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Microorganisms Jul 2022Chiggers are vectors of rickettsial pathogenic bacteria, spp., that cause the human disease, scrub typhus, in the Asian-Pacific area and northern Australia (known as...
Chiggers are vectors of rickettsial pathogenic bacteria, spp., that cause the human disease, scrub typhus, in the Asian-Pacific area and northern Australia (known as the Tsutsugamushi Triangle). More recently, reports of scrub typhus in Africa, southern Chile, and the Middle East have reshaped our understanding of the epidemiology of this disease, indicating it has a broad geographical distribution. Despite the growing number of studies and discoveries of chigger-borne human disease outside of the Tsutsugamushi Triangle, rickettsial pathogens in chigger mites in the US are still undetermined. The aim of our study was to investigate possible DNA in chiggers collected from rodents in North Carolina, USA. Of 46 chiggers tested, 47.8% tested positive for amplicons of the 23S-5S gene, 36.9% tested positive for 17 kDa, and 15.2% tested positive for . Nucleotide sequence analyses of the -specific 23S-5S intergenic spacer (IGS), 17 kDa, and gene fragments indicated that the amplicons from these chiggers were closely related to those in , , , and unidentified species. In this study, we provide the first evidence of infection in chiggers collected from rodents within the continental USA. In North Carolina, a US state with the highest annual cases of spotted fever rickettsioses, these results suggest chigger bites could pose a risk to public health, warranting further study.
PubMed: 35889061
DOI: 10.3390/microorganisms10071342 -
Journal of Vector Borne Diseases 2022Fleas (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... (Review)
Review
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.
Topics: Animals; Cats; Dogs; Flea Infestations; Humans; India; Mice; Plague; Public Health; Rats; Siphonaptera
PubMed: 35708399
DOI: 10.4103/0972-9062.328977 -
PLoS Neglected Tropical Diseases May 2022Murine typhus, which is caused by Rickettsia typhi, has a wide range of clinical manifestations. It has a low mortality rate but may result in meningoencephalitis and...
Murine typhus, which is caused by Rickettsia typhi, has a wide range of clinical manifestations. It has a low mortality rate but may result in meningoencephalitis and interstitial pneumonia in severe cases. Comparisons of complete genome sequences of R. typhi isolates from North Carolina, USA (Wilmington), Myanmar (B9991PP), and Thailand (TH1527) identified only 26 single nucleotide polymorphism (SNP) and 7 insertion-deletion (INDEL) sites in these highly syntenic genomes. Assays were developed to further define the distribution of these variant sites among 15 additional isolates of R. typhi with different histories from Asia, the USA, and Africa. Mismatch amplification mutation assays (MAMA) were validated for 22 SNP sites, while the 7 INDEL sites were analyzed directly on agarose gels. Six SNP types, 9 INDEL types, 11 total types were identified among these 18 isolates. Replicate DNA samples as well as comparisons of isolates with different passage and source histories gave consistent genetic typing profiles. Comparison of the SNP and INDEL markers to R. typhi's nearest neighbor Rickettsia prowazekii demonstrated that the majority of the SNPs represent intra-species variation that arose post divergence of these two species while several INDEL sites also exhibited intraspecies variability among the R. prowazekii genomes that have been completely sequenced. The assays for the presence of these SNP and INDEL sites, particularly the latter, comprise a low technology gel method for consistently distinguishing R. typhi and R. prowazekii as well as for differentiating genetic types of R. typhi.
Topics: Animals; Mice; Rickettsia; Rickettsia prowazekii; Rickettsia typhi; Sequence Analysis, DNA; Thailand; Typhus, Endemic Flea-Borne
PubMed: 35639778
DOI: 10.1371/journal.pntd.0010354 -
BMC Medicine May 2022Persistent fever, defined as fever lasting for 7 days or more at first medical evaluation, has been hardly investigated as a separate clinical entity in the tropics....
BACKGROUND
Persistent fever, defined as fever lasting for 7 days or more at first medical evaluation, has been hardly investigated as a separate clinical entity in the tropics. This study aimed at exploring the frequencies and diagnostic predictors of the ubiquitous priority (i.e., severe and treatable) infections causing persistent fever in the tropics.
METHODS
In six different health settings across four countries in Africa and Asia (Sudan, Democratic Republic of Congo [DRC], Nepal, and Cambodia), consecutive patients aged 5 years or older with persistent fever were prospectively recruited from January 2013 to October 2014. Participants underwent a reference diagnostic workup targeting a pre-established list of 12 epidemiologically relevant priority infections (i.e., malaria, tuberculosis, HIV, enteric fever, leptospirosis, rickettsiosis, brucellosis, melioidosis, relapsing fever, visceral leishmaniasis, human African trypanosomiasis, amebic liver abscess). The likelihood ratios (LRs) of clinical and basic laboratory features were determined by pooling all cases of each identified ubiquitous infection (i.e., found in all countries). In addition, we assessed the diagnostic accuracy of five antibody-based rapid diagnostic tests (RDTs): Typhidot Rapid IgM, Test-it Typhoid IgM Lateral Flow Assay, and SD Bioline Salmonella typhi IgG/IgM for Salmonella Typhi infection, and Test-it Leptospira IgM Lateral Flow Assay and SD Bioline Leptospira IgG/IgM for leptospirosis.
RESULTS
A total of 1922 patients (median age: 35 years; female: 51%) were enrolled (Sudan, n = 667; DRC, n = 300; Nepal, n = 577; Cambodia, n = 378). Ubiquitous priority infections were diagnosed in 452 (23.5%) participants and included malaria 8.0% (n = 154), tuberculosis 6.7% (n = 129), leptospirosis 4.0% (n = 77), rickettsiosis 2.3% (n = 44), enteric fever 1.8% (n = 34), and new HIV diagnosis 0.7% (n = 14). The other priority infections were limited to one or two countries. The only features with a positive LR ≥ 3 were diarrhea for enteric fever and elevated alanine aminotransferase level for enteric fever and rickettsiosis. Sensitivities ranged from 29 to 67% for the three RDTs targeting S. Typhi and were 9% and 16% for the two RDTs targeting leptospirosis. Specificities ranged from 86 to 99% for S. Typhi detecting RDTs and were 96% and 97% for leptospirosis RDTs.
CONCLUSIONS
Leptospirosis, rickettsiosis, and enteric fever accounted each for a substantial proportion of the persistent fever caseload across all tropical areas, in addition to malaria, tuberculosis, and HIV. Very few discriminative features were however identified, and RDTs for leptospirosis and Salmonella Typhi infection performed poorly. Improved field diagnostics are urgently needed for these challenging infections.
TRIAL REGISTRATION
NCT01766830 at ClinicalTrials.gov.
Topics: Adult; Antibodies, Bacterial; Female; HIV Infections; Humans; Immunoglobulin G; Immunoglobulin M; Leptospirosis; Malaria; Male; Prospective Studies; Rickettsia Infections; Sensitivity and Specificity; Typhoid Fever
PubMed: 35491421
DOI: 10.1186/s12916-022-02347-8 -
Socio-ecological determinants of rickettsial seroprevalence in a rural community of Yucatán, Mexico.Infection, Genetics and Evolution :... Aug 2022Rickettsial diseases have seen a re-emergence in the Americas in the last few decades, with concerning morbidity, mortality and economic implications that result from...
Rickettsial diseases have seen a re-emergence in the Americas in the last few decades, with concerning morbidity, mortality and economic implications that result from loss of productivity, income, curbs in liberal trade agreements, and reduction in agricultural practices. The aim of this study is to determine the socioecological determinants and seroprevalence for Rickettsia typhi and Rickettsia rickettsii among residents of Teabo, a rural community of Yucatán, Mexico. Sociodemographic data and serum samples were obtained from 180 consenting participants. Antibody titers for R. typhi and R. rickettsii were determined by indirect immunofluorescence assay (IFA). Participants also submitted tick samples collected from their residential area. We conducted logistic regression models to evaluate the association between exposure variables and seroprevalence. Rhipicephalus sanguineus s.l. (37%; n = 65), and Amblyomma cajennense Fabricius (17%; n = 29) were the predominant tick species in peri-domestic areas. Out of the 180 participants, there was significantly higher seroprevalence of R. typhi (n = 77; 46%) compared to R. rickettsii [n = 27, 15%, (p < 0.05)]. Pearson's chi-square test of independence revealed significant differences in R. rickettsii seroprevalence by gender (X [n = 175, df = 4, (p < 0.001)] = 180.26), level of education, (X [n = 180, df = 4, (p < 0.001)] = 44.0), and by tick species found in residential area, (X [n = 180, df = 4, (p = 0.050)] = 9.48). After adjusting for other variables in a logistic regression model, for each unit increase in the number of dogs present in the residential area, there was a 27% increase in the odds of human seroprevalence for R. typhi IgG (AOR = 1.27, 95% CI: 1.01-1.63). Compared to study participants living in residential areas with a 'low' height of vegetation, those living in residential areas with a 'medium' height of vegetation had 2.5 times greater odds of human seroprevalence for R. typhi IgG (AOR = 2.51, 95% CI: 1.19-5.40). Potentially modifiable existing factors in the peri-domestic area may constitute a high-risk source of seroprevalence for rickettsial antibodies among residents of the rural community of Teabo, Yucatán, Mexico.
Topics: Animals; Dog Diseases; Dogs; Humans; Immunoglobulin G; Mexico; Rhipicephalus sanguineus; Rickettsia; Rural Population; Seroepidemiologic Studies
PubMed: 35490957
DOI: 10.1016/j.meegid.2022.105291 -
PLoS Neglected Tropical Diseases Apr 2022Murine typhus is a flea-borne zoonotic disease with acute febrile illness caused by Rickettsia typhi and is distributed widely throughout the world, particularly in port...
Delayed correlation between the incidence rate of indigenous murine typhus in humans and the seropositive rate of Rickettsia typhi infection in small mammals in Taiwan from 2007-2019.
Murine typhus is a flea-borne zoonotic disease with acute febrile illness caused by Rickettsia typhi and is distributed widely throughout the world, particularly in port cities and coastal regions. We observed that murine typhus was an endemic disease (number of annual indigenous cases = 29.23±8.76) with a low incidence rate (0.13±2.03*10-4 per 100,000 person-years) in Taiwan from 2007-2019. Most (45.79%, 174/380) indigenous infections were reported in May, June, and July. The incidence rates in both May and June were statistically higher than those in other months (p<0.05). Correspondingly, sera collected from small mammals (rodents and shrews) trapped in airports and harbors demonstrated anti-R. typhi antibody responses (seropositive rate = 8.24±0.33%). Interestingly, the ports with the highest seropositivity rates in small mammals are all inside/near the areas with the highest incidence rates of indigenous murine typhus. In addition, incidence rates in humans were positively correlated with the 1-month and 2-month prior seropositive rates in small mammals (R = 0.31 and 0.37, respectively). As early treatment with appropriate antibiotics for murine typhus could effectively shorten the duration of illness and reduce the risk of hospitalization and fatality, flea-related exposure experience should be considered in clinics during peak seasons and the months after a rise in seropositivity rates in small mammals. Surveillance in small mammals might be helpful for the development of real-time reporting or even early reminders for physicians of sporadic murine typhus cases based on the delayed correlation observed in this study.
Topics: Animals; Humans; Incidence; Mice; Rickettsia typhi; Shrews; Siphonaptera; Taiwan; Typhus, Endemic Flea-Borne
PubMed: 35468137
DOI: 10.1371/journal.pntd.0010394 -
The American Journal of Tropical... Apr 2022Scrub typhus group (STG), typhus group (TG), and spotted fever group (SFG) rickettsiae are pathogens distributed worldwide and are important causes of febrile illnesses...
Scrub typhus group (STG), typhus group (TG), and spotted fever group (SFG) rickettsiae are pathogens distributed worldwide and are important causes of febrile illnesses in southeast Asia. The levels of rickettsioses burden and distribution in Thai communities are still unclear. Nonspecific symptoms, limit diagnostic capacity and underdiagnoses contribute to the absence of clarity. The objective of this study was to determine the nationwide IgG seroprevalence of STG, TG, and SFG by ELISA in repository sera from the Royal Thai Army recruits collected during 2007-2008 and 2012 to estimate rickettsiae exposure in young Thai men to better understand rickettsiae exposure distribution in the Thai population. IgG seroprevalence of STG, Orientia tsutsugamushi; TG, Rickettsia typhi; and SFG, R. rickettsii was 12.4%, 6.8%, and 3.3% in 2007-2008 and 31.8%, 4.2%, and 4.5% in 2012, respectively. The STG had the highest seroprevalence of Rickettsia assessed, with the highest regional seroprevalence found in southern Thailand. The STG seroprevalence changed significantly from 2007 to 2008 (P value < 0.05), which corresponds with morbidity rate of scrub typhus from the last decade in Thailand. We were unable to determine the causality for seroprevalence changes between the two periods due to the limitation in sample numbers for intervening years and limited information available for archived specimens. Additional research would be required to determine agency. However, study results do confirm Rickettsia endemicity in Thailand lends weight to reports of increasing STG seroprevalence. It also corroborates the need to raise rickettsial disease awareness and educate the general public in prevention measures.
PubMed: 35378507
DOI: 10.4269/ajtmh.20-1512 -
The Indian Journal of Medical Research Mar 2021
Topics: Animals; Chiroptera; Felis; Humans; Mexico; Rickettsia
PubMed: 35345080
DOI: 10.4103/ijmr.IJMR_1083_19 -
Emerging Infectious Diseases Apr 2022We tested animals from wildlife trade sites in Laos for the presence of zoonotic pathogens. Leptospira spp. were the most frequently detected infectious agents, found in...
We tested animals from wildlife trade sites in Laos for the presence of zoonotic pathogens. Leptospira spp. were the most frequently detected infectious agents, found in 20.1% of animals. Rickettsia typhi and R. felis were also detected. These findings suggest a substantial risk for exposure through handling and consumption of wild animal meat.
Topics: Animals; Animals, Wild; Humans; Laos; Leptospira; Rickettsia typhi; Zoonoses
PubMed: 35318932
DOI: 10.3201/eid2804.210249 -
Tropical Medicine and Infectious Disease Feb 2022The order Rickettsiales includes species that cause a range of human diseases such as human granulocytic anaplasmosis (), human monocytic ehrlichiosis (), scrub typhus... (Review)
Review
The order Rickettsiales includes species that cause a range of human diseases such as human granulocytic anaplasmosis (), human monocytic ehrlichiosis (), scrub typhus (), epidemic typhus (), murine typhus (), Mediterranean spotted fever (), or Rocky Mountain spotted fever (). These diseases are gaining a new momentum given their resurgence patterns and geographical expansion due to the overall rise in temperature and other human-induced pressure, thereby remaining a major public health concern. As obligate intracellular bacteria, Rickettsiales are characterized by their small genome sizes due to reductive evolution. Many pathogens employ moonlighting/multitasking proteins as virulence factors to interfere with multiple cellular processes, in different compartments, at different times during infection, augmenting their virulence. The utilization of this multitasking phenomenon by Rickettsiales as a strategy to maximize the use of their reduced protein repertoire is an emerging theme. Here, we provide an overview of the role of various moonlighting proteins in the pathogenicity of these species. Despite the challenges that lie ahead to determine the multiple potential faces of every single protein in Rickettsiales, the available examples anticipate this multifunctionality as an essential and intrinsic feature of these obligates and should be integrated into available moonlighting repositories.
PubMed: 35202227
DOI: 10.3390/tropicalmed7020032