Molecular Detection of Zoonotic Rickettsiae and Anaplasma spp. in Domestic Dogs and Their Ectoparasites in Bushbuckridge, South Africa

The case of Mediterranean spotted fever of the traveler returned from Zambia

We report the case of a traveler who returned from Zambia and was diagnosed with Mediterranean spotted fever (MSF), an infectious disease caused by Rickettsia conorii conorii. The patient presented to Sapporo City General Hospital with symptoms of fever, malaise, headache, and rash. The pathogen was identified by Polymerase Chain Reaction assays and subsequent analyses. The patient improved with 10-day treatment of oral doxycycline. Although some cases of MSF have been reported in sub-Saharan Africa, none have been reported in Zambia. Rhipicephalus sanguineus sensu lato, the vector of the Rickettsia conorii conorii, has been found in various areas of Zambia. Our case report highlights the potential threat of Mediterranean spotted fever in urban areas of Zambia.

Rickettsia asembonensis Isolated from Four Human Cases with Acute Undifferentiated Febrile Illness in Peru

Rickettsioses, often underreported, pose public health challenges. Rickettsia asembonensis is a potential emerging pathogen that was previously detected in humans, animals, and a variety of arthropods. While its pathogenicity in humans remains unclear, it poses a potential public health threat. Here, we present an extended epidemiological, diagnostic, and genetic analysis of the information provided in a preliminary report on the investigation of rickettsiae in Peru. In particular, we report the detection of R. asembonensis in blood specimens collected from four human patients with an acute undifferentiated fever of a seven- to nine-day duration, all of whom tested negative for other vector-borne pathogens. Additionally, we describe the replicative capacity of the R. asembonensis isolates in cell cultures.

Evidence on the prevalence of emerging and re-emerging tick- and flea-borne rickettsial agents in acute encephalitis syndrome endemic areas of northeast Uttar Pradesh, India

Outbreaks of acute encephalitis syndrome (AES) with unknown aetiology are reported every year in Gorakhpur district, Uttar Pradesh, India, and Orientia tsutsugamushi, the rickettsial pathogen, responsible for scrub typhus has been attributed as the primary cause of AES problem. However, information on the prevalence of other rickettsial infections is lacking. Hence, this study was carried out to assess any occurrence of tick- and flea-borne rickettsial agents in villages reporting AES cases in this district. In total, 825 peridomestic small mammals were trapped, by setting 9254 Sherman traps in four villages with a trap success rate of 8.9%. The Asian house shrew, Suncus murinus, constituted the predominant animal species (56.2%) and contributed to the maximum number (87.37%) of ectoparasites. In total, 1552 ectoparasites comprising two species of ticks and one species each of flea and louse were retrieved from the trapped rodents/shrews. Rhipicephalus sanguineus, the brown dog tick, was the predominant species retrieved from the trapped rodents/shrews, and the overall infestation rate was 1.75 per animal. In total, 4428 ectoparasites comprising five tick species, three louse species and one flea species were collected from 1798 domestic animals screened. Rhipicephalus microplus was the predominant tick species collected from the domestic animals. The cat flea, Ctenocephalides felis, constituted 1.5% of the total ectoparasites. Of all the ectoparasite samples (5980) from domestic animals and rodents, tested as 1211 pools through real-time PCR assays, 64 pools were positive for 23S rRNA gene of rickettsial agents. The PCR-positive samples were subjected to multi-locus sequence typing (MLST). In BLAST and phylogenetic analysis, the ectoparasites were found to harbour Rickettsia asembonensis (n = 9), Rickettsia conorii (n = 3), Rickettsia massiliae (n = 29) and Candidatus Rickettsia senegalensis (n = 1). A total of 22 pools were detected to have multiple rickettsial agents. The prevalence of fleas and high abundance of tick vectors with natural infections of rickettsial agents indicates the risk of transmission of tick- and flea-borne rickettsial diseases in rural villages of Gorakhpur. Further epidemiological studies are required to confirm the transmission of these agents to humans.

Distribution of Rhipicephalus sanguineus and Heamaphysalis elliptica dog ticks and pathogens they are carrying: A systematic review

The role of ixodid ticks especially Rhipicephalus sanguineus and Heamaphysalis elliptica in the epidemiology of several diseases of veterinary and public health importance have been documented. This study conducted a systematic review focusing on the distribution of R. sanguineus and H. elliptica, as well as the common tick-borne pathogens they harbour. The Scopus, ScienceDirect, PubMed, and Web of Science databases were used to search for English journal articles published between January 1990 and June 2021. The articles were assessed by following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. This systematic review was registered on PROSPERO [(ID no: CRD42022327372). Of the studies included in the systematic review, 247 and 19 articles had identified R. sanguineus and H. elliptica respectively, whereas 15 articles had identified both tick species. There is a reported worldwide distribution of R. sanguineus from 64 countries, whereas H. elliptica was only reported in the African continent from 6 countries. In total, 120 articles that were included in this systematic review reported detection of tick-borne pathogens from R. sanguineus (n = 118 articles) and/or H. elliptica (n = 2 articles) ticks. According to the studies tick-borne pathogens harboured by R. sanguineus included protozoa such as Babesia spp., Hepatozoon spp., Leishmania spp., and Theileria spp., as well as bacteria such as Acinetobacter spp. Anaplasma spp., Bacillus spp., Borrelia spp., Brucella spp., Coxiella spp., and Staphylococcus spp. The H. elliptica was reported to be harbouring Babesia spp., Ehrlichia spp. and Rickettsia spp. Most of the studies (50%) used the conventional polymerase chain reaction (PCR) technique for the detection of tick-borne pathogens, followed by real-time PCR (qPCR) (n = 26), and nested PCR (n = 22). This systematic review has shed light on the distribution of two common dog ticks as well as the tick-borne pathogens of veterinary and zoonotic importance they are harbouring. This data will enable surveillance studies that can report whether the distribution of these ticks and their associated tick-borne pathogens is expanding or shrinking or is stable.

An ecological and epidemiological single-season survey of Anaplasma and Ehrlichia positive ticks in Victoria Falls National Park, Zimbabwe

There is an urgent need for continued research on the ecology of tick-borne diseases in Africa. Our objective was to provide a preliminary description of the ecology and epidemiology of tick species, tick-borne pathogens, and animal hosts in Zimbabwe, focusing efforts at Victoria Falls National Park, for a single season. We tested the hypothesis that tick surveillance and pathogen screening data can be used to model associations among ticks, hosts, and pathogens. We collected ticks from domesticated animals and wildlife in Zimbabwe and screened the ticks for the presence of Anaplasma and Ehrlichia bacteria. Nearly 30% of the screened ticks were PCR-positive; 89% of tick species were PCR-positive, and 88% of animal species carried at least one PCR-positive tick. We sequenced a subset of amplicons that were similar to three Anaplasma species and three Ehrlichia species. The odds of a tick being PCR-positive increased when many ticks were collected from the host or the tick was collected from a cow (domesticated animal). Tick species shared host species more often than expected. We demonstrate that ticks in northwestern Zimbabwe present a One Health problem for nearby wildlife and humans.

Anaplasma Species in Africa-A Century of Discovery: A Review on Molecular Epidemiology, Genetic Diversity, and Control

Anaplasma species, belonging to the family Anaplasmataceae in the order Rickettsiales, are obligate intracellular bacteria responsible for various tick-borne diseases of veterinary and human significance worldwide. With advancements in molecular techniques, seven formal species of Anaplasma and numerous unclassified species have been described. In Africa, several Anaplasma species and strains have been identified in different animals and tick species. This review aims to provide an overview of the current understanding of the molecular epidemiology and genetic diversity of classified and unclassified Anaplasma species detected in animals and ticks across Africa. The review also covers control measures that have been taken to prevent anaplasmosis transmission on the continent. This information is critical when developing anaplasmosis management and control programs in Africa.

Distribution and Prevalence of Anaplasmataceae, Rickettsiaceae and Coxiellaceae in African Ticks: A Systematic Review and Meta-Analysis

In Africa, ticks continue to be a major hindrance to the improvement of the livestock industry due to tick-borne pathogens that include Anaplasma, Ehrlichia, Rickettsia and Coxiella species. A systemic review and meta-analysis were conducted here and highlighted the distribution and prevalence of these tick-borne pathogens in African ticks. Relevant publications were searched in five electronic databases and selected using inclusion/exclusion criteria, resulting in 138 and 78 papers included in the qualitative and quantitative analysis, respectively. Most of the studies focused on Rickettsia africae (38 studies), followed by Ehrlichia ruminantium (27 studies), Coxiella burnetii (20 studies) and Anaplasma marginale (17 studies). A meta-analysis of proportions was performed using the random-effects model. The highest prevalence was obtained for Rickettsia spp. (18.39%; 95% CI: 14.23–22.85%), R. africae (13.47%; 95% CI: 2.76–28.69%), R. conorii (11.28%; 95% CI: 1.77–25.89%), A. marginale (12.75%; 95% CI: 4.06–24.35%), E. ruminantium (6.37%; 95% CI: 3.97–9.16%) and E. canis (4.3%; 95% CI: 0.04–12.66%). The prevalence of C. burnetii was low (0%; 95% CI: 0–0.25%), with higher prevalence for Coxiella spp. (27.02%; 95% CI: 10.83–46.03%) and Coxiella-like endosymbionts (70.47%; 95% CI: 27–99.82%). The effect of the tick genera, tick species, country and other variables were identified and highlighted the epidemiology of Rhipicephalus ticks in the heartwater; affinity of each Rickettsia species for different tick genera; dominant distribution of A. marginale, R. africae and Coxiella-like endosymbionts in ticks and a low distribution of C. burnetii in African hard ticks.

Epidemiological Survey on Tick-Borne Pathogens with Zoonotic Potential in Dog Populations of Southern Ethiopia

Dogs are known to host several tick-borne pathogens with zoonotic potential; however, scant information is available on the epidemiology of these pathogens in low-income tropical countries and in particular in sub-Saharan Africa. With the aim of investigating a wide range of tick-borne pathogens (i.e., Rickettsia spp., Anaplasma spp., Erhlichia spp., Borrelia spp., Hepatozoon spp. and Babesia spp.), 273 blood samples were collected from dogs in selected districts of Ethiopia and analyzed by real-time and/or end-point PCR. The results of the study showed that Hepatozoon canis was the most prevalent pathogen (53.8%), followed by Anaplasma phagocythophilum (7.0%), Babesia canis rossi (3.3%), Ehrlichia canis (2.6%) and Anaplasma platys (2.2%). Furthermore, five samples tested positive for Borrelia spp., identified as Borrelia afzelii (n = 3) and Borrelia burgdorferi (n = 2), and two samples for Rickettsia spp., identified as Rickettsia conorii (n = 1) and Rickettsia monacensis (n = 1). The finding of Anaplasma phagocythophilum and different species of the genera Borrelia and Rickettsia with zoonotic potential was unexpected and alarming, and calls for further investigation on the roles of dogs and on the tick, species acting as vector in this specific context. Other pathogens (Hepatozoon canis, Babaesia canis rossi, Anaplasma platys, Ehrlichia canis) are already known to have an important impact on the dogs' health but have minor zoonotic potential as they were rarely or never reported in humans. Dogs from rural areas were found to be at higher risk for different pathogens, probably due to the presence of other wild canids in the same environment. The findings of the present study contribute to a better knowledge of the epidemiology of tick-borne pathogens, which is relevant to human and animal health.

Transmission Cycle of Tick-Borne Infections and Co-Infections, Animal Models and Diseases

Tick-borne pathogens such as species of Borrelia, Babesia, Anaplasma, Rickettsia, and Ehrlichia are widespread in the United States and Europe among wildlife, in passerines as well as in domestic and farm animals. Transmission of these pathogens occurs by infected ticks during their blood meal, carnivorism, and through animal bites in wildlife, whereas humans can become infected either by an infected tick bite, through blood transfusion and in some cases, congenitally. The reservoir hosts play an important role in maintaining pathogens in nature and facilitate transmission of individual pathogens or of multiple pathogens simultaneously to humans through ticks. Tick-borne co-infections were first reported in the 1980s in white-footed mice, the most prominent reservoir host for causative organisms in the United States, and they are becoming a major concern for public health now. Various animal infection models have been used extensively to better understand pathogenesis of tick-borne pathogens and to reveal the interaction among pathogens co-existing in the same host. In this review, we focus on the prevalence of these pathogens in different reservoir hosts, animal models used to investigate their pathogenesis and host responses they trigger to understand diseases in humans. We also documented the prevalence of these pathogens as correlating with the infected ticks’ surveillance studies. The association of tick-borne co-infections with other topics such as pathogens virulence factors, host immune responses as they relate to diseases severity, identification of vaccine candidates, and disease economic impact are also briefly addressed here.

Unraveling the epidemiological relationship between ticks and rickettsial infection in Africa

Tick-borne rickettsioses are emerging and re-emerging diseases of public health concern caused by over 30 species of Rickettsia. Ticks are obligate hematophagous arthropods with over 700 species of Ixodid ticks known worldwide. The escalating geographical dispersal of tick vectors and concomitant increase in the incidences of tick-borne diseases have fueled interest in the ecology of tick-borne pathogens. This review focuses on aspects of the Rickettsia pathogen, including biology, taxonomy, phylogeny, genetic diversity, epidemiology of the disease, and the role of vertebrate host in the perpetuation of rickettsioses in Africa. Our review also highlights some of the species of Rickettsia that are responsible for disease, the role of tick vectors (both hard and soft ticks) and the species of Rickettsia associated with diverse tick species across the continent. Additionally, this article emphasizes the evolutionary perspective of rickettsiae perpetuation and the possible role of amplifying vertebrate host and other small mammals, domestic animals and wildlife in the epidemiology of Rickettsia species. We also specifically, discussed the role of avian population in the epidemiology of SFG rickettsiae. Furthermore, we highlighted tick-borne rickettsioses among travelers due to African tick-bite fever (ATBF) and the challenges to surveillance of rickettsial infection, and research on rickettsiology in Africa. Our review canvasses the need for more rickettsiologists of African origin based within the continent to further research towards understanding the biology, characterization, and species distribution, including the competent tick vectors involved in their transmission of rickettsiae across the continent in collaboration with established researchers in western countries. We further highlighted the need for proper funding to encourage research despite competing demands for resources across the various sectors. We finalize by discussing the similarities between rickettsial diseases around the world and which steps need to be taken to help foster our understanding on the eco-epidemiology of rickettsioses by bridging the gap between the growing epidemiological data and the molecular characterization of Rickettsia species.

Detection of Ticks and Tick-Borne Pathogens of Urban Stray Dogs in South Africa

This study aimed to identify ticks infesting dogs admitted to the Potchefstroom Animal Welfare Society (PAWS) and to detect tick-borne pathogens they are harbouring. A total of 592 ticks were collected from 61 stray dogs admitted to PAWS originating from several suburbs in and near Potchefstroom, South Africa. The dog ticks were identified as Haemaphysalis elliptica (39%) and Rhipicephalus sanguineus (61%) by both morphological and DNA analyses. Of these ticks, H. elliptica consisted of 67.5% (156/231) and 32.5% (75/231) female and male ticks, respectively, whilst R. sanguineus consisted of 48.5% (175/361) and 51.5% (186/361) female and male ticks, respectively. Microscopic examination of blood smears from engorged female ticks indicated overall occurrences of 0.5% (1/204) for Babesia spp. from R. sanguineus, 1% (2/204) of Anaplasma spp. from H. elliptica, and 22% (45/204) of Rickettsia spp. from both H. elliptica and R. sanguineus. Using pooled samples molecular detection of tick-borne pathogens indicated overall occurrences of 1% (1/104) for A. phagocytophilum in H. elliptica, 9.6% (10/104) of Rickettsia spp. in H. elliptica and R. sanguineus, 5.8% (6/104) of Ehrlichia canis in H. elliptica and R. sanguineus, and 13.5% (14/104) of Coxiella spp. in both H. elliptica and R. sanguineus. Additionally, PCR detected 6.5% (2/31) of Coxiella spp. DNA from H. elliptica eggs. Our data indicate that urban stray dogs admitted at PAWS are infested by H. elliptica and R. sanguineus ticks which are harbouring several pathogenic organisms known to cause tick-borne diseases.

Rickettsiae in fleas infesting domestic pets of eastern Himalayan terrains of India

Background

Flea-borne rickettsioses have been limitedly explored in the Indian sub-Himalayan belt, including the North Eastern Region (NER) of India. This study investigates the presence of rickettsiae hosts and their probable pathogens in the disease-endemic hilly state of the NER of India.

Methods

Entomological surveys were carried out in disease-reporting localities in a hilly state in India. Fleas collected from domesticated animals were processed for detection of a Rickettsia-specific 17-kDa gene.

Results

Sequence analysis revealed Rickettsia felis in six flea pools (40%), Candidatus Rickettsia senegalensis in two pools (13.3%) and Rickettsia asembonensis in one pool (6.6%).

Conclusions

Our findings suggest Ctenocephalides felis, Ctenocephalides canis and Pulex irritans as potential carriers of R. felis and R. felis–like organisms in India.

Survey of Ticks and Tick-Borne Rickettsial and Protozoan Pathogens in Eswatini

Ticks are widespread parasites of vertebrates and major vectors of pathogens to humans, domestic animals, and wildlife. In southern Africa, numerous tick species transmit diseases of economic and health importance. This study aimed to describe the occurrence of ticks and tick-borne pathogens in multiple land-use types and the possible role of ticks in the transmission of pathogen species. Using molecular techniques, we screened 1716 ticks for infection by rickettsial bacteria and protozoans. To characterize pathogen identity, we sequenced multiple loci from positive samples and analyzed sequences within a phylogenetic framework. Across the seven tick species collected as nymphs or adults, we detected Rickettsia, Anaplasma, Ehrlichia, Babesia, Hepatozoon, and Theileira species. We found that some tick species and tick-borne pathogens differed according to land use. For example, we found a higher density of Haemaphysalis elliptica and higher prevalence of Rickettsia in H. elliptica collected from savanna grasses used for livestock grazing near human settlements than savanna grasses in conservation areas. These findings highlight the importance of comprehensive surveillance to achieve a full understanding of the diversity and ecology of the tick-borne pathogens that can infect humans, domestic animals, and wildlife.

Epidemiological and Clinicopathological Features of Anaplasma phagocytophilum Infection in Dogs: A Systematic Review

Anaplasma phagocytophilum is a worldwide emerging zoonotic tick-borne pathogen transmitted by Ixodid ticks and naturally maintained in complex and incompletely assessed enzootic cycles. Several studies have demonstrated an extensive genetic variability with variable host tropisms and pathogenicity. However, the relationship between genetic diversity and modified pathogenicity is not yet understood. Because of their proximity to humans, dogs are potential sentinels for the transmission of vector-borne pathogens. Furthermore, the strong molecular similarity between human and canine isolates of A. phagocytophilum in Europe and the USA and the positive association in the distribution of human and canine cases in the USA emphasizes the epidemiological role of dogs. Anaplasma phagocytophilum infects and survives within neutrophils by disregulating neutrophil functions and evading specific immune responses. Moreover, the complex interaction between the bacterium and the infected host immune system contribute to induce inflammatory injuries. Canine granulocytic anaplasmosis is an acute febrile illness characterized by lethargy, inappetence, weight loss and musculoskeletal pain. Hematological and biochemistry profile modifications associated with this disease are unspecific and include thrombocytopenia, anemia, morulae within neutrophils and increased liver enzymes activity. Coinfections with other tick-borne pathogens (TBPs) may occur, especially with Borrelia burgdorferi, complicating the clinical presentation, diagnosis and response to treatment. Although clinical studies have been published in dogs, it remains unclear if several clinical signs and clinicopathological abnormalities can be related to this infection.

Molecular Detection and Characterization of Rickettsia Species in Ixodid Ticks Collected From Cattle in Southern Zambia

Tick-borne zoonotic pathogens are increasingly becoming important across the world. In sub-Saharan Africa, tick-borne pathogens identified include viruses, bacteria and protozoa, with Rickettsia being the most frequently reported. This study was conducted to screen and identify Rickettsia species in ticks (Family Ixodidae) infesting livestock in selected districts of southern Zambia. A total of 236 ticks from three different genera (Amblyomma, Hyalomma, and Rhipicephalus) were collected over 14 months (May 2018-July 2019) and were subsequently screened for the presence of Rickettsia pathogens based on PCR amplification targeting the outer membrane protein B (ompB). An overall Rickettsia prevalence of 18.6% (44/236) was recorded. Multi-locus sequencing and phylogenetic characterization based on the ompB, ompA, 16S rRNA and citrate synthase (gltA) genes revealed the presence of Rickettsia africae (R. africae), R. aeschlimannii-like species and unidentified Rickettsia species. While R. aeschlimannii-like species are being reported for the first time in Zambia, R. africae has been reported previously, with our results showing a wider distribution of the bacteria in the country. Our study reveals the potential risk of human infection by zoonotic Rickettsia species and highlights the need for increased awareness of these infections in Zambia's public health systems.

Targeted capture and sequencing of Orientia tsutsugamushi genomes from chiggers and humans

Scrub typhus is a febrile disease caused by Orientia tsutsugamushi, transmitted by larval stage Trombiculid mites (chiggers), whose primary hosts are small mammals. The phylogenomics of O. tsutsugamushi in chiggers, small mammals and humans remains poorly understood. To combat the limitations imposed by the low relative quantities of pathogen DNA in typical O. tsutsugamushi clinical and ecological samples, along with the technical, safety and cost limitations of cell culture, a novel probe-based target enrichment sequencing protocol was developed. The method was designed to capture variation among conserved genes and facilitate phylogenomic analysis at the scale of population samples. A whole-genome amplification step was incorporated to enhance the efficiency of sequencing by reducing duplication rates. This resulted in on-target capture rates of up to 93% for a diverse set of human, chigger, and rodent samples, with the greatest success rate in samples with real-time PCR C_t values below 35. Analysis of the best-performing samples revealed phylogeographic clustering at local, provincial and international scales. Applying the methodology to a comprehensive set of samples could yield a more complete understanding of the ecology, genomic evolution and population structure of O. tsutsugamushi and other similarly challenging organisms, with potential benefits in the development of diagnostic tests and vaccines.

The Orientia tsutsugamushi ScaB Autotransporter Protein Is Required for Adhesion and Invasion of Mammalian Cells

Autotransporter proteins are widely present in Gram-negative bacteria. They play a pivotal role in processes related to bacterial pathogenesis, including adhesion, invasion, colonization, biofilm formation, and cellular toxicity. Bioinformatics analysis revealed that Orientia tsutsugamushi, the causative agent of scrub typhus, encodes six different autotransporter genes (scaA-scaF). Although four of these genes (scaA, scaC, scaD, and scaE) are present in diverse strains, scaB and scaF have been detected in only a limited number of strains. Previous studies have demonstrated that ScaA and ScaC are involved in the adherence of host cells. However, the putative function of other O. tsutsugamushi Sca proteins has not been studied yet. In this study, we show that scaB is transcribed and expressed on the surface of O. tsutsugamushi Boryong strain. Using a heterologous Escherichia coli expression system, we demonstrated that ScaB-expressing E. coli can successfully mediate adherence to and invasion into non-phagocytic cells, including epithelial and endothelial cells. In addition, pretreatment with a recombinant ScaB polypeptide inhibits the entry of O. tsutsugamushi into cultured mammalian cells. Finally, we also identified the scaB gene in the Kuroki and TA686 strains and observed high levels of sequence variation in the passenger domains. Here, we propose that the ScaB protein of O. tsutsugamushi can mediate both adhesion to and invasion into host cells in the absence of other O. tsutsugamushi genes and may play important roles in bacterial pathogenesis.

Amplicon-Based Next Generation Sequencing for Rapid Identification of Rickettsia and Ectoparasite Species from Entomological Surveillance in Thailand

BACKGROUND

Next generation sequencing (NGS) technology has been used for a wide range of epidemiological and surveillance studies. Here, we used amplicon-based NGS to species identify Rickettsia and their arthropod hosts from entomological surveillance.

METHODS

During 2015-2016, we screened 1825 samples of rodents and ectoparasites collected from rodents and domestic mammals (dog, cat, and cattle) across Thailand for Rickettsia. The citrate synthase gene was amplified to identify Rickettsia to species, while the Cytochrome Oxidase subunit I (COI) and subunit II (COII) genes were used as target genes for ectoparasite identification. All target gene amplicons were pooled for library preparation and sequenced with Illumina MiSeq platform.

RESULT

The highest percentage of Rickettsia DNA was observed in fleas collected from domestic animals (56%) predominantly dogs. Only a few samples of ticks from domestic animals, rodent fleas, and rodent tissue were positive for Rickettisia DNA. NGS based characterization of Rickettsia by host identified Rickettsia asembonensis as the most common bacteria in positive fleas collected from dogs (83.2%) while "Candidatus Rickettsia senegalensis" was detected in only 16.8% of Rickettsia positive dog fleas. Sequence analysis of COI and COII revealed that almost all fleas collected from dogs were Ctenocephalides felis orientis. Other Rickettsia species were detected by NGS including Rickettsia heilongjiangensis from two Haemaphysalis hystricis ticks, and Rickettsia typhi in two rodent tissue samples.

CONCLUSION

This study demonstrates the utility of NGS for high-throughput sequencing in the species characterization/identification of bacteria and ectoparasite for entomological surveillance of rickettsiae. A high percentage of C. f. orientis are positive for R. asembonensis. In addition, our findings indicate there is a risk of tick-borne Spotted Fever Group rickettsiosis, and flea-borne murine typhus transmission in Tak and Phangnga provinces of Thailand.

Manifestations and Management of Flea-Borne Rickettsioses

Murine typhus and flea-borne spotted fever are undifferentiated febrile illnesses caused by Rickettsia typhi and Rickettsia felis, respectively. These organisms are small obligately intracellular bacteria and are transmitted to humans by fleas. Murine typhus is endemic to coastal areas of the tropics and subtropics (especially port cities), where rats are the primary mammalian host and rat fleas (Xenopsylla cheopis) are the vector. In the United States, a cycle of transmission involving opossums and cat fleas (Ctenocephalides felis) are the presumed reservoir and vector, respectively. The incidence and distribution of murine typhus appear to be increasing in endemic areas of the US. Rickettsia felis has also been reported throughout the world and is found within the ubiquitous cat flea. Flea-borne rickettsioses manifest as an undifferentiated febrile illness. Headache, malaise, and myalgia are frequent symptoms that accompany fever. The incidence of rash is variable, so its absence should not dissuade the clinician to consider a rickettsial illness as part of the differential diagnosis. When present, the rash is usually macular or papular. Although not a feature of murine typhus, eschar has been found in 12% of those with flea-borne spotted fever. Confirmatory laboratory diagnosis is usually obtained by serology; the indirect immunofluorescence assay is the serologic test of choice. Antibodies are seldom present during the first few days of illness. Thus, the diagnosis requires acute- and convalescent-phase specimens to document seroconversion or a four-fold increase in antibody titer. Since laboratory diagnosis is usually retrospective, when a flea-borne rickettsiosis is considered, empiric treatment should be initiated. The treatment of choice for both children and adults is doxycycline, which results in a swift and effective response. The following review is aimed to summarize the key clinical, epidemiological, ecological, diagnostic, and treatment aspects of flea-borne rickettsioses.

Molecular detection of Candidatus Rickettsia asembonensis in fleas collected from pets and domestic animals in Puducherry, India

Rickettsia are obligate intracellular pathogens transmitted by arthropod vectors. The re-emergence of several rickettsioses imposes severe global health burden. In addition to the well-established rickettsial pathogens, newer rickettsial species and their pathogenic potentials are being uncovered. There are many reports of spotted and typhus fever caused by rickettsiae in India. Hence, in this study we screened the ectoparasites of pet and domestic animals for the presence of rickettsia using polymerase chain reaction. Nine cat flea samples (Ctenocephalides felis felis), that tested positive for the presence of rickettsia were subjected to Multi Locus Sequence Typing. Nucleotide sequencing and Phylogenetic analysis of gltA, ompB and 16rrs genes revealed that the rickettsiae detected in cat fleas was Rickettsia asembonensis. Further studies are required to assess Rickettsia asembonensis pathogenic potential to human and its enzootic maintenance of in various hosts and vectors.

Wentzel J, Wills-Berriman S, Boni LD, Weyer J, Rossouw J, Oosthuizen MC. Anaplasma phagocytophilum and Other Anaplasma spp. in Various Hosts in the Mnisi Community, Mpumalanga Province, South Africa

DNA samples from 74 patients with non-malarial acute febrile illness (AFI), 282 rodents, 100 cattle, 56 dogs and 160 Rhipicephalus sanguineus ticks were screened for the presence of Anaplasma phagocytophilum DNA using a quantitative PCR (qPCR) assay targeting the msp2 gene. The test detected both A. phagocytophilum and Anaplasma sp. SA/ZAM dog DNA. Microbiome sequencing confirmed the presence of low levels of A. phagocytophilum DNA in the blood of rodents, dogs and cattle, while high levels of A. platys and Anaplasma sp. SA/ZAM dog were detected in dogs. Directed sequencing of the 16S rRNA and gltA genes in selected samples revealed the presence of A. phagocytophilum DNA in humans, dogs and rodents and highlighted its importance as a possible contributing cause of AFI in South Africa. A number of recently described Anaplasma species and A. platys were also detected in the study. Phylogenetic analyses grouped Anaplasma sp. SA/ZAM dog into a distinct clade, with sufficient divergence from other Anaplasma species to warrant classification as a separate species. Until appropriate type-material can be deposited and the species is formally described, we will refer to this novel organism as Anaplasma sp. SA dog.

Investigation of Ctenocephalides felis on domestic dogs and Rickettsia felis infection in the Democratic Republic of Sao Tome and Principe

Rickettsia felis is an obligate intracellular Gram-negative bacterium which causes flea-borne spotted fever in humans. In the past decades, R. felis has been detected worldwide in Ctenocephalides felis fleas and various other arthropods. However, due to its shared symptoms with other common vector-borne diseases, human infection is prone to be underestimated or misdiagnosed, especially in the malaria-endemic areas including sub-Saharan Africa, where confirmatory laboratory diagnoses are not usually available. In this study, a 'One Health' approach was adopted to explore potential vector-borne and zoonotic pathogens in the Democratic Republic of Sao Tome and Principe (DRSTP), an island nation in the Gulf of Guinea. By collaborating with local veterinarians, 1,187 fleas were collected from 95 domestic dogs across the country and later identified as Ct. felis using taxonomic keys. A cytochrome oxidase gene-based phylogenetic analysis revealed that all collected fleas belonged to a single haplotype and were identical to isolates from Ivory Coast and Brazil that clustered into a clade of tropical distribution. Additional samples of 14 chigoe fleas (Tunga penetrans) were collected from the surrounding environment of the dogs' resting spots. Rickettsia felis infection in fleas was examined by molecular methods targeting the citrate synthase (gltA)- and outer membrane protein A (ompA)-coding genes as well as the R. felis-specific pRF plasmid. The bacterial DNA was detected in 21.01% (146/695) of cat fleas but none of the chigoe fleas. Microimmunofluorescence assay was then performed to assess pathogen exposure of the residents. Of 240 dried blood spots from participants with dog contacts, 8 (3.33%) exhibited R. felis antibodies. Our findings demonstrated the presence of R. felis in DRSTP. Further extensive epidemiological studies regarding its prevalence and its role in causing febrile illness while the nation is entering pre-elimination stage of malaria will be carried out.

Molecular detection of Rickettsia in fleas from micromammals in Chile

Background

Rickettsial diseases are considered important in public health due to their dispersal capacity determined by the particular characteristics of their reservoirs and/or vectors. Among the latter, fleas play an important role, since the vast majority of species parasitize wild and invasive rodents, so their detection is relevant to be able to monitor potential emerging diseases. The aim of this study was to detect, characterize, and compare Rickettsia spp. from the fleas of micromammals in areas with different human population densities in Chile.

Methods

The presence of Rickettsia spp. was evaluated by standard polymerase chain reaction (PCR) and sequencing in 1315 fleas collected from 1512 micromammals in 29 locations, with different human population densities in Chile. A generalized linear model (GLM) was used to identify the variables that may explain Rickettsia prevalence in fleas.

Results

DNA of Rickettsia spp. was identified in 13.2% (174 of 1315) of fleas tested. Fifteen flea species were found to be Rickettsia-positive. The prevalence of Rickettsia spp. was higher in winter, semi-arid region and natural areas, and the infection levels in fleas varied between species of flea. The prevalence of Rickettsia among flea species ranged between 0–35.1%. Areas of lower human density showed the highest prevalence of Rickettsia. The phylogenetic tree showed two well-differentiated clades with Rickettsia bellii positioned as basal in one clade. The second clade was subdivided into two subclades of species related to Rickettsia of the spotted fever group.

Conclusions

To our knowledge, this is the first report of the occurrence and molecular characterization of Rickettsia spp. in 15 flea species of micromammals in Chile. In this study, fleas were detected carrying Rickettsia DNA with zoonotic potential, mainly in villages and natural areas of Chile. Considering that there are differences in the prevalence of Rickettsia in fleas associated with different factors, more investigations are needed to further understand the ecology of Rickettsia in fleas and their implications for human health.

Diagnosis of scrub typhus: recent advancements and challenges

Scrub typhus is a mite-borne, acute febrile illness caused by the bacterium Orientia tsutsugamushi. It is a re-emerging infectious disease of the tsutsugamushi triangle. Scrub typhus is transmitted through bites of contaminated chiggers (larval stage). Diagnosis of scrub typhus is challenging as its symptoms mimic with other acute febrile illnesses. Several methods are effectual for diagnosis of scrub typhus that includes enzyme-linked immunosorbent assay (ELISA), immunofluorescence assay (IFA), immunochromatographic test (ICT), Weil-Felix, polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP). Weil-Felix test was initially used for the diagnosis of scrub typhus in underdeveloped countries but not preferred due to a lack of both specificity and sensitivity. Other immuno-based methods like IFA and ELISA are most outrank for detection of scrub typhus due to their higher sensitivity and specificity, but not vigorous to lay bare the infection at early stages and need the convalescent sampling for verification of positive samples. On another deed, PCR based methods becoming acceptable over era due to its dexterity of early-stage diagnosis with higher specificity and sensitivity but lack its applicability in circumstances of scrub typhus due to the variegated genetic makeup of Orientia tsutsugamushi among its serotypes. The present review focused on various detection methods along with their advantages and disadvantages used in the diagnosis of scrub typhus. A comparison between available methods of diagnosis with challenges in the detection of scrub typhus is also summarized.

First molecular evidence of Anaplasma spp. co-infection in stray dogs from Anhui, China

Anaplasma species are obligate intracellular pathogens that threaten the health of both humans and animals worldwide. This study aimed to determine the prevalence of Anaplasma species in stray dogs in Anhui Province, China. Blood samples from 201 apparently healthy stray dogs were collected from August 2017 to January 2018, and Anaplasma spp. infection in these dogs was evaluated by nested PCR and phylogenetic analysis. The overall infection rate of Anaplasma spp. in stray dogs was 38.3% (77/201). The prevalences of single infection of A. platys, A. phagocytophilum and A. ovis were 15.4%, 11.9%, and 8.5%, respectively. Co-infection rate of A. platys and A. phagocytophilum was 1.5% and that of A. platys and A. ovis was 0.5%. Co-infection by these three pathogens was found in one sample (0.5%). This is the first report of Anaplasma spp. infections in stray dogs from Anhui, China.

Spotted Fever Group Rickettsia Infection of Cats and Cat Fleas in Northeast Thailand

Rickettsia species cause rickettsioses, which are zoonotic diseases found worldwide, and are transmitted by arthropods such as lice, fleas, ticks, and mites. In Thailand, flea infestations are common among cats and dogs. This study aimed at determining the exposure to spotted fever group rickettsiae (SFGR) of cats in surrounding areas of Rajabhat Maha Sarakham University, Muang district, Maha Sarakham province and rickettsial infection among cat fleas, Ctenocephalides felis, collected from dogs of the surrounding area of Waeng Noi district, Khon Kaen province. Forty-two cat sera were assessed for IgG antibody titers against SFGR by a group-specific enzyme-linked immunosorbent assay. The prevalence of seroreactive cats was 4.76% (2/42). DNA preparations from 23 individual cat fleas from three dogs were assessed by Rickettsia genus-specific, group-specific, and species-specific quantitative real-time PCR (qPCR) assays. Positive results were confirmed by ompB gene fragment sequencing. Twenty-one of 23 cat fleas were positive for Rickettsia asembonensis, and the other two DNA preparations were negative for rickettsial DNA. This study's finding indicates that companion cats and dogs in Northeast Thailand are exposed to SFGR and that exposure may be due to infection with R. asembonensis, an organism known to infect humans, monkeys, and dogs. Clinicians for humans and animals in Northeast Thailand should be aware of rickettsial infections among their patients.

Scrub Typhus: Historic Perspective and Current Status of the Worldwide Presence of Orientia Species

Scrub typhus and its etiological agents, Orientia species, have been around for a very long time. Historical reference to the rickettsial disease scrub typhus was first described in China (313 AD) by Hong Ge in a clinical manual (Zhouhofang) and in Japan (1810 AD) when Hakuju Hashimoto described tsutsuga, a noxious harmful disease in the Niigata prefecture. Other clinicians and scientists in Indonesia, Philippines, Taiwan, Australia, Vietnam, Malaysia, and India reported on diseases most likely to have been scrub typhus in the early 1900s. All of these initial reports about scrub typhus were from an area later designated as the Tsutsugamushi Triangle-an area encompassing Pakistan to the northwest, Japan to the northeast and northern Australia to the south. It was not until the 21st century that endemic scrub typhus occurring outside of the Tsutsugamushi Triangle was considered acceptable. This report describes the early history of scrub typhus, its distribution in and outside the Tsutsugamushi Triangle, and current knowledge of the causative agents, Orientia species.

Scrub typhus ecology: a systematic review of Orientia in vectors and hosts

Scrub typhus, caused by Orientia tsutsugamushi, is an important and neglected vector-borne zoonotic disease with an expanding known distribution. The ecology of the disease is complex and poorly understood, impairing discussion of public health interventions. To highlight what we know and the themes of our ignorance, we conducted a systematic review of all studies investigating the pathogen in vectors and non-human hosts. A total of 276 articles in 7 languages were included, with 793 study sites across 30 countries. There was no time restriction for article inclusion, with the oldest published in 1924. Seventy-six potential vector species and 234 vertebrate host species were tested, accounting for over one million trombiculid mites ('chiggers') and 83,000 vertebrates. The proportion of O. tsutsugamushi positivity was recorded for different categories of laboratory test and host species. Vector and host collection sites were geocoded and mapped. Ecological data associated with these sites were summarised. A further 145 articles encompassing general themes of scrub typhus ecology were reviewed. These topics range from the life-cycle to transmission, habitats, seasonality and human risks. Important gaps in our understanding are highlighted together with possible tools to begin to unravel these. Many of the data reported are highly variable and inconsistent and minimum data reporting standards are proposed. With more recent reports of human Orientia sp. infection in the Middle East and South America and enormous advances in research technology over recent decades, this comprehensive review provides a detailed summary of work investigating this pathogen in vectors and non-human hosts and updates current understanding of the complex ecology of scrub typhus. A better understanding of scrub typhus ecology has important relevance to ongoing research into improving diagnostics, developing vaccines and identifying useful public health interventions to reduce the burden of the disease.

Molecular Survey of Rickettsia spp., Anaplasma spp., Ehrlichia spp., Bartonella spp., and Borrelia spp. in Fleas and Lice in Ethiopia

Bacterial arthropod-borne pathogens can often cause fever in Africa, but rural laboratories in these settings are usually too basic to provide a precise picture of their epidemiological impact. Our aim was to determine the prevalence of bacterial pathogens in fleas and lice in a rural area of southeast Ethiopia. Between July and November 2013, we extracted DNA from 91 fleas (Ctenocephalides felis [n = 50; 54.9%], Pulex irritans [n = 37; 40.1%], and C. canis [n = 4; 4.4%] and 30 lice (Pediculus humanus capitis [n = 16; 53.3%] and Pediculus humanus humanus [n = 14; 46.7%]), using two quantitative PCR (qPCR) analyses to look for bacteria from the genera: Anaplasma, Bartonella, Borrelia, Coxiella, Ehrlichia, Francisella, and Rickettsia. Of the 91 fleas analyzed, pathogens were present in 79 (86.8%), including Rickettsia felis (n = 41; 45%), Anaplasma platys (n = 40; 44.0%), Rickettsia monacensis (n = 2; 2.2%), Ehrlichia muris-like agent (n = 1; 1.1%), and Bartonella clarridgeiae (n = 1; 1.1%). P. irritans was the flea species most frequently infected with A. platys (67.7%), followed by C. felis (30.7%) (p < 0.001). Of the 30 lice identified, pathogens were present in 7 (23.3%): Bartonella quintana (n = 4; 16.7%), E. muris (n = 2, 6.7%), and Borrelia recurrentis (n = 1, 3.3%). Thus, in this rural area of Africa, fleas and lice can transmit parasitic pathogens to humans, causing febrile symptoms.

Scrub Typhus in Continental Chile, 2016-20181

Endemic scrub typhus was recently detected on Chiloé Island in southern Chile. We report a series of cases, acquired over a wide geographical range in continental Chile during 2016-2018, demonstrating that this emerging rickettsial infection is also found on the mainland of South America.

Risk factors for bacterial zoonotic pathogens in acutely febrile patients in Mpumalanga Province, South Africa

Endemic zoonoses, such as Q fever and spotted fever group (SFG) rickettsiosis, are prevalent in South Africa, yet often undiagnosed. In this study, we reviewed the demographics and animal exposure history of patients presenting with acute febrile illness to community health clinics in Mpumalanga Province to identify trends and risk factors associated with exposure to Coxiella burnetii, the causative agent of Q fever, and infection by SFG Rickettsia spp. Clinical and serological data and questionnaires elucidating exposure to animals and their products were obtained from 141 acutely febrile patients between 2012 and 2016. Exposure or infection status to C. burnetii and SFG Rickettsia spp. was determined by presence of IgG or IgM antibodies. Logistic regression models were built for risk factor analysis. Clinical presentation of patients infected by SFG rickettsiosis was described. There were 37/139 (27%) patients with a positive C. burnetii serology, indicative of Q fever exposure. Patients who had reported attending cattle inspection facilities ("dip tanks") were 9.39 times more likely to be exposed to Q fever (95% CI: 2.9-30.4). Exposure risk also increased with age (OR: 1.03, 95% CI: 1.002-1.06). Twenty-one per cent of febrile patients (24/118) had evidence of acute infection by SFG Rickettsia spp. Similarly, attending cattle inspection facilities was the most significant risk factor (OR: 8.48, 95% CI: 1.58-45.60). Seropositivity of females showed a significant OR of 8.0 when compared to males (95% CI: 1.49-43.0), and consumption of livestock was associated with a decreased risk (OR: 0.02, 95% CI: 0.001-0.54). A trend between domestic cat contact and SFG rickettsiosis was also noted, albeit borderline non-significant. In this endemic region of South Africa, an understanding of risk factors for zoonotic pathogens, including exposure to domestic animals, can help clinic staff with diagnosis and appropriate therapeutic management of acutely febrile patients as well as identify target areas for education and prevention strategies.

Rickettsia asembonensis Characterization by Multilocus Sequence Typing of Complete Genes, Peru

While studying rickettsial infections in Peru, we detected Rickettsia asembonensis in fleas from domestic animals. We characterized 5 complete genomic regions (17kDa, gltA, ompA, ompB, and sca4) and conducted multilocus sequence typing and phylogenetic analyses. The molecular isolate from Peru is distinct from the original R. asembonensis strain from Kenya.

Worldwide Presence and Features of Flea-Borne Rickettsia asembonensis

Rickettsia asembonensis, the most well-characterized rickettsia of the Rickettsia felis-like organisms (RFLO), is relatively unknown within the vector-borne diseases research community. The agent was initially identified in peri-domestic fleas from Asembo, Kenya in an area in which R. felis was associated with fever patients. Local fleas collected from domestic animals and within homes were predominately infected with R. asembonensis with < 10% infected with R. felis. Since the identification of R. asembonensis in Kenya, it has been reported in other locations within Africa, Asia, the Middle East, Europe, North America, and South America. With the description of R. asembonensis-like genotypes across the globe, a need exists to isolate these R. asembonensis genotypes in cell culture, conduct microscopic, and biological analysis, as well as whole genome sequencing to ascertain whether they are the same species. Additionally, interest has been building on the potential of R. asembonensis in infecting vertebrate hosts including humans, non-human primates, dogs, and other animals. The current knowledge of the presence, prevalence, and distribution of R. asembonensis worldwide, as well as its arthropod hosts and potential as a pathogen are discussed in this manuscript.

Identification and Characterization of Orientia chuto in Trombiculid Chigger Mites Collected from Wild Rodents in Kenya

We present data that concurs with the reported geographical expansion of scrub typhus outside the "Tsutsugamushi Triangle" and addition of Orientia chuto as a second species in the Orientia genus. Wild rodents were caught in Marigat, Baringo County, Kenya, and ectoparasites, including chiggers, were recovered. Rodent and chigger species were identified by taxonomic features. DNA was extracted from the chiggers and used to amplify and/or sequence the 47-kDa high temperature transmembrane protein (TSA47), the 56-kDa type-specific antigen (TSA56), and the 16S rRNA (rrs) Orientia genes. The main rodent hosts identified were Acomys wilsoni, Crocidura sp., and Mastomys natalensis, which accounted for 59.2% of the total collection. Of these, A. wilsoni and M. natalensis harbored most of the chiggers that belonged to the Neotrombicula and Microtrombicula genera. A pool of chiggers from one of M. natalensis was positive for Orientia by TSA47 PCR, but Orientia did not amplify with the TSA56 primers. On sequencing the 850 bp of the TSA47 gene, the closest phylogenetic relative was O. chuto, with 97.65% sequence homology compared to 84.63 to 84.76% for O. tsutsugamushi 16S rRNA deep sequencing also revealed O. chuto as the closest phylogenetic relative, with 99.75% sequence homology. These results and the existing immunological and molecular reports are strongly suggestive of the existence of Orientia species in Kenya.

Molecular Detection of Vector-Borne Pathogens in Rural Dogs and Associated Ctenocephalides felis Fleas (Siphonaptera: Pulicidae) in Easter Island (Chile)

The presence of vector-borne pathogens of veterinary and public health interest have received little attention in Chile. In Easter Island, in particular, a Chilean territory in the southeastern Pacific Ocean, no information is available. To fill this gap, 153 rural dogs were inspected for ectoparasites during a sterilization campaign carried out in 2016. Fleas were observed in 46% of the dogs, and Ctenocephalides felis (Bouché, 1835) was the only species present. Morphological identification of fleas was genetically confirmed using conventional polymerase chain reaction targeting the cox2 gene. No tick was observed in any dog. The presence of DNA of Rickettsia sp. (gltA and ompA fragment genes), Anaplasmataceae (16S rRNA), and Bartonella sp. (16S-23S ribosomal RNA intergenic spacer) was investigated in blood samples of 70 of the dogs and in 126 fleas analyzed in 68 pools that included 1-5 fleas. Rickettsial DNA was detected in 97% (n = 66) of the flea pools. Of these, 57 showed between 99 and 100% identity for both genes with published sequences of Candidatus Rickettsia asemboensis (CRa), six with Rickettsia felis, and one with Candidatus Rickettsia senegalensis. For two pools, gltA amplicons were identical to CRa but ompB amplicions showed 99-100% identity with R. felis. Anaplasmataceae DNA was detected in 16% (n = 11) pools. Sequenced amplicons showed highest identity with the endosymbiont Wolbachia pipientis. Bartonella DNA, showing 99% identity to Bartonella clarridgeiae, was detected in one pool (1.4%). No positive reaction was observed for any dog. This is the first detection of members of the 'R. felis-like' group other than R. felis in Chile.

Prevalence of Selected Zoonotic Diseases and Risk Factors at a Human-Wildlife-Livestock Interface in Mpumalanga Province, South Africa

A lack of surveillance and diagnostics for zoonotic diseases in rural human clinics limits clinical awareness of these diseases. We assessed the prevalence of nine zoonotic pathogens in a pastoral, low-income, HIV-endemic community bordering wildlife reserves in South Africa. Two groups of participants were included: malaria-negative acute febrile illness (AFI) patients, called febrilers, at three clinics (n = 74) and second, farmers, herders, and veterinary staff found at five government cattle dip-tanks, called dip-tanksters (n = 64). Blood samples were tested using one PCR (Bartonella spp.) and eight antibody-ELISAs, and questionnaires were conducted to assess risk factors. Seventy-seven percent of febrilers and 98% of dip-tanksters had at least one positive test. Bartonella spp. (PCR 9.5%), spotted fever group (SFG) Rickettsia spp. (IgM 24.1%), Coxiella burnetii. (IgM 2.3%), and Leptospira spp. (IgM 6.8%) were present in febrilers and could have been the cause of their fever. Dip-tanksters and febrilers had evidence of past infection to Rickettsia spp. (IgG 92.2% and 63.4%, respectively) and C. burnetii (IgG 60.9% and 37.8%, respectively). No Brucella infection or current Bartonella infection was found in the dip-tanksters, although they had higher levels of recent exposure to Leptospira spp. (IgM 21.9%) compared to the febrilers. Low levels of West Nile and Sindbis, and no Rift Valley fever virus exposure were found in either groups. The only risk factor found to be significant was attending dip-tanks in febrilers for Q fever (p = 0.007). Amoxicillin is the local standard treatment for AFI, but would not be effective for Bartonella spp. infections, SFG rickettsiosis, Q fever infections, or the viral infections. There is a need to revise AFI treatment algorithms, educate medical and veterinary staff about these pathogens, especially SFG rickettsiosis and Q fever, support disease surveillance systems, and inform the population about reducing tick and surface water contact.

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.

Occurrence of Hepatozoon canis (Adeleorina: Hepatozoidae) and Anaplasma spp. (Rickettsiales: Anaplasmataceae) in black-backed jackals (Canis mesomelas) in South Africa

Background

Domestic dogs are not native to sub-Saharan Africa, which may account for their susceptibility to Babesia rossi, of which endemic black-backed jackals (Canis mesomelas) are natural reservoirs. There is virtually no information on the occurrence of potentially pathogenic haemogregarines (e.g. Hepatozoon canis) or even rickettsial bacteria (e.g. Ehrlichia spp. and Anaplasma spp.) in indigenous canids in sub-Saharan Africa. Such organisms could pose a risk to domestic dogs, as well as to populations of endangered indigenous canid species.

Results

Genomic DNA extracted from blood samples taken from 126 free-ranging and 16 captive black-backed jackals was subjected to reverse line blot (RLB) hybridization assay; 82 (57.8%) specimens reacted only with the Ehrlichia/Anaplasma genera-specific probe. Full-length bacterial 16S rRNA gene of five of these specimens was cloned and the recombinants sequenced. The ten 16S rDNA sequences obtained were most closely related, with approximately 99% identity, to Anaplasma sp. South African Dog, various uncultured Anaplasma spp., as well as various Anaplasma phagocytophilum genotypes. Ninety-one specimens were screened for haemogregarines through PCR amplification using the 18S rRNA gene; 20 (21.9%) specimens reacted positively, of which 14 (15.4%) were confirmed positive for Hepatozoon genotypes from within H. canis. Two (2.2%) specimens were found positive for two different Hepatozoon genotypes.

Conclusions

Sequence analyses confirmed the presence of 16S rDNA sequences closely related to A. phagocytophilum and Anaplasma sp. South African Dog as well as two H. canis genotypes in both free-ranging and captive black-backed jackals. Distinguishing between closely related lineages may provide insight into differences in pathogenicity and virulence of various Anaplasma and H. canis genotypes. By building up a more comprehensive understanding of the range and diversity of the bacteria and eukaryotic organisms (piroplasms and haemogregarines) in the blood of indigenous canids, we may gain insight to such infections in these often-endangered species and the potential for horizontal transmission to and from domestic dogs via ticks where favourable conditions exist.

Scrub Typhus: No Longer Restricted to the Tsutsugamushi Triangle

Scrub typhus is the most important rickettsial disease in the world. Its previous endemic region was considered to be in Asia, Australia and islands in the Indian and Pacific Oceans; this area was referred to as the Tsutsugamushi Triangle. Accumulation of serological, molecular, genetic, and culture data have shown that not only is scrub typhus not limited to the Tsutsugamushi Triangle, but can be caused by orientiae other than Orientia tsutsugamushi. This review describes evidence currently available that will be instrumental to researchers, healthcare providers and medical leaders in developing new research projects, performing diagnosis, and preventing scrub typhus in locations not previously thought to be endemic.

Tick-, Flea-, and Louse-Borne Diseases of Public Health and Veterinary Significance in Nigeria

Mosquito-borne diseases are common high-impact diseases in tropical and subtropical areas. However, other non-mosquito vector-borne pathogens (VBPs) may share their geographic distribution, seasonality, and clinical manifestations, thereby contributing their share to the morbidity and mortality caused by febrile illnesses in these regions. The purpose of this work was to collect and review existing information and identify knowledge gaps about tick, flea-, and louse-borne diseases of veterinary and public health significance in Nigeria. Full-length articles about VBPs were reviewed and relevant information about the vectors, their hosts, geographic distribution, seasonality, and association(s) with human or veterinary diseases was extracted. Specific laboratory tools used for detection and identification of VBPs in Nigeria were also identified. A total of 62 original publications were examined. Substantial information about the prevalence and impacts of ticks and fleas on pet and service dogs (18 articles), and livestock animals (23 articles) were available; however, information about their association with and potential for causing human illnesses was largely absent despite the zoonotic nature of many of these peri-domestic veterinary diseases. Recent publications that employed molecular methods of detection demonstrated the occurrence of several classic (Ehrlichia canis, Rickettsia africae, Bartonella sp.) and emerging human pathogens (R. aeschlimannii, Neoehrlichia mikurensis) in ticks and fleas. However, information about other pathogens often found in association with ticks (R. conorii) and fleas (R. typhi, R. felis) across the African continent was lacking. Records of louse-borne epidemic typhus in Nigeria date to 1947; however, its current status is not known. This review provides an essential baseline summary of the current knowledge in Nigeria of non-mosquito VBPs, and should stimulate improvements in the surveillance of the veterinary and human diseases they cause in Nigeria. Due to increasing recognition of these diseases in other African countries, veterinary and public health professionals in Nigeria should expand the list of possible diseases considered in patients presenting with fever of unknown etiology.

Rickettsia diversity in southern Africa: A small mammal perspective

Worldwide, including Africa, rickettsioses are recognized as emerging or re-emerging infections. To date, little is known about the diversity of Rickettsia species that are naturally associated with small mammals in southern Africa. The aim of the study was to screen a diversity of small mammals for the presence of rickettsial DNA. Animals were trapped at 38 localities in South Africa and Namibia. In total, 1616 ear-tissue samples from 23 species representing 17 genera were tested using real-time (rt)PCR and multi-locus sequence typing (MLST). Of the 1616 samples 251 (15.5%) were positive in an initial rtPCR. In 16 of the 23 investigated animal species rickettsial DNA was detected with an average prevalence of 15.7%. We herein describe for the first time four Rickettsia (R.) species known to be pathogenic for humans in rodents from South Africa, R. conorii, R. massiliae, R. felis and R. helvetica. In addition, by MLST and subsequent phylogenetic analyses so far undescribed Rickettsia species, Candidatus Rickettsia africaustralis, Candidatus Rickettsia rhabdomydis, and Candidatus Rickettsia muridii were confirmed. Further four new genotypes, genotype Rickettsia hofmannii, genotype Rickettsia stutterheimensis, genotype Rickettsia hogsbackensis and genotype Rickettsia kaalplaasensis, respectively, are described. The data indicate a surprisingly high diversity of Rickettsia in small mammals in South Africa and might indicate their possible role as reservoirs for Rickettsia. Ecological questions concerning their natural hosts such as small mammals, but also the role of livestock or pet animals, require further investigation. Particularly, data on the relevance of these rickettsiae for diseases in humans are of further interest.

High Prevalence of Rickettsia spp. in Dog Fleas (Siphonaptera: Pulicidae) in Rural Uganda

Fleas are known vectors of zoonotic agents. Thirty-five fleas, including 28 Ctenocephalides felis (Bouché), four Pulex irritans (L.), and three Echidnophaga gallinacea (Westwood) from 19 rural dogs from southwestern Uganda were analyzed for the presence of Rickettsia spp. (ompB, gltA, and 17 kDa fragment genes) and Bartonella spp. (rpoB and ITS genes) by PCR. Rickettsial DNA was detected in 27 out of 28 of Ct. felis and in two out of four P. irritans. None of the E. gallinacea specimens harbored Rickettsia DNA. Rickettsia felis was confirmed in 12 Ct. felis and in the two P. irritans specimens with positive PCR-results. In addition, the presence of Candidatus Rickettsia asemboensis was evidenced in 15 Ct. felis. Bartonella spp. was not amplified in any sample. Our survey indicates that R. felis, the agent of the flea-borne spotted fever, is present in the study area. Besides, this is the first description of Ca. R. asemboensis in Uganda.

Rabies vaccine is associated with decreased all-cause mortality in dogs

Evidence suggests that rabies vaccine may have non-specific protective effects in animals and children. We analyzed four years of data (2012-2015) from an observational study of the health and demographics of a population of owned, free-roaming dogs in a low-income community in South Africa. The objective of this analysis was to assess the association between rabies vaccine and all-cause mortality in dogs, stratified by age group (0-3months, 4-11months, and 12months and older), and controlling for the effects of sex and number of dogs in the residence. Rabies vaccination reduced the risk of death from any cause by 56% (95% CI=16-77%) in dogs aged 0-3months, by 44% (95% CI=21-60%) in dogs aged 4-11months and by 16% (95% CI=0-29%) in dogs aged 12months and older. We hypothesize that the protective association between rabies vaccination status and all-cause mortality is due to a protective effect of rabies vaccine against diseases other than rabies. Existence of a strong non-specific protective effect of rabies vaccine on mortality in dogs would have implications for the design of dog rabies control programs that aim to eliminate dog-mediated human rabies cases. Further, we propose that owned domestic dogs in high mortality settings provide a useful animal model to better understand any non-specific protective effect of rabies vaccine in children, due to dogs' high numbers, high morbidity and mortality rates, relatively short lifespan, exposure to a variety of infectious and parasitic diseases, and shared environment with people.

Detection of Anaplasma spp. and Ehrlichia spp. anibodies, and Dirofilaria immitis antigens in dogs from seven locations of Morocco

In Morocco no data has been published on canine exposure to Anaplasma spp., Borrrelia burgdorferi, and Ehrlichia spp., and only one report is available on the occurrence of Dirofilaria immitis in dogs. Therefore, the aim of this study was to collect current data on the canine exposure to these vector-borne pathogens (VBPs) in Morocco. A total of 217 urban (n=57), rural (n=110) and military (n=50) dogs from seven Moroccan locations were screened for Anaplasma spp., B. burgdorferi and Ehrlichia spp. antibodies and for D. immitis antigens using a commercial in-clinic ELISA test. Of these dogs, 182 (83.9%) tested positive for at least one pathogen and positivity to two or three pathogens was found in 14.3% and 2.3% of the dogs, respectively. Ehrlichia spp. antibodies (34.6%) were the most frequently detected followed by Anaplasma spp. antibodies (16.6%) and D. immitis antigens (16.1%). None of the dogs was tested seropositive to B. burgdorferi. Statistically significant differences in seropositivity rates were found for Ehrlichia spp. and D. immitis in rural dogs especially those from the north central region (p<0.001) but not for Anaplasma spp. No significant difference was found according to the health status of the dog. This study demonstrates that Moroccan dogs are at high risk of acquiring a vector-borne infection.

"Candidatus Rickettsia asemboensis" in Rhipicephalus sanguineus ticks, Brazil

"Candidatus Rickettsia asemboensis" is an obligate intracellular bacterium of the Rickettsiales order, genetically related to species belonging to the Rickettsia felis group, agents of flea-borne spotted fever. Here we report for the first time the detection of "Ca. R. asemboensis", a flea-associated organism, in Rhipicephalus sanguineus ticks. It is the first occurrence of this emerging bacterium in Brazil, which increases the geographical distribution of this R. felis-like agent.

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.

First molecular evidence of mixed infections of Anaplasma species in dogs in Henan, China

In recent years, tick-borne diseases like anaplasmosis have become widespread worldwide threatening the health of both human and animals. Dogs play an important role in the epidemiology of several zoonotic tick-borne pathogens by acting as reservoirs. In this study, the status of Anaplasma phagocytophilum, A. platys, A. bovis and A. ovis infection were assessed in dogs in Henan, China, with PCR and phylogenetic analyses. Nested PCRs on 243 blood samples collected from dogs from different sampling sites revealed that thirty-three (13.6%) dogs were positive for one or more pathogens. The prevalence of Anaplasma spp. in stray dogs was 40.7% (24/59), which was much higher than that of pet dogs (4.0%, 7/175). The prevalence for A. ovis, A. bovis and A. phagocytophilum was 6.2%, 4.1% and 0.4%, respectively and mixed-infection of these three pathogens was found in only one stray dog (prevalence, 0.4%). None of the dogs was positive for A. platys. Phylogenetic analyses classified A. phagocytophilum into two distinct groups (East Asia and south Africa group, Europe and America group), whereas A. ovis and A. bovis showed a general classification into two groups (cluster 1 and cluster 2), respectively. The isolate (KX190783) of A. ovis from a stray dog fell in a clade with a human isolate from Cyprus (FJ460443) and shared 99.8% similarity with it. To the best of our knowledge, this study is the first report to identify A. bovis and A. ovis DNA in dogs in China and the mixed-infection of the three Anaplasma spp. (A. phagocytophilum, A. bovis and A. ovis) in dogs.

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.