Rickettsioses in Denmark: A retrospective survey of clinical features and travel history

Imported Rickettsial Infections to the United Kingdom, 2015-2020

OBJECTIVE

The burden of imported rickettsial infection in the UK is not previously described. This retrospective review identifies rickettsial cases diagnosed at the national reference laboratory between 2015-2022.

METHODS

Samples testing positive for spotted fever group, typhus group and scrub typhus IgG/IgM on acute and convalescent blood samples, and/or PCR on tissue/blood were categorised as suspected, confirmed or past infection.

RESULTS

220 patients had rickettsioses, the commonest import was acute spotted fever group infection (61%, 125/205), 54% (62/114) from South Africa. Acute typhus group cases, 60% (40/67) from Southeast Asia. One patient with Rickettsia typhi bacteremia died. Scrub typhus group infections (5%, 10/205) were exclusively from Asia and the Western Pacific regions. Overall, 43% of confirmed cases (39/91) had not received doxycycline prior to results.

CONCLUSIONS

Rickettsial infections are important and under-recognised causes of imported fever in the UK. Thorough history, examination and timely treatment with doxycycline should be considered if there is suspicion of Rickettsia infection before testing.

Recent Advances in the Immunologic Method Applied to Tick-Borne Diseases in Brazil

Zoonotic-origin infectious diseases are one of the major concerns of human and veterinary health systems. Ticks, as vectors of several zoonotic diseases, are ranked second only to mosquitoes as vectors. Many ticks’ transmitted infections are still endemic in the Americas, Europe, and Africa and represent approximately 17% of their infectious diseases population. Although our scientific capacity to identify and diagnose diseases is increasing, it remains a challenge in the case of tick-borne conditions. For example, in 2017, 160 cases of the Brazilian Spotted Fever (BSF, a tick-borne illness) were confirmed, alarming the notifiable diseases information system. Conversely, Brazilian borreliosis and ehrlichiosis do not require notification. Still, an increasing number of cases in humans and dogs have been reported in southeast and northeastern Brazil. Immunological methods applied to human and dog tick-borne diseases (TBD) show low sensitivity and specificity, cross-reactions, and false IgM positivity. Thus, the diagnosis and management of TBD are hampered by the personal tools and indirect markers used. Therefore, specific and rapid methods urgently need to be developed to diagnose the various types of tick-borne bacterial diseases. This review presents a brief historical perspective on the evolution of serological assays and recent advances in diagnostic tests for TBD (ehrlichiosis, BSF, and borreliosis) in humans and dogs, mainly applied in Brazil. Additionally, this review covers the emerging technologies available in diagnosing TBD, including biosensors, and discusses their potential for future use as gold standards in diagnosing these diseases.

An update on spotted fever group serology in Kerman Province, Iran

Rickettsia conorii is the causative agent of Mediterranean spotted fever (MSF) and reports of its geographical distribution are spreading every day. Recently, some cases of the MSF have been reported from Iran. However, little information is available about the MSF epidemiology in Iran. The aim of the current study was to investigate anti-R. conorii IgG seroprevalence among farmers living in the rural regions of Kerman province (in southeastern Iran). In this study, 281 blood samples were collected from farmers in Zarand and Jiroft counties and tested for detection of anti-R. conorii IgG antibodies using the ELISA method. Among the 281 samples, 14 farmers (4.98%, CI 95%; 2.45-7.55%) had anti-R. conorii IgG antibodies. Seroprevalence of MSF in Zarand and Jiroft counties were 4.58% and 5.33%, respectively. The serological evidence of this study indicates the seroprevalence of R. conorii in rural areas of the Kerman province of Iran. So, it is recommended that the Iranian health care system pay attention to the MSF.

Evaluation of factors influencing tick bites and tick-borne infections: a longitudinal study

BACKGROUND

Various tick-borne infections like borreliosis and rickettsiosis pose a health risk to humans in many parts of the world. We investigated seroprevalence of and seroconversion to Borrelia burgdorferi and Rickettsia spp. and relation to tick-bites, weather and clinical manifestations in Denmark.

METHODS

Blood donors were enrolled at the Hospital of Southern Jutland in June-July with follow-up November-February of 2018 and 2019. Blood samples were collected, and a questionnaire regarding tick bites, potential exposures and symptoms was completed at each visit. Samples were tested for presence of IgM and IgG antibodies directed against B. burgdorferi and Rickettsia spp. using R. helvetica and R. felis as antigens. Data were examined for correlation between tick bites, serological results, potential exposures and symptoms.

RESULTS

Two-hundred and fourteen (93 follow-ups) and 130 (38 follow-ups) blood donors were included in 2018 and 2019, respectively. The total borrelia seroconversion rate was 6.3% (CI 2.1-10.5), while the prevalence of IgM and IgG antibodies was 7.8% (CI 4.9-10.6) and 6.7% (CI 4-9.3), respectively. Seroconversion to Rickettsia spp. was detected in one participant. Tick bites and seroconversion were not significantly associated with the reported unspecific symptoms, but unspecific symptoms were common in the study population. There was no significant difference in number of tick bites or seroconversion/prevalence between seasons with highly alternating weather.

CONCLUSIONS

Results suggest that weather conditions in an individual year have a limited impact. Anti-Borrelia-antibodies do not seem to persist in serum for several years. Rickettsiosis is of limited concern in Denmark.

Laboratory Diagnostics of Rickettsia Infections in Denmark 2008-2015

Rickettsiosis is a vector-borne disease caused by bacterial species in the genus Rickettsia. Ticks in Scandinavia are reported to be infected with Rickettsia, yet only a few Scandinavian human cases are described, and rickettsiosis is poorly understood. The aim of this study was to determine the prevalence of rickettsiosis in Denmark based on laboratory findings. We found that in the Danish individuals who tested positive for Rickettsia by serology, the majority (86%; 484/561) of the infections belonged to the spotted fever group. In contrast, we could confirm 13 of 41 (32%) PCR-positive individuals by sequencing and identified all of these as R. africae, indicating infections after travel exposure. These 13 samples were collected from wound/skin material. In Denmark, approximately 85 individuals test positive for Rickettsia spp. annually, giving an estimated 26% (561/2147) annual prevalence among those suspected of rickettsiosis after tick bites. However, without clinical data and a history of travel exposure, a true estimation of rickettsiosis acquired endemically by tick bites cannot be made. Therefore, we recommend that both clinical data and specific travel exposure be included in a surveillance system of Rickettsia infections.

The Rickettsioses: A Practical Update

Rickettsia are small, obligately intracellular, gram-negative bacilli. They are distributed among a variety of hematophagous arthropod vectors and cause illness throughout the world. Rickettsioses present as an acute undifferentiated febrile illness and are often accompanied by headache, myalgias, and malaise. Cutaneous manifestations include rash and eschar, which both occur at varying incidence depending on the infecting species. Serology is the mainstay of diagnosis, and the indirect immunofluorescence assay is the test of choice. Reactive antibodies are seldom present during early illness, so testing should be performed on both acute-phase and convalescent-phase sera. Doxycycline is the treatment of choice.