Flea-Borne Rickettsioses and Scrub Typhus in Patients with Suspected Arbovirus Infection in Bangkok, Thailand.

Background: In urban Thailand, arboviral infections dominate diagnoses of acute undifferentiated fevers (AUFs) owing to their well-defined epidemiology and characteristic clinical presentations. However, rickettsial diseases, also endemic in this setting, remain under-recognized owing to challenges in early detection. Objective: This study aimed to identify potential rickettsial infections among patients with AUF in Bangkok and vicinity utilizing leftover nucleic acid extracted from serum samples from patients initially suspected of but negative for arbovirus infections. Materials and Methods: A total of 609 nucleic acid samples were screened for rickettsial bacteria using real-time PCR, targeting the 17-kDa common antigen gene of Rickettsia spp. and the 47-kDa gene of Orientia tsutsugamushi. Results: Nine samples were positive for Rickettsia spp. and two were positive for O. tsutsugamushi. DNA sequence and phylogenetic analyses based on partial 17-kDa antigen and citrate synthase (gltA) genes identified the Rickettsia-positive samples as R. typhi in eight cases and R. felis in one case. Analysis of the 56-kDa type-specific antigen gene identified the two O. tsutsugamushi isolates as Gilliam-related genotypes. Although rickettsial diseases typically present with mild symptoms, two patients with R. typhi infection (murine typhus) developed respiratory distress syndrome, highlighting the potential for rare but serious complications. Conclusion: This study underscores the critical importance of differential diagnosis and prompt, effective intervention to prevent complications in suspected cases.

A case of mistaken identity: a systematic review, meta-analysis, and reinvestigation of hemotropic Mycoplasma spp. infection in Ctenocephalides felis (cat flea).

BACKGROUND: Feline-associated hemotropic Mycoplasma (hemoplasmas) are believed to be transmitted by two primary mechanisms: (1) direct transmission via fighting and (2) vector-borne transmission by the cat flea (Ctenocephalides felis). While the efficiency of transmission by C. felis appears low, most manuscripts focus on the prevalence of hemoplasmas in wild-caught fleas and report either a very low (< 3%) or a high (> 26%) prevalence. Therefore, we aimed to assess the influence of sample processing and PCR methods on C. felis hemoplasma infection prevalence. METHODS: A systemic review of PubMed articles identified 13 manuscripts (1,531 fleas/flea pools) that met the inclusion criteria (performed PCR for >1 hemoplasma on C. felis collected from cats). Risk of bias was assessed utilizing the ROBINS-E tool. Meta-analysis performed in R of these manuscripts found that not washing samples and a common set of 16S rRNA primers first published in Jensen et al. 2001 were associated with increased hemoplasma prevalence. To evaluate the influence of washing on newly collected fleas, we assessed the hemoplasma status of 20 pools of 5 C. felis each, half of which were washed and half not washed. RESULTS: Flea washing did not influence the detection of hemoplasma but instead amplified Spiroplasma. To assess non-specific amplification with the Jensen et al. 2001 primers, 67 C. felis samples (34% previously reported hemoplasma infected) were subject to PCR and sequencing. By this method, hemoplasma was detected in only 3% of samples. In the remaining "hemoplasma infected" fleas, PCR amplified Spiroplasma or other bacteria. CONCLUSIONS: Therefore, we concluded that hemoplasma infection in C. felis is rare, and future flea prevalence studies should sequence all positive amplicons to validate PCR specificity. Further investigation of alternative methods of feline-associated hemoplasma transmission and the ability of C. felis to maintain hemoplasma infection is necessary.

Molecular Identification, Multigenic Characterization and Phylogenetic Analysis of Ctenocephalides Canis Fleas from Humans and Domestic Animals in Iran.

BACKGROUND: Fleas belonging to the Pulicidae are prevalent ectoparasites infesting mammals and birds in Iran. This study focused on genetically identifying and characterizing Ctenocephalides canis collected both off-host and infesting humans and various domestic animals in the country. METHODS: A total of 918 adult flea samples were collected from 10 sites in western and northwestern Iran between April 2018 and May 2019. Out of these, 71 specimens were found off-host, while the remaining fleas were collected from humans (121), sheep (126), goats (184), and dogs (416). Morphological identification at the genus level was performed on all fleas, and ten selected specimens selected based on the sampling sites and hosts were subjected to molecular detection at the species level by using partial amplification and sequencing of the internal transcribed spacer 1 and 2, as well as the cytochrome oxidase I (COXI) markers. RESULTS: The morphological identification confirmed all fleas as Ctenocephalides spp. Alignment and phylogenetic analysis of nuclear and mitochondrial partial sequences confirmed the presence of C. canis. However, molecular divergence was observed among the ten isolates based on the ITS1 and ITS2 with diversity rates estimated at 0.15% and 3.36%, respectively. Notably, the analysis of the COXI marker revealed no molecular divergence among the partial sequences representing the ten studied isolates from C. canis. CONCLUSIONS: This study explores the diversity of C. canis in the western and northwestern regions of Iran, providing insights into their molecular taxonomy and potential role as disease vectors in these areas.

Severe flea-borne typhus complicated by hemophagocytic lymphohistiocytosis: A case report and review of literature.

Flea-borne typhus (FBT), also known as murine typhus, is a zoonotic infection caused by R. typhi with world-wide distribution. In the United States, the infection is uncommon but remains endemic in some areas, including Los Angeles County. It typically manifests as a benign acute febrile illness but can be complicated in a minority of cases. Associated hemophagocytic lymphohistiocytosis (HLH) has been described in a limited number of cases. Here, we present a case of a patient with FBT complicated by HLH treated empirically with doxycycline with subsequent resolution of HLH. Also included is a review of the literature of other published cases.

Knowledge and practices related to louse- and flea-borne diseases among staff providing services to people experiencing homelessness in the United States.

BACKGROUND AND AIMS: Louse-borne Bartonella quintana infection and flea-borne murine typhus are two potentially serious vector-borne diseases that have led to periodic outbreaks among people experiencing homelessness in the United States. Little is known about louse- and flea-borne disease awareness and prevention among staff who provide services to the population. We surveyed staff in seven US states to identify gaps in knowledge and prevention practices for these diseases. METHODS AND RESULTS: Surveys were administered to 333 staff at 89 homeless shelters and outreach teams in California, Colorado, Georgia, Maryland, Minnesota, New York and Washington from August 2022 to April 2023. Most participants (>68%) agreed that body lice and fleas are a problem for people experiencing homelessness. About half were aware that diseases could be transmitted by these vectors; however, most could not accurately identify which diseases. Less than a quarter of staff could describe an appropriate protocol for managing body lice or fleas. Misconceptions included that clients must isolate or be denied services until they are medically cleared. CONCLUSIONS: Our findings reveal significant knowledge gaps among staff who provide services to people experiencing homelessness in the prevention and control of louse- and flea-borne diseases. This demonstrates an urgent need for staff training to both reduce disease and prevent unnecessary restrictions on services and housing.

Cat Flea Coinfection with Rickettsia felis and Rickettsia typhi.

Purpose: Flea-borne rickettsioses, collectively referred to as a term for etiological agents Rickettsia felis, Rickettsia typhi, and RFLOs (R. felis-like organisms), has become a public health concern around the world, specifically in the United States. Due to a shared arthropod vector (the cat flea) and clinical signs, discriminating between Rickettsia species has proven difficult. While the effects of microbial coinfections in the vector can result in antagonistic or synergistic interrelationships, subsequently altering potential human exposure and disease, the impact of bacterial interactions within flea populations remains poorly defined. Methods: In this study, in vitro and in vivo systems were utilized to assess rickettsial interactions in arthropods. Results: Coinfection of both R. felis and R. typhi within a tick-derived cell line indicated that the two species could infect the same cell, but distinct growth kinetics led to reduced R. felis growth over time, regardless of infection order. Sequential flea coinfections revealed the vector could acquire both Rickettsia spp. and sustain coinfection for up to 2 weeks, but rickettsial loads in coinfected fleas and feces were altered during coinfection. Conclusion: Altered rickettsial loads during coinfection suggest R. felis and R. typhi interactions may enhance the transmission potential of either agent. Thus, this study provides a functional foundation to disentangle transmission events propelled by complex interspecies relationships during vector coinfections.

Murine Typhus: A Review of a Reemerging Flea-Borne Rickettsiosis with Potential for Neurologic Manifestations and Sequalae.

Murine typhus is an acute febrile illness caused by Rickettsia typhi, an obligately intracellular Gram-negative coccobacillus. Rats (Rattus species) and their fleas (Xenopsylla cheopis) serve as the reservoir and vector of R. typhi, respectively. Humans become infected when R. typhi-infected flea feces are rubbed into flea bite wounds or onto mucous membranes. The disease is endemic throughout much of the world, especially in tropical and subtropical seaboard regions where rats are common. Murine typhus is reemerging as an important cause of febrile illness in Texas and Southern California, where an alternate transmission cycle likely involves opossums (Didelphis virginiana) and cat fleas (Ctenocephalides felis). Although primarily an undifferentiated febrile illness, a range of neurologic manifestations may occur, especially when treatment is delayed. Serology is the mainstay of diagnostic testing, but confirmation usually requires demonstrating seroconversion or a fourfold increase in antibody titer from acute- and convalescent-phase sera (antibodies are seldom detectable in the first week of illness). Thus, early empiric treatment with doxycycline, the drug of choice, is imperative. The purpose of this review is to highlight murine typhus as an important emerging and reemerging infectious disease, review its neurologic manifestations, and discuss areas in need of further study.

Nonnegligible Seroprevalence and Predictors of Murine Typhus, Japan.

To elucidate the epidemiology of murine typhus, which is infrequently reported in Japan, we conducted a cross-sectional study involving 2,382 residents of rickettsiosis-endemic areas in Honshu Island during August-November 2020. Rickettsia typhi seroprevalence rate was higher than that of Orientia tsutsugamushi, indicating that murine typhus is a neglected disease.

Complete bacterial profile and potential pathogens of cat fleas Ctenocephalides felis.

Fleas are important ectoparasites and vectors associated with a wide range of pathogenic diseases, posing threats to public health concerns, especially cat fleas that spread worldwide. Understanding the microbial components is essential due to cat fleas are capable of transmitting pathogens to humans, causing diseases like plague and murine typhus. In the present study, metagenomic next-generation sequencing was applied to obtain the complete microbiota and related functions in the gut of Ctenocephalides felis. A total of 1,870 species was taxonomically recognized including 1,407 bacteria, 365 eukaryotes, 69 viruses, and 29 archaea. Proteobacteria was the dominant phylum among the six samples. Pathogens Rickettsia felis, Acinetobacter baumannii, Coxiella burnetii, and Anaplasma phagocytophilum were taxonomically identified and had high abundances in all samples. The resistance gene MexD was predominant in microbial communities of all cat fleas. We also performed epidemiological surveys of pathogens R. felis, A. baumannii, C. burnetii, and A. phagocytophilum among 165 cat fleas collected from seven provinces in China, while only the DNAs of R. felis (38/165, 23.03%) and C. burnetii (2/165, 1.21%) were obtained. The data provide new insight and understanding of flea intestinal microbiota and support novel information for preventing and controlling fleas and their transmitted diseases.

Molecular identification of Bartonella spp. and Rickettsia felis in fox fleas, Chile.

Seventy-five flea pools (one to ten fleas per pool) from 51 Andean foxes (Lycalopex culpaeus) and five South American grey foxes or chillas (Lycalopex griseus) from the Mediterranean region of Chile were analyzed for the presence of DNA of Bartonella spp. and Rickettsia spp. through quantitative real-time PCR for the nouG and gltA genes, respectively. Positive samples were further characterized by conventional PCR protocols, targeting gltA and ITS genes for Bartonella, and gltA, ompA, and ompB genes for Rickettsia. Bartonella was detected in 48 % of the Pulex irritans pools (B. rochalimae in three pools, B. berkhoffii in two pools, B. henselae in one pool), and 8 % of the Ctenocephalides felis felis pools (B. rochalimae, one pool). Rickettsia was confirmed in 11 % of P. irritans pools and 92 % of the Ct. felis pools. Characterization confirmed R. felis in all sequenced Rickettsia-positive pools. All Ct. canis pools were negative. A Ct. felis pool from a wild-found domestic ferret (Mustela putorius furo) also resulted positive for R. felis. Although opportunistic, this survey provides the first description of zoonotic pathogens naturally circulating in fleas parasitizing Chilean free-living carnivores.

Identification of Vietnamese Flea Species and Their Associated Microorganisms Using Morphological, Molecular, and Protein Profiling.

Fleas are obligatory blood-sucking ectoparasites of medical and veterinary importance. The identification of fleas and associated flea-borne microorganisms, therefore, plays an important role in controlling and managing these vectors. Recently, Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) has been reported as an innovative and effective approach to the identification of arthropods, including fleas. This study aims to use this technology to identify ethanol-preserved fleas collected in Vietnam and to use molecular biology to search for microorganisms associated with these fleas. A total of 502 fleas were collected from wild and domestic animals in four provinces in Vietnam. Morphological identification led to the recognition of five flea species, namely Xenopsylla cheopis, Xenopsylla astia, Pulex irritans, Ctenocephalides canis, and Ctenocephalides felis. The cephalothoraxes of 300 individual, randomly selected fleas were tested using MALDI-TOF MS and molecular analysis for the identification and detection of microorganisms. A total of 257/300 (85.7%) of the obtained spectra from the cephalothoraxes of each species were of good enough quality to be used for our analyses. Our laboratory MALDI-TOF MS reference database was upgraded with spectra achieved from five randomly selected fleas for every species of Ctenocephalides canis and Ctenocephalides felis. The remaining spectra were then queried against the upgraded MALDI-TOF MS database, which showed 100% correspondence between morphology and MALDI-TOF MS identification for two flea species (Ctenocephalides canis and Ctenocephalides felis). The MS spectra of the remaining species (three P. irritans, five X. astia, and two X. cheopis) were visually generated low-intensity MS profiles with high background noise that could not be used to update our database. Bartonella and Wolbachia spp. were detected in 300 fleas from Vietnam using PCR and sequencing with primers derived from the gltA gene for Bartonella and the 16S rRNA gene for Wolbachia, including 3 Bartonella clarridgeiae (1%), 3 Bartonella rochalimae (1%), 1 Bartonella coopersplainsensis (0.3%), and 174 Wolbachia spp. endosymbionts (58%).

Flea-Borne Typhus Causing Hemophagocytic Lymphohistiocytosis: An Autopsy Case.

Infection with members of the order Rickettsiales (the genera Rickettsia, Anaplasma, Orientia, and Ehrlichia) is known to cause hemophagocytic lymphohistiocytosis (HLH). The literature is scant on flea-borne typhus (FBT) being implicated in this process. We present a case of autopsy-proven HLH caused by FBT in a 71-year-old diabetic female who was initially suspected of having diabetic ketoacidosis who rapidly suffered decompensated multi-organ failure. Although she was suspected of having FBT and HLH pre-mortem, due to her rapid progression to multi-organ failure, she was transitioned to comfort care by her family five days after admission. A literature search yielded five other cases of HLH secondary to FBT, which are analyzed in this review. The literature on HLH occurring with infection due to other members of the order Rickettsiales is also surveyed.

Rickettsioses in Colombia during the 20th century: A historical review.

Rickettsioses are vector-borne zoonotic diseases whose etiological agents are bacteria of the genera Rickettsia and Orientia. In Colombia, literature published on rickettsioses during the 20th century is limited and disperse; to date, there are no detailed publications that compile the affected regions or the involved Rickettsia species in each outbreak. Since early works of Luis Patiño-Camargo, the study of rickettsioses gained major importance with the subsequent description of significant outbreaks in some departments of the country. During the 1940s, many articles were published reporting outbreaks probably caused by Rickettsia rickettsii, Rickettsia typhi, and Rickettsia prowazekii, as well as studies on their diagnosis, vaccination, and prophylaxis. One of the most notorious works was published by Patiño-Camargo where he named the R. rickettsii rickettsiosis as "Tobia fever". However, in the subsequent decades, these entities entered a prolonged period of neglected research and surveillance, and just gained importance until the 21st century, when new fatal cases began to be reported in the country; thus, many questions remained unanswered during this overlooked period. The present work reviewed online databases, repositories, and libraries to compile literature related to rickettsioses in Colombia published during the 20th century. Gathered data show that typhus group rickettsioses (including infections by R. typhi and R. prowazekii) were broadly distributed in departments from the Andean and Caribbean regions, and that spotted fever group rickettsioses cases (including infections by R. rickettsii) were registered in other locations different from Tobia (Cundinamarca), like Atlántico, Bolivar, and Santander departments. These findings contribute to the knowledge of these diseases, their historical distribution, public health burden, and set new horizons for rickettsioses research in different Colombian locations.

Molecular detection of Rickettsia felis in fleas and ticks collected from dogs and cats of Puebla, Mexico.

Fleas and ticks represent the two main groups of ectoparasites that infest companion animals. In particular, the flea Ctenocephalides felis felis and several members of the Rhipicephalus sanguineus complex are the main vectors of a wide range of pathogens on the American continent. They are competent vectors for several members of the genus Rickettsia, which encompass at least 15 pathogenic obligate intracellular bacteria that colonize the endothelial cells of vertebrates. In Mexico, 10 species of Rickettsia belonging to three groups have been detected in six species of ectoparasites from dogs in 9 of the 32 states of the country. However, in some larger regions of the country, active epidemiological surveillance has not been carried out. For this reason, the aim of this study was to identify the presence of members of the genus Rickettsia in fleas and ticks of dogs and cats in the state of Puebla, Mexico. A cross-sectional study was carried out to collect ectoparasites of dogs and cats during August to November 2019. Samples were fixed in 70% ethanol and examined to identify the presence of Rickettsia DNA by the amplification and sequencing of specific fragments of the gltA and ompB genes using conventional PCR. The recovered sequences were compared with those deposited in GenBank, and phylogenetic analyses were carried out to identify the position of the pathogens detected with respect to the valid species previously reported worldwide. Additionally, ecological parameters of the ectoparasite infestations were also calculated. We recovered 196 ectoparasites belonging to two species, 33 C. felis felis and 163 R. sanguineus s.l. (Rhipicephalus linnaei), parasitizing 46 hosts (42 dogs and 4 cats) in 11 localities of the state of Puebla. We detected the presence of Rickettsia felis in three pools of C. felis felis, and five from R. sanguineus s.l. Our work provides the first record of R. felis in hard ticks of Mexico and Central America, with new collection localities for this pathogen in central Mexico.

Co-infection patterns of vector-borne zoonotic pathogens in owned free-ranging dogs in central Chile.

We investigated the co-occurrence of the nine of the most relevant canine vector-borne pathogens (CVBP) using conventional and real-time PCR and evaluated risk factors and potential non-apparent haematological alterations associated with co-infection in 111 rural, owned, free-ranging dogs in the Metropolitan Region of Chile.At least one pathogen was detected in 75% of the dogs. DNA of Anaplasma platys (Ap; 36%), Candidatus Mycoplasma haematoparvum (CMhp; 31%), Mycoplasma haemocanis (Mhc; 28%), Trypanosoma cruzi (17%), Leishmania spp. (4.5%), and Acanthocheilonema reconditum (1%) was detected. All dogs were negative for Ehrlichia spp., Rickettsia spp., Bartonella spp., Piroplasmida, and Hepatozoon spp. Thirty-eight dogs (34%) were coinfected. CMhp was involved in 71%, Mhc in 58%, and Ap in 50% of the co-infections. The most common co-infection pattern was CMhp-Mhc (37% of the cases). The prevalence of Ap was higher in juvenile than in adult dogs, whereas the opposite was found for CMhp and Mhc. Adult dogs were four times more likely of being co-infected than juveniles. Co-infected animals showed higher white blood cell count, segmented neutrophil count, and GGT levels than non-co-infected dogs. Clinically healthy but infected dogs may act as reservoirs of CVBP, and their free-ranging behavior would facilitate the spread of these pathogens to other dogs as well as human beings or wild carnivores.

Increased Seroprevalence of Typhus Group Rickettsiosis, Galveston County, Texas, USA.

Whether increases in typhus group rickettsiosis in Galveston County, Texas, USA, are caused by increased recognition or true reemergence is unclear. We conducted a serosurvey that demonstrated Rickettsia typhi antibodies increased from 1.2% in 2013 to 7.8% in 2021 (p<0.001). These findings support pathogen reemergence rather than enhanced recognition alone.

Human Rickettsia felis infections in Mainland China.

We identified four flea-borne spotted fever cases caused by Rickettsia felis in a retrospective survey of 182 patients with fever of unknown origin (FUO) in China between 2021 and 2022. The clinical signs and symptoms of the patients were similar to those of other rickettsioses, including fever, rash, and liver and kidney dysfunction. All four patients in the present study developed pneumonia or lung lesions after R. felis infection. The cases of R. felis infection, a neglected infectious disease, were sporadic in multiple provinces of the country. The high prevalence (2.14%, 4/187) of R. felis among patients with FUO highlights the risk posed by this pathogen to public health in China.

A review of public health important fleas (Insecta, Siphonaptera) and flea-borne diseases in India.

Fleas (Insecta, Siphonaptera) are important vectors of plague and murine typhus in many parts of the world. Currently, about 2700 flea species were described in the world. The most common vector flea Xenopsylla cheopis is found throughout India, but X. astia, and X. brasiliensis are found less and limited in distribution associated with the domestic rats such as Rattus rattus, R. norvegicus, Mus musculus, and Bandicota bengalensis. Bubonic plague is a major flea-borne disease caused by the bacterial pathogen Yersinia pestis, transmitted from rats to humans via the rodent flea, X. cheopis. A major outbreak of plague and high mortality occurred in India. After 1966 with the 3 decadal intervals, plague cases occurred only during the year 1994 reported in 5 different states (Gujarat, Maharashtra, Karnataka, Uttar Pradesh, Madhya Pradesh and New Delhi and subsequently plague cases occurred during 2002 and 2004 after the one-decade interval in Himachal Pradesh (2002). Another outbreak of bubonic plague was reported in Dangud village, Barkhot tehsil, Uttarkashi district, Uttarakhand during October 2004. Ctenocephalides fleas are common in cats and dogs, which are the main vectors of bacteria rickettsiae, such as Rickettsia typhi, R. felis, R. conorii, and Bartonella henselae. Molecular and serological evidence also confirms the presence of R. typhi, R. conorii R. felis and B. henselae pathogens in cats and other fleas in India. Flea bites and flea-borne dermatitis are common in men and pet animals. Because of the re-emergence of the plague, updated information on fleas and flea-borne diseases are essential to control the flea vectors and flea-borne diseases in India. Hence, this comprehensive review updates the available information on fleas and fleas transmitted diseases in India.

Is vertical transmission the only pathway for Rickettsia felis?

The genus Rickettsia encompasses several species grouped into two main clusters, Typhus and the Transitional groups. The latter group contains Rickettsia felis, an endosymbiont of several arthropods with an uncertain human pathogenicity and whose most efficient transmission mechanism described thus far is transovarial. The aim of this study was to evaluate whether this pathway exists using phylogenetic analysis and partial sequences of the 17kDa and gltA genes and comparing them with host phylogeny using the cytb region. This is the first study that evaluates the vertical transmission of R. felis. In general, both phylogenies of R. felis showed no polytomies, as suspected if this pathway was the only pathway occurring. When phylogenies of the invertebrates and the gltA of R. felis were compared for strong coevolutionary insight, intricate relationships were observed, suggesting that other transmission pathways must occur, such as horizontal transmission. Further studies are needed to determine which other transmission routes occur in hematophagous arthropods.