Molecular Detection and Characterization of Rickettsia asembonensis in Human Blood, Zambia.

Rickettsia asembonensis is a flea-related Rickettsia with unknown pathogenicity to humans. We detected R. asembonensis DNA in 2 of 1,153 human blood samples in Zambia. Our findings suggest the possibility of R. asembonensis infection in humans despite its unknown pathogenicity.

Functional Characterization of Multiple Ehrlichia chaffeensis Sodium (Cation)/Proton Antiporter Genes Involved in the Bacterial pH Homeostasis.

Ehrlichia chaffeensis causes human monocytic ehrlichiosis. Little is known about how this and other related tick-borne rickettsia pathogens maintain pH homeostasis in acidified phagosomes and the extracellular milieu. The membrane-bound sodium (cation)/proton antiporters are found in a wide range of organisms aiding pH homeostasis. We recently reported a mutation in an antiporter gene of E. chaffeensis (ECH_0379) which causes bacterial in vivo attenuation. The E. chaffeensis genome contains 10 protein coding sequences encoding for predicted antiporters. We report here that nine of these genes are transcribed during the bacterial growth in macrophages and tick cells. All E. chaffeensis antiporter genes functionally complemented antiporter deficient Escherichia coli. Antiporter activity for all predicted E. chaffeensis genes was observed at pH 5.5, while gene products of ECH_0179 and ECH_0379 were also active at pH 8.0, and ECH_0179 protein was complemented at pH 7.0. The antiporter activity was independently verified for the ECH_0379 protein by proteoliposome diffusion analysis. This is the first description of antiporters in E. chaffeensis and demonstrates that the pathogen contains multiple antiporters with varying biological functions, which are likely important for the pH homeostasis of the pathogen's replicating and infectious forms.

Scrub Typhus and Other Rickettsial Infections.

Scrub typhus and other rickettsial infections contribute to 25 - 50% of acute undifferentiated febrile illnesses in endemic regions. Delayed recognition and therapy increase the morbidity and mortality. The constellation of fever with eschar or rash and multisystem involvement should facilitate the diagnosis and initiation of appropriate therapy. The pathological hallmark of rickettsial infections is endothelial infection and inflammation causing vasculitis. Endothelial inflammation results in microvascular dysfunction and increased vascular permeability. Immune and endothelial activation may worsen microvascular dysfunction, predisposing to multi-organ failure. Serology is the mainstay of diagnosis, although false negatives occur early in the disease. Point-of-care rapid diagnostic tests and molecular techniques, such as quantitative polymerase chain reaction (qPCR), can hasten diagnostic processes. Intravenous doxycycline with a loading dose is the most widely used antibiotic in critically ill patients, with azithromycin as a suitable alternative. Early appropriate treatment and organ support can decrease the duration of illness and be life-saving. How to cite this article: Gunasekaran K, Bal D, Varghese GM, et al. Scrub Typhus and Other Rickettsial Infections. Indian J Crit Care Med 2021;25(Suppl 2):S138-S143.

Laboratory Diagnosis of Tropical Infections.

HIGHLIGHTS: (1) Blood culture is the gold standard for the diagnosis of bacterial infections. (2) Bone marrow culture is more sensitive than blood culture even in patients with enteric fever receiving antibiotics. (3) Microscopic agglutination test is considered the gold standard for diagnosing leptospirosis; however, now IgM ELISA and polymerase chain reaction (PCR) are more frequently used for diagnosis. (4) Tuberculosis is diagnosed with the help of nucleic acid amplification tests like Xpert MTB/RIF Ultra which also detects rifampicin resistance. Other tests include microscopy, Lowenstein-Jensen and mycobacteria growth indicator tube culture, line probe assay. (5) Tropical rickettsial infections are diagnosed by serological reactions (Weil-Felix, ELISA for antibodies) and PCR. (6) For Brucellosis culture from blood, bone marrow or tissue specimens remain the mainstay in diagnosis. (7) Dengue, Zika, Crimean-Congo hemorrhagic fever, Ebola, hantavirus, rabies are diagnosed with reverse transcriptase-polymerase chain reaction. Serological tests like IgM ELISA or paired sera samples for IgG are also used for diagnosis. HOW TO CITE THIS ARTICLE: Basu S, Shetty A. Laboratory Diagnosis of Tropical Infections. Indian J Crit Care Med 2021;25(Suppl 2):S122-S126.

Serologic evidence of rickettsial diseases associated with tick bites in workers of urban veterinary clinics.

BACKGROUND & OBJECTIVES: Rickettsial and other zoonotic diseases are a latent risk for workers of veterinary clinics. The objective of this study was to evaluate the prevalence and the associated risk factors of parasitosis caused by Rhipicephalus sanguineus, and to estimate the seroprevalence of rickettsial diseases in workers of urban veterinary clinics of Juárez city, México. METHODS: The participants of the study were recruited from 63 private veterinary clinics and hospitals. The serological analysis of the blood samples collected was carried out using immunofluorescence assay (IFA). The statistical analysis for prevalences, risk factors, and correlation was performed with the SAS program. RESULTS: In total, 167 veterinary workers were included in the study. The prevalence of tick bites was 40% (67/167), and the risk factors associated with the occurrence of bites included the activities performed in the clinic and the number of labour hours spent per week. About 21% (35/167) of participants were seropositive to R. rickettsii, 28% (47/167) to Ehrlichia chaffeensis, and 24% (40/167) to Anaplasma phagocytophilum. A correlation was observed between: the number of workers in the clinics and the proportion of tick bites (r2 = 0.865); the prevalence of bites and the seropositivity of the participants to at least one pathogen (r2 = 0.924); and the number of bites per individual and infection to pathogens (r2 = 0.838). INTERPRETATION & CONCLUSION: Workers in urban veterinary clinics are highly exposed to tick bites and, therefore, to the diseases they transmit. Hence, it is important to implement prevention measures and perform constant monitoring of these diseases.

Clinical Manifestations and Molecular Diagnosis of Scrub Typhus and Murine Typhus, Vietnam, 2015-2017.

Rickettsioses are endemic to Vietnam; however, only a limited number of clinical studies have been performed on these vectorborne bacteria. We conducted a prospective hospital-based study at 2 national referral hospitals in Hanoi to describe the clinical characteristics of scrub typhus and murine typhus in northern Vietnam and to assess the diagnostic applicability of quantitative real-time PCR assays to diagnose rickettsial diseases. We enrolled 302 patients with acute undifferentiated fever and clinically suspected rickettsiosis during March 2015-March 2017. We used a standardized case report form to collect clinical information and laboratory results at the time of admission and during treatment. We confirmed scrub typhus in 103 (34.1%) patients and murine typhus in 12 (3.3%) patients. These results highlight the need for increased emphasis on training for healthcare providers for earlier recognition, prevention, and treatment of rickettsial diseases in Vietnam.

Risk Factors for Acquiring Scrub Typhus among Children in Deoria and Gorakhpur Districts, Uttar Pradesh, India, 2017.

Scrub typhus is associated with outbreaks of acute encephalitis syndrome in Uttar Pradesh, India. A case-control study indicated that children residing, playing, or visiting fields; living with firewood stored indoors; handling cattle fodder; and practicing open defecation were at increased risk for scrub typhus. Communication messages should focus on changing these behaviors.

Antinuclear antibodies in scrub typhus: Transient occurrence during acute illness.

BACKGROUND & OBJECTIVES: The pathological hallmark of scrub typhus infection is focal or disseminated vasculitis. As with other infections, antinuclear antibodies (ANA) have been previously described in scrub typhus. However, the underlying mechanisms and implications of this immunological phenomenon is not well understood. In the present work it was assessed whether ANA is associated with illness severity and outcomes. METHODS: In this prospective study spanning one year, patients fulfilling the diagnostic criteria for scrub typhus were recruited. Patients with other acute infective febrile illnesses were taken as controls. ANA positivity was compared between the cases and controls. ANA in scrub typhus was assessed for correlation with disease severity, organ dysfunction and outcomes. RESULTS: The cohort comprised of 149 patients (scrub 89; controls 60) with mean age 46.5 (SD=16.9) yr; 48.3% were female. ANA was detected in 48 (53.9%) patients with scrub typhus and 9(15%) controls (p < 0.001). The ANA pattern was predominantly speckled (93.8%) in both scrub typhus patients and controls. In patients with scrub typhus, ANA positivity was associated with increasing APACHE-III score [Odds ratio (OR) 1.01; 95% CI 0.99-1.03; p = 0.09]. On bivariate analysis, ANA tended to be correlated with acute respiratory distress syndrome (OR 2.32; 95% CI 0.98-5.46; p = 0.06), hepatic dysfunction (OR 2.25; 95% CI 0.94-5.39, p = 0.06) and aseptic meningitis (OR 6.83; 95% CI 0.80-58.05, p = 0.08). The presence of these antibodies did not correlate with duration of hospitalization or mortality. Convalescent sera on 31 ANA positive scrub typhus patients demonstrated persistence of ANA in only 5 (16.1%) patients. INTERPRETATION & CONCLUSION: The disappearance of ANA during the convalescent phase suggests that ANA is expressed during the acute phase of scrub typhus infection. Its association with organ dysfunction warrants further study of the mechanisms and impact of autoantibody formation in scrub typhus.

Acute Febrile Illness and Complications Due to Murine Typhus, Texas, USA1,2.

Murine typhus occurs relatively commonly in southern Texas, as well as in California. We reviewed records of 90 adults and children in whom murine typhus was diagnosed during a 3-year period in 2 hospitals in southern Texas, USA. Most patients lacked notable comorbidities; all were immunocompetent. Initial signs and symptoms included fever (99%), malaise (82%), headache (77%), fatigue (70%), myalgias (68%), and rash (39%). Complications, often severe, in 28% of patients included bronchiolitis, pneumonia, meningitis, septic shock, cholecystitis, pancreatitis, myositis, and rhabdomyolysis; the last 3 are previously unreported in murine typhus. Low serum albumin and elevated procalcitonin, consistent with bacterial sepsis, were observed in >70% of cases. Rash was more common in children; thrombocytopenia, hyponatremia, elevated hepatic transaminases, and complications were more frequent in adults. Murine typhus should be considered as a diagnostic possibility in cases of acute febrile illness in southern and even in more northern US states.

Newly Recognized Pediatric Cases of Typhus Group Rickettsiosis, Houston, Texas, USA.

An increase in typhus group rickettsiosis and an expanding geographic range occurred in Texas, USA, over a decade. Because this illness commonly affects children, we retrospectively examined medical records from 2008-2016 at a large Houston-area pediatric hospital and identified 36 cases. The earliest known cases were diagnosed in 2011.

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.

Rickettsia asembonensis Isolated from Four Human Cases with Acute Undifferentiated Febrile Illness in Peru.

Rickettsioses, often underreported, pose public health challenges. Rickettsia asembonensis is a potential emerging pathogen that was previously detected in humans, animals, and a variety of arthropods. While its pathogenicity in humans remains unclear, it poses a potential public health threat. Here, we present an extended epidemiological, diagnostic, and genetic analysis of the information provided in a preliminary report on the investigation of rickettsiae in Peru. In particular, we report the detection of R. asembonensis in blood specimens collected from four human patients with an acute undifferentiated fever of a seven- to nine-day duration, all of whom tested negative for other vector-borne pathogens. Additionally, we describe the replicative capacity of the R. asembonensis isolates in cell cultures.

A Case Series on Spotted Fever and Typhus Fever Seropositivity at National Center for Disease Control and Epidemiological Perspective.

Background: The rickettsioses, except for typhus fever and scrub typhus (ST), were not really recognized as distinct clinical entities until the early 20th century. Only when specific rickettsial serologic testing was introduced in the 1940s could the precise etiologies of various rickettsial diseases (RDs) be determined with certainty. Although ST is a well- recognized zoonotic disease entity, but non-scrub typhus rickettsial infection like spotted fever group and typhus group are not well studied in India and are still underestimated. Methods: We report cases who had shown seropositivity of spotted fever and typhus fever RD in IgM and IgG ELISA whose samples were referred from various hospitals of Delhi/National Capital Region in which clinicians had strong suspicion of rickettsiosis other than ST or Weil-Felix test found positive for any of the OX2, 19, and K antigens. Results: We reported 18 cases of SFG and TGRD with mostly cases presented with fever followed by hepato-intestinal symptoms. Conclusion: The vast variability and nonspecific presentation of rickettsiosis in spotted and typhus fever at times have often made it difficult to diagnose clinically. Prompt antibiotic therapy shortens the course of the disease, lowers the risk of complications, and in turn, reduces morbidity and mortality owing to RDs. There is a distinct need for physicians and health care workers at all levels of care in India to be aware of the clinical features, available diagnostic tests and their interpretation, and the therapy for these infections.

Severe murine typhus complicated by multiple organ dysfunctions: A case report.

Background: Rickettsioses are infectious diseases which are caused by intracellular bacteria which belong to the family Rickettsiaceae. This zoonosis endemically prefers tropical and subtropical regions of which the Mediterranean is included. Murine typhus is a type of rickettsial disease that commonly presents with undulating fever, headache rash, chills, malaise, and myalgias. It can lead to complications such as multi-organ failure and has a lethality rate of <5% in such cases. Case Presentation: A 70-year-old male was hospitalized at the Unit of Infectious Diseases, Mother Teresa Hospital, Tirana, Albania in a comatose condition. He had a seven-day history of fever up to 39-40°C, headache, fatigue, anorexia, vomiting, cough, and myalgia. He was a farmer and had contact with animals. Upon admission, he had scleral hemorrhages, hepatosplenomegaly, jaundice, maculopapular rash over the trunk, abdomen, and palms of his hands as well as severe acidosis, depressed bicarbonate levels, alteration in liver, kidney, and pancreas function tests. He was urgently transferred to the Intensive care unit of the Infectious Diseases Department. He was hemodynamically unstable and was put immediately on vasoactive agents and mechanical ventilation. ELISA Rickettsia typhi IgM resulted positive. Supportive treatment along with antibiotics Levofloxacin and Ceftriaxone was initiated. However, the patient died on the 4th day of hospitalization and the 11th of the disease onset. Conclusion: Murine typhus should be included in the investigation of possible causes when dealing with patients presenting with fever and maculopapular rash complicated by multi-organ failure and coming from a typhus-endemic area, especially in the summer season.

Experimental infection and co-infection with Chinese strains of Ehrlichia canis and Babesia vogeli in intact and splenectomized dogs: Insights on clinical, hematologic and treatment responses.

Animal infection models are crucial for studying various aspects of Ehrlichia canis infections. To understand the pathogenesis of the first Chinese isolate of E. canis and simulate the natural progression of canine ehrlichiosis, we developed a model with 18 Beagle dogs that consisted of E. canis initial infection (days 0-17), treatment with doxycycline or rifampicin (days 18-32), recovery (days 33-66), E. canis reinfection (days 67-91), and Babesia vogeli superinfection (days 92-116). We measured body weight and rectal temperature every other day, drew blood every 4 days for routine hematology and biochemistry tests, and for quantification of E. canis and B. vogeli by quantitative PCRs. In this study, the first isolate of E. canis from China was used to experimentally infect dogs, and the infected dogs exhibited clinical signs of acute severe ehrlichiosis, including high fever, loss of appetite, dehydration, and body weight loss, confirming the similar pathogenicity of E. canis in China as compared to isolates from other regions. Infection with E. canis and B. vogeli led to reduced body weight and fever in dogs. Doxycycline treatment led to absence of E. canis DNA in infected dogs, while rifampicin treatment lowered the blood E. canis copy number up to 1.5 folds. E. canis-free infected dogs after doxycycline treatment were successfully re-infected with E. canis, indicating dogs with antibodies are still at risk of re-infection. Super-infection with B. vogeli resulted in higher fever, more severe anemia, and a reduced number of platelets. Splenectomized dogs showed significantly higher E. canis numbers during recovery and re-infection than intact dogs. The histological changes were observed in brain, lung, kidney, liver and spleen of the infected dogs. The findings in this study provide insights into clinical and hematologic responses, as well as effective treatment options, for dogs infected with the first Chinese isolate of E. canis, and may contribute to our understanding of the diagnosis and prevention of tick-borne diseases in dogs, including canine monocytic ehrlichiosis.

Optical Coherence Tomography and Optical Coherence Tomography Angiography in Neglected Diseases.

A group of self-limiting and frequently neglected diseases exist in the literature like Rickettsial disease, Malaria, Dengue fever, Chikungunya, West Nile virus infection, Rift Valley fever, Bartonellosis, or Lyme disease which are poorly understood due to lack of proper diagnostic testing. Currently, multimodal imaging has become a critical modality in the diagnosis and management of ocular diseases. Optical coherence tomography (OCT) is one such remarkable imaging modality in the field of ophthalmology providing high-resolution, cross-sectional images of the retina and choroid with the recent advances such as enhanced depth imaging and swept source OCT. Additionally, OCT angiography (OCTA) has further revolutionised dynamic imaging of retinal and choroidal vasculature non-invasively. This review article highlights the OCT and OCTA biomarkers in the diagnosis and prognosis of the aforementioned neglected diseases.

Clustered Incidence of Leukocytoclastic Vasculitis and Purpura Fulminans: A Case Series of a Rare Dermatological Manifestation of Rickettsial Disease.

Rickettsiae are a group of eukaryotic obligatory intracellular parasites with ticks and mites as vectors. Rickettsia conorii is the Indian counterpart of Rocky Mountain spotted fever causing the endemic variant - Indian tick typhus. This disease can cause severe illness in adults and children and can be missed despite the availability of serological tests. Initial screening for rickettsial diseases (RD) may include blood workup and a non-specific agglutination test, Weil-Felix (WF). In WF, agglutination against Proteus antigens is analyzed and can show false-negative results within the first week of presentation. Delayed immune reaction in patients with RD in the first week could also be responsible for negative specific IgM serology. The challenge for physicians is to differentiate between the two common diagnoses for fever with rash - viral exanthematous fever and rickettsial fever. By its endothelial cell tropism, RD rarely can lead to purpura fulminans, which is characterized by widespread progressive dermal vascular necrosis and hemorrhage. This case series demonstrates dermatologic presentations of rickettsial fever in three individuals from the same neighborhood within the same week. Based on serologic IgM levels, the patients were treated with doxycycline and made a full recovery. This case series aimed to highlight the need for awareness regarding the variable presentations of rickettsial fever including leukocytoclastic vasculitis and purpura fulminans.

An update on spotted fever group serology in Kerman Province, Iran.

Rickettsia conorii is the causative agent of Mediterranean spotted fever (MSF) and reports of its geographical distribution are spreading every day. Recently, some cases of the MSF have been reported from Iran. However, little information is available about the MSF epidemiology in Iran. The aim of the current study was to investigate anti-R. conorii IgG seroprevalence among farmers living in the rural regions of Kerman province (in southeastern Iran). In this study, 281 blood samples were collected from farmers in Zarand and Jiroft counties and tested for detection of anti-R. conorii IgG antibodies using the ELISA method. Among the 281 samples, 14 farmers (4.98%, CI 95%; 2.45-7.55%) had anti-R. conorii IgG antibodies. Seroprevalence of MSF in Zarand and Jiroft counties were 4.58% and 5.33%, respectively. The serological evidence of this study indicates the seroprevalence of R. conorii in rural areas of the Kerman province of Iran. So, it is recommended that the Iranian health care system pay attention to the MSF.

Systematic Surveillance of Rickettsial Diseases in 27 Hospitals from 26 Provinces throughout Vietnam.

In Vietnam, the public health burden of rickettsial infections continues to be underestimated due to knowledge gaps in the epidemiology of these diseases. We conducted a systematic study among 27 hospitals from 26 provinces in eight ecological regions throughout Vietnam to investigate the prevalence, distribution, and clinical characteristics of rickettsial diseases. We recruited 1834 patients in the study from April 2018 to October 2019. The findings showed that rickettsial diseases were common among undifferentiated febrile patients, with 564 (30.8%) patients positive by qPCR for scrub typhus, murine typhus or spotted fever. Scrub typhus (484, 85.8%) was the most common rickettsial disease, followed by murine typhus (67, 11.9%) and spotted fever (10, 1.8%). Rickettsial diseases were widely distributed in all regions of Vietnam and presented with nonspecific clinical manifestations.