Rickettsia species in African Anopheles mosquitoes

A novel Rickettsia species closely related to Rickettsia felis in Anopheles mosquitoes from Yingkou City, Northeast China

Mosquitoes are generally recognized as the most important vector of many zoonotic pathogens. In this study, seven mosquitoes species were identified (Anopheles pullus, Anopheles sinensis, Anopheles lesteri, Anopheles kleini, Ochlerotatus dorsalis, Aedes koreicus and Culex inatomii) in samples collected from Yingkou City, Liaoning Province, Northeastern China. A novel Rickettsia species was detected in Anopheles sinensis (two of 71, 2.82%) and Anopheles pullus (one of 106, 0.94%) mosquitoes. Genetic analysis indicated that the rrs and ompB genes have highest 99.60% and 97.88%-98.14% identities to Rickettsia felis, an emerging human pathogen of global concern mainly harboured by fleas, mosquitoes and booklice. The gltA sequences of these strains have 99.72% of nucleotide similarity with Rickettsia endosymbiont of Medetera jacula. The groEL sequences have 98.37% similarity to both Rickettsia tillamookensis and Rickettsia australis. The htrA sequences have 98.77% similarity to Rickettsia lusitaniae. In the phylogenetic tree based on concatenated nucleotide sequences of rrs, gltA, groEL, ompB and htrA genes, these strains are closely related to R. felis. Herein, we name it 'Candidatus Rickettsia yingkouensis'. Its human pathogenicity to humans and animals is still to be determined.

Deep learning and wing interferential patterns identify Anopheles species and discriminate amongst Gambiae complex species

We present a new and innovative identification method based on deep learning of the wing interferential patterns carried by mosquitoes of the Anopheles genus to classify and assign 20 Anopheles species, including 13 malaria vectors. We provide additional evidence that this approach can identify Anopheles spp. with an accuracy of up to 100% for ten out of 20 species. Although, this accuracy was moderate (> 65%) or weak (50%) for three and seven species. The accuracy of the process to discriminate cryptic or sibling species is also assessed on three species belonging to the Gambiae complex. Strikingly, An. gambiae, An. arabiensis and An. coluzzii, morphologically indistinguishable species belonging to the Gambiae complex, were distinguished with 100%, 100%, and 88% accuracy respectively. Therefore, this tool would help entomological surveys of malaria vectors and vector control implementation. In the future, we anticipate our method can be applied to other arthropod vector-borne diseases.

Internal and external microbiota of home-caught Anopheles coluzzii (Diptera: Culicidae) from Côte d'Ivoire, Africa: Mosquitoes are filthy

Over the past 10 years, studies using high-throughput 16S rRNA gene sequencing have shown that mosquitoes harbor diverse bacterial communities in their digestive system. However, no previous research has examined the total bacteria community inside versus outside of mosquitoes and whether bacteria found on the outside could represent a potential health threat through mechanical transfer. We examined the bacterial community of the external surface and internal body of female Anopheles coluzzii adults collected from homes in Côte d'Ivoire, Africa, by Illumina sequencing of the V3 to V4 region of 16S rRNA gene. Anopheles coluzzii is in the Anopheles gambiae sensu lato (s.l.) species complex and important in the transmission of malaria. The total 16S rRNA reads were assigned to 34 phyla, 73 orders, 325 families, and 700 genera. At the genus level, the most abundant genera inside and outside combined were Bacillus, Staphylococcus, Enterobacter, Corynebacterium, Kocuria, Providencia, and Sphingomonas. Mosquitoes had a greater diversity of bacterial taxa internally compared to the outside. The internal bacterial communities were similar between homes, while the external body samples were significantly different between homes. The bacteria on the external body were associated with plants, human and animal skin, and human and animal infections. Internally, Rickettsia bellii and Rickettsia typhi were found, potentially of importance, since this genus is associated with human diseases. Based on these findings, further research is warranted to assess the potential mechanical transmission of bacteria by mosquitoes moving into homes and the importance of the internal mosquito microbiota in human health.

Mosquito Vectors (Diptera: Culicidae) and Mosquito-Borne Diseases in North Africa

Mosquitoes (Diptera: Culicidae) are of significant public health importance because of their ability to transmit major diseases to humans and animals, and are considered as the world's most deadly arthropods. In recent decades, climate change and globalization have promoted mosquito-borne diseases' (MBDs) geographic expansion to new areas, such as North African countries, where some of these MBDs were unusual or even unknown. In this review, we summarize the latest data on mosquito vector species distribution and MBDs affecting both human and animals in North Africa, in order to better understand the risks associated with the introduction of new invasive mosquito species such as Aedes albopictus. Currently, 26 mosquito species confirmed as pathogen vectors occur in North Africa, including Aedes (five species), Culex (eight species), Culiseta (one species) and Anopheles (12 species). These 26 species are involved in the circulation of seven MBDs in North Africa, including two parasitic infections (malaria and filariasis) and five viral infections (WNV, RVF, DENV, SINV and USUV). No bacterial diseases have been reported so far in this area. This review may guide research studies to fill the data gaps, as well as helping with developing effective vector surveillance and controlling strategies by concerned institutions in different involved countries, leading to cooperative and coordinate vector control measures.

Discovery of Rickettsia spp. in mosquitoes collected in Georgia by metagenomics analysis and molecular characterization

Arthropods have a broad and expanding worldwide presence and can transmit a variety of viral, bacterial, and parasite pathogens. A number of Rickettsia and Orientia species associated with ticks, fleas, lice, and mites have been detected in, or isolated from, patients with febrile illness and/or animal reservoirs throughout the world. Mosquitoes are not currently considered vectors for Rickettsia spp. pathogens to humans or to animals. In this study, we conducted a random metagenome next-generation sequencing (NGS) of 475 pools of Aedes, Culex, and Culiseta species of mosquitoes collected in Georgia from 2018 to 2019, identifying rickettsial gene sequences in 33 pools of mosquitoes. We further confirmed the findings of the Rickettsia by genus-specific quantitative PCR (qPCR) and multi-locus sequence typing (MLST). The NGS and MLST results indicate that Rickettsia spp. are closely related to Rickettsia bellii, which is not known to be pathogenic in humans. The results, together with other reports of Rickettsia spp. in mosquitoes and the susceptibility and transmissibility experiments, suggest that mosquitoes may play a role in the transmission cycle of Rickettsia spp.

Booklice Liposcelis bostrychophila naturally infected by Rickettsia felis cause fever and experimental pneumonia in mammals

BACKGROUND

Rickettsia felis is emergent in tropical areas. Despite its high morbidity, its natural history has not yet been fully determined. We investigated the role of the common household booklouse, Liposcelis bostrychophila, recently found to harbour R. felis.

METHODS

Blood samples from 372 febrile patients from Senegalese villages, as well as nasal and skin samples from 264 asymptomatic individuals, were tested for cat flea-associated and booklice-associated strains of R. felis. Dust samples from beds were collected to isolate booklice and R. felis. Mice were infected with aerosol of R. felis strain from naturally infected booklice.

RESULTS

Forty febrile patients (11%) were infected by R. felis, including 26 (7%) by the booklice-associated strain. Nine nasal samples (3.4%) and 28 skin samples (10.6%) contained R. felis, including seven and 24, respectively, with the booklice-associated strain. The presence of live L. bostrychophila was observed in 32 dust samples (16.8%); R. felis was identified in 62 dust samples (32.5%). Several mice samples were positive for R. felis; interstitial lymphohistiocytic infiltrates were identified in lungs.

CONCLUSIONS

L. bostrychophila may be a reservoir of R. felis. The booklice-associated strain is pathogenic in mammals causing pneumonia. Human infection may be acquired via inhalation of infected booklice particles.

The role of cofeeding arthropods in the transmission of Rickettsia felis

Rickettsia felis is an emerging etiological agent of rickettsioses worldwide. The cosmopolitan cat flea (Ctenocephalides felis) is the primary vector of R. felis, but R. felis has also been reported in other species of hematophagous arthropods including ticks and mosquitoes. Canines can serve as a bacteremic host to infect fleas under laboratory conditions, yet isolation of R. felis from the blood of a vertebrate host in nature has not been realized. Cofeeding transmission is an efficient mechanism for transmitting rickettsiae between infected and uninfected fleas; however, the mechanism of transmission among different orders and classes of arthropods is not known. The potential for R. felis transmission between infected fleas and tick (Dermacentor variabilis) and mosquito (Anopheles quadrimaculatus) hosts was examined via cofeeding bioassays. Donor cat fleas infected with R. felis transmitted the agent to naïve D. variabilis nymphs via cofeeding on a rat host. Subsequent transstadial transmission of R. felis from the engorged nymphs to the adult ticks was observed with reduced prevalence in adult ticks. Using an artificial host system, An. quadrimaculatus exposed to a R. felis-infected blood meal acquired rickettsiae and maintained infection over 12 days post-exposure (dpe). Similar to ticks, mosquitoes were able to acquire R. felis while cofeeding with infected cat fleas on rats infection persisting in the mosquito for up to 3 dpe. The results indicate R. felis-infected cat fleas can transmit rickettsiae to both ticks and mosquitoes via cofeeding on a vertebrate host, thus providing a potential avenue for the diversity of R. felis-infected arthropods in nature.

Primarily associated with the common cat flea, Rickettsia felis is an intracellular bacterial pathogen that can be transmitted from the flea to vertebrate hosts. This flea-borne infection has now been identified worldwide as a human pathogen. In addition to fleas, other blood feeding arthropods including ticks and mosquitoes are being recognized as possible vectors of R. felis. Although the mammalian infectious source for arthropods is still unknown, cofeeding transmission of Rickettsia is known to occur between vectors of the same species. However, potential for flea transmission of R. felis to other orders and classes of arthropods is unknown. Here, we examined the potential for fleas to transmit R. felis to American dog ticks and mosquitoes during feeding events on rat hosts. Our data suggested that ticks and mosquitoes can be infected when simultaneously feeding on a host with R. felis-infected cat fleas.

Systematic Review on Diversity and Distribution of Anopheles Species in Gabon: A Fresh Look at the Potential Malaria Vectors and Perspectives

Gabon is located in the malaria hyper-endemic zone, where data concerning malaria vector distribution remains fragmentary, making it difficult to implement an effective vector control strategy. Thus, it becomes crucial and urgent to undertake entomological surveys that will allow a better mapping of the Anopheles species present in Gabon. In this review, we examined different articles dealing with Anopheles in Gabon from ProQuest, Web of Science, PubMed, and Google scholar databases. After applying the eligibility criteria to 7543 articles collected from four databases, 42 studies were included that covered a 91-year period of study. The review revealed a wide diversity of Anopheles species in Gabon with a heterogeneous distribution. Indeed, our review revealed the presence of 41 Anopheles species, of which the most abundant were members of the Gambiae and Nili complexes and those of the Funestus and Moucheti groups. However, our review also revealed that the major and minor vectors of malaria in Gabon are present in both sylvatic, rural, and urban environments. The observation of human malaria vectors in sylvatic environments raises the question of the role that the sylvatic environment may play in maintaining malaria transmission in rural and urban areas. Ultimately, it appears that knowledge of biodiversity and spatial distribution of Anopheles mosquitoes is fragmentary in Gabon, suggesting that additional studies are necessary to complete and update these entomological data, which are useful for the implementation of vector control strategies.

Surveillance Studies Reveal Diverse and Potentially Pathogenic-Incriminated Vector Mosquito Species across Major Botswana Touristic Hotspots

Vector mosquitoes contribute significantly to the global burden of diseases in humans, livestock and wildlife. As such, the spatial distribution and abundance of mosquito species and their surveillance cannot be ignored. Here, we surveyed mosquito species across major tourism hotspots in semi-arid Botswana, including, for the first time, the Central Kalahari Game Reserve. Our results reported several mosquito species across seven genera, belonging to Aedes, Anopheles, Culex, Mansonia, Mimomyia, Coquillettidia and Uranotaenia. These results document a significant species inventory that may inform early warning vector-borne disease control systems and likely help manage the risk of emerging and re-emerging mosquito-borne infections.

Current tools for the diagnosis and detection of spotted fever group Rickettsia

Spotted fever group (SFG) rickettsiae causes a number of diseases in humans worldwide, which can range from mild to highly lethal. Since the clinical presentations of rickettsioses caused by SFG rickettsiae are variable and may be similar to the diseases caused by other rickettsiae, such as Orientia tsutsugamushi (agent for scrub typhus), Coxiella burnetii (agent for Q fever) and the typhus group rickettsiae (agents for epidemic and murine typhus), the accurate diagnosis of infections caused by SFG Rickettsia remains challenging especially in resource-poor settings in developing countries. This review summarizes the various diagnostic and detection tools that are currently available for the confirmation of infections by SFG rickettsiae. The advantages and challenges pertaining to the different serological and molecular detections methods, as well as new assays in development, are discussed. The utility of the detection tools contributing to the surveillance of SFG rickettsiae in arthropods and animals are reviewed.

New records of bacteria in different species of fleas from France and Spain

In this study, we assessed the presence of vector-borne microorganisms in different species of fleas collected from different hosts in diverse areas of South-Western Europe by molecular methods. A total of 319 fleas belonging to eight different species was tested for the presence of eight microorganisms. Wolbachia spp. endosymbionts were detected in Ctenocephalides felis, Pulex irritans, Archaeopsylla erinacei and Ctenophthalmus baeticus boisseauorum specimens. Rickettsia felis, an emerging pathogen, was detected in C. felis, A. erinacei and Ct. b. boisseauorum. Rickettsia typhi, the agent of murine typhus was detected for the first time in A. erinacei and Mycobacterium spp. were detected for the first time in fleas (C. felis, P. irritans and A. erinacei). Lastly, five different species of Bartonella were detected in fleas' DNA in this study, including a possible new bacterium belonging to this genus. With this study, we updated the knowledge of the flea-borne bacteria present in the South-West of Europe reinforcing the idea about the necessity to expand and increase the current knowledge on flea-borne pathogens.

Crystal structure of acetoacetyl-CoA reductase from Rickettsia felis

Rickettsia felis, a Gram-negative bacterium that causes spotted fever, is of increasing interest as an emerging human pathogen. R. felis and several other Rickettsia strains are classed as National Institute of Allergy and Infectious Diseases priority pathogens. In recent years, R. felis has been shown to be adaptable to a wide range of hosts, and many fevers of unknown origin are now being attributed to this infectious agent. Here, the structure of acetoacetyl-CoA reductase from R. felis is reported at a resolution of 2.0 Å. While R. felis acetoacetyl-CoA reductase shares less than 50% sequence identity with its closest homologs, it adopts a fold common to other short-chain dehydrogenase/reductase (SDR) family members, such as the fatty-acid synthesis II enzyme FabG from the prominent pathogens Staphylococcus aureus and Bacillus anthracis. Continued characterization of the Rickettsia proteome may prove to be an effective means of finding new avenues of treatment through comparative structural studies.

Molecular-based Survey of Rickettsia spp. and Coxiella burnetii in Mosquitoes (Diptera: Culicidae) from Fars Province, Southern Iran, during 2017-18

Objectives:

Since there have not been any studies on the roles of the Iranian mosquitoes in the transmission of Rickettsia spp. and Coxiella burneti, the present study investigates the roles of mosquitoes in the transmission of the pathogens using the PCR techniques for the first time in Iran.

Methods:

The present study was conducted in Fars province during the activity seasons of mosquitoes in 2017-18. The primer design was done to investigate the probability of mosquito’s contamination with Rickettsia spp. and Coxiella burnetii. The conventional PCR was used after the extraction of DNA from mosquitoes to study the contamination.

Results:

A total of 1103 adult mosquitoes were collected and identified. Among them, 3 genera and 11 species were identified, including Anopheles (25.74%), Culex (51.84%) and Culiseta (22.39%) genera. All tested mosquitoes were negative in terms of contamination to Rickettsia spp. and Coxiella burnetii.

Conclusion:

Based on the results, mosquitoes are not considered as vectors of Rickettsia spp. and Coxiella burnetii in this part of the country currently. Further studies on a larger scale are needed to examine the exact role of mosquitoes (as a possible vector with high abundance and mobility) in the transmission of these pathogens in tropical areas of Iran.

Bartonella species in medically important mosquitoes, Central Europe

Here, we provide the first mass molecular screening of medically important mosquitoes for Bartonella species using multiple genetic markers. We examined a total of 72,115 mosquito specimens, morphologically attributed to Aedes vexans (61,050 individuals), Culex pipiens (10,484 individuals) and species of the Anopheles maculipennis complex (581 individuals) for Bartonella spp. The initial screening yielded 63 Bartonella-positive A. vexans mosquitoes (mean prevalence 0.1%), 34 Bartonella-positive C. pipiens mosquitoes (mean prevalence 0.3%) and 158 Bartonella-positive A. maculipennis group mosquitoes (mean prevalence 27.2%). Several different Bartonella ITS sequences were recovered. This study highlights the need for molecular screening of mosquitoes, the most important vectors of arthropod-borne pathogens, for potential bacterial agents.

Emerging and re-emerging bacterial zoonoses in Nigeria: current preventive measures and future approaches to intervention

A characteristic of bacterial zoonoses, diseases caused by bacteria that can be transmitted to humans from animals, is a propensity to re-emerge. Several studies demonstrate their ongoing transmission in Nigeria, the most populous country in Africa. However, as local epidemiological data on bacterial zoonoses are inadequate the extent and impact of these infectious diseases is under-reported. Consequently, they are not a targeted priority of national public health policies. This limited recognition is despite indications of their possible roles in the widespread prevalence of non-malarial undifferentiated fever in Nigeria. While a number of animal reservoirs and arthropod vectors have been identified in the transmission routes of these diseases, an escalation of cases of undiagnosed febrile illness highlights the urgent need for a comprehensive assessment of other potential reservoirs, vectors and transmission cycles that may increase the local risk of infection with bacterial zoonoses. Animal health interventions have been proposed as a cost-effective strategy. Here, we present a broad overview of bacterial zoonotic infections of humans in Nigeria in the context of evolving epidemiological patterns. Further, we propose that facilitating the operation of a community-based One Health program is essential to providing the comprehensive epidemiological information that is required to improve prioritization of bacterial zoonoses. This would provide a driver for much needed investment in relevant public health interventions in Africa's most populous country.

Prevalence of plasmodium, leptospira and rickettsia species in Northern Tanzania: a community based survey

BACKGROUND

The overlap of symptoms, geographic and seasonal co-occurrence of Plasmodium, Leptospira and Rickettsia infections makes malaria diagnosis difficult, increasing the chances of misdiagnosis. The paucity of data on the prevalence Plasmodium, Leptospira and Rickettsia infections contributes to an overly diagnosis of malaria. We aimed to determine the prevalence and distribution of Plasmodium, Leptospira and Rickettsia infections in northern Tanzania.

METHODS

A community based, cross sectional survey was conducted in two sites in Northern Tanzania. PCR was used to detect Plasmodium, Leptospira and Rickettsia infections.

RESULTS

The prevalence of P. falciparum and Leptospira spp were 31/128 (24.2%) and 3/128 (2.3%), respectively. No Rickettsia infection was detected in any of the two sites. Taking study sites separately, Plasmodium infection was detected in 31/63(49.2%) of participants in Bondo while Leptospira infection was detected in 3/65(4.6%) of participants in Magugu. Plasmodium was not detected in Magugu while no Leptospira infections were detected in Bondo. Fever was significantly associated with Plasmodium infection (χ2= 12.44, p<0.001) and age (χ2=17.44, p=0.000).

CONCLUSION

Results from this study indicate Plasmodium infection as the main cause of fever in the studied sites. While Plasmodium and Leptospira contribute to fevers, Rickettsia infection is an insignificant cause of fever in Northern Tanzania.

Molecular identification and prevalence of tick-borne pathogens in zebu and taurine cattle in North Cameroon

Background

Public interest for tick-borne pathogens in cattle livestock is rising due to their veterinary and zoonotic importance. Consequently, correct identification of these potential pathogens is crucial to estimate the level of exposition, the risk and the detrimental impact on livestock and the human population.

Results

Conventional PCR with generic primers was used to identify groups of tick-borne pathogens in cattle breeds from northern Cameroon. The overall prevalence in 1260 blood samples was 89.1%, with 993 (78.8%) positive for Theileria/Babesia spp., 959 (76.1%) for Anaplasma/Ehrlichia spp., 225 (17.9%) for Borrelia spp., and 180 (14.3%) for Rickettsia spp. Sanger sequencing of a subset of positively-tested samples revealed the presence of Theileria mutans (92.2%, 130/141), T. velifera (16.3%, 23/141), Anaplasma centrale (10.9%, 15/137), A. marginale (30.7%, 42/137), A. platys (51.1%, 70/137), Anaplasma sp. ‘Hadesa’ (10.9%, 15/137), Ehrlichia ruminantium (0.7%, 1/137), E. canis (0.7%, 1/137), Borrelia theileri (91.3%, 42/46), Rickettsia africae (59.4%, 19/32) and R. felis (12.5%, 4/32). A high level of both intra- and inter-generic co-infections (76.0%) was observed. To the best of our knowledge, B. theileri, T. mutans, T. velifera, A. platys, Anaplasma sp. ‘Hadesa’, R. felis and E. canis are reported for the first time in cattle from Cameroon, and for R. felis it is the first discovery in the cattle host. Babesia spp. were not detected by sequencing. The highest number of still identifiable species co-infections was up to four pathogens per genus group. Multifactorial analyses revealed a significant association of infection with Borrelia theileri and anemia. Whereas animals of older age had a higher risk of infection, the Gudali cattle had a lower risk compared to the other local breeds.

Conclusion

Co-infections of tick-borne pathogens with an overall high prevalence were found in all five study sites, and were more likely to occur than single infections. Fulani, Namchi and Kapsiki were the most infected breed in general; however, with regions as significant risk factor. A better-adapted approach for tick-borne pathogen identification in co-infected samples is a requirement for epidemiological investigations and tailored control measures.

Molecular Detection of Rickettsia felis and Rickettsia bellii in Mosquitoes

To add to the limited information on Rickettsia in mosquitoes in China, we carried out a PCR survey on convenience samples of 3051 mosquitoes collected with hand nets in and around domestic dwellings in 25 provinces. Five species of mosquitoes were identified: Culex pipiens pallens (n = 1620), Aedes albopictus (806), Armigeres subalbatus (377), Anopheles sinensis (168), and Culex tritaeniorhynchus (80). A Rickettsia nested-PCR targeting the variable domain of gltA showed Rickettsia felis in four mosquito species of 16 provinces Cx. pipiens pallens (1.8%, 29/1620); Ae. albopictus (1.2%, 10/806); An. sinensis (1.2%, 2/168); and Ar. subalbatus (2.1%, 8/377). Rickettsia bellii was also widespread, occurring in 12 provinces and 2 species: Cx. pipiens pallens (4.3%, 69/1620) and An. sinensis (0.6%, 1/168). R. felis and R. bellii were found in almost similar numbers in female [1.5% (27/1809) and 1.2% (21/1809), respectively] as in male mosquitoes [1.8% (22/1242) and 4.0% (49/1242), respectively]. Our results indicated that mosquitoes in China are widely infected with R. felis, the agent of human flea-borne spotted fever, and that R. bellii can also occur outside of the Americas and its usual tick hosts.

Molecular detection of Rickettsia felis in dogs, rodents and cat fleas in Zambia

Background

Flea-borne spotted fever is a zoonosis caused by Rickettsia felis, a Gram-negative obligate intracellular bacterium. The disease has a worldwide distribution including western and eastern sub-Saharan Africa where it is associated with febrile illness in humans. However, epidemiology and the public health risks it poses remain neglected especially in developing countries including Zambia. While Ctenocephalides felis (cat fleas) has been suggested to be the main vector, other arthropods including mosquitoes have been implicated in transmission and maintenance of the pathogen; however, their role in the epidemiological cycle remains to be elucidated. Thus, the aim of this study was to detect and characterize R. felis from animal hosts and blood-sucking arthropod vectors in Zambia.

Methods

Dog blood and rodent tissue samples as well as cat fleas and mosquitoes were collected from various areas in Zambia. DNA was extracted and screened by polymerase chain reaction (PCR) targeting genus Rickettsia and amplicons subjected to sequence analysis. Positive samples were further subjected to R. felis-specific real-time quantitative polymerase chain reactions.

Results

Rickettsia felis was detected in 4.7% (7/150) of dog blood samples and in 11.3% (12/106) of rodent tissue samples tested by PCR; this species was also detected in 3.7% (2/53) of cat fleas infesting dogs, co-infected with Rickettsia asembonensis. Furthermore, 37.7% (20/53) of cat flea samples tested positive for R. asembonensis, a member of spotted fever group rickettsiae of unknown pathogenicity. All the mosquitoes tested (n = 190 pools) were negative for Rickettsia spp.

Conclusions

These observations suggest that R. felis is circulating among domestic dogs and cat fleas as well as rodents in Zambia, posing a potential public health risk to humans. This is because R. felis, a known human pathogen is present in hosts and vectors sharing habitat with humans.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3435-6) contains supplementary material, which is available to authorized users.

Identification of Rickettsial Infections (Rickettsia sp. TH2014) in Ctenocephalides orientis Fleas (Siphonaptera: Pulicidae)

Rickettsia felis (Rickettsiales: Rickettsiaceae) is an emergent human pathogen that causes febrile illnesses in various parts of the world. This study describes the identification and growth characteristics of a R. felis-like organism (designated as Rickettsia sp. TH2014) cultured from Ctenocephalides orientis fleas in rural Malaysia. In this study, culturing of rickettsiae from filtered triturated flea lysates was performed in Aedes albopictus C6/36 cells. Cytopathic effects were observed from one of the samples 4 d post-inoculation. Electron microscopy revealed actively replicating intracytosolic coccobacillary organisms in the rickettsia-infected cells. Sequence analysis of amplified citrate synthase (gltA) gene fragment shows complete match of the rickettsia with Rickettsia sp. Rf31 in Southeast Asia, and 'Candidatus Rickettsia senegalensis' strain PU01-02 in Africa. The whole-genome sequence of Rickettsia sp. TH2014 was determined and assembled. The estimated genome size and guanine + cytosine content of the rickettsia are 1.37 Mb and 32.9%, respectively. The high values of average nucleotide identity and tetra-nucleotide signature correlation index obtained from pairwise genome comparison study suggest the identification of the rickettsia as R. felis. The whole-genome single-nucleotide polymorphism analysis demonstrates close genetic relatedness of the rickettsia with R. felis and Rickettsia asemboensis. However, based on sequence analyses of rickettsial genes (16S rDNA, gltA, ompB, and sca4), Rickettsia sp. TH2014 is found to be distinct from R. felis and R. asemboensis. The sequence analyses reveal that Rickettsia sp. TH2014 is highly similar to 'Ca. Rickettsia senegalensis' detected in fleas from Africa, Asia, and North America. Further investigation to provide insights on pathogenic potential and transmission dynamics of the rickettsia is warranted.

P. Lopes S, Fé NF, Lima JBP, Guerra MGB, Pimenta PFP, Bassat Q, Mueller I, Lacerda MVG, Monteiro WM. Use of anthropophilic culicid-based xenosurveillance as a proxy for Plasmodium vivax malaria burden and transmission hotspots identification

Vector-borne diseases account for more than 17% of all infectious diseases, causing more than one million deaths annually. Malaria remains one of the most important public health problems worldwide. These vectors are bloodsucking insects, which can transmit disease-producing microorganisms during a blood meal. The contact of culicids with human populations living in malaria-endemic areas suggests that the identification of Plasmodium genetic material in the blood present in the gut of these mosquitoes may be possible. The process of assessing the blood meal for the presence of pathogens is termed 'xenosurveillance'. In view of this, the present work investigated the relationship between the frequency with which Plasmodium DNA is found in culicids and the frequency with which individuals are found to be carrying malaria parasites. A cross-sectional study was performed in a peri-urban area of Manaus, in the Western Brazilian Amazon, by simultaneously collecting human blood samples and trapping culicids from households. A total of 875 individuals were included in the study and a total of 13,374mosquito specimens were captured. Malaria prevalence in the study area was 7.7%. The frequency of households with at least one culicid specimen carrying Plasmodium DNA was 6.4%. Plasmodium infection incidence was significantly related to whether any Plasmodium positive blood-fed culicid was found in the same household [IRR 3.49 (CI95% 1.38-8.84); p = 0.008] and for indoor-collected culicids [IRR 4.07 (CI95%1.25-13.24); p = 0.020]. Furthermore, the number of infected people in the house at the time of mosquito collection was related to whether there were any positive blood-fed culicid mosquitoes in that household for collection methods combined [IRR 4.48 (CI95%2.22-9.05); p<0.001] or only for indoor-collected culicids [IRR 4.88 (CI95%2.01-11.82); p<0.001]. Our results suggest that xenosurveillance can be used in endemic tropical regions in order to estimate the malaria burden and identify transmission foci in areas where Plasmodium vivax is predominant.

Bacterial symbionts in human blood-feeding arthropods: Patterns, general mechanisms and effects of global ecological changes

Due to their high impact on public health, human blood-feeding arthropods are one of the most relevant animal groups. Bacterial symbionts have been long known to play a role in the metabolism, and reproduction of these arthropod vectors. Nowadays, we have a more complete picture of their functions, acknowledging the wide influence of bacterial symbionts on processes ranging from the immune response of the arthropod host to the possible establishment of pathogens and parasites. One or two primary symbiont species have been found to co-evolve along with their host in each taxon (being ticks an exception), leading to various kinds of symbiosis, mostly mutualistic in nature. Moreover, several secondary symbiont species are shared by all arthropod groups. With respect to gut microbiota, several bacterial symbionts genera are hosted in common, indicating that these bacterial groups are prone to invade several hematophagous arthropod species feeding on humans. The main mechanisms underlying bacterium-arthropod symbiosis are discussed, highlighting that even primary symbionts elicit an immune response from the host. Bacterial groups in the gut microbiota play a key role in immune homeostasis, and in some cases symbiont bacteria could be competing directly or indirectly with pathogens and parasites. Finally, the effects climate change, great human migrations, and the increasingly frequent interactions of wild and domestic animal species are analyzed, along with their implications on microbiota alteration and their possible impacts on public health and the control of pathogens and parasites harbored in arthropod vectors of human parasites and pathogens.

A Concise Review of the Epidemiology and Diagnostics of Rickettsioses: Rickettsia and Orientia spp

Rickettsioses are globally distributed and caused by the family Rickettsiaceae, which comprise a diverse and expanding list of organisms. These include two genera, Rickettsia and Orientia Serology has been traditionally the mainstay of diagnosis, although this has been limited by cross-reactions among closely related members and diminished sensitivity/utility in the acute phase of illness. Other techniques, such as nucleic acid amplification tests using blood specimens or tissue swabs/biopsy specimens, sequencing, and mass spectrometry, have emerged in recent years for both pathogen and vector identification. This paper provides a concise review of the rickettsioses and the traditional and newer technologies available for their diagnosis.

Parallel Decline of Malaria and Rickettsia felis Infections in Senegal

Rickettsia felis is a common emerging pathogen in sub-Saharan Africa. Comparing dynamics of morbidities due to malaria and R. felis infections in two Senegalese villages, we found a strong and significant correlation between them. Malaria morbidity is strongly decreasing because of the implementation of long-lasting insecticidal nets, so we hypothesize that the same measure may decrease the R. felis infections.

Medical Entomology: A Reemerging Field of Research to Better Understand Vector-Borne Infectious Diseases

In the last decade, the Chikungunya and Zika virus outbreaks have turned public attention to the possibility of the expansion of vector-borne infectious diseases worldwide. Medical entomology is focused on the study of arthropods involved in human health. We review here some of the research approaches taken by the medical entomology team of the University Hospital Institute (UHI) Méditerranée Infection of Marseille, France, with the support of recent or representative studies. We propose our approaches to technical innovations in arthropod identification and the detection of microorganisms in arthropods, the use of arthropods as epidemiological or diagnostic tools, entomological investigations around clinical cases or within specific populations, and how we have developed experimental models to decipher the interactions between arthropods, microorganisms, and humans.

A 2015 outbreak of flea-borne rickettsiosis in San Gabriel Valley, Los Angeles County, California

Although flea-borne rickettsiosis is endemic in Los Angeles County, outbreaks are rare. In the spring of 2015 three human cases of flea-borne rickettsiosis among residents of a mobile home community (MHC) prompted an investigation. Fleas were ubiquitous in common areas due to presence of flea-infested opossums and overabundant outdoor cats and dogs. The MHC was summarily abated in June 2015, and within five months, flea control and removal of animals significantly reduced the flea population. Two additional epidemiologically-linked human cases of flea-borne rickettsiosis detected at the MHC were suspected to have occurred before control efforts began. Molecular testing of 106 individual and 85 pooled cat fleas, blood and ear tissue samples from three opossums and thirteen feral cats using PCR amplification and DNA sequencing detected rickettsial DNA in 18.8% of the fleas. Seventeen percent of these cat fleas tested positive for R. felis-specific DNA compared to under two (<2) percent for Candidatus R. senegalensis-specific DNA. In addition, serological testing of 13 cats using a group-specific IgG-ELISA detected antibodies against typhus group rickettsiae and spotted fever group rickettsiae in six (46.2%) and one (7.7%) cat, respectively. These results indicate that cats and their fleas may have played an active role in the epidemiology of the typhus group and/or spotted fever group rickettsial disease(s) in this outbreak.

Outbreaks of flea-borne rickettsiosis are rare despite the endemic status in Los Angeles County. In the spring of 2015 three human cases of flea-borne rickettsiosis among residents of a mobile home community (MHC) prompted an investigation. Fleas were found in all common areas at the MHC due to presence of flea-infested opossums and overabundant outdoor cats and dogs. The MHC was summarily abated in June 2015, and within five months, flea control and removal of animals significantly reduced the flea population. Two additional epidemiologically-linked human cases detected at the MHC were considered to have occurred before control efforts began. Molecular testing of cat fleas, immunological testing of opossums and feral cats collected at the site indicated active transmission of flea-borne rickettsiosis. This study represents the first flea-borne rickettsial outbreak that summary abatement approach was used to reduce its intensity.

Rickettsia felis: A Review of Transmission Mechanisms of an Emerging Pathogen

Rickettsia felis is an emerging pathogen of the transitional group of Rickettsia species and an important cause of febrile illness in Africa. Since the organism’s original discovery in the early 1990s, much research has been directed towards elucidating transmission mechanisms within the primary host and reservoir, the cat flea (Ctenocephalides felis). Several mechanisms for vertical and horizontal transmission within this vector have been thoroughly described, as well as transmission to other arthropod vectors, including other species of fleas. However, while a growing number of human cases of flea-borne spotted fever are being reported throughout the world, a definitive transmission mechanism from arthropod host to vertebrate host resulting in disease has not been found. Several possible mechanisms, including bite of infected arthropods and association with infectious arthropod feces, are currently being investigated.

John H, Jarman RG, Hang J, Richards AL. Molecular characterization of novel mosquito-borne Rickettsia spp. from mosquitoes collected at the Demilitarized Zone of the Republic of Korea

Rickettsiae are associated with a diverse range of invertebrate hosts. Of these, mosquitoes could emerge as one of the most important vectors because of their ability to transmit significant numbers of pathogens and parasites throughout the world. Recent studies have implicated Anopheles gambiae as a potential vector of Rickettsia felis. Herein we report that a metagenome sequencing study identified rickettsial sequence reads in culicine mosquitoes from the Republic of Korea. The detected rickettsiae were characterized by a genus-specific quantitative real-time PCR assay and sequencing of rrs, gltA, 17kDa, ompB, and sca4 genes. Three novel rickettsial genotypes were detected (Rickettsia sp. A12.2646, Rickettsia sp. A12.2638 and Rickettsia sp. A12.3271), from Mansonia uniformis, Culex pipiens, and Aedes esoensis, respectively. The results underscore the need to determine the Rickettsia species diversity associated with mosquitoes, their evolution, distribution and pathogenic potential.

Bacterial arthropod-borne diseases in West Africa

Arthropods such as ticks, lice, fleas and mites are excellent vectors for many pathogenic agents including bacteria, protozoa and viruses to animals. Moreover, many of these pathogens can also be accidentally transmitted to humans throughout the world. Bacterial vector-borne diseases seem to be numerous and very important in human pathology, however, they are often ignored and are not well known. Yet they are in a phase of geographic expansion and play an important role in the etiology of febrile episodes in regions of Africa. Since the introduction of molecular techniques, the presence of these pathogens has been confirmed in various samples from arthropods and animals, and more rarely from human samples in West Africa. In this review, the aim is to summarize the latest information about vector-borne bacteria, focusing on West Africa from 2000 until today in order to better understand the epidemiological risks associated with these arthropods. This will allow health and veterinary authorities to develop a strategy for surveillance of arthropods and bacterial disease in order to protect people and animals.

Limited Evidence for Rickettsia felis as a Cause of Zoonotic Flea-Borne Rickettsiosis in Southern California

Over 90% of human flea-borne rickettsioses cases in California are reported from suburban communities of Los Angeles and Orange counties and are presumed to be associated with either Rickettsia typhi or Rickettsia felis infection. Ctenocephalides felis (Bouché) is considered the principal vector for both rickettsiae, and R. felis has largely replaced R. typhi as the presumptive etiologic agent based on the widespread incidence of R. felis in cat flea populations. However, with no evidence to confirm R. felis as the cause of human illness in southern California, coupled with recent findings that showed R. felis to be widespread in cat fleas statewide, we propose that this hypothesis should be reconsidered. Evidence of only limited numbers of R. typhi-infected cat fleas in the environment may indicate a very rare infection and explain why so few cases of flea-borne rickettsioses are reported each year in southern California relative to the population.

Survey for Rickettsiae Within Fleas of Great Gerbils, Almaty Oblast, Kazakhstan

Little is known of the endemicity of flea-borne rickettsiae in Kazakhstan. Thus, a survey for rickettsiae within great gerbil fleas was conducted in Almaty oblast. High prevalence of Rickettsia asembonensis was detected among Xenopsylla gerbilli, demonstrating that flea-borne rickettsiae are endemic to southeastern Kazakhstan. Interestingly, no Rickettsia typhi were detected in these same fleas.

Flea-Borne Rickettsioses and Rickettsiae

Rickettsia typhi and Rickettsia felis are flea-borne rickettsiae that are distributed throughout the world. This mini-review outlines the ecology and epidemiology of flea-borne rickettsioses; highlights important clinical, diagnostic, and therapeutic considerations; and discusses areas of uncertainty regarding Rickettsia felis and other rickettsiae harbored by fleas.

Rickettsia felis: The Complex Journey of an Emergent Human Pathogen

Rickettsia felis is an obligate intracellular bacterium that is different from other officially recognized rickettsial species. It has multiple genes of different origins, an incubation temperature of less than 32°C, and a conjugative plasmid. This Rickettsia is commonly detected in febrile patients in sub-Saharan Africa. R. felis is frequently detected in cat fleas, but recently mosquitoes have been suspected to be able to transmit the bacterium. However, many aspects of the ecology and epidemiology of R. felis are not completely understood and remain to be uncovered. We aim here to give an update of the current knowledge about this fascinating organism.

Rickettsia felis, an Emerging Flea-Borne Rickettsiosis

Rickettsia felis is an emerging insect-borne rickettsial pathogen and the causative agent of flea-borne spotted fever. First described as a human pathogen from the USA in 1991, R. felis is now identified throughout the world and considered a common cause of fever in Africa. The cosmopolitan distribution of this pathogen is credited to the equally widespread occurrence of cat fleas (Ctenocephalides felis), the primary vector and reservoir of R. felis. Although R. felis is a relatively new member of the pathogenic Rickettsia, limited knowledge of basic R. felis biology continues to hinder research progression of this unique bacterium. This is a comprehensive review examining what is known and unknown relative to R. felis transmission biology, epidemiology of the disease, and genetics, with an insight into areas of needed investigation.

Approach for classification and taxonomy within family Rickettsiaceae based on the Formal Order Analysis

Genome sequences of 36 Rickettsia and Orientia were analyzed using Formal Order Analysis (FOA). This approach takes into account arrangement of nucleotides in each sequence. A numerical characteristic, the average distance (remoteness) - "g" was used to compare of genomes. Our results corroborated previous separation of three groups within the genus Rickettsia, including typhus group, classic spotted fever group, and the ancestral group and Orientia as a separate genus. Rickettsia felis URRWXCal2 and R. akari Hartford were not in the same group based on FOA, therefore designation of a so-called transitional Rickettsia group could not be confirmed with this approach.

Rickettsia species in fleas collected from small mammals in Slovakia

Epidemiological and epizootiological studies of Rickettsia felis and other Rickettsia spp. are very important, because their natural cycle has not yet been established completely. In total, 315 fleas (Siphonaptera) of 11 species of Ceratophyllidae, Hystrichopsyllidae and Leptopsyllidae families were tested for the presence of Rickettsia species and Coxiella burnetii with conventional and specific quantitative real-time PCR assays. Fleas were collected from five rodent hosts (Myodes glareolus, Apodemus flavicollis, Apodemus agrarius, Microtus subterraneus, Microtus arvalis) and three shrew species (Sorex araneus, Neomys fodiens, Crocidura suaveolens) captured in Eastern and Southern Slovakia. Overall, Rickettsia spp. was found in 10.8% (34/315) of the tested fleas of Ctenophthalmus agyrtes, Ctenophthalmus solutus, Ctenophthalmus uncinatus and Nosopsyllus fasciatus species. Infected fleas were coming from A. flavicollis, A. agrarius, and M. glareolus captured in Eastern Slovakia. C. burnetii was not found in any fleas. R. felis, Rickettsia helvetica, unidentified Rickettsia, and rickettsial endosymbionts were identified in fleas infesting small mammals in the Košice region, Eastern Slovakia. This study is the first report of R. felis infection in C. solutus male flea collected from A. agrarius in Slovakia.

Transmission potential of Rickettsia felis infection by Anopheles gambiae mosquitoes

A growing number of recent reports have implicated Rickettsia felis as a human pathogen, paralleling the increasing detection of R. felis in arthropod hosts across the globe, primarily in fleas. Here Anopheles gambiae mosquitoes, the primary malarial vectors in sub-Saharan Africa, were fed with either blood meal infected with R. felis or infected cellular media administered in membrane feeding systems. In addition, a group of mosquitoes was fed on R. felis-infected BALB/c mice. The acquisition and persistence of R. felis in mosquitoes was demonstrated by quantitative PCR detection of the bacteria up to day 15 postinfection. R. felis was detected in mosquito feces up to day 14. Furthermore, R. felis was visualized by immunofluorescence in salivary glands, in and around the gut, and in the ovaries, although no vertical transmission was observed. R. felis was also found in the cotton used for sucrose feeding after the mosquitoes were fed infected blood. Natural bites from R. felis-infected An. gambiae were able to cause transient rickettsemias in mice, indicating that this mosquito species has the potential to be a vector of R. felis infection. This is particularly important given the recent report of high prevalence of R. felis infection in patients with "fever of unknown origin" in malaria-endemic areas.

The detection of vector-borne-disease-related DNA in human stool paves the way to large epidemiological studies

The detection of Plasmodium spp. by the molecular analysis of human feces was reported to be comparable to detection in the blood. We believe that for epidemiological studies using molecular tools, it would be simpler to use feces, which are easier to obtain and require no training for their collection. Our aim was to evaluate the usefulness of feces for the detection of these pathogens towards developing a new tool for their surveillance. Between 2008 and 2010, 451 human fecal samples were collected in two Senegalese villages in which malaria and rickettsioses are endemic. Rickettsia and Plasmodium DNA were detected using quantitative PCR targeting Rickettsia of the spotted fever group, R. felis and Plasmodium spp. Two different sequences were systematically targeted for each pathogen. Twenty of the 451 fecal samples (4.4 %) were positive for Rickettsia spp., including 8 for R. felis. Inhabitants of Dielmo were more affected (18/230, 7.8 %; p = 0.0008) compared to those of Ndiop (2/221, 0.9 %). Children under 15 years of age were more often positive (19/285, 6.7 %) than were older children (1/166, 0.6 %; p = 0.005, odds ratio = 11.79). Only one sample was positive for Plasmodium spp. This prevalence is similar to that found in the blood of the Senegalese population reported previously. This preliminary report provides a proof of concept for the use of feces for detecting human pathogens, including microorganisms that do not cause gastroenteritis, in epidemiological studies.

First report of Rickettsia felis in China

Background

Rickettsia felis is a recently described flea-borne spotted fever group Rickettsia that is an emerging human pathogen. Although there is information on the organism from around the world, there is no information on the organism in China.

Methods

We used a commercial ELISA to detect antibodies reactive against R. felis in blood samples and developed a PCR to detect the gltA of the organism in blood samples and external parasites.

Results

We found reactive antibodies in people (16%; 28/180), dogs (47%; 128/271) and cats (21%; 19/90) and positive PCRs with DNA from people (0.1%; 1/822), dogs (0.8%; 8/1,059), mice (10%; 1/10), ticks (Rhipicephalus sanguineus; 10%; 15/146), lice (Linognathus setosus; 16%; 6/37), fleas (Ctenocephalides felis felis; 95%; 57/60) and mosquitoes (Anopheles sinensis, Culex pipiens pallens; 6%; 25/428), but not from cats (0/135) or canine fecal swabs (0/43).

Conclusions

This is the first report of R. felis in China where there is serological and/ or PCR evidence of the organism in previously reported [people, dogs, cats, ticks (Rhipicephalus sanguineus), fleas (Ctenocephalides felis felis) and mosquitoes (Anopheles sinensis, Culex pipiens pallens)] and novel species [mice and lice (Linognathus setosus)].

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0682-1) contains supplementary material, which is available to authorized users.

Candidatus 'Rickettsia senegalensis' in cat fleas in Senegal

Epidemiological studies of Rickettsia felis and related bacteria are very important, because the natural cycle of this important infection has not yet been established. The recent emergence of R. felis-associated febrile diseases in West and East Africa demands insightful epidemiological studies of the vectors and reservoirs of this bacterium in Africa. Twenty-nine cat fleas, Ctenocephalides felis, were tested for the presence of rickettsiae, including R. felis, bartonellae, and borreliae, with specific quantitative real-time PCR assays. Supporting our previous studies, R. felis was not detected in the fleas collected. In addition, neither Bartonella nor Borrelia was found. In five (17%) examined fleas, we found another species of rickettsia. We isolated three rickettsial strains, and genetic analysis demonstrated that these strains represent a probable new species, provisionally called Candidatus Rickettsia senegalensis here.

Development and validation of a quantitative real-time polymerase chain reaction assay specific for the detection of Rickettsia felis and not Rickettsia felis-like organisms

Human infections with Rickettsia felis have been reported worldwide. Recent studies have revealed the presence of many closely related but unique rickettsiae, referred to as Rickettsia felis-like organisms (RFLO), identified in various arthropods. Due to the recent discovery of the lack of specificity of earlier R. felis-specific assays, there has become a need to develop a new generation of R. felis-specific molecular assays that will differentiate R. felis not only from other rickettsiae but more importantly from other members of the R. felis genogroup that may not be pathogenic to humans. This new generation of assays is essential for determining the true risk for flea-borne spotted fever (FBSF) by surveying arthropod vectors/hosts. Because of the lack of specificity of previous assays developed to detect R. felis infections, prior surveys may have overestimated the prevalence of R. felis in arthropod vectors and thus the perceived risk of FBSF. We have developed a specific quantitative real-time polymerase chain reaction (qPCR) assay to detect R. felis (RfelB). Specificity of the assay was determined by testing it with a panel of 17 related Rickettsia species and 12 nonrickettsial bacterial DNA preparations. The RfelB qPCR assay was positive for R. felis DNA and negative for all of the 17 related Rickettsia species and 12 nonrickettsia bacterial DNA preparations. The limit of detection of the RfelB qPCR assay was determined to be two copies (two genoequivalents) per microliter of R. felis target ompB fragment-containing plasmid. Validation of the RfelB qPCR assay was accomplished by testing 83 previously sequence-confirmed R. felis and RFLOs containing DNA preparations from human and flea samples collected from different geographical locations around the world. This assay will be useful for rapid detection, identification, and enumeration of R. felis, an emerging human pathogen of worldwide importance, from both clinical and environmental samples.

Rickettsia felis in Ctenocephalides felis felis from five geographic regions of Brazil

This study evaluated rickettsial infection in 701 Ctenocephalides felis felis fleas that were collected from dogs and cats in 31 municipalities, encompassing all regions and major biomes of Brazil. A total of 268 (38.2%) fleas from 30 municipalities were polymerase chain reaction (PCR) positive for the rickettsial gltA gene. The PCR products from 44 fleas, consisting of at least 1 PCR-positive flea from each of 30 municipalities, generated DNA sequences identical to Rickettsia felis. Rickettsial prevalence was highly variable among 30 municipalities, with values ranging from 2.9% to 100%. Significantly higher infection rates by R. felis were associated with the Pampa biome (southern Brazil), and the temperate climate that prevails in southern Brazil. In contrast, lowest R. felis-infection rates were significantly associated with the Caatinga biome, and its semiarid climate. Further studies should evaluate the effect of temperature and moisture on the R. felis infection in Ctenocephalides fleas world widely.

Human spotted fever group rickettsioses are underappreciated in southern Taiwan, particularly for the species closely-related to Rickettsia felis

Background

Despite increased identification of spotted fever group rickettsioses (SFGR) in animals and arthropods, human SFGR are poorly characterized in Taiwan.

Methods

Patients with suspected Q fever, scrub typhus, murine typhus, leptospirosis, and dengue fever from April 2004 to December 2009 were retrospectively investigated for SFGR antibodies (Abs). Sera were screened for Rickettsia rickettsii Abs by indirect immunofluorescence antibody assay (IFA), and those with positive results were further examined for Abs against R. rickettsii, R. typhi, R. felis, R. conorii, and R. japonica using micro-immunofluorescence (MIF) tests. Polymerase chain reaction (PCR) for detection of SFGR DNA was applied in those indicated acute infections. Case geographic distribution was made by the geographic information system software.

Results

A total of 413 cases with paired serum, including 90 cases of Q fever, 47 cases of scrub typhus, 12 cases of murine typhus, 6 cases of leptospirosis, 3 cases of dengue fever, and 255 cases of unknown febrile diseases were investigated. Using IFA tests, a total of 49 cases with 47 (11.4%) and 4 (1.0%) cases had sera potentially positive for R. rickettsii IgG and IgM, respectively. In the 49 cases screened from IFA, MIF tests revealed that there were 5 cases of acute infections (3 possible R. felis and 2 undetermined SFGR) and 13 cases of past infections (3 possible R. felis and 10 undetermined SFGR). None of the 5 cases of acute infection had detectable SFGR DNA in the blood specimen by PCR. Possible acute infection of R. felis was identified in both one case of Q fever and scrub typhus. The geographic distribution of SFGR cases is similar with that of scrub typhus.

Conclusions

Human SFGR exist and are neglected diseases in southern Taiwan, particularly for the species closely-related to R. felis.

Molecular detection of Rickettsia felis and Bartonella henselae in dog and cat fleas in Central Oromia, Ethiopia

Fleas are important vectors of several Rickettsia and Bartonella spp. that cause emerging zoonotic diseases worldwide. In this study, 303 fleas collected from domestic dogs and cats in Ethiopia and identified morphologically as Ctenocephalides felis felis, C. canis, Pulex irritans, and Echidnophaga gallinacea were tested for Rickettsia and Bartonella DNA by using molecular methods. Rickettsia felis was detected in 21% of fleas, primarily C. felis, with a similar prevalence in fleas from dogs and cats. A larger proportion of flea-infested dogs (69%) than cats (37%) harbored at least one C. felis infected with R. felis. Rickettsia typhi was not detected. Bartonella henselae DNA was detected in 6% (2 of 34) of C. felis collected from cats. Our study highlights the likelihood of human exposure to R. felis, an emerging agent of spotted fever, and B. henselae, the agent of cat-scratch disease, in urban areas in Ethiopia.