Murine typhus, Reunion, France, 2011-2013

Clinical and Epidemiological Aspects of Acute Q Fever in Reunion Island over Fourteen Years: A Retrospective Cohort Study

The clinical characteristics and epidemiology of Q fever in the Tropics are poorly described. We performed a retrospective cohort study of hospitalized cases between 2004 and 2017 in Reunion Island. Acute Q fever was defined in presence of a positive serology (phase II IgG ≥ 200 and phase II IgM ≥ 50), or a seroconversion (4-fold increase in phase II IgG between paired samples), or a positive PCR (blood or serum). Forty-two cases matched the diagnostic criteria. The most common clinical manifestations were fever (85.7%) and pulmonary symptoms (61.9%), including pneumonia (45.2%). Ninety percent of the patients were living in a farming area. Cumulative incidence was estimated at 9.3 per 100,000 inhabitants (95%CI: 6.4-12.1) with cases diagnosed yearly all throughout the study period except in 2006. Together with the seroprevalence figures, these data suggest that Q fever reaches low to moderate endemic levels on Reunion Island. As previously reported, pulmonary symptoms are in the foreground.

Sunbathing, a possible risk factor of murine typhus infection in Greece

BACKGROUND

There are few studies about the presence of murine typhus in Greece. Our objective was to conduct a large scale retrospective investigation to determine the clinical and epidemiological features of patients diagnosed with murine typhus in Greece.

METHODOLOGY/PRINCIPAL FINDINGS

From 2012 to 2019 serum samples from hospitalized patients and outpatients throughout Greece suspected for murine typhus infection were tested by immunofluorescence assay for Rickettsia typhi. Immunofluorescence positive samples obtained since 2016 were also tested by qPCR targeting R. typhi. Clinical and epidemiological data were retrospectively collected for the patients with confirmed murine typhus. Overall, we tested 5,365 different patients and, in total, 174 patients from all geographic regions of Greece were diagnosed with murine typhus. The most frequently reported sign or symptom was fever (89%), followed by headache (84%) and rash (81%). The classical triad of fever, headache, and rash was present in 72% of patients during their illness. Severe infections with complications including acute renal failure or septic shock were not recorded. The majority of cases (81%) occurred during May-October and peaked in June and September. Most of patients (81%) infected in Athens, recalled that their only activity the last weeks before symptoms onset was swimming on the beach and 59% of them also reported an insect bite while sunbathing.

CONCLUSIONS/SIGNIFICANCE

Our results may reflect the reemergence of murine typhus in Greece and we highlight the importance of awareness of this difficult-to-recognize undifferentiated febrile illness.

Describing fine spatiotemporal dynamics of rat fleas in an insular ecosystem enlightens abiotic drivers of murine typhus incidence in humans

Murine typhus is a flea-borne zoonotic disease that has been recently reported on Reunion Island, an oceanic volcanic island located in the Indian Ocean. Five years of survey implemented by the regional public health services have highlighted a strong temporal and spatial structure of the disease in humans, with cases mainly reported during the humid season and restricted to the dry southern and western portions of the island. We explored the environmental component of this zoonosis in an attempt to decipher the drivers of disease transmission. To do so, we used data from a previously published study (599 small mammals and 175 Xenopsylla fleas from 29 sampling sites) in order to model the spatial distribution of rat fleas throughout the island. In addition, we carried out a longitudinal sampling of rats and their ectoparasites over a 12 months period in six study sites (564 rats and 496 Xenopsylla fleas) in order to model the temporal dynamics of flea infestation of rats. Generalized Linear Models and Support Vector Machine classifiers were developed to model the Xenopsylla Genus Flea Index (GFI) from climatic and environmental variables. Results showed that the spatial distribution and the temporal dynamics of fleas, estimated through the GFI variations, are both strongly controlled by abiotic factors: rainfall, temperature and land cover. The models allowed linking flea abundance trends with murine typhus incidence rates. Flea infestation in rats peaked at the end of the dry season, corresponding to hot and dry conditions, before dropping sharply. This peak of maximal flea abundance preceded the annual peak of human murine typhus cases by a few weeks. Altogether, presented data raise novel questions regarding the ecology of rat fleas while developed models contribute to the design of control measures adapted to each micro region of the island with the aim of lowering the incidence of flea-borne diseases.

Murine typhus is a neglected zoonotic disease, as the number of human cases is likely underestimated in the absence of specific symptoms. It is caused by Rickettsia typhi, a pathogenic bacterium transmitted by rat fleas (Xenospylla spp). The distribution and dynamics of this disease result from complex interactions involving vectors, reservoirs and humans within a shared environment. In this study, we explored the environmental drivers of rat fleas’ abundance on Reunion Island, where murine typhus has recently emerged. Results showed that i) rat fleas’ abundance is highly dynamic, characterized by a peak at the end of the dry season and ii) among the factors investigated, rainfall, temperature and land cover are the main determinants of rat fleas’ abundance. We modeled a predictive map of flea distribution that strongly correlates with the spatial distribution of human cases on the island. This study highlights the importance of accounting for environmental and climatic characteristics to better understand the spatial and temporal drivers of flea-borne diseases.

Selection of Diagnostic Cutoffs for Murine Typhus IgM and IgG Immunofluorescence Assay: A Systematic Review

Murine typhus is a neglected but widespread infectious disease that results in acute fever. The immunofluorescence assay (IFA) is the "gold standard" to identify IgM or IgG antibodies, although there is a lack of standardization in methodologies. The objective of this review is to summarize 1) the differences in published methodologies, 2) the diagnostic cutoff titers, and 3) the justification of diagnostic cutoffs. Searches were performed by combining the following search terms: "murine typhus," "rickettsia typhi," "immunofluorescence," "IFA," and "serologic" with restrictions (i.e., "rickettsia typhi" or "murine typhus," and "IFA" or "immunofluorescence," or "serologic*"). The search identified 78 studies that used IFA or immunoperoxidase assay (IIP) antibody cutoffs to diagnose murine typhus, 39 of which were case series. Overall, 45 studies (57.7%) provided little to no rationale as to how the cutoff was derived. Variation was seen locally in the cutoff titers used, but a 4-fold or greater increase was often applied. The cutoffs varied depending on the antibody target. No consensus was observed in establishing a cutoff, or for a single-value diagnostic cutoff. In conclusion, there is a lack of consensus in the establishment of a single-value cutoff. Further studies will need to be executed at each distinct geographic location to identify region-specific cutoffs, while also considering background antibody levels to distinguish between healthy and infected patients.

Epidemiological characteristics and spatiotemporal patterns of typhus group rickettsiosis at the county level in China, 2005-2017

OBJECTIVE

To explore the epidemiological characteristics and spatiotemporal patterns of typhus group rickettsiosis (TGR) in mainland China.

METHODS

A chi-squared test was used to compare the differences in the age and occupation distributions across the different years. Time-series analyses, spatial clustering analyses, and spatiotemporal scan statistics were used to detect the spatiotemporal patterns of the TGR incidence.

RESULTS

A total of 29,211 TGR cases were collected. Of these cases, 63.1% occurred from May to October, and 88.4% occurred in individuals between 0 and 59 years old. There was a significant spatial TGR heterogeneity from 2005 to 2017. The hotspots were located mainly in the southwestern, southern, and circum-Bohai Sea regions of northern China. Eighteen spatiotemporal clusters were observed using Kulldorff's space-time scan statistic, and the primary cluster included three counties, Jinghong city, Menghai county, and Mengla county.

CONCLUSIONS

TGR is widely distributed in China, and it is a serious threat to public health. The hotspots were located mainly in the southwestern, southern, and circum-Bohai Sea regions of northern China, and the primary spatiotemporal cluster showed a trend shifting from circum-Bohai Sea regions to the southwestern regions. Targeted interventions should be executed in high-risk regions for precise prevention and control.

Emergence of murine typhus in La Réunion, France, 2012-2017

OBJECTIVE

Murine typhus (MT) is an acute zoonosis caused by Rickettsia typhi, a flea-borne rickettsiosis. The first autochthonous case was reported in 2012. Once autochthonous transmission of Rickettsia typhi was proven, we performed a prospective study to describe and raise awareness of this often-misdiagnosed disease among physicians.

PATIENTS AND METHODS

We performed a prospective observational study of MT cases in La Réunion from 2012 to 2017. MT cases were defined as clinically compatible illnesses with a specific positive serology and/or PCR.

RESULTS

Sixty-one confirmed cases were collected. The main clinical features were prolonged fever (90%), asthenia (87%), and headaches (79%). The main biological abnormalities were elevated liver enzymes (84%) and thrombopenia (75%). Renal function was normal in 90% of cases; it was an important feature because leptospirosis is a frequent cause of acute renal failure. A seasonal factor was observed with 79% of cases reported in the warm season and most of them in the west and south of the island (i.e., the dry areas).

CONCLUSION

MT is an emerging disease in La Réunion, and local conditions could lead to an endemic situation. Cases of acute undifferentiated fever with headaches should guide to the diagnosis of MT especially in the warm season and dry areas. Leptospirosis is an alternative diagnosis, which differs from MT by its epidemiological characteristics and by the associated frequent renal dysfunction.

Seroprevalence of typhus group and spotted fever group Rickettsia exposures on Reunion island

Objective

Murine typhus has been increasingly reported on Reunion island, Indian ocean, following documentation of eight autochthonous infections in 2012–2013. We conducted a serosurvey to assess the magnitude of the seroprevalence of rickettsioses in the population. Two hundred and forty-one stored frozen sera taken from the 2009 Copanflu-RUN cohort were analysed using an immunofluorescence assay allowing to distinguish typhus group (TGR) and spotted fever group Rickesttsiae (SFGR). Seropositivity was defined for a dilution titre of Rickettsia IgG antibodies ≥ 1:64. Seroprevalence was weighted to account for the discrepancy between the Copanflu-RUN subset and the general population, as to infer prevalence at community level. Prevalence proportion ratios (PPR) were measured using log-binomial models.

Results

The weighted seroprevalences of typhus group rickettsioses and spotted fever group rickettsioses were of 12.71% (95% CI 8.84–16.58%) and 17.68% (95% CI 13.25–22.11%), respectively. Pooled together, data suggested that a fifth of the population had been exposed at least to one Rickettsia group. Youths (< 20 years) were less likely seropositive than adults (adjusted PPR 0.13, 95% CI 0.01–0.91). People living in the western dryer part of the island were more exposed (adjusted PPR 2.53, 95% CI 1.07–5.97). Rickettsioses are endemic on Reunion island and circulated before their first identification as murine typhus in year 2011. Surprisingly, since isolation of Rickettsia africae from Amblyomma variegatum in year 2004 or isolation of Rickettsia felis from Amblyomma loculosum, no autochthonous cases of African tick-bite fever or flea-borne spotted fever has yet been diagnosed.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4416-8) contains supplementary material, which is available to authorized users.

Molecular and serological evidence of flea-associated typhus group and spotted fever group rickettsial infections in Madagascar

Background

Rickettsiae are obligate intracellular bacteria responsible for many febrile syndromes around the world, including in sub-Saharan Africa. Vectors of these pathogens include ticks, lice, mites and fleas. In order to assess exposure to flea-associated Rickettsia species in Madagascar, human and small mammal samples from an urban and a rural area, and their associated fleas were tested.

Results

Anti-typhus group (TGR)- and anti-spotted fever group rickettsiae (SFGR)-specific IgG were detected in 24 (39%) and 21 (34%) of 62 human serum samples, respectively, using indirect ELISAs, with six individuals seropositive for both. Only two (2%) Rattus rattus out of 86 small mammals presented antibodies against TGR. Out of 117 fleas collected from small mammals, Rickettsia typhi, a TGR, was detected in 26 Xenopsylla cheopis (24%) collected from rodents of an urban area (n = 107), while two of these urban X. cheopis (2%) were positive for Rickettsia felis, a SFGR. R. felis DNA was also detected in eight (31%) out of 26 Pulex irritans fleas.

Conclusions

The general population in Madagascar are exposed to rickettsiae, and two flea-associated Rickettsia pathogens, R. typhi and R. felis, are present near or in homes. Although our results are from a single district, they demonstrate that rickettsiae should be considered as potential agents of undifferentiated fever in Madagascar.