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CDC Health Information for International Travel 2008

Chapter 4
Prevention of Specific Infectious Diseases

Rickettsial Infections


Many species of Rickettsia can cause illnesses in humans (Table 4-18). The term “rickettsiae” conventionally embraces a polyphyletic group of microorganisms in the class Proteobacteria, comprising species belonging to the genera Rickettsia, Orientia, Ehrlichia, Anaplasma, Neo-rickettsia, Coxiella, and Bartonella. These agents are usually not transmissible directly from person to person except by blood transfusion or organ transplantation, although sexual and placental transmission has been proposed for Coxiella. Transmission generally occurs via an infected arthropod vector or through exposure to an infected animal reservoir host. However, sennetsu fever is acquired following consumption of raw fish products. The clinical severity and duration of illnesses associated with different rickettsial infections vary considerably, even within a given antigenic group. Rickettsioses range in severity from diseases that are usually relatively mild (rickettsialpox, cat scratch disease, and African tick-bite fever) to those that can be life-threatening (epidemic and murine typhus, Rocky Mountain spotted fever, scrub typhus and Oroya fever), and they vary in duration from those that can be self-limiting to chronic (Q fever and bartonelloses) or recrudescent (Brill-Zinsser disease). Most patients with rickettsial infections recover with timely use of appropriate antibiotic therapy.

Travelers may be at risk for exposure to agents of rickettsial diseases if they engage in occupational or recreational activities which bring them into contact with habitats that support the vectors or animal reservoir species associated with these pathogens (1-2).

Occurrence and Risk for Travelers

The geographic distribution and the risks for exposure to rickettsial agents are described below and in Table 4-18 by disease.


Epidemic typhus and trench fever, which are caused by Rickettsia prowazkeii and Bartonella quintanta, respectively, are transmitted from one person to another by the human body louse (3-4). Contemporary outbreaks of both diseases are rare in most developed countries and generally occur only in communities and populations in which body louse infestations are frequent, especially during the colder months when louse-infested clothing is not laundered. Foci of trench fever have also been recognized among homeless populations in urban centers of industrialized countries. Travelers who are not at risk of exposure to body lice or to persons with lice are unlikely to acquire these illnesses. However, health-care workers who care for these patients may be at risk for acquiring louse-borne illnesses through inhalation or inoculation of infectious louse feces into the skin or conjunctiva. In the eastern United States, campers, inhabitants of wooded areas, and wildlife workers can acquire sylvatic epidemic typhus if they come in close contact with flying squirrels, their ectoparasites, or their nests, which can be made in houses, cabins, and tree-holes.


Murine typhus, which is caused by infection with Rickettsia typhi, is transmitted to humans by rat fleas, particularly during exposure in rat-infested buildings (3). Flea-infested rats can be found throughout the year in humid tropical environments, especially in harbor or riverine environments. In temperate regions, they are most common during the warm summer months. Similarly, cat-flea rickettsiosis, which is caused by infection with Rickettsia felis, occurs worldwide from exposure to flea-infested domestic cats and dogs, as well as peridomestic animals, and is responsible for a murine typhus-like febrile disease in humans.


Mites (“chiggers”) transmit Orientia tsutsugamushi, the agent of scrub typhus, to humans (5). These mites occur year-round in a large area from South Asia to Australia and in much of East Asia, including Japan, China, Korea, Maritime Provinces and Sakhalin Island of Russia, and Tajikistan. Their prevalence, however, fluctuates with temperature and rainfall. Infection may occur on coral atolls in both the Indian and Pacific Oceans, in rice paddies and along canals and fields, on oil palm plantations, in tropical to desert climates and in elevated river valleys. Humans typically encounter the arthropod vector of scrub typhus in recently disturbed habitat (e.g., forest clearings) or other persisting mite foci infested with rats and other rodents.


Tick-borne rickettsial diseases are most common in temperate and subtropical regions (6). These diseases include numerous well-known classical spotted fever rickettsioses (7) and an expanding group of newly recognized diseases (Table 4-18) (6,8). In general, peak transmission of tick-borne rickettsial pathogens occurs during spring and summer months. Travelers who participate in outdoor activities in grassy or wooded areas (e.g., trekking, camping, or going on safari) may be at risk for acquiring tick-borne illnesses, including those caused by Rickettsia, Anaplasma, and Ehrlichia species (see below) (2,7).


Rickettsialpox is generally an urban, mite-vectored disease associated with R. akari-infected house mice, although feral rodent-mite reservoirs also have been described (3). Outbreaks of this illness have occurred shortly after rodent extermination programs or natural viral infections that depleted rodent populations and caused the mites to seek new hosts. R. akari-infected rodents have been found in urban centers in the former Soviet Union, South Africa, Korea, Croatia, and the United States. Travelers may be at risk for exposure to rodent mites when staying in old urban hostels and cabins.


Human ehrlichiosis and anaplasmosis are acute tick-borne diseases, associated with the lone star tick, Amblyomma americanum, and Ixodes ticks, respectively (3,7). Because one tick may be infected with more than one tick-borne pathogen (e.g. Borrelia burgdorferi, the causative agent of Lyme disease, or various Babesia species, agent of human babesiosis), patients may present with atypical clinical symptoms that complicate treatment. Ehrlichioses and anaplasmosis are characterized by infection of different types of leukocytes, where the causative agent multiplies in cytoplasmic membrane-bound vacuole called morulae. Morulae can sometimes be detected in Giemsa-stained blood smears.


Q fever occurs worldwide, most often in persons who have contact with infected goat, sheep, cat and cattle, particularly parturient animals (especially farmers, veterinarians, butchers, meat packers, and seasonal workers) (1,3). Travelers who visit farms or rural communities can be exposed to Coxiella burnetii, the agent of Q fever, through airborne transmission (via animal-contaminated soil and dust) or less commonly through consumption of unpasteurized milk products or by exposure to infected ticks. These infections may initially result in only mild and self-limiting influenza-like illnesses, but if untreated, infections may become chronic, particularly in persons with preexisting heart valve abnormalities or with prosthetic valves. Such persons can develop chronic and potentially fatal endocarditis.


Cat-scratch disease is contracted through scratches and bites from domestic cats, particularly kittens, infected with Bartonella henselae, and possibly from their fleas (3,4). Exposure can therefore occur wherever cats are found. Oroya fever is transmitted by sandflies infected with B. bacilliformis, which is endemic in the Andean highlands.

Clinical Presentation

Clinical presentations of rickettsial illnesses vary (Table 4-18), but common early symptoms, including fever, headache, and malaise, are generally nonspecific (1-4). Illnesses resulting from infection with rickettsial agents may go unrecognized or are attributed to other causes. Atypical presentations are common and may be expected with poorly characterized nonindigenous agents (4,5,8,9), so appropriate samples for examination by specialized reference laboratories should be obtained. A diagnosis of rickettsial diseases is based on two or more of the following: 1) clinical symptoms and an epidemiologic history compatible with a rickettsial disease, 2) the development of specific convalescent-phase antibodies reactive with a given pathogen or antigenic group, 3) a positive polymerase chain reaction test result, 4) specific immunohistologic detection of rickettsial agent, or 5) isolation of a rickettsial agent. Ascertaining the likely place and the nature of potential exposures is particularly helpful for accurate diagnostic testing.


With the exception of the louse-borne diseases described above, for which contact with infectious arthropod feces is the primary mode of transmission (through autoinoculation into a wound, conjunctiva, or inhalation), travelers and health-care providers are generally not at risk for becoming infected via exposure to an ill person. Limiting exposures to vectors or animal reservoirs remains the best means for reducing the risk for disease. Travelers should be advised that prevention is based on avoidance of vector-infested habitats, use of repellents and protective clothing (see Chapter 2), prompt detection and removal of arthropods from clothing and skin, and attention to hygiene (7).

Q fever and Bartonella group diseases may pose a special risk for persons with abnormal or prosthetic heart valves, and Rickettsia, Ehrlichia, and Bartonella for persons who are immunocompromised.


Treatments for most rickettsial illnesses are similar and include administration of appropriate antibiotics (e.g., tetracyclines, chloramphenicol, azithromycin, fluoroquinolones, and rifampin) and supportive care. Treatment should usually be given empirically prior to disease confirmation, and the particular antimicrobial agent and the length of treatment are dependent upon the disease and the host. No licensed vaccines for prevention of rickettsial infections are commercially available in the United States


  1. Imbert P, Rapp C, Jagou M, Saillol A, Debord T. Q fever in travelers: 10 cases. J Travel Med. 2004;11(6):383-5.
  2. Jensenius M, Fournier PE, Raoult D. Tick-borne rickettsioses in international travellers. Int J Infect Dis. 2004;8(3):139-46.
  3. Comer JA, Paddock CD, Childs JE. Urban zoonoses caused by Bartonella, Coxiella, Ehrlichia, and Rickettsia species. Vector Borne Zoonotic Dis. 2001;1(2):91-118.
  4. Rolain JM, Brouqui P, Koehler JE, Maguina C, Dolan MJ, Raoult D. Recommendations for treatment of human infections caused by Bartonella species. Antimicrob Agents Chemother. 2004;48(6):1921-33.
  5. Watt G, Parola P. Scrub typhus and tropical rickettsioses. Curr Opin Infect Dis. 2003;16(5):429-36.
  6. Parola P, Paddock CD, Raoult D. Tick-borne rickettsioses around the world: emerging diseases challenging old concepts. Clin Microbiol Rev. 2005;18(4):719-56.
  7. Chapman AS, Bakken JS, Folk SM, Paddock CD, Bloch KC, Krusell A, et al. Diagnosis and management of tick-borne rickettsial diseases in the United States: Rocky Mountain spotted fever, ehrlichioses and anaplasmosis. A primer for physicians and other health care professionals. MMWR Recomm Rep. 2006;55(RR-4):1-29.
  8. Oteo JA, Ibarra V, Blanco JR, Martinez de Artola V, Marquez FJ, Portillo A, et al. Dermacentor-borne necrosis erythema and lymphadenopathy: clinical and epidemiological features of a new tick-borne disease. Clin Microbiol Infect. 2004;10(4):327-31.
  9. Zaidi SA, Singer C. Gastrointestinal and hepatic manifestations of tick-borne diseases in the United States. Clin Infect Dis. 2002; 34:1206-12.

TABLE 4-18. Epidemiologic features and symptoms of rickettsial diseases

Typhus feversEpidemic typhus,


Sylvatic typhus

Rickettsia prowazekiiHeadache, chills, fever, prostration, confusion, photophobia, vomiting, rash (generally starting on trunk) Human body louse, squirrel flea and louse Humans, flying squirrels (US)Cool mountainous regions of Africa, Asia, and Central and South America
 Murine typhusR. typhiAs above, generally less severe Rat flea Rats, miceWorldwide
Spotted feversAfrican tickbite feverR. africaeFever, eschar(s), regional adenopathy, maculopapular or vesicular rash subtle or absent Tick RodentsSub-Saharan Africa
 Aneruptive feverR. helveticaFever, headache, myalgia Tick RodentsOld World
 Australian spotted feverR. marmioniiFever, eschar, maculopapular or vesicular rash, adenopathy Tick Rodents, reptilesAustralia
 Cat flea rickettsiosisR. felisAs murine typhus, generally less severe Cat and dog fleas Domestic cats, opossumsEurope, South America
 Far Eastern spotted feverR. heilongjiangensisFever, eschar, macular or maculopapular rash, lymphadenopathy, enlarged lymph nodes Tick RodentsFar East of Russia, Northern China
 Flinders Island spotted fever, Thai tick typhusR. honeiMild spotted fever, eschar and adenopathy are rare Tick Not definedAustralia, Thailand
 Lymphangitis associated rickettsiosisR. sibirica subsp. mongolotimonaeFever, multiple eschars, regional adenopathy and lymphangitis, maculopapular rash Tick RodentsSouthern France, Portugal, Asia, Africa
 Maculatum infectionR. parkeriFever, eschar, rash maculopapular to vesicular Tick RodentsBrazil, Uruguay
 Mediterranean spotted fevers‡R. conoriiFever, eschar, regional adenopathy, maculopapular rash on extremities Tick Dogs, rodentsAfrica, India, Europe, Middle East, Mediterranean
 North Asian tick typhusR. sibiricaFever, eschar(s), regional adenopathy, maculopapular rash Tick RodentsRussia, China, Mongolia
 Oriental spotted feverR. japonicaAs above Tick RodentsJapan
 Queensland tick typhusR. australis Fever, eschar, regional adenopathy, rash on extremities Tick Not definedAustralia, Tasmania
 RickettsialpoxR. akariFever, eschar, adenopathy, disseminated vesicular rash Mite House miceRussia, South Africa, Korea, Turkey, Balkan countries
 Rocky Mountain spotted fever, Sao Paulo exanthematic typhus, Minas Gerais exanthematic typhus, Brazilian spotted feverR. rickettsiiHeadache, fever, abdominal pain, macular rash progressing into papular or petechial (generally starting on extremities) Tick RodentsMexico, Central, and South America
 Tick-borne lymphadenopathy (TIBOLA), Dermacentor- borne necrosis and lymphadenopathy (DEBONEL)R. slovacaNecrosis erythema, cervical lymphadenopathy and enlarged lymph nodes, rare maculopapular rash Tick Lagomorphs, rodentsEurope, Asia
 Unnamed rickettsiosisR. aeschlimanniiFever, eschar, maculopapular rash Tick Domestic and wild animalsAfrica
OrientiaScrub typhusOrientia tsutsugamushiFever, headache, sweating, conjunctival injection, adenopathy, eschar, rash (starting on trunk), respiratory distress Mite RodentsSouth, Central, Eastern, and Southeast Asia and Australia
CoxiellaQ feverCoxiella burnetiiFever, headache, chills, sweating, pneumonia, hepatitis, endocarditis Most human infections are acquired by inhalation of infectious aerosols; tick Goats, sheep, cattle, domestic cats, otherWorldwide
BartonellaCat-scratch diseaseBartonella henselaeFever, adenopathy, neuroretinitis, encephalitis Cat flea Domestic catsWorldwide
 Trench feverB. quintanaFever, headache, pain in shins, splenomegaly, disseminated rash Human body louse HumansWorldwide
 Oroya feverB. bacilliformisFever, headache, anemia, shifting joint and muscle pain, nodular dermal eruption Sand fly UnknownPeru, Ecuador, Colombia
EhrlichiaEhrlichosisEhrlichia chaffeensis#Fever, headache, nausea, occasionally rash Tick Various large and small mammals, including deer and rodentsWorldwide
AnaplasmaAnaplasmosisAnaplasma phagocytophilum#Fever, headache, nausea, occasionally rash Tick Small mammals, and rodentsEurope, Asia, Africa
NeorickettsiaSennetsu feverNeorickettsia sennetsuFever, chills, headache, sore throat, insomnia Fish, fluke FishJapan, Malaysia

* This represents only a partial list of symptoms. Patients may have different symptoms or only a few of those listed.
‡ 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).
# Organisms antigenically related to these species are associated with ehrlichial diseases outside the continental United States.

  • Page last updated: January 07, 2009
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    Division of Global Migration and Quarantine
    National Center for Preparedness, Detection, and Control of Infectious Diseases
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