Search Results (83)

Spotted fever group (SFG) rickettsioses are tick-borne infectious diseases caused by more than 30 Rickettsia species. As ticks may harbor and transmit multiple pathogens during a single blood meal, sensitive and specific molecular detection methods are essential for early diagnosis. Conventional nested PCR is commonly used but is time-consuming and prone to cross-contamination due to multiple amplification steps. This study evaluated a dual-target one-step nested PCR assay developed as a rapid alternative to conventional nested PCR for SFG Rickettsia detection. Gene-specific primers targeting the Rickettsia outer membrane protein A (ompA) gene and the 17 kDa antigen gene were designed, with a Plasmodium falciparum thrombospondin-related anonymous protein (TRAP) gene included as an internal amplification control. Primer specificity was verified in silico, and assay performance was assessed using synthetic DNA templates. The dual-target one-step nested PCR achieved detection limits of 10 gene copies for the 17 kDa gene and 1000 gene copies for ompA, compared with 10 and 100,000 gene copies, respectively, using conventional nested PCR. Screening of 184 tick specimens identified one positive sample (0.54%) for the Rickettsia 17 kDa gene. Overall, the dual-target one-step nested PCR demonstrated comparable sensitivity to conventional nested PCR while reducing assay time and contamination risk, indicating its potential as a reliable tool for SFG Rickettsia detection. Full article

Background: Rickettsial diseases are endemic in southeastern Mexico, yet their potential subclinical cardiac effects remain poorly understood. Although severe spotted fever and typhus group infections may cause myocarditis and arrhythmias, limited evidence exists regarding cardiac alterations in individuals previously diagnosed with rickettsiosis who later show Rickettsia spp. IgG seropositivity. Methods: This follow-up observational study was conducted at a tertiary referral hospital in the Yucatan Peninsula. From an initial cohort of 390 patients evaluated for suspected rickettsial disease, 284 were confirmed as IgG-positive during follow-up. Among them, 18 adults who were asymptomatic for acute rickettsiosis at reassessment, but reported mild or nonspecific cardiac symptoms, underwent standardized cardiological evaluation. Procedures included a 12-lead electrocardiogram (ECG), transthoracic echocardiography, and 24 h Holter monitoring. All studies were reviewed independently by two blinded cardiologists with senior adjudication. Results: Global systolic function was preserved in all participants. However, subclinical abnormalities were identified, including right ventricular dilation in 16.7%, clinically relevant QTc prolongation in 22.2%, sinus pauses in 11.1%, reduced heart rate variability in 11.1%, atrial flutter in one patient, and complete left bundle branch block in one patient. QTc prolongation was detected exclusively through Holter monitoring. Conclusions: Adults previously diagnosed with rickettsiosis may exhibit subclinical cardiac involvement despite apparent recovery. Holter monitoring appears more sensitive than ECG for identifying electrical disturbances, warranting larger prospective studies. Full article

Background: Rickettsioses disproportionately affect vulnerable populations and are frequently misdiagnosed as other febrile illnesses in Yucatan, the Mexican state with the greatest diversity of Rickettsia spp. Although significant seroprevalence has been reported in rural communities, the last population-based study was conducted over two decades ago, despite environmental and social changes that have likely increased transmission risk. This study aimed to estimate the seroprevalence of spotted fever group (SFG) and typhus group (TG) of Rickettsia in an endemic area of southeastern Mexico. Methods: A cross-sectional analytical study was conducted among 390 participants. Indirect immunofluorescence was used to detect IgG antibodies against SFG and TG of Rickettsia. Sociodemographic characteristics of participants, along with environmental and community-level variables from their regions of residence, were analyzed. Results: The overall seroprevalence of both Rickettsia groups was 31.2%. Higher maximum temperatures were associated with an increase in Rickettsia seroprevalence (PR = 4.18; 95% CI: 3.40–5.14), while higher population density was associated with a decrease in seroprevalence (PR = 0.97; 95% CI: 0.96–0.98). Conclusions: Rickettsia seroprevalence in Yucatan remains high and is shaped by both environmental and demographic factors. These findings highlight the need to strengthen surveillance and prevention strategies that integrate ecological and social determinants within a One Health framework. Full article

Tick-borne pathogens pose a significant threat to human health. In this study, a multiple droplet digital PCR (ddPCR) assay was developed to detect four tick-borne pathogens: Borrelia burgdorferi sensu lato (Bbsl), Coxiella burnetii (C. burnetii), spotted fever group Rickettsia (SFGR), and Borrelia miyamotoi (B. miyamotoi). Based on the singleplex ddPCR reaction system of Bbsl, the primer probes of the other three species were incorporated to develop a multiplex ddPCR reaction system. The annealing temperature and the final concentration of the primer probes were then optimized for multiplex ddPCR. The multiplex ddPCR assay was assessed for its sensitivity, specificity, repeatability, and ability to detect simulated and actual samples. The developed multiplex ddPCR approach enables the simultaneous detection of Bbsl, C. burnetii, SFGR, and B. miyamotoi. The positive target microtitre clusters are closely grouped and distinctly separated from each other, with the multiplex ddPCR assay demonstrating a dynamic range of five orders of magnitude. The limits of detection (LOD) for the multiplex ddPCR assay were 4 copies/20 µL for Bbsl, 3 copies/20 µL for C. burnetii, 3 copies/20 µL for SFGR, and 2 copies/20 µL for B. miyamotoi. The assay demonstrated high specificity, with no observed cross-reactivity against non-target pathogens. Performance was validated using both spiked samples and field-collected clinical specimens. In the evaluation of 30 ticks and 30 serum samples, the ddPCR method (in both singleplex and multiplex formats) achieved higher positive detection rates for all four target pathogens compared to quantitative real-time PCR (qPCR). In addition, the detection proportions of multiplex and singleplex ddPCR were consistent. Multiplex ddPCR can detect low DNA concentrations in samples and enables the absolute quantification of Bbsl, C. burnetii, SFGR, and B. miyamotoi, providing a novel detection approach for the clinical diagnosis of tick-borne diseases. Full article

Candidatus Rickettsia colombiensis is a new candidate species of Rickettsiae spotted fever group that have been isolated only from ticks. The pathogenicity of Ca. R. colombiensis to human and animals is unknown. This study evaluated the pathogenic potential of Ca. R. colombiensis in Syrian hamsters and assessed the cross-reactivity between Ca. R. colombiensis and other Rickettsia in human and hamster sera. Shell vial technique was employed to isolate Ca. R. colombiensis. Subsequently, five male Syrian hamsters were inoculated intraperitoneally (IP) and five intradermally (ID) with 1 × 10⁶ Vero cells infected with Ca. R. colombiensis. One control hamster was used in each group. The health status was assessed daily, and necropsies were performed. Serum samples were tested by indirect immunofluorescence and tissues were processed by qPCR and histological stains. All Syrian hamsters remained healthy during the trial. No histopathological damages associated with rickettsial infection were observed. No Rickettsial DNA was detected in tissues. Syrian hamsters showed IgG antibody titers ranging from 1:64 to 1:1024. Control hamsters were negative. Regarding human sera, 56% (84/150) had IgG cross-reactivity antibodies against Ca. R. colombiensis. Subsequently, in a selected subset of 30 sera with moderate to high titers, all samples reacted with Ca. R. colombiensis antigen. Under specific conditions of this study, Ca. R. colombiensis did not behave as a highly virulent pathogen in the hamster model, although all infected Syrian hamsters developed IgG antibodies responses. Regarding cross-reactivity, it is possible to serologically diagnose rickettsial infection using Ca. R. colombiensis as an antigen. Full article

Ticks are one of the most important vectors of zoonotic pathogens in Europe, including Rickettsia spp. In Romania, several pathogenic species belonging to the Spotted Fever Group (SFG) transmitted primarily through tick bites have been identified. The aim of the present study was to determine the prevalence of Rickettsia spp. infection in ticks collected from public shelter dogs in Tulcea County, Romania, as an indicator of pathogen circulation within shelter environments and their potential epidemiological relevance. A total of 730 ticks collected between March 2023 and September 2024 from 216 public shelter dogs, belonging to four species (Rhipicephalus sanguineus s.l., Ixodes ricinus, Dermacentor marginatus, and Dermacentor reticulatus), were morphologically identified and pooled by species, sex, and developmental stage resulting in 132 pools. DNA extracted from pools was tested by Real-Time PCR, targeting the gltA gene, specific for Rickettsia spp. Overall, 123/132 (93.2%) pools tested positive for Rickettsia spp. DNA, while the Minimum Infection Rate (MIR) at tick level was 16.8%. High pool positivity rates were consistently observed across all four species: 93.6% positive pools for Rhipicephalus sanguineus s.l. (MIR 15%), 88.2% for Ixodes ricinus (MIR 20.5%), 87.5% for Dermacentor marginatus (MIR 58.3%), and 100% for Dermacentor reticulatus (MIR 21.7%). These findings demonstrate a substantial circulation of Rickettsia spp. in dog-shelter associated ticks, highlighting the role of dogs as sentinel hosts. Continuous molecular surveillance and identifying circulating species is needed for a better determination of the zoonotic risk. Full article

Rickettsia rickettsii is the most virulent agent of the genus Rickettsia that causes one of the most relevant vector-borne diseases in the Americas (RRSF). RRSF manifests with many non-specific acute clinical symptoms complicating its diagnosis and can lead to death if not treated appropriately. RRSF has been reported in Canada, the United States of America, Mexico, Costa Rica, Panama, Colombia, Brazil, and Argentina. In addition to R. rickettsii, mild and severe spotted fever group rickettsioses (SFGR) have been reported in the Americas; however, the true prevalence of these diseases is unknown. In Panama, RRSF have been reported in four of 14 provinces during two outbreak periods: five cases including two fatalities were identified in 1950–1951, and 23 cases including 17 fatalities between 2004 and 2025. This paper presents the clinical characterization of a fatal case of RRSF in Coclé province and a severe case of SFGR in a mountainous area of the Gnäbe Buglé Indigenous Comarca (GBIC). Laboratory confirmation was performed by molecular analysis of tissues obtained from necropsies in the case of RRSF and by immunofluorescence assay (IFA) in the case of SFGR. Furthermore, this paper identifies existing gaps in the initial clinical suspicion and pertinent to SFGR in Panama, which may be applicable to other countries in the region. In the last 21 years, cases have occurred upon contact with ticks in rural areas (13), urban and suburban locations (7), rural woodlands (2), and forests (1). Provinces with more cases are Panamá (7 of 23, 6 died), Coclé (5 of 23, 5 died), Colón (3 of 23, 1 died), Panamá Oeste (1 of 23, 1 died), and GBIC (7 of 23, 4 died), including a cluster of seven cases in 2019. Therefore, Coclé province is considered one of the endemic areas for RRSF in Panama, while the latest cases from the GBIC since 2019 indicate that mountainous areas are an eco-epidemiological scenario to include in the transmission of these diseases. Although this disease has a low prevalence, patients who present symptoms commonly associated with more common diseases such as dengue, other arboviruses, malaria, and leptospirosis, among others, should be included in the diagnostic suspicion. Without diagnostic suspicion and adequate treatment, the patient can die. Full article

The tick Amblyomma sculptum is the vector of the bacterium Rickettsia rickettsii (which causes Brazilian Spotted Fever in humans). It can be found in domestic and wild animals, as well as humans. The objective of this work was to evaluate the efficacy of baits containing fluazuron in the control of A. sculptum in guinea pigs that were artificially infested. The work was conducted in two studies: descriptive pharmacokinetics and efficacy. Descriptive pharmacokinetics was assessed after administering one fluazuron-containing bait per animal (10 mg/kg). To determine the pharmacokinetic profile, blood samples were collected over several days. For the efficacy test, the animals were divided into four groups: a control group (untreated) and three treated groups that received a single dose of 10 mg/kg on days −21 (G1), −14 (G2) and −7 (G3). All animals were infested with A. sculptum larvae on day 0 and recovered on days +4, +5, +6, and +7. Fluazuron plasma concentrations increased rapidly, indicating rapid absorption, and decreased slowly. In all treated groups, engorged larvae with morphological and behavioral changes were observed. Although fluazuron did not show acaricidal efficacy, it was able to interfere with tick molting. Fluazuron was effective in controlling the A. sculptum tick in guinea pigs. Full article

Several diseases caused by tick-borne pathogens, including Lyme borreliosis (LB) and spotted fever group rickettsioses, are endemic in the Balkan Peninsula, positioned between Central Europe and the Middle East. This cross-sectional study aimed to assess serological exposure to Borrelia spp. and spotted fever group Rickettsiae (SFGR) among individuals with recent tick bites and healthy controls in two Balkan countries—Serbia and North Macedonia. Serum samples from 223 participants were tested for anti-Borrelia and anti-SFGR IgG antibodies. SFGR exposure was significantly higher in tick-exposed individuals from Skopje (North Macedonia) compared to those from Novi Sad (Serbia) (30.9% vs. 8.0%; p = 0.003). In contrast, anti-Borrelia IgG was more frequently detected in Novi Sad, though differences did not reach statistical significance. The findings support a north-to-south gradient in Borrelia exposure and a reverse trend for SFGR, consistent with earlier studies and regional tick infection data. Given the high SFGR exposure and limited clinical reporting in North Macedonia, the results highlight the likelihood that tick-borne rickettsioses remain under-recognized. Additionally, Borrelia exposure in North Macedonia warrants further investigation. These findings emphasize the need for enhanced tick-borne disease surveillance, identification of endemic zones, and improved diagnostic and public health infrastructure in both countries. Full article

The Kaliningrad Oblast, located in the westernmost part of Russia and bordering European Union countries, is a popular tourist destination. However, limited research has been conducted on the bacteria found in ticks in this region. We, therefore, investigated the prevalence of certain bacteria, including Borrelia, Rickettsia, Anaplasma, and Ehrlichia, as well as the genospecies of the spotted fever group Rickettsia (SFGR) in Ixodes ricinus and Dermacentor reticulatus tick species. To accomplish this, we employed commercial qPCR for pathogen screening. We identified specific genospecies by sequencing the gltA and ompA gene fragments. In I. ricinus ticks, we found Borrelia burgdorferi sensu lato DNA in 35.6% of samples. We also found Rickettsia helvetica in 17.5% of ticks. Additionally, we detected Borrelia miyamotoi in 1.7% and Anaplasma phagocytophilum in 2.6%, while Ehrlichia chaffeensis/Ehrlichia muris were present in 0.6%. In D. reticulatus ticks, we detected only Rickettsia conorii subsp. raoultii DNA, with a prevalence of 6.1%. These findings demonstrate a substantial risk of Lyme disease and other tick-borne infections from early spring through late autumn, emphasizing the importance of ongoing monitoring for these pathogens in the region. Full article

Introduction: Spotted fever group (SFG) rickettsioses are tick-transmitted infections caused by Gram-negative, obligately intracellular bacteria in the genus Rickettsia. They present as an acute undifferentiated febrile illness, and they are often accompanied by rash and/or eschar. Although the rash of SFG rickettsioses usually consists of macules and papules, some, like in Rickettsia parkeri rickettsiosis, can also manifest with papulovesicular or pustular lesions. Case: We herein present a case of SFG rickettsiosis, due to R. parkeri, that masqueraded as Sweet syndrome (the prototype neutrophilic dermatosis) after the initial results of a shave biopsy. Further investigation of the biopsy specimen by immunohistochemical and PCR analysis would eventually confirm SFG rickettsiosis, with R. parkeri being detected by real-time PCR. Discussion:Rickettsia parkeri is transmitted by the Gulf Coast tick (Amblyomma maculatum) and is an increasingly recognized cause of SFG rickettsiosis in the United States. Rickettsia parkeri should be considered in those with an acute undifferentiated febrile illness with lesions that are pustular or papulovesicular, as prompt recognition and empirical administration of doxycycline results in the rapid resolution of symptoms. Full article

Bats (Chiroptera) are among the most diverse and geographically dispersed mammals. They are of great importance to the ecosystem, as pollinators, seed dispersers and pest controllers, in addition to being hosts to several parasitic arthropods, including ticks, mites, lice, fleas and flies. Their diet includes the tissue and blood or other body fluids of bats. Bats are reservoirs of several disease-causing agents, many of them pathogenic to humans, such as bacteria, as well as protozoa, viruses and fungi. This study was conducted in Monte Negro, Rondônia, Brazil and the occurrence of parasitic arthropods in bats was evaluated, as well as a screening of bacteria that these ectoparasites can carry. Through a total of 69 nocturnal captures, 217 chiropterans were sampled, representing 23 species and six families. A total of 592 specimens of parasitic arthropods (ticks, mites and flies) were collected from these bats (9% dipterans, 59% ticks and 32% mites). Bartonella spp. were found in two species of bat flies (Trichobius joblingi and Strebla mirabilis) in peri-urban and forest areas with an infection rate of 62% and 38%, respectively. We report for the first time in Rondônia the argasid tick Ornithodoros hasei and its infection by a spotted fever group bacterium ‘Candidatus Rickettsia wissemanii’ in a peri-urban area. Full article

This study investigated tick species and spotted fever group rickettsiae (SFGR) infection rates in ticks from yaks in Jiulong County, Sichuan Province, China. Firstly, ticks collected from yaks were meticulously classified through morphological identification. Subsequently, the total DNA of ticks was extracted, and specific partial sequences of their ITS-2 region, as well as the ompA and ompB genes of SFGR, were amplified using PCR. The positive PCR products were sequenced and compared thoroughly against the NCBI database. A phylogenetic analysis was conducted for ITS-2, ompA, and ompB to determine the species of tick and the SFGR. The results revealed that a total of 585 ticks were collected, with the most abundant species being R. microplus, which accounted for 52.65% (308/585) of the total and was followed by I. ovatus (32.99%, 193/585), I. acutitarsus (8.89%, 52/585), and D. everestianus (5.50%, 32/585). Furthermore, SFGR was detected in 63.93% (374/585) of the ticks. Notably, the infection rate of SFGR in semi-agricultural and pastoral areas was significantly higher at 70.60%, compared to 45.10% in pastoral areas (p < 0.01). Overall, this study marks the first investigation into the prevalence of SFGR in Jiulong County and highlights the high infection rate of SFGR in ticks, with R. raoultii being the predominant species. Full article

Ticks and tick-borne pathogens pose a significant threat to human and animal health, yet the diversity and prevalence of tick-borne microorganisms in karst regions remains inadequately explored. In October 2023, a total of 274 Rhipicephalus microplus ticks were collected from livestock in Guizhou Province, which boasts the largest karst area in China. Pathogen identification was subsequently performed using PCR amplification, Sanger sequencing, and phylogenetic analysis. High microbial diversity was noted, with five bacterial species from the order Rickettsiales detected, including those from the genera Rickettsia (family Rickettsiaceae), Anaplasma, and Ehrlichia (family Anaplasmataceae). The overall prevalence of infection with at least one pathogen was remarkably high at 94.5%. The highest positive rate was observed for Candidatus Rickettsia jingxinensis at 90.9%. A novel Ehrlichia species, provisionally designated as Candidatus Ehrlichia carsus, was identified with a positive rate of 16.8%. In addition, Anaplasma marginale, Ehrlchia minasensis and Ehrlichia canis were detected in 15.3%, 4.7% and 1.5%, respectively. The co-infections involving two or three rickettsial species were observed in 34.3% ticks. These findings highlight the high diversity and prevalence of tick-borne rickettsial agents in the karst area, underscoring the need for enhanced surveillance and effective tick control to mitigate disease risks to both humans and livestock. Full article

Rickettsia infection in Haemaphysalis hystricis ticks infesting dogs was first screened in Taiwan by nested-PCR assay targeting the citrate synthase gene (gltA) of Rickettsia. A general infection rate (3.46%) was detected in a total of 1186 examined ticks, and infection rates of 3.20%, 3.6%, and 4.27% were detected in females, males, and nymphs, respectively. The monthly prevalence of Rickettsia infection was observed from March to November, and the highest infection was detected in April (6.92%) followed by a higher infection in July (5.56%), October (4.72%), September (3.57%), and May (3.54%). The prevalence of Rickettsia infection in ticks infesting stray dogs (4.15%) is significantly higher than ticks infesting domestic dogs (1.11%) (chi-square test, p = 0.015). Genetic analysis based on the gltA gene sequences from 13 Taiwan specimens, compared with 13 genospecies of Rickettsia strains documented in GenBank, revealed that the genetic identities of these Taiwan strains were phylogenetically affiliated with the genospecies of the transitional group (R. felis) and the spotted fever group (R. aeschlimannii and R. raoultii) of Rickettsia. This study demonstrates the first molecular screening of Rickettsia spp. in H. hystricis ticks infesting dogs in Taiwan. The human pathogenic strain of R. aeschlimannii was first discovered in H. hystricis ticks infesting dogs. Because dogs serve as companion animals to humans, the presence of various Rickettsia species existing in H. hystricis ticks may pose a potential threat to human health in Taiwan. Full article