associated rickettsiosis	Rickettsia siberica mongolotimonae	Southern France, Portugal, China, Sub-saharan Africa	Fever, multiple eschars, regional adenopathy and lymphangitis, maculopapular rash
Tick-borne lymphadenopathy (TIBOLA), Dermacentor-borne necrosis and lymphadenopathy (DEBONEL)	Rickettsia slovaca	Southern and eastern Europe, Asia	Necrosis erythema, cervical lymphadenopathy and enlarged lymph nodes, rare maculopapular rash

‡ Includes 4 different subspecies that can be distinguished serologically and by PCR assay, and respectively are the etiologic agents of Boutonneuse fever and Mediterranean tick fever in Southern Europe and Africa (R. conorii subsp. conorii), Indian tick typhus in South Asia (R. conorii subsp. indica), Israeli tick typhus in Southern Europe and Middle East (R. conorii subsp. israelensis), and Astrakhan spotted fever in the North Caspian region of Russia (R. conorii subsp. caspiae).

In the United States, the most frequently diagnosed rickettsial infection associated with residents returning from international travel is Rickettsia africae (the agent of African spotted fever). This is most often diagnosed among U.S. visitors returning from travel to South Africa, particularly those engaged in safari or ecotourism activities.

How are other tickborne spotted fevers diagnosed and treated?

Many other tickborne spotted fevers exhibit strong immunlogic cross-reactivity with assays for R. rickettsii. It is possible to utilize commercially available serologic assays as a surrogate diagnostic tool, coupled with patient presentation and possible travel history that may point to a specific rickettsial illness. The Centers for Disease Control and Prevention can offer more specialized serologic assays for assessment of the etiologic agent, although these are limited in their ability to clearly define an etiologic agent due to cross-reactivity. If a more specific diagnosis is desired, a skin biopsy of a rash or eschar site can be submitted to CDC for more assessment through PCR or culture.

As with other TBRD, the other spotted fever tickborne diseases described here respond well to treatment with doxycycline, and this is considered the antibiotic of choice. Be sure to tell your physician if you become ill within 2 weeks of a tick bite or exposure to tick habitat, either within the United States or internationally.

How can other tickborne spotted fevers be prevented?

The best prevention is to prevent tick bites. Information on preventing tick bites includes use of personal insect repellents, choosing clothing that limits tick attachment, and avoiding areas where ticks may be present.

 

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