Murine typhus in elderly patients: a prospective study of 49 patients

Detection of Severe Murine Typhus by Nanopore Targeted Sequencing, China

We report a case of murine typhus in China caused by Rickettsia typhi and diagnosed by nanopore targeted sequencing of a bronchoalveolar lavage fluid sample. This case highlights that nanopore targeted sequencing can effectively detect clinically unexplained infections and be especially useful for detecting infections in patients without typical signs and symptoms.

Genetic typing of isolates of Rickettsia typhi

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.

Rickettsia typhi is an obligately intracellular bacterium which is most commonly transmitted by rat fleas to humans and can cause the disease murine (endemic) typhus wherever both humans and infected rats are present. However, this agent is also present in a variety of other arthropod species associated with other vertebrate animals. Its closest relative is Rickettsia prowazekii, the etiologic agent of epidemic typhus (human louse-borne) and sylvatic typhus (associated with flying squirrels and its ectoparasites in the Eastern United States). Both classic louse-borne and flea-borne typhus rickettsiae can cause fatal infections and have the potential for use as biothreat agents as they can be grown in large quantities. We investigated the genetic differences that can be found in different stocks of R. typhi. Our work is important for two reasons. We have developed robust and sensitive methods for distinguishing isolates of R. typhi originating from different continents; these new assays require only simple instrumentation which is available in nearly all biology laboratories. Our results also provided new insights confirming the probable origin of R. typhi in Asia and its likely cosmopolitan spread by rats on ships around the world.

Murine Typhus in Canary Islands, Spain, 1999-2015

To document the epidemiology, clinical features, and outcomes of murine typhus patients in the Canary Islands (Spain), we analyzed data that were retrospectively collected for 16 years for 221 patients. Murine typhus in the Canary Islands is characterized by a high rate of complications (31.6%), mainly liver, lung, kidney or central nervous system involvement.

Sunbathing, a possible risk factor of murine typhus infection in Greece

BACKGROUND

There are few studies about the presence of murine typhus in Greece. Our objective was to conduct a large scale retrospective investigation to determine the clinical and epidemiological features of patients diagnosed with murine typhus in Greece.

METHODOLOGY/PRINCIPAL FINDINGS

From 2012 to 2019 serum samples from hospitalized patients and outpatients throughout Greece suspected for murine typhus infection were tested by immunofluorescence assay for Rickettsia typhi. Immunofluorescence positive samples obtained since 2016 were also tested by qPCR targeting R. typhi. Clinical and epidemiological data were retrospectively collected for the patients with confirmed murine typhus. Overall, we tested 5,365 different patients and, in total, 174 patients from all geographic regions of Greece were diagnosed with murine typhus. The most frequently reported sign or symptom was fever (89%), followed by headache (84%) and rash (81%). The classical triad of fever, headache, and rash was present in 72% of patients during their illness. Severe infections with complications including acute renal failure or septic shock were not recorded. The majority of cases (81%) occurred during May-October and peaked in June and September. Most of patients (81%) infected in Athens, recalled that their only activity the last weeks before symptoms onset was swimming on the beach and 59% of them also reported an insect bite while sunbathing.

CONCLUSIONS/SIGNIFICANCE

Our results may reflect the reemergence of murine typhus in Greece and we highlight the importance of awareness of this difficult-to-recognize undifferentiated febrile illness.

Hyponatremia in Infectious Diseases-A Literature Review

Hyponatremia is one of the most common water-electrolyte imbalances in the human organism. A serum sodium concentration threshold of less than 135 mmol/L is diagnostic for hyponatremia. The disorder is usually secondary to various diseases, including infections. Our review aims to summarize the diagnostic value and impact of hyponatremia on the prognosis, length of the hospitalization, and mortality among patients with active infection. The scientific literature regarding hyponatremia was reviewed using PubMed, ClinicalKey, and Web of Science databases. Studies published between 2011 and 2020 were screened and eligible studies were selected according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement and specific inclusion criteria. The most common infections that were associated with hyponatremia were viral and bacterial infections, including COVID-19 (coronavirus disease 2019). The etiology varied according to the infection site, setting and patient cohort it concerned. In several studies, hyponatremia was associated with prolonged hospitalization, worse outcomes, and higher mortality rates. Hyponatremia can also play a diagnostic role in differentiating pathogens that cause a certain infection type, as it was observed in community-acquired pneumonia. Although many mechanisms leading to hyponatremia have already been described, it is impossible with any certainty to ascribe the etiology of hyponatremia to any of them.

Selection of Diagnostic Cutoffs for Murine Typhus IgM and IgG Immunofluorescence Assay: A Systematic Review

Murine typhus is a neglected but widespread infectious disease that results in acute fever. The immunofluorescence assay (IFA) is the "gold standard" to identify IgM or IgG antibodies, although there is a lack of standardization in methodologies. The objective of this review is to summarize 1) the differences in published methodologies, 2) the diagnostic cutoff titers, and 3) the justification of diagnostic cutoffs. Searches were performed by combining the following search terms: "murine typhus," "rickettsia typhi," "immunofluorescence," "IFA," and "serologic" with restrictions (i.e., "rickettsia typhi" or "murine typhus," and "IFA" or "immunofluorescence," or "serologic*"). The search identified 78 studies that used IFA or immunoperoxidase assay (IIP) antibody cutoffs to diagnose murine typhus, 39 of which were case series. Overall, 45 studies (57.7%) provided little to no rationale as to how the cutoff was derived. Variation was seen locally in the cutoff titers used, but a 4-fold or greater increase was often applied. The cutoffs varied depending on the antibody target. No consensus was observed in establishing a cutoff, or for a single-value diagnostic cutoff. In conclusion, there is a lack of consensus in the establishment of a single-value cutoff. Further studies will need to be executed at each distinct geographic location to identify region-specific cutoffs, while also considering background antibody levels to distinguish between healthy and infected patients.

High Morbidity Due to Murine Typhus Upsurge in Urban Neighborhoods in Central Israel

The incidence of murine typhus in Israel has decreased substantially since 1950 to a low of 0.04/100,000 population in 2010. We present the experience of a single university medical center in central Israel. Hospitalized patients serologically positive for Rickettsia typhi by indirect immunofluorescence antibody assay during 2006-2016 were retrospectively identified. Clinical and laboratory data from patients' charts were used to analyze disease trends and distribution. Seventy-eight patients were studied (mean age: 27.9 years), mostly of Arab ethnicity (68, 87.2%). Seventy-one (91%) patients resided in two large mixed Jewish-Arab cities-Lod and Ramla. The incidence of murine typhus among the Arab population in Lod increased 8.4-fold from 6.4/100,000 in 2006 to a peak of 53.4/100,000 in 2013. The average annual incidence among Arabs in Ramla was 10.1/100,000. Among Jews, incidences were 0.8/100,000 in Lod and 0.4/100,000 in Ramla. The classical triad of fever, headache, and rash was noted in 20.8% patients. Substantial morbidity included prolonged fever before hospitalization and hospital stay (mean of 8.4 and 5.1 days, respectively), and severe complications in six patients, including pneumonitis in three patients, and splenic infarctions, pericardial effusion, and retinitis, each in one. One previously healthy patient died of multiorgan failure. The study describes a high incidence of murine typhus with a recent upsurge in an urban setting in central Israel. High morbidity and a single fatal outcome challenge the concept of murine typhus being a mild disease. The study calls for better rodent control and sanitation measures in the affected neighborhoods.

Case Report: Fulminant Murine Typhus Presenting with Status Epilepticus and Multi-Organ Failure: an Autopsy Case and a Review of the Neurologic Presentations of Murine Typhus

Murine typhus (MT) is an important cause of febrile illness in endemic areas, and there is an epidemiologic resurgence of this infection currently transpiring in Texas and California. Fatal cases and severe neurological complications are rare. A fatal case of MT in a middle-aged man is reported with a course culminating in multi-organ failure and refractory status epilepticus. An autopsy revealed hemorrhagic pneumonia, acute tubular necrosis, and ischemic necrosis in the liver, adrenals, and brain. We have also reviewed the neurologic complications of MT.

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.

Fatal Flea-Borne Typhus in Texas: A Retrospective Case Series, 1985-2015

AbstractFlea-borne (murine) typhus is a global rickettsiosis caused by Rickettsia typhi. Although flea-borne typhus is no longer nationally notifiable, cases are reported for surveillance purposes in a few U.S. states. The infection is typically self-limiting, but may be severe or life-threatening in some patients. We performed a retrospective review of confirmed or probable cases of fatal flea-borne typhus reported to the Texas Department of State Health Services during 1985-2015. When available, medical charts were also examined. Eleven cases of fatal flea-borne typhus were identified. The median patient age was 62 years (range, 36-84 years) and 8 (73%) were male. Patients presented most commonly with fever (100%), nausea and vomiting (55%), and rash (55%). Respiratory (55%) and neurologic (45%) manifestations were also identified frequently. Laboratory abnormalities included thrombocytopenia (82%) and elevated hepatic transaminases (63%). Flea or animal contact before illness onset was frequently reported (55%). The median time from hospitalization to administration of a tetracycline-class drug was 4 days (range, 0-5 days). The median time from symptom onset to death was 14 days (range, 1-34 days). Flea-borne typhus can be a life-threatening disease if not treated in a timely manner with appropriate tetracycline-class antibiotics. Flea-borne typhus should be considered in febrile patients with animal or flea exposure and respiratory or neurologic symptoms of unknown etiology.

Clinical and laboratory characteristics, epidemiology, and outcomes of murine typhus: A systematic review

Murine or endemic typhus, a febrile disease caused by Rickettsia typhi, is often misdiagnosed due to its non-specific presentation. We sought to evaluate all available evidence in the literature regarding the clinical and laboratory manifestations, epidemiological characteristics, and outcomes of murine typhus. Pubmed was searched for all articles providing available data. In an effort to incorporate contemporary data, only studies from 1980 were included. Thirty-three case series including 2074 patients were included in final analysis. Available evidence suggests that the classic triad of fever, headache and rash is encountered in only one-third of patients. Other frequent symptoms were chills, malaise, myalgia, and anorexia. A tetrad of reported laboratory abnormalities consisting of elevated liver enzymes, lactate dehydrogenase, erythrocyte sedimentation rate and hypoalbuminemia was detected. Complications were observed in one-fourth of patients, reported mortality was extremely low, but untreated patients had notably longer duration of fever. Among epidemiological characteristics, a seasonal distribution with most cases reported during warmer months, was the most prominent finding. Murine typhus in children exhibits several different characteristics, with abdominal pain, diarrhea, and sore throat reported more commonly, higher frequency of anemia, lower frequency of hypoalbuminemia, hematuria and proteinuria and a much lower rate of complications. This systematic review of published evidence provides a thorough description of the clinical and laboratory features of murine typhus and highlights important differences in children.

Spotted Fever Group Rickettsioses and Murine Typhus in a Malaysian Teaching Hospital

Limited information is available on the etiological agents of rickettsioses in southeast Asia. Herein, we report the molecular investigation of rickettsioses in four patients attending a teaching hospital in Malaysia. DNA of Rickettsia sp. RF2125, Rickettsia typhi, and a rickettsia closely related to Rickettsia raoultii was detected in the blood samples of the patients. Spotted fever group rickettsioses and murine typhus should be considered in the diagnosis of patients with nonspecific febrile illness in this region.