Tickborne Diseases Abroad

African Tick Bite Fever (ATBF)

Agent

Rickettsia africae

African tick bite fever (ATBF) is the most commonly diagnosed rickettsial disease among returning international travelers. ATBF is transmitted by Amblyomma hebraeum and A. variegatum ticks. Travel-associated cases of ATBF often occur in clusters with exposure during activities such as safari tours, game hunting, and bush hiking.

Where Found

Sub-Saharan Africa, Caribbean (French West Indies), and Oceania

Incubation Period

Typically 5–7 days but may be as long as 10 days

Signs and Symptoms

ATBF is typically a mild-to-moderate disease; no known deaths are attributable to infection with R. africae. ATBF is almost always associated with an inoculation eschar (see R. parkeri rickettsiosis) at the site of tick attachment. Multiple eschars are described in approximately 20–50% of patients with ATBF. Several days after eschar(s) appear, the following can develop:

• Fever
• Headache
• Myalgia
• Regional lymphadenopathy
• Rash (generalized with maculopapular or vesicular eruptions)

General Laboratory Findings

• Similar to other Rickettsia, see R. parkeri rickettsiosis.

Laboratory Diagnosis

Confirmation of the diagnosis is based on laboratory testing, but antibiotic treatment should not be delayed pending laboratory confirmation.

• ATBF can be confirmed using IFA or detection of Rickettsial DNA by PCR of eschar swab, skin biopsy, or whole blood. See R.parkeri rickettsiosis.
• ATBF can be confirmed by comparing acute and convalescent (taken 4–6 weeks following illness onset) samples for evidence of seroconversion in IgG antibodies.

Treatment

See RMSF treatment.

Lyme Disease (Europe and Asia)

Agent

Borrelia afzelii, B. garinii, B. burgdorferi sensu stricto

Outside North America, Lyme disease is transmitted through the bite of infected Ixodes ricinus and I. persulcatus ticks.

Where Found

In Europe, endemic from southern Scandinavia into the northern Mediterranean countries of Italy, Spain, Portugal, and Greece and east from the British Isles into central Russia. Incidence is highest in Central and Eastern European countries. In Asia, infected ticks occur from western Russia through Mongolia, northeastern China, and Japan; however, human infection appears to be uncommon in most of these areas.

Incubation Period

3–30 days

Signs and Symptoms

In contrast to North America, Lyme disease can be caused by several different species of B. burgdorferi and may have somewhat different symptoms. The erythema migrans rash (EM) may last longer but have less associated inflammation than the EM produced by U.S. strains.

Laboratory Confirmation

Not all tests in the United States will reliably detect infection with European/Asian Borrelia species. Providers who suspect internationally-acquired Lyme disease should request testing using a C6 ELISA assay as a stand-alone diagnostic test.

Treatment

See Lyme disease treatment.

Tickborne Encephalitis (TBE)

Agent

Tick-borne encephalitis virus

TBE is transmitted through the bite of infected Ixodes ricinus and I. persulcatus ticks.

Where Found

Endemic in focal areas of Europe and Asia, extending from eastern France to northern Japan and from northern Russia to Albania. The highest disease incidence has been reported from western Siberia, Slovenia, and the Baltic States. Asian countries with reported cases or virus activity include China, Japan, Kazakhstan, Kyrgyzstan, Mongolia, and South Korea. TBE may also be acquired by ingestion of unpasteurized dairy products from infected goats, sheep, or cows.

Incubation Period

8 days (range, 4–28 days)

Signs and Symptoms

TBE disease often presents with mild illness but can follow a more severe, biphasic course:

• First phase: nonspecific febrile illness with headache, myalgia, and fatigue. Usually lasts for several days and may be followed by an afebrile and relatively asymptomatic period. Up to two-thirds of patients recover without any further illness.
• Second phase: central nervous system involvement resulting in aseptic meningitis, encephalitis, or myelitis. Findings include meningeal signs, altered mental status, cognitive dysfunction, ataxia, rigidity, seizures, tremors, cranial nerve palsies, and limb paresis.

Laboratory Confirmation

During the first phase of the illness, TBE virus or viral RNA can sometimes be detected in serum samples by virus isolation or RT-PCR. However, by the time neurologic symptoms are recognized, the virus or viral RNA is usually undetectable. Therefore, virus isolation and RT-PCR should not be used to rule out a diagnosis of TBE. Clinicians should contact their state or local health department, CDC’s Division of Vector-Borne Diseases (970-221-6400), or CDC’s Viral Special Pathogens Branch (404-639-1115) for assistance with diagnostic testing.

Treatment

There is no specific antiviral treatment for TBE; therapy consists of supportive care and management of complications.

Selected Travel-Associated Tickborne Infections

References

Centers for Disease Control and Prevention. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever and other spotted fever group rickettsioses, ehrlichioses, and anaplasmosis—United States: a practical guide for health care and public health professionals. MMWR 2016;65 (No.RR-2).

Centers for Disease Control and Prevention. Brunette GW, Kozarsky PE, Cohen NJ, et al. CDC Health Information for International Travel 2016 (Yellow Book). New York, NY: Oxford University Press; 2016.

European Centre for Disease Prevention and Control, Tick-borne diseases.

Fournier PE, Jensenius M, Laferl H, et al. Kinetics of antibody responses in Rickettsia africae and Rickettsia conorii infections. Clin Diag Lab Immunol 2002;9(2):324-328.

Goodman JL, Dennis DT, Sonenshine DE, editors. Tick-borne diseases of humans. Washington, DC: ASM Press; 2005.

Jensenius M, Fournier PE, Kelly P, et al. African tick bite fever. Lancet Infect Dis 2003;3(9):557-564.

Parola P, Paddock CD, Socolovschi C, et al. Update on tick-borne rickettsioses around the world: a geographic approach. Clin Microbiol Rev 2013;26(4):657-702.