Newly Recognized Spotted Fever Group Rickettsia as Cause of Severe Rocky Mountain Spotted Fever-Like Illness, Northern California, USA.

The incidence of spotted fever group (SFG) rickettsioses in the United States has tripled since 2010. Rocky Mountain spotted fever, the most severe SFG rickettsiosis, is caused by Rickettsia rickettsii. The lack of species-specific confirmatory testing obfuscates the relative contribution of R. rickettsii and other SFG Rickettsia to this increase. We report a newly recognized rickettsial pathogen, Rickettsia sp. CA6269, as the cause of severe Rocky Mountain spotted fever-like illness in 2 case-patients residing in northern California. Multilocus sequence typing supported the recognition of this pathogen as a novel Rickettsia genotype most closely related to R. rickettsii. Cross-reactivity observed for an established molecular diagnostic test indicated that Rickettsia sp. CA6269 might be misidentified as R. rickettsii. We developed a Rickettsia sp. CA6269-specific real-time PCR to help resolve this diagnostic challenge and better characterize the spectrum of clinical disease and ecologic epidemiology of this pathogen.

Discovery of a novel spotted fever group Rickettsia, "Candidatus Rickettsia kedanie," in unfed larval chigger mites, Leptotrombidium scutellare.

Spotted fever group (SFG) rickettsia, the causative agent of SFG rickettsiosis, is predominantly carried by ticks, whereas Orientia tsutusgamushi, the causative agent of scrub typhus, is primarily transmitted by chigger mites in Japan. In this study, we attempted to isolate intracellular eubacteria from Leptotrombidium scutellare, a major vector of O. tsutsugamushi; moreover, we isolated an SFG rickettsia using a mosquito-derived cell line. Draft genome sequences of this unique isolate, by applying criteria for species delimitation, classified this isolate as a novel strain, proposed as "Rickettsia kedanie." Further genetic analysis identified conserved virulence factors, and the isolate successfully propagated in mammalian cells, suggesting its ability to cause diseases in humans. The presence of SFG rickettsia in unfed larvae implies potential dual-pathogen carriage and reflects a symbiotic relationship similar to that between the mites and O. tsutsugamushi, indicating possibility of its transovarial transmission from female adults. Furthermore, conserved genomic similarity of the novel isolate to known SFG rickettsia suggests potential multiple hosts, including chiggers and ticks. In the natural environment, ticks, chigger mites, and wild animals may carry new isolates, complicating the infection cycle and increasing the transmission risks to humans. This discovery challenges the conventional association of SFG rickettsia with ticks, emphasizing its implications for research and disease control. However, this study was confined to a particular species of chigger mites and geographic area, underscoring the necessity for additional studies to comprehend the ecological dynamics, host interactions, and health implications linked to this newly identified SFG rickettsia.

Distribution of ticks and their possession of spotted fever group Rickettsia in Ibaraki prefecture.

INTRODUCTION: Tick-borne diseases (TBDs) are a growing threat in Japan. However, distribution of ticks and their possession of human pathogens remain poorly understood. METHODS: In the present study, we collected 3477 ticks at 6 remote, woodland sites in Ibaraki prefecture between May 23 and November 4, 2021, and investigated the distribution and the possession of spotted fever group Rickettia (SFGR). RESULTS: The collected ticks included Haemaphysalis flava (78.3 %), Haemaphysalis longicornis (9.0 %), Haemaphysalis hystricis (4.6 %), Ixodes turdus (4.3 %), Amblyomma testudinarium (2.1 %), Haemaphysalis cornigera (0.9 %), Haemaphysalis formosensis (0.9 %), Haemaphysalis megaspinosa (0.2 %), Ixodes ovatus (0.1 %), Ixodes nipponensis (0.09 %), and Ixodes columnae (0.03 %). Of 2160 DNA samples extracted from the ticks, the gltA gene and the 17-kDa antigen gene of SFGR were detected in 67 samples. Among 1682 samples from adult and nymph ticks, the positive rate of SFGR was 2.7 %. Sequence analyses of the partial 17-kDa antigen gene demonstrated that the detected SFGR were classified into 8 groups (G1 to G8). The sequences of G2, G4, G5, G6, and G7 were either identical to or differed by one base pair from those of Rickettsia asiatica, Rickettsia tamurae, Rickettsia monacensis, Rickettsia canadensis, and Rickettsia felis, respectively. CONCLUSION: The present study revealed a diverse tick fauna in Ibaraki prefecture, including detection of species commonly found in southwestern Japan. Although the prevalence of SFGR in ticks was lower than in previous studies, several SFGR causing human infection may be present.

Single particle cryo-EM analysis of Rickettsia conorii Sca2 reveals a formin-like core.

Spotted fever group Rickettsia undergo actin-based motility inside infected eukaryotic cells using Sca2 (surface cell antigen 2): an âˆ¼ 1800 amino-acid monomeric autotransporter protein that is surface-attached to the bacterium and responsible for the assembly of long unbranched actin tails. Sca2 is the only known functional mimic of eukaryotic formins, yet it shares no sequence similarities to the latter. Using structural and biochemical approaches we have previously shown that Sca2 uses a novel actin assembly mechanism. The first âˆ¼ 400 amino acids fold into helix-loop-helix repeats that form a crescent shape reminiscent of a formin FH2 monomer. Additionally, the N- and C- terminal halves of Sca2 display intramolecular interaction in an end-to-end manner and cooperate for actin assembly, mimicking a formin FH2 dimer. Towards a better structural understanding of this mechanism, we performed single-particle cryo-electron microscopy analysis of Sca2. While high-resolution structural details remain elusive, our model confirms the presence of a formin-like core: Sca2 indeed forms a doughnut shape, similar in diameter to a formin FH2 dimer and can accommodate two actin subunits. Extra electron density, thought to be contributed by the C-terminal repeat domain (CRD), covering one side is also observed. This structural analysis allows us to propose an updated model where nucleation proceeds by encircling two actin subunits, and elongation proceeds either by a formin-like mechanism that necessitates conformational changes in the observed Sca2 model, or via an insertional mechanism akin to that observed in the ParMRC system.

Spotted fever rickettsia-induced microvascular endothelial barrier dysfunction is delayed by the calcium channel blocker benidipine.

The tick-borne bacterium Rickettsia parkeri is an obligate intracellular pathogen that belongs to spotted fever group rickettsia (SFGR). The SFG pathogens are characterized by their ability to infect and rapidly proliferate inside host vascular endothelial cells that eventually result in impairment of vascular endothelium barrier functions. Benidipine, a wide range dihydropyridine calcium channel blocker, is used to prevent and treat cardiovascular diseases. In this study, we tested whether benidipine has protective effects against rickettsia-induced microvascular endothelial cell barrier dysfunction in vitro. We utilized an in vitro vascular model consisting of transformed human brain microvascular endothelial cells (tHBMECs) and continuously monitored transendothelial electric resistance (TEER) across the cell monolayer. We found that during the late stages of infection when we observed TEER decrease and when there was a gradual increase of the cytoplasmic [Ca2+], benidipine prevented these rickettsia-induced effects. In contrast, nifedipine, another cardiovascular dihydropyridine channel blocker specific for L-type Ca2+ channels, did not prevent R. parkeri-induced drop of TEER. Additionally, neither drug was bactericidal. These data suggest that growth of R. parkeri inside endothelial cells is associated with impairment of endothelial cell monolayer integrity due to Ca2+ flooding through specific, benidipine-sensitive T- or N/Q-type Ca2+ channels but not through nifedipine-sensitive L-type Ca2+ channels. Further study will be required to discern the exact nature of the Ca2+ channels and Ca2+ transporting system(s) involved, any contributions of the pathogen toward this process, as well as the suitability of benidipine and new dihydropyridine derivatives as complimentary therapeutic drugs against Rickettsia-induced vascular failure.

Mononucleosis-like illnesses due to co-infection with severe fever with thrombocytopenia syndrome virus and spotted fever group rickettsia:a case report.

BACKGROUND: We report a mononucleosis-like illnesses case due to co-infection with severe fever with thrombocytopenia syndrome virus (SFTSV) and spotted fever group rickettsia (SFGR), which to the best of our knowledge, has never been reported . CASE PRESENTATION: A 64-year-old male with an 11-day history of fever, sore throat, malaise, nausea, and non-pruritic rash was admitted to our emergency department. Prior to admission, he was bitten by ticks. Laboratory tests revealed a white blood cell count of 24,460 cells/µL with 25% atypical lymphocytes and 20% mononucleosis, thrombocytopenia. Test results were positive for SFTSV RNA, SFTSV-specific IgM antibody, and SFGR-specific IgM antibody. He was diagnosed with mononucleosis-like illnesses due to co-infection with SFTSV and SFGR. After administration of doxycycline, he recovered completely. CONCLUSIONS: The clinical presentation may be atypical in co-infection with SFTSV and SFGR. This finding highlighted the importance of considering SFGR infection, as well as a SFSTV and SFGR co-infection for the differential diagnosis of patients bitten by ticks in SFTSV-endemic areas.

Novel Rickettsia Species Infecting Dogs, United States.

In 2018 and 2019, spotted fever was suspected in 3 dogs in 3 US states. The dogs had fever and hematological abnormalities; blood samples were Rickettsia seroreactive. Identical Rickettsia DNA sequences were amplified from the samples. Multilocus phylogenetic analysis showed the dogs were infected with a novel Rickettsia species related to human Rickettsia pathogens.

Probable African Tick Bite Fever in the United States.

African tick bite fever (ATBF) is a tick-borne rickettsial disease most often observed in North American and European tourists returning home from the southern portion of Africa. Ticks infected with Rickettsia africae transmit this parasitic bacterium to humans, who subsequently develop an influenza-like illness, one or more inoculation eschars, and in some cases, a cutaneous rash. Because ATBF often presents with non-specific symptoms that suggest other infectious diseases, establishing the diagnosis may be difficult. Confirmatory assays, including serology and nucleic acid amplification, may take weeks to return and cannot help with acute treatment decisions. We present a case of a previously healthy 60-year-old woman who developed an illness strongly suggestive of ATBF after a missionary trip to Zimbabwe and discuss the disease's diagnostic challenges. Our paper also reviews the epidemiology of this disease and the currently available diagnostic laboratory tests and recommended treatment options.

Molecular identification of spotted fever group Rickettsia in ticks collected from dogs and small ruminants in Greece.

Spotted fever group (SFG) Rickettsia are zoonotic and emerging pathogens with considerable impact in public and animal health. Greece is an endemic country of diseases caused by SFG Rickettsia. This work aims to evaluate the prevalence of SFG Rickettsia in ticks collected from domestic hosts including sheep, goats and dogs. Several genetic markers for bacterial genes, such as 16S rRNA, ompA, ompB, atpA, gltA, recA, dnaA and dnaK, were amplified and sequenced to accurately classified the rickettsial pathogens in the ticks. Taxonomy and species classification of the Rickettsia was achieved by combining phylogenetic and in silico digestion analysis of the gene sequences obtained. A total of 187 ticks were collected and classified at the species level as Ixodes gibosus, Dermacentor marginatus, Haemaphysalis parva, H. sulcata, H. punctata, Hyalomma scavatum, Rhipicephalus sanguineus, R. bursa and Rhipicephalus sp. The results showed that 7.5% of ticks were infected with at least one SFG Rickettsia including R. massiliae (n = 3), R. slovaca (n = 5), R. raoultii (n = 1) and R. hoogstraalii (n = 5), collected from sheep (n = 4), goats (n = 5) and dogs (n = 3). Molecular analysis revealed the presence of novel genetic variants of R. hoogstraalii (in H. sulcata and H. parva from goat and sheep) and R. raoultii (in D. marginatus from goat). These results proof the presence of SFG Rickettsia in domestic hosts in Greece, and support the need for continued monitoring, surveillance and further analyses of other hosts and study areas.

[Investigation and research on ticks carrying spotted fever group rickettsia in the border area of Tumen River Basin].

Objective: To understand the situation and genotype distribution of spotted fever group rickettsia (SFGR) in the border area of Tumen River Basin in free ticks in Yanbian Korean Autonomous Prefecture (Yanbian Prefecture), Jilin Province. Methods: From April to September, 2017, ticks were collected using flagging method from Hunchun, Tumen, Helong and Longjing cities in the Tumen River basin of Yanbian Prefecture. Outer membrane protein A (ompA) was detected by Polymerase Chain Reaction (PCR), then, the species were identified by gene sequencing and analyzed systematically. The positive rate of pools and MIR(minimum infection rate per 100 ticks,MIR) of SFGR were calculated, and the difference of positive rate of pools among ticks with different characteristics was compared by Chi-square test. Results: A total of 3 079 ticks were collected and divided into 536 pools. The positive rate of pools of SFGR nucleic acid was 39.7% (213 pools). The MIR of SFGR was 6.9%.The positive rate of pools of SFGR in Dermacentor silvarum, Haemaphysalis concinna, Haemaphysalis japonica, Haemaphysalis longicornis and Ixodes persulcatus were 80.4% (41/51), 14.0% (25/179), 20.2% (18/89), 78.9% (101/128) and 25.9% (21/81), and the difference was statistically significant (P<0.001). There was statistical difference in the positive rate of pools of SFGR in developmental stages of ticks (P<0.001); the positive rate of pools of female adults, male adults, nymph and larvae were 36.4% (95/261), 34.2% (67/196), 56.3% (40/71) and 7/8, and the MIR was 7.9%, 7.7%, 4.9% and 3.5%. The five genotype was detected which was Candidatus Rickettsia longicornii, Rickettsia raoultii, Rickettsia heilongjiangensis, Candidatus Rickettsia tarasevichiae,Rickettsia monacensis and have 98%-100% homology with known gene sequences. Candidatus Rickettsia longicornii, Rickettsia raoultii, Rickettsia heilongjiangensis and Candidatus Rickettsia tarasevichiae showed close evolutionary relationship with known specie (have 98%-100% homology with known gene sequences); Rickettsia monacensis showed Far from evolutionary relationship with known species (have 98% homology with known gene sequences). Conclusion: SFGR infection of ticks is common in the border areas of the Tumen River Basin. There was high diversity in SFGR species and tick species in the areas surveyed.

First isolation of Rickettsia monacensis from a patient in South Korea.

A Rickettsia sp. was isolated from the blood of a patient with an acute febrile illness using the shell vial technique; the isolate was named CN45Kr and was identified by molecular assay as Rickettsia monacensis, which was first recognized as a pathogen in Spain. Sequencing analysis showed that the gltA sequence of the isolate was identical to that of Rickettsia sp. IRS3. The ompA-5mp fragment sequence showed 100% identity to those of R. monacensis and Rickettsia sp. In56 and ompA-3pA In56 and 100% identity to that of Rickettsia sp. IRS3. The ompB sequence was found to have 99.9% similarity to that of R. monacensis IrR/Munich. This study confirms the pathogenicity of this agent and provides additional information about its geographic distribution.

Q Fever, Scrub Typhus, and Rickettsial Diseases in Children, Kenya, 2011-2012.

To increase knowledge of undifferentiated fevers in Kenya, we tested paired serum samples from febrile children in western Kenya for antibodies against pathogens increasingly recognized to cause febrile illness in Africa. Of patients assessed, 8.9%, 22.4%, 1.1%, and 3.6% had enhanced seroreactivity to Coxiella burnetii, spotted fever group rickettsiae, typhus group rickettsiae, and scrub typhus group orientiae, respectively.

Human spotted fever group Rickettsia seroprevalence and associated epidemiologic factors among diverse, marginalized populations in South Carolina.

Illness caused by spotted fever group Rickettsia (SFGR) is increasing nationally, with affluent, white residents most likely to be diagnosed. The common under-representativeness of marginalized populations in research studies and these vulnerable populations' health inequities make veritable epidemiologic risk factor profiling challenging, which inhibits equitable public health intervention. The current study leveraged 749 banked sera and associated surveys from a cross-sectional minority-represented COVID-19 study to perform an SFGR seroprevalence investigation. SFGR titers (1:64, 1:128, 1:256, 1:512, and 1:1024) were measured using commercially available indirect fluorescent antibody slides-SFGR positive cases were defined as titers ≥1:128. Multivariable logistic regression and Getis-Ord-Gi* hotspot analyses were used to identify seropositivity-associated factors and determine seropositive clusters. Among a mostly minority and lower socioeconomic population, a 3.4 % SFGR seropositivity was noted at the ≥1:128 titer level. Male gender (Odds Ratio (OR): 3.20; adjusted Odds Ratio (aOR)s: 3.73), age (aOR: 1.05), any frequency of tick bite (OR: 2.29), and spending time working outdoors (OR: 5.05) were associated with SFGR IgG seropositivity. Moreover, the geospatial analysis showed clusters of seropositivity in areas where previous case reports occurred, suggesting potential endemic foci.

Spotted Fever Group Rickettsia spp. Molecular and Serological Evidence among Colombian Vectors and Animal Hosts: A Historical Review.

Spotted fever group Rickettsia spp. (SFGR) are a large group of tick-borne bacteria causing important emerging and re-emerging diseases that affect animals and humans. While SFGR are found worldwide, a lack of surveillance and misdiagnosis particularly affect South American countries. Colombia is a high burdened country in South America, yet rickettsioses are not deemed a nationally reportable condition limiting disease-specific public health resources. As mortality rates are high for one Rickettsia pathogen species, there is a great need to better understand the epidemiological and ecological factors that increase SFGR transmission risk regionally. This literature review provides an overview of Colombia-based SFGR studies connecting knowledge about both vectors and hosts.

Surveillance of tick-borne bacteria infection in ticks and forestry populations in Inner Mongolia, China.

Ticks are one of the most important vectors that can transmit pathogens to animals and human beings. This study investigated the dominant tick-borne bacteria carried by ticks and tick-borne infections in forestry populations in Arxan, Inner Mongolia, China. Ticks were collected by flagging from May 2020 to May 2021, and blood samples were collected from individuals at high risk of acquiring tick-borne diseases from March 2022 to August 2023. The pooled DNA samples of ticks were analyzed to reveal the presence of tick-borne bacteria using high-throughput sequencing of the 16S rDNA V3-V4 region, and species-specific polymerase chain reaction (PCR) related to sequencing was performed to confirm the presence of pathogenic bacteria in individual ticks and human blood samples. All sera samples were examined for anti-SFGR using ELISA and anti-B. burgdorferi using IFA and WB. A total of 295 ticks (282 Ixodes persulcatus and 13 Dermacentor silvarum) and 245 human blood samples were collected. Rickettsia, Anaplasma, Borrelia miyamotoi, and Coxiella endosymbiont were identified in I. persulcatus by high-throughput sequencing, while Candidatus R. tarasevichiae (89.00%, 89/100), B. garinii (17.00%, 17/100), B. afzelii (7.00%, 7/100), and B. miyamotoi (7.00%, 7/100) were detected in I. persulcatus, as well the dual co-infection with Candidatus R. tarasevichiae and B. garinii were detected in 13.00% (13/100) of I. persulcatus. Of the 245 individuals, B. garinii (4.90%, 12/245), R. slovaca (0.82%, 2/245), and C. burnetii (0.41%, 1/245) were detected by PCR, and the sequences of the target genes of B. garinii detected in humans were identical to those detected in I. persulcatus. The seroprevalence of anti-SFGR and anti-B. burgdorferi was 5.71% and 13.47%, respectively. This study demonstrated that Candidatus R. tarasevichiae and B. garinii were the dominant tick-borne bacteria in I. persulcatus from Arxan, and that dual co-infection with Candidatus R. tarasevichiae and B. garinii was frequent. This is the first time that B. miyamotoi has been identified in ticks from Arxan and R. solvaca has been detected in humans from Inner Mongolia. More importantly, this study demonstrated the transmission of B. garinii from ticks to humans in Arxan, suggesting that long-term monitoring of tick-borne pathogens in ticks and humans is important for the prevention and control of tick-borne diseases.

A mutation associated with resistance to synthetic pyrethroids is widespread in US populations of the tropical lineage of Rhipicephalus sanguineus s.l.

The brown dog tick, Rhipicephalus sanguineus sensu lato (s.l.), is an important vector for Rickettsia rickettsii, causative agent of Rocky Mountain spotted fever. Current public health prevention and control efforts to protect people involve preventing tick infestations on domestic animals and in and around houses. Primary prevention tools rely on acaricides, often synthetic pyrethroids (SPs); resistance to this chemical class is widespread in ticks and other arthropods. Rhipicephalus sanguineus s.l. is a complex that likely contains multiple unique species and although the distribution of this complex is global, there are differences in morphology, ecology, and perhaps vector competence among these major lineages. Two major lineages within Rh. sanguineus s.l., commonly referred to as temperate and tropical, have been documented from multiple locations in North America, but are thought to occupy different ecological niches. To evaluate potential acaricide resistance and better define the distributions of the tropical and temperate lineages throughout the US and in northern Mexico, we employed a highly multiplexed amplicon sequencing approach to characterize sequence diversity at: 1) three loci within the voltage-gated sodium channel (VGSC) gene, which contains numerous genetic mutations associated with resistance to SPs; 2) a region of the gamma-aminobutyric acid-gated chloride channel gene (GABA-Cl) containing several mutations associated with dieldrin/fipronil resistance in other species; and 3) three mitochondrial genes (COI, 12S, and 16S). We utilized a geographically diverse set of Rh sanguineus s.l. collected from domestic pets in the US in 2013 and a smaller set of ticks collected from canines in Baja California, Mexico in 2021. We determined that a single nucleotide polymorphism (T2134C) in domain III segment 6 of the VGSC, which has previously been associated with SP resistance in Rh. sanguineus s.l., was widespread and abundant in tropical lineage ticks (>50 %) but absent from the temperate lineage, suggesting that resistance to SPs may be common in the tropical lineage. We found evidence of multiple copies of GABA-Cl in ticks from both lineages, with some copies containing mutations associated with fipronil resistance in other species, but the effects of these patterns on fipronil resistance in Rh. sanguineus s.l. are currently unknown. The tropical lineage was abundant and geographically widespread, accounting for 79 % of analyzed ticks and present at 13/14 collection sites. The temperate and tropical lineages co-occurred in four US states, and as far north as New York. None of the ticks we examined were positive for Rickettsia rickettsii or Rickettsia massiliae.

Emerging tick-borne spotted fever group rickettsioses in the Balkans.

The impact of tick-borne pathogens (TBPs) on human health has increased in the last decades, since the incidence of emerging and re-emerging infectious and zoonotic tick-borne diseases has increased worldwide. Tick-borne rickettsiae of the Spotted Fever group (SFGR) are considered as emerging pathogens that can infect humans and cause a variety of non-specific clinical symptoms. Here, we report nine cases of atypical tick-borne diseases (9/460; 1.95%) that occurred over a period of four months (from 15 April 2021 to 16 August 2021) in Serbia, from which five cases were classified as confirmed SFGR infection, two cases as probable SFGR infection and two cases as suspected SFGR infection. Within cases of confirmed SFGR infection, R. helvetica was detected as the causative agent in two cases. The most common clinical finding was non-expanding persistent circular redness, followed by eschar and enlargement of regional lymph nodes, and pain at lesion site. Rickettsia outer membrane protein B (ompB) and citrate synthase (gltA) gene fragments were amplified from clinical samples and ticks attached to patients and IgG reacting with Rickettsia conorii antigen were detected in sera samples of patients, which are highly suggestive of exposure to SFGR. Surveillance and monitoring of rickettsial diseases in Serbia should continue and extended to new areas due to the increasing trend of clinical infections caused by SFGR in the country.

High Prevalence of Rickettsia raoultii Found in Dermacentor Ticks Collected in Barnaul, Altai Krai, Western Siberia.

The prevalence of the tick-borne spotted fever group rickettsioses pathogens in ticks collected in Barnaul, the administrative center of Altai Krai, Western Siberia, was studied. The causative agent of tick-borne lymphadenopathy (TIBOLA) Rickettsia raoultii was revealed to be present in 61.9% of the samples from Dermacentor ticks. Moreover, Rickettsia helvetica has been identified in 5.1% of Ixodes ticks.

Seasonality of Amblyomma americanum (Acari: Ixodidae) Activity and Prevalence of Infection with Tick-Borne Disease Agents in North Central Oklahoma.

Background: Amblyomma americanum is the most common tick infesting both animals and humans in the southern United States and transmits a variety of zoonotic agents. The rise in tick-borne diseases (TBD) globally imparts a need for more active surveillance of tick populations to accurately quantify prevalence and risk of tick-borne infectious organisms. To better understand TBD risk in north central Oklahoma, this study aimed to describe the current seasonal activity of A. americanum in this region and investigate the seasonality of tick-borne infectious agents. Materials and Methods: Tick collections were performed twice a month for a duration of 2 years at a field site in Payne County, Oklahoma. Total nucleic acid was extracted from a subset of adult A. americanum and tested for Rickettsia spp., Ehrlichia spp., and Borrelia spp. using established PCR protocols. Results: Peak activity times for each life stage were observed, with adults primarily active 1 month earlier than historical seasonal trends describe, and male A. americanum active earlier in the year than female A. americanum. Rickettsia spp., Ehrlichia chaffeensis, Ehrlichia ewingii, and Borrelia lonestari were found in 26.4%, 6.1%, 2.5%, and 1.1% of adult A. americanum, respectively. No seasonal trend in spotted fever group Rickettsia spp. (SFGR) was observed in peak activity months. Conclusions: This study found an apparently shifting phenology for A. americanum adults in Oklahoma. While these results did not show a trend in SFGR, further investigation is needed to better understand the potential seasonality of infection prevalence within A. americanum across the expanding range of this vector, especially considering the extended activity of males in winter months.

Serological profile of patients suspected with non-scrub typhus rickettsioses.

BACKGROUND: Rickettsial pathogens are Gram-negative, obligate intracellular bacteria. They are transmitted by arthropods and are responsible for a wide variety of disease, from minor to life-threatening, which have a global effect on human health. Limited data are available on the prevalence of rickettsial diseases from India, and the disease epidemiology is not fully described. This study aimed to diagnose non-scrub typhus rickettsioses including spotted fever and typhus group of Rickettsia in clinically suspected patients by using standard serological tests and recognition of common epidemiological conditions and clinical manifestations. METHODS: During the study period, a total of 700 patients of all ages with acute febrile illness were enrolled. Patients were screened for rickettsial infection using IgM Enzyme-linked immunosorbent assay (ELISA) and Immunofluorescence assay (IFA) was performed to confirm the ELISA positive results. The relevant demographic, clinical, and laboratory details of patients were documented and analyzed. RESULTS: Of 700 samples tested, 141 (20.2%) were found to be positive for IgM antibodies against rickettsioses using ELISA and IFA. SFGR was positive in 15 (2.2%), TGR was positive in 112 (16%) and 14 (2%) samples were positive for both groups. 20 (14.2%) patients required admission to the intensive care unit (ICU), and 24 (17%) in-hospital deaths occurred. CONCLUSIONS: The prevalence of rickettsioses in India appears to be underestimated; therefore, increased awareness and improved diagnostic testing could facilitate early detection of cases, pathogen-targeted appropriate treatment, and improved outcomes for patients. Despite the fact that Rickettsiae can be isolated or detected using molecular techniques in clinical specimens, serology still remains the most commonly used diagnostic method for rickettsioses around the world. Our study helps bridge the gap of limited data on Rickettsia in north India and could be useful for future epidemiological investigation of rickettsial diseases and outbreaks.