Visual loss in a returning traveller with tick typhus

Rickettsial diseases in travelers

Often undiagnosed in travelers with acute nonspecific febrile illness, gastrointestinal, abdominal, pulmonary, neurologic, or cutaneous signs and symptoms, rickettsial diseases are transmitted in particular geographic and ecologic settings by ticks, fleas, chiggers, and lice. Recognition of an eschar at the vector inoculation site can be a key diagnostic clue for scrub typhus, African tick bite fever, and other tick-borne spotted fevers. Although laboratory confirmation is necessary, usually during convalescence, for an accurate diagnosis, a clinical diagnosis and empiric treatment with doxycycline are the standard practical approach. Knowledge of potential exposure, the natural history of the infection, and incubation periods of each rickettsiosis assist in considering particular rickettsioses.

Scrub typhus and rickettsial diseases in international travelers: a review

Physicians caring for febrile returned travelers face the difficult task of recognizing the typical and atypical features of more than 16 known rickettsial diseases and separating these diseases from potentially serious nonrickettsial diseases. Currently available diagnostic tools are inadequate for timely diagnosis. This review summarizes the English-language literature concerning imported rickettsial diseases in international travelers and describes important clinical principles in diagnosis and treatment of these illnesses. -Travelers with imported rickettsial disease often become sick before or within a few days of return from an endemic region. Illness that begins more than 18 days after return is unlikely to be rickettsial in origin. The absence of a skin rash or exposure to a vector should not dissuade clinicians from considering the possibility of a rickettsial disease in a returned traveler. Finally, if empiric therapy does not result in defervescence within 48 hours, an alternative nonrickettsial illness should be strongly considered.

Threats to international travellers posed by tick-borne diseases

To date, 14 tick-borne diseases have been reported in international travellers, the majority of cases being Lyme borreliosis caused by Borrelia burgdorferi sensu lato in North America and Eurasia, African tick bite fever caused by Rickettsia africae in sub-Saharan Africa and eastern Caribbean, and Central European encephalitis caused by tick-borne encephalitis virus in Europe. The clinical presentation is frequently non-specific, and tick-borne diseases should always, in the absence of other likely diagnoses, be suspected in travellers with flu-like symptoms following a recent visit to tick-infested areas. Feasible microbiological diagnostic tests are widely unavailable, at least outside areas of endemicity where many infected travellers present. Empiric treatment with doxycycline should be considered in suspected cases of tick-borne bacterial diseases. Since ecotourism and adventure travel are increasingly popular worldwide, the incidence of travel-associated tick-borne diseases is likely to increase in the future.

Rickettsioses and the international traveler

The rickettsioses--zoonotic bacterial infections transmitted to humans by arthropods--were for many years considered to be oddities in travel medicine. During the previous 2 decades, however, reports of >450 travel-associated cases have been published worldwide, the vast majority being murine typhus caused by Rickettsia typhi, Mediterranean spotted fever caused by Rickettsia conorii, African tick bite fever caused by Rickettsia africae, and scrub typhus caused by Orientia tsutsugamushi. Most patients present with a benign febrile illness accompanied by headache, myalgia, and cutaneous eruptions, but severe complications and fatalities are occasionally seen. Current microbiological tests include culture, polymerase chain reaction, and serological analysis, of which only the latter method is widely available. Tetracyclines are the drugs of first choice and should be prescribed whenever a case of rickettsiosis is suspected. Preventive measures rely on minimizing the risk of arthropod bites when traveling in areas of endemicity.

Tick-borne rickettsioses in international travellers

BACKGROUND

Tick-borne rickettsioses are of emerging importance in today's travel medicine but have until recently received little attention. We describe the current knowledge of tick-borne rickettsioses as they relate to international travel, their microbiological diagnosis, treatment, possible prevention, and future prospects.

METHODS

Literature-based review and personal observations.

RESULTS

During the last decade, some 400 cases of tick-borne rickettsioses have been reported in international travellers, the vast majority being African tick bite fever caused by Rickettsia africae and Mediterranean spotted fever caused by Rickettsia conorii. Only a minority of infected travellers can recall a preceding tick bite. Most patients present with a mild-to-moderately severe flu-like illness typically accompanied by a cutaneous rash and an inoculation eschar at the site of the tick bite, but potentially life-threatening disease with disseminated vaculitis is occasionally seen. Definite microbiological confirmation of tick-borne rickettsioses by isolation or antigen detection is only available at reference laboratories and diagnosis must in most cases rely on clinical and epidemiological data supported by serology. Doxycycline is the recommended treatment for tick-borne rickettsioses and prevention is based on personal protective measures against tick bites when travelling in endemic areas.

CONCLUSION

Tick-borne rickettsiosis should be suspected in febrile returnees from endemic areas, especially in cases with skin eruptions. Travellers to endemic areas should be encouraged to use personal protective measures against tick bites.

Clinical features and epidemiology of tick typhus in travelers

BACKGROUND

Epidemiologic features of tick typhus among German travelers has not been surveyed recently.

METHODS

Clinical features, travel and medical histories in 78 patients with tick typhus who presented to a German outpatient clinic for Infectious and Tropical Diseases were investigated, in order to identify common epidemiological factors and potential strategies of prevention. Diagnosis was confirmed by serological detection of IgG- and IgM-antibodies to Rickettsia conorii by indirect immunofluorescence.

RESULTS

The majority of patients (71.8%) had visited southern Africa prior to presentation. All patients presented with fever as the main symptom. An eschar was still present in 68 patients (87.2%) with regional lymphadenitis in 19.2%. However, only a minority of patients (17.9%) remembered a tick bite at the location of the eschar.

CONCLUSION

Efforts to reduce the incidence of tick typhus in travelers should focus on preventive measures targeting behavioral changes. Avoiding tick bites during travel to endemic areas appears to be the single most important prophylactic action. Taking this into consideration, it should be possible to decrease the number of travelers returning with tick typhus significantly by adequate pretravel counseling.