Imported African tick bite fever: a case report

Rickettsia africae infection rates and transovarial transmission in Amblyomma hebraeum ticks in Mnisi, Bushbuckridge, South Africa

Rickettsia africae is a gram-negative bacterium, which causes African tick bite fever (ATBF) in humans. ATBF is a febrile disease mainly affecting travellers to southern Africa. This bacterium is known to be transmitted by Amblyomma hebraeum and Amblyomma variegatum ticks. In southern Africa, the principal vector is A. hebraeum. Febrile disease is a serious issue in the study area. There is a high prevalence of non-malaria illness caused by Rickettsia, so there is a need to have more knowledge on these species. Infection rates and transovarial transmission efficiency of R. africae in A. hebraeum ticks were investigated in a rural area of Mpumalanga province, South Africa. Adult and engorged A. hebraeum female ticks were collected from cattle. Larvae were collected by dragging a cloth at ground level using 100 steps, equivalent to an area of 100 m². Tick identification was performed according to standard taxonomic keys using a microscope. Engorged ticks were incubated to oviposit and egg masses were collected. DNA was extracted from the ticks, larvae and egg masses, and screened for gltA and ompA genes, using quantitative real-time PCR and conventional PCR, respectively. Positive ompA amplicons were sequenced and phylogenetic analysis showed 99.8-100% identity with R. africae. Infection rates were 13.7 and 12.7% for adults and larvae, respectively. Transovarial transmission of R. africae in A. hebraeum from this study was 85.7%. The results provide a clear indication that people living in the study area and travellers that visit the area are at risk of contracting ATBF.

Clinical, epidemiological, and laboratory features of Rickettsia africae infection, African tick-bite fever: A systematic review

African tick-bite fever (ATBF), caused by Rickettsia africae, is the main tick-borne rickettsiosis and the second most frequent cause of fever after malaria in travelers returning from sub-Saharan Africa. General descriptions on ATBF were made in the first two decades after recognized as a new infectious entity, and since then, many authors have contributed to the knowledge of the disease by reporting clinical cases in scientific literature. We developed a systematic review that evaluated all available evidence in the literature regarding clinical, epidemiological, and laboratory features of confirmed R. africae rickettsiosis cases. We followed the recommendations made by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guide. A total of 48 scientific publications (108 confirmed cases) were analyzed in order to extract data for developing this review. Overall, our results show that R. africae rickettsiosis is more frequent in males in the age group of 18-64 years, more than 80% of the cases occurred in European travelers, South Africa was the country where most infections were acquired, and almost 40% of cases occurred in clusters. Clinically, more than 80% of the cases had fever and eschar (55% developed multiple eschars), rash was present in less than the half of cases, and lymphangitis was not a common sign (11%). Headache, myalgia and regional lymphadenopathy were predominant nonspecific clinical manifestation (mean of 60%, 49% and 51%, respectively). Our results show that at least 70% of R. africae cases had altered laboratory parameters, most often showing an increase in transaminases and C-reactive protein. Tetracycline-class antibiotics, as monotherapy, were used in most (>90%) of the patients. Overall, only 4% of cases had complications, 12% required hospitalization, and there was a 100% rate of clinical recovery.

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.

A case of spotted fever group rickettsiosis imported into the United Kingdom and treated with ciprofloxacin: a case report

Introduction

Spotted fever group rickettsioses are an interesting group of infections, which are increasing in incidence worldwide.

Case presentation

Here we describe an imported case to the United Kingdom occurring in a patient who had recently visited Kruger National Park in South Africa – a highly endemic area for Rickettsia infections. Initial treatment with doxycycline failed but the patient made a prompt recovery after commencement of ciprofloxacin.

Conclusion

This finding raises the possibility that there are resistant strains of Rickettsia present.

Travel medicine

This review covers significant recent developments in the field of travel medicine. New vaccines related to travel are discussed: cholera, Lyme disease, and rotavirus. Pertinent travel vaccine-related issues with varicella, polio, meningitis, Japanese encephalitis, and tick-borne encephalitis are described. New developments in malaria prophylaxis, diagnosis and treatment are discussed. Imported cases of African tick bite fever, arboviruses, African trypanosomiasis, and Helicobacter pylori, and diarrheal illness are reviewed.

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.

African tick bite fever

African tick bite fever is an acute febrile illness that is frequently accompanied by headache, prominent neck muscle myalgia, inoculation eschars, and regional lymphadenitis. The disease is caused by Rickettsia africae, a recently identified spotted fever group rickettsia, which is transmitted by ungulate ticks of the Amblyomma genus in rural sub-Saharan Africa and the French West Indies. Whereas reports on African tick bite fever in indigenous populations are scarce, the number of reported cases in travellers from Europe and elsewhere has recently increased significantly. Treatment with doxycycline is associated with rapid recovery in most patients. An immunofluorescence assay is recommended for the diagnosis but seroconversion is commonly delayed and this limits the usefulness of the test. Travellers to endemic areas should be informed of the risk of contracting African tick bite fever and be encouraged to take personal protective measures against tick bites.

African tick bite fever in travelers to rural sub-Equatorial Africa

To estimate the incidence of, identify risk factors for, and describe the clinical presentation of travel-associated African tick bite fever (ATBF), a rapidly emerging disease in travel medicine, we prospectively studied a cohort of 940 travelers to rural sub-Equatorial Africa. Diagnosis was based on suicide polymerase chain reaction and the detection of specific antibodies to Rickettia africae in serum samples by multiple-antigen microimmunofluorescence assay, Western blotting, and cross-adsorption assays. Thirty-eight travelers, 4.0% of the cohort and 26.6% of those reporting flulike symptoms, had ATBF diagnosed. More than 80% of the patients had fever, headache, and/or myalgia, whereas specific clinical features such as inoculation eschars, lymphadenitis, cutaneous rash, and aphthous stomatitis were seen in < or = 50% of patients. Game hunting, travel to southern Africa, and travel during November through April were found to be independent risk factors. Our study suggests that ATBF is not uncommon in travelers to rural sub-Saharan Africa and that many cases have a nonspecific presentation.

Evaluation of fever in the returned traveler

The primary care practitioner often is the first clinician sought out by a returning traveler, and it is important that he or she be alert to the possibility of exotic illness while remembering the more mundane causes of fever. Malaria remains one of the most serious diagnoses in a febrile traveler and should be looked for repeatedly. Other diagnoses may be suggested by exposure history and patterns of laboratory findings. A directed diagnostic workup, rational empiric therapy, and appropriate consultation are the tools with which the primary care provider successfully can manage the challenging dilemma posed by the returning traveler with fever.

Manifestations of tick-borne illness. Incidence and variety are increasing worldwide

The incidence and variety of diseases associated with tick bites have continued to grow worldwide. Lyme disease, the most common tick-borne disease in the United States, has received extensive media coverage because of its protean manifestations and propensity for causing chronic disease. Our ability to prevent, identify, and effectively treat Lyme disease and other tick-borne diseases has significantly improved in the last decade. Tick-borne illnesses should be one of the differential diagnostic considerations in patients with consistent clinical findings and exposure history. In addition, the prudent use of laboratory testing ensures an accurate diagnosis while avoiding the cost and risk of inappropriate diagnostic tests and antibiotic therapy.