Pathologic Characterization of Coinfection with Histomonas meleagridis, Marek's Disease Virus, and Subtype J Avian Leukosis Virus in Chickens.

Histomonas meleagridis is a trichomonad protozoan parasite that can cause an important poultry disease known as histomoniasis; Marek's disease virus (MDV) and subtype J avian leukosis virus (ALV-J) usually cause avian oncogenic diseases. Although these diseases have been reported in a single pathogen infection, information about their coinfection is scarce. This study reports a naturally occurring case of coinfection with H. meleagridis, MDV, and ALV-J in a local chicken flock at the age of 150 days. Necropsy revealed necrosis and swelling in the liver and spleen. Histologic analysis showed large areas of mild to severe necrosis of hepatocytes, with numerous intralesional trophozoites of H. meleagridis by H&E and periodic acid-Schiff staining; H&E staining showed pleomorphic and neoplastic lymphoid tumor cells in the liver and myeloid cells with eosinophilic cytoplasmic granules in the spleen. Coexpression of MDV and ALV-J antigens was detected in the liver by fluorescence multiplex immunohistochemistry staining. The 18S rRNA gene of H. meleagridis, meq gene of MDV, and gp85 gene of ALV-J were identified in mixed liver and spleen tissues by PCR and sequencing, respectively.

Reporte de caso­Caracterización patológica de la coinfección con Histomonas meleagridis, el virus de la enfermedad de Marek y el virus de la leucosis aviar subtipo J en pollos Histomonas meleagridis es un parásito protozoario tricomonial que puede causar una enfermedad avícola importante conocida como histomoniasis; El virus de la enfermedad de Marek (MDV) y el virus de la leucosis aviar subtipo J (ALV-J) suelen causar enfermedades oncogénicas aviares. Aunque estas enfermedades se han reportado como infecciones patógenas separadas, la información sobre coinfección es escasa. Este estudio reporta un caso natural de coinfección con H. meleagridis, el virus de la enfermedad de Marek y el virus de la leucosis aviar subtipo J en una parvada de pollos local a la edad de 150 días. La necropsia reveló necrosis e inflamación del hígado y el bazo. El análisis histológico mostró grandes áreas de necrosis de hepatocitos de leve a severa, con numerosos trofozoítos intralesionales de H. meleagridis por tinción de hematoxilina y eosina y por tinción de ácido periódico-Schiff. La tinción de hematoxilina y eosina mostró células linfoides neoplásicas y pleomórficas en el hígado y en el bazo presencia de células mieloides con gránulos citoplásmicos eosinofílicos. La coexpresión de antígenos del virus de Marek y de la leucosis aviar subtipo J se detectó en el hígado mediante tinción inmunohistoquímica de fluorescencia múltiple. El gene de ARNr 18S de H. meleagridis, el gene meq del virus de Marek y el gene gp85 del virus de la leucosis aviar subtipo J se identificaron en tejidos mixtos de hígado y bazo mediante PCR y secuenciación, respectivamente.

Climate change: how it impacts the emergence, transmission, resistance and consequences of viral infections in animals and plants.

The ongoing COVID-19 pandemic has made us wonder what led to its occurrence and what can be done to avoid such events in the future. As we document, one changing circumstance that is resulting in the emergence and changing the expression of viral diseases in both plants and animals is climate change. Of note, the rapidly changing environment and weather conditions such as excessive flooding, droughts, and forest fires have raised concerns about the global ecosystem's security, sustainability, and balance. In this review, we discuss the main consequences of climate change and link these to how they impact the appearance of new viral pathogens, how they may facilitate transmission between usual and novel hosts, and how they may also affect the host's ability to manage the infection. We emphasize how changes in temperature and humidity and other events associated with climate change influence the reservoirs of viral infections, their transmission by insects and other intermediates, their survival outside the host as well the success of infection in plants and animals. We conclude that climate change has mainly detrimental consequences for the emergence, transmission, and outcome of viral infections and plead the case for halting and hopefully reversing this dangerous event.

Preventing the re-establishment of malaria in Sri Lanka amidst the COVID-19 pandemic.

The COVID-19 pandemic has had a considerable impact on other health programmes in countries, including on malaria, and is currently under much discussion. As many countries are accelerating efforts to eliminate malaria or to prevent the re-establishment of malaria from recently eliminated countries, the COVID-19 pandemic has the potential to cause major interruptions to ongoing anti-malaria operations and risk jeopardizing the gains that have been made so far. Sri Lanka, having eliminated malaria in 2012, was certified by the World Health Organization as a malaria-free country in 2016 and now implements a rigorous programme to prevent its re-establishment owing to the high receptivity and vulnerability of the country to malaria. Sri Lanka has also dealt with the COVID-19 epidemic quite successfully limiting the cumulative number of infections and deaths through co-ordinated efforts between the health sector and other relevant sectors, namely the military, the Police Department, Departments of Airport and Aviation and Foreign Affairs, all of which have been deployed for the COVID-19 epidemic under the umbrella of a Presidential Task Force. The relevance of imported infections and the need for a multi-sectoral response are features common to both the control of the COVID-19 epidemic and the Prevention of Re-establishment (POR) programme for malaria. Sri Lanka's malaria POR programme has, therefore, creatively integrated its activities with those of the COVID-19 control programme. Through highly coordinated operations the return to the country of Sri Lankan nationals stranded overseas by the COVID-19 pandemic, many from malaria endemic countries, are being monitored for malaria as well as COVID-19 in an integrated case surveillance system under quarantine conditions, to the success of both programmes. Twenty-three imported malaria cases were detected from February to October through 2773 microscopic blood examinations performed for malaria in quarantine centres, this number being not much different to the incidence of imported malaria during the same period last year. This experience highlights the importance of integrated case surveillance and the need for a highly coordinated multi-sectoral approach in dealing with emerging new infections. It also suggests that synergies between the COVID-19 epidemic control programme and other health programmes may be found and developed to the advantage of both.

Clinical management of sepsis resulting from infections including COVID-19.

Sepsis is an important disorder in intensive care medicine, and the emphasis is not on infections but the imbalance in body reactions and life-threatening organ dysfunction. The infection, the imbalance in the body's reaction, and the deadly organ dysfunction are three aspects of sepsis. Currently, there is still a debate on suitable criteria for the diagnosis of patients with sepsis with continuing changes in the guidelines on sepsis management. Here we summarize recent advances on the definitions, diagnosis, and treatment in the clinical practice of sepsis management in the emergency department. We also highlight future research directions on sepsis. In particular, given the global outbreak of coronavirus disease 2019 (COVID-19), we briefly describe the relationship between COVID-19 and sepsis. How to manage sepsis caused by emerging pathogens such as COVID-19 is a new challenge for care professionals in the emergency department.

COVID-19 en niños y adolescentes: manejo de casos incluido el síndrome inflamatorio multisistémico

COVID-19 en niños y adolescentes: manejo de casos incluido el síndrome inflamatorio multisistémico

Prediction Rule for Scrub Typhus Meningoencephalitis in Children: Emerging Disease in North India.

OBJECTIVES: To evaluate the proportion of scrub typhus meningoencephalitis among children with acute encephalitis syndrome and to outline its differentiating features. To develop a prediction rule for scrub typhus meningoencephalitis. METHODS: A prospective cohort study was conducted at a tertiary care public hospital in Northern India. Consecutive patients of acute encephalitis syndrome who met our inclusion criteria were enrolled over 2 years. Standardized workup including serum IgM against Orientia tsutsugamushi was performed. Clinical and laboratory features were compared between IgM-positive and IgM-negative patients. The area under the receiver operating characteristic curve of the score derived from "independent predictors" was measured. Sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios were calculated at different cut-offs of the score. RESULTS: Scrub typhus IgM enzyme-linked immunosorbent assay was positive in 66/352 patients (18.8%). Longer duration of fever and prodromal stage along with eschar, hepatomegaly, lymphadenopathy, and pneumonia were significantly more prevalent in scrub typhus meningoencephalitis. However, petechiae were frequent in non-scrub typhus patients. Leucocytosis, lymphocytosis, thrombocytopenia, hypoalbuminemia, and elevated levels of serum bilirubin, serum transaminases, and cerebrospinal fluid protein were associated with scrub typhus meningoencephalitis. Logistic regression revealed fever for >8 days, pneumonia, absence of petechiae, cerebrospinal fluid protein >1000 mg/L, and serum glutamic oxaloacetic transaminase >100 IU/L as independent "predictors" of scrub typhus meningoencephalitis. The area under the receiver operating characteristic curve (95% confidence interval) of the prediction score was 0.832 (0.78-0.89). Score at cutoff ≥1 had 91% sensitivity, 96.1% negative predictive value, and at cutoff ≥4 had 99.7% specificity, 88.9% positive predictive value, 83.1% negative predictive value, 40.3 positive likelihood ratio, 0.88 negative likelihood ratio for identifying scrub typhus meningoencephalitis. CONCLUSION: Prediction score may help physicians in peripheral areas to identify and treat scrub typhus meningoencephalitis, an emerging cause of acute encephalitis syndrome in India.

Scrub typhus as a rare cause of acute pyelonephritis: case report.

BACKGROUND: Scrub typhus can present with atypical signs and symptoms such as those of acute kidney injury, gastroenteritis, pneumonitis, and acute respiratory distress syndrome. Meningitis, encephalitis, and hepatic dysfunction have also been reported, particularly in severe cases with multisystem involvement. Scrub typhus has never been reported in the literature to cause urinary tract infections (UTIs) which includes cystitis and pyelonephritis. CASE PRESENTATION: A 45-year old male presenting to the outpatient unit with fever, right flank pain, and burning micturition for three days was initially treated for UTI. However, he returned to the hospital on the fourth day of illness with persistent symptoms. He was hospitalized, with intravenous (IV) ceftriaxone. Computerized tomography scan of his abdomen-pelvis showed features of acute pyelonephritis, so his antibiotics were upgraded to meropenem and teicoplanin. Despite this, the patient's condition deteriorated. Laboratory investigations showed multisystem involvement: decreasing platelets, raised creatinine, and deranged liver panel. As Kathmandu was hit by dengue epidemic during the patient's hospitalization, on the seventh day of his illness, blood samples were sent for tropical fever investigation. All tests came out negative except for scrub typhus-IgM antibodies positive on rapid diagnostic test. The patient's symptoms subsided after 48 h of starting doxycycline and he became fully asymptomatic four days later. Fever did not recur even after discontinuing other IV antibiotics, favoring scrub typhus disease rather than systemic bacterial sepsis. CONCLUSIONS: Scrub typhus is an emerging infectious disease of Nepal. Therefore, every unexplained fever cases (irrespective of clinical presentation) should be evaluated for potential Rickettsiosis. Moreover, for cases with acute pyelonephritis, atypical causative agents should be investigated, for example scrub typhus in this case.

A new coronavirus associated with human respiratory disease in China.

Emerging infectious diseases, such as severe acute respiratory syndrome (SARS) and Zika virus disease, present a major threat to public health1-3. Despite intense research efforts, how, when and where new diseases appear are still a source of considerable uncertainty. A severe respiratory disease was recently reported in Wuhan, Hubei province, China. As of 25 January 2020, at least 1,975 cases had been reported since the first patient was hospitalized on 12 December 2019. Epidemiological investigations have suggested that the outbreak was associated with a seafood market in Wuhan. Here we study a single patient who was a worker at the market and who was admitted to the Central Hospital of Wuhan on 26 December 2019 while experiencing a severe respiratory syndrome that included fever, dizziness and a cough. Metagenomic RNA sequencing4 of a sample of bronchoalveolar lavage fluid from the patient identified a new RNA virus strain from the family Coronaviridae, which is designated here 'WH-Human 1' coronavirus (and has also been referred to as '2019-nCoV'). Phylogenetic analysis of the complete viral genome (29,903 nucleotides) revealed that the virus was most closely related (89.1% nucleotide similarity) to a group of SARS-like coronaviruses (genus Betacoronavirus, subgenus Sarbecovirus) that had previously been found in bats in China5. This outbreak highlights the ongoing ability of viral spill-over from animals to cause severe disease in humans.

Factors influencing nurses' intention to care for patients with emerging infectious diseases: Application of the theory of planned behavior.

Emerging infectious diseases have caused many health problems and have been identified as a major health issue worldwide. The aim of this descriptive, cross-sectional survey study was to investigate nursing intention among nurses caring for emerging infectious disease patients in Korea and to describe factors influencing nurses' intention to care by applying the theory of planned behavior. A total of 147 Korean nurses were included and data accrued using an online questionnaire. Among the independent variables, perceived behavioral control, attitudes toward the behavior, and sex significantly influenced nursing intention. These variables explained 55.1% of nursing intention to care for patients with emerging infectious diseases, and perceived behavioral control (confidence or self-efficacy in caring for patients) was the strongest predictor. These findings showed the usefulness of the theory of planned behavior in predicting nurses' intention to care for patients with emerging infectious diseases. Providing an educational program on caring for patients with pandemic diseases would also increase self-confidence and reduce concerns. In addition, institutional support, such as compensation payments and recognition from administrators, would also strengthen positive attitudes among nurses.

Non-typeable Haemophilus influenzae-associated early pregnancy loss: an emerging neonatal and maternal pathogen.

OBJECTIVES: There is increasing evidence indicating an association between invasive non-typeable Haemophilus influenzae (NTHi) infection in pregnancy and early pregnancy loss. As the diagnosis relies on microbiological investigation of post-mortem placental and foetal samples, a significant proportion of NTHi-related pregnancy loss remains unrecognised. To better characterise NTHi in septic abortion, we report NTHi cases associated with early pregnancy loss. METHODS: We reviewed all post-mortems at <24 weeks gestation with histologically proven acute chorioamnionitis on placental histology and enrolled cases with at least one matched foetal and placental sample culture positive for NTHi. The study was approved by the NHS Lothian Caldicott Guardian. RESULTS: In our cohort, invasive NTHi has accounted for 20% of infections associated with early pregnancy loss prior to 24 weeks gestation. All patients were young and healthy pregnant women at < 20 weeks' gestation who presented with abdominal pain, PV bleed /discharge and were septic at the time of presentation. One patient with previous history of miscarriage who presented with cervical incompetence had more severe pathology suggestive of early intrauterine pneumonia. CONCLUSION: The burden of invasive NTHi disease in early pregnancy loss is likely to be much larger than currently recognised. NTHi should be considered in pregnant women presenting with abdominal pain and PV bleed/discharge in whom clinical signs of sepsis are present. Active surveillance should be considered in this patient group including septic abortion to capture the true prevalence of this emerging pathogen to inform preventative and therapeutic approaches.

Persistent Crimean-Congo hemorrhagic fever virus infection in the testes and within granulomas of non-human primates with latent tuberculosis.

Crimean-Congo hemorrhagic fever (CCHF) is the most medically important tick-borne viral disease of humans and tuberculosis is the leading cause of death worldwide by a bacterial pathogen. These two diseases overlap geographically, however, concurrent infection of CCHF virus (CCHFV) with mycobacterial infection has not been assessed nor has the ability of virus to persist and cause long-term sequela in a primate model. In this study, we compared the disease progression of two diverse strains of CCHFV in the recently described cynomolgus macaque model. All animals demonstrated signs of clinical illness, viremia, significant changes in clinical chemistry and hematology values, and serum cytokine profiles consistent with CCHF in humans. The European and Asian CCHFV strains caused very similar disease profiles in monkeys, which demonstrates that medical countermeasures can be evaluated in this animal model against multiple CCHFV strains. We identified evidence of CCHFV persistence in the testes of three male monkeys that survived infection. Furthermore, the histopathology unexpectedly revealed that six additional animals had evidence of a latent mycobacterial infection with granulomatous lesions. Interestingly, CCHFV persisted within the granulomas of two animals. This study is the first to demonstrate the persistence of CCHFV in the testes and within the granulomas of non-human primates with concurrent latent tuberculosis. Our results have important public health implications in overlapping endemic regions for these emerging pathogens.

Fulminant myocarditis associated with severe fever with thrombocytopenia syndrome: a case report.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral infectious disease with high mortality. It causes multiple organ dysfunction; however, myocarditis has never been reported as a complication with SFTS. CASE PRESENTATION: A 62-year-old previously healthy woman developed fever, fatigue, diarrhea, and a mild consciousness disorder. She visited a local clinic, and laboratory data showed leukocytopenia, thrombocytopenia, and elevation of the aspartate aminotransferase level. She was transferred to Kagoshima University Hospital and diagnosed as having SFTS by real-time reverse transcription polymerase chain reaction. Subsequently, her blood pressure gradually decreased despite fluid resuscitation and vasopressor administration. Based on elevated toroponin I levels in serum, a transient diffuse left ventricular hypokinesis and wall thickening in echocardiography, diffuse ST elevation in electrocardiography, and exclusion of other heart diseases, she was diagnosed as having fulminant myocarditis. After hemodynamic support with inotropic agents, she recovered near normal cardiac function. She was discharged to home on day 28. CONCLUSIONS: We report the first case of fulminant myocarditis associated with SFTS.

Familiar barriers still unresolved-a perspective on the Zika virus outbreak research response.

Research is an important component of an effective response to the increasing frequency of widespread infectious disease outbreaks. In turn, the ability to do such studies relies on willingness of partners in different regions to collaborate and the capacity to mount a rapid research response. The EU-funded ZIKAlliance Consortium has initiated a multicountry epidemiological, clinical, and laboratory research agenda to determine the incidence, risk factors, and outcomes of Zika virus infection in pregnant women and their children. We reviewed the timeline of patient cohort initiation in relation to the Zika virus epidemic and mapped key events regarding funding, regulatory approvals, and site preparation during this timeline. We then assessed barriers and delays that the international research team experienced through a systematic telephone interview. We have identified three major bottlenecks in the implementation of a swift response: the absence of a timeline for the funding process, delays in regulatory and ethical approval, and the challenging logistics of laboratory support, including diagnostics. These bottlenecks illustrate the clear and urgent need for implementing a strong and permanent global emerging infectious diseases research capacity that has structured funding, enables long-term partnerships, and develops basic clinical and laboratorial research and a response infrastructure that is ready to deploy.

Endogenous endophthalmitis caused by a multidrug-resistant hypervirulent Klebsiella pneumoniae strain belonging to a novel single locus variant of ST23: first case report in China.

BACKGROUND: Endogenous endophthalmitis caused by hypervirulent Klebsiella pneumoniae (HVKP) is an emerging infectious disease commonly with a devastating visual outcome. Most HVKP strains display a wild-type susceptibility profile to antibiotics. However, reports of antimicrobial-resistant HVKP have increased over time, which poses a serious therapeutic dilemma. CASE PRESENTATION: A 25-year-old man with a liver abscess and poorly controlled diabetes mellitus was admitted for endophthalmitis due to K. pneumoniae. The isolate displayed hypermucoviscosity as determined by a positive string test and exhibited resistance to ceftazidime, piperacillin-tazobactam and amikacin. Whole genome sequencing (WGS) analysis demonstrated the isolate to be a K1-serotype strain and belong to a novel single locus variant of ST23, ST2922. In addition to the virulence genes linked to HVKP, rmpA, magA, iucABCDiutA (aerobactin), ybtAPSTUX (yersiniabactin) and iroBDN (salmochelin), it was found to harbor extended-spectrum ß-lactamase (ESBL) gene (blaCTX-M-14), AmpC ß-lactamase gene (blaDHA), and 16S rRNA methylase gene (armA). CONCLUSIONS: This is the first known case of endogenous endophthalmitis caused by a multidrug-resistant HVKP strain ever reported in China. Early diagnosis and treatment with intravenous and intravitreal injection of carbapenem were essential for a favorable visual outcome.

[Ocular manifestations of emerging arboviruses: Dengue fever, Chikungunya, Zika virus, West Nile virus, and yellow fever (French translation of the article)]. / Manifestations oculaires des arboviroses émergentes : dengue, chikungunya, infection à virus Zika, fièvre du Nil occidental et fièvre jaune.

Arboviruses are viral diseases transmitted by mosquitoes and tics bites. They are a major cause of morbidity and sometimes mortality. Their expansion is constant and due in part to climate change and globalization. Mostly found in tropical regions, arboviruses are sometimes the source of epidemics in Europe. Recently, the Chikungunya virus and the Zika virus were responsible for very large epidemics impacting populations that had never been in contact with those viruses. There are currently no effective antiviral treatments or vaccines. Ocular manifestations due to those infections are thus more frequent and increasingly better described. They are sometimes, as with Zika, complicated by a congenital ocular syndrome. The goal of this review is to describe the ophthalmological manifestations of Dengue fever, Chikungunya virus, Zika virus, West Nile virus, and yellow fever.

Clinical Manifestations and Ophthalmic Outcomes of Ocular Syphilis at a Time of Re-Emergence of the Systemic Infection.

Recent reports from different world regions suggest ocular syphilis is re-emerging, in parallel with an increasing incidence of the systemic infection globally. We conducted a large observational study of 127 persons consecutively treated for ocular syphilis at public medical centers in Brazil over a 2.5-year period ending July 2015. Of 104 individuals serologically tested for human immunodeficiency virus (HIV), 34.6% were positive. Ophthalmological evaluations included measurement of Snellen visual acuity and intraocular pressure, and assessment of inflammation by slit lamp examination and dilated posterior eye examination. Involvements in 214 eyes were anterior (6.1%), intermediate (8.4%), posterior (76.2%) and pan- (8.4%) uveitis, and scleritis (0.9%). Multiple anterior and posterior eye complications were observed, including cataract in the anterior eye (incidence rate, 0.18/eye-year) and epiretinal membrane in the posterior eye (incidence rate, 0.09/eye-year); incidence rates of reduction in best-corrected visual acuity to ≤20/50 and ≤20/200 were 0.10 and 0.06/eye-year, respectively. Rates of complications and visual acuity loss did not differ significantly between HIV- positive and negative individuals. In an era of re-emergence, syphilis has ocular complications that may compromise vision, despite treatment with appropriate anti-microbial drugs.

Parechovirus: an important emerging infection in young infants.

Epidemics of human parechovirus (HPeV) causing disease in young children have occurred every 2 years in Australia since 2013. HPeV genotype 3 caused the epidemic from late 2017 to early 2018. Most HPeV infections cause no or mild symptoms including gastroenteritis or influenza-like illness. Characteristically, young infants present with fever, irritability and on occasions a diffuse rash ("red, hot and angry" babies). Severe disease can manifest as meningoencephalitis, seizures or sepsis-like presentations (including septic shock), or less common presentations including signs of surgical abdomen. Testing for HPeV by specific molecular tests is indicated in children younger than 6 months of age with characteristic presentations without another confirmed diagnosis including febrile illnesses with other suggestive features (eg, rash, seizures), sepsis syndromes (including shock), and suspected meningoencephalitis (which may be detected by magnetic resonance imaging only). There are no effective antiviral therapies. Treatment is primarily supportive, including management of complications. Some infants with severe HPeV infection may have adverse neurodevelopment. Follow-up by a paediatrician is recommended.

Prevalence and risk factors associated with Leishmania infection in Trang Province, southern Thailand.

BACKGROUND: Autochthonous cutaneous and visceral leishmaniasis (VL) caused by Leishmania martiniquensis and Leishmania siamensis have been considered emerging infectious diseases in Thailand. The disease burden is significantly underestimated, especially the prevalence of Leishmania infection among HIV-positive patients. METHODS: A cross-sectional study was conducted to determine the prevalence and risk factors associated with Leishmania infection among patients with HIV/AIDS living in Trang province, southern Thailand, between 2015 and 2016. Antibodies against Leishmania infection were assayed using the direct agglutination test (DAT). DNA of Leishmania was detected by ITS1-PCR using the buffy coat. Species of Leishmania were also identified. RESULTS: Of 724 participants, the prevalence of Leishmania infection was 25.1% (182/724) using either DAT or PCR assays. Seroprevalence of Leishmania infection was 18.5% (134/724), while Leishmania DNA detected by the PCR method was 8.4% (61/724). Of these, 24.9% (180/724) were asymptomatic, whereas 0.3% (2/724) were symptomatic VL and VL/CL (cutaneous leishmaniasis). At least five species were identified: L. siamensis, L. martiniquensis, L. donovani complex, L. lainsoni, and L. major. Multivariate analysis showed that CD4+ levels <500 cells/µL and living in stilt houses were independently associated with Leishmania infection. Those who were PCR positive for Leishmania DNA were significantly associated with a detectable viral load, whereas non-injection drug use (NIDU) and CD4+ levels <500 cells/µL were potential risk factors of Leishmania seropositivity. CONCLUSIONS: A magnitude of the prevalence of underreporting Leishmania infection among Thai patients with HIV was revealed in this study. Effective public health policy to prevent and control disease transmission is urgently needed.

Rickettsiae as Emerging Infectious Agents.

With advances in molecular genetics, more pathogenic rickettsial species have been identified. Pathogenic rickettsiae are transmitted by vectors, such as arthropods, into the patient's skin and then spread into the microvascular endothelial cells. Clinical manifestations are characterized by fever with headache and myalgias, followed by rash 3 to 5 days later. The undifferentiated nature of clinical symptoms, knowledge of the epidemiology, and the patient's history of travel and exposure to arthropod vectors are critical to the empiric administration of antimicrobial therapy. Doxycycline is currently the most effective antibiotic for treatment of all spotted fever group and typhus group rickettsioses.