Increased Seroprevalence of Typhus Group Rickettsiosis, Galveston County, Texas, USA

The Seroprevalence and Risk Factors for Spotted Fever Group and Typhus Group Rickettsia Along the Texas-Mexico Border

Rickettsial pathogens are an endemic and emergent source of disease in Texas, with a historically high rate of transmission along the United States-Mexico border. To better understand the prevalence and risk factors for spotted fever group Rickettsia (SFGR) and typhus group Rickettsia (TGR) along the Texas-Mexico border, we conducted a seroprevalence study of adults residing in Starr County, Texas (N = 616). Plasma samples were screened for IgG reactivity to SFGR and TGR using commercially available ELISA. ELISA-positive samples were confirmed using a dual spot IgG indirect immunofluorescent assay. Seropositivity was defined as having a ≥1:128 titer. Analysis was conducted to assess risk factors associated with seropositivity. A higher seroprevalence of TGR (10.9%) was identified compared with SFGR (4.6%) and Rickettsia unspecified (2.0%). These findings add to the growing body of evidence suggesting that both SFGR and TGR are endemic along the Texas-Mexico border.

Typhus group Rickettsia community-acquired bacterial central nervous system infections: We must think outside the box!

Typhus group rickettsiosis (TGR), caused by Rickettsia typhi and Rickettsia prowazekii, are globally distributed vector-borne diseases with increasing cases. Diagnosis is usually clinical, confirmed by seroconversion of IgG antibodies. Human infection occurs in diverse geographic areas with some developing CNS infection characterized by fever, headache, meningismus, and/or focal signs - usually beyond the first week of initial symptomatology. Seizures and other CNS manifestations have been observed. When untreated, infection may result in neurologic sequelae and even death. This study presents a systematic review of all documented cases of Rickettsia typhi meningoencephalitis published since 2015 with the addition of five cases of TGR in South Coastal Texas, USA. This review followed the guidelines outlined in PRISMA. A schematic explanation of the pathophysiology is offered. CSF may present with high opening pressure, mild to moderate pleocytosis, mildly elevated protein levels, and low csf/serum glucose ratio, or normal findings. Meningeal enhancement, intracranial hypertension, and focal abnormalities have been described in imaging studies, but can be normal. Treatment with doxycycline leads to prompt resolution of symptoms. Failure to initiate early empiric treatment can lead to serious consequences. The study recommends routine testing for TGR in patients from endemic areas with classical symptoms when other diagnoses are inconclusive or in cases with atypical presentations. The authors advocate for incorporating empiric treatment for murine typhus into community-acquired bacterial meningitis guidelines in endemic areas; and stress the importance of enhancing laboratory diagnostic capabilities in public health entities world-wide. Further studies of community acquired mengingoencephalitis caused by TGR are highly encouraged.

Knowledge and practices related to louse- and flea-borne diseases among staff providing services to people experiencing homelessness in the United States

BACKGROUND AND AIMS

Louse-borne Bartonella quintana infection and flea-borne murine typhus are two potentially serious vector-borne diseases that have led to periodic outbreaks among people experiencing homelessness in the United States. Little is known about louse- and flea-borne disease awareness and prevention among staff who provide services to the population. We surveyed staff in seven US states to identify gaps in knowledge and prevention practices for these diseases.

METHODS AND RESULTS

Surveys were administered to 333 staff at 89 homeless shelters and outreach teams in California, Colorado, Georgia, Maryland, Minnesota, New York and Washington from August 2022 to April 2023. Most participants (>68%) agreed that body lice and fleas are a problem for people experiencing homelessness. About half were aware that diseases could be transmitted by these vectors; however, most could not accurately identify which diseases. Less than a quarter of staff could describe an appropriate protocol for managing body lice or fleas. Misconceptions included that clients must isolate or be denied services until they are medically cleared.

CONCLUSIONS

Our findings reveal significant knowledge gaps among staff who provide services to people experiencing homelessness in the prevention and control of louse- and flea-borne diseases. This demonstrates an urgent need for staff training to both reduce disease and prevent unnecessary restrictions on services and housing.

Pathogenic Rickettsia spp. as emerging models for bacterial biology

Our understanding of free-living bacterial models like Escherichia coli far outpaces that of obligate intracellular bacteria, which cannot be cultured axenically. All obligate intracellular bacteria are host-associated, and many cause serious human diseases. Their constant exposure to the distinct biochemical niche of the host has driven the evolution of numerous specialized bacteriological and genetic adaptations, as well as innovative molecular mechanisms of infection. Here, we review the history and use of pathogenic Rickettsia species, which cause an array of vector-borne vascular illnesses, as model systems to probe microbial biology. Although many challenges remain in our studies of these organisms, the rich pathogenic and biological diversity of Rickettsia spp. constitutes a unique backdrop to investigate how microbes survive and thrive in host and vector cells. We take a bacterial-focused perspective and highlight emerging insights that relate to new host-pathogen interactions, bacterial physiology, and evolution. The transformation of Rickettsia spp. from pathogens to models demonstrates how recalcitrant microbes may be leveraged in the lab to tap unmined bacterial diversity for new discoveries. Rickettsia spp. hold great promise as model systems not only to understand other obligate intracellular pathogens but also to discover new biology across and beyond bacteria.

Murine Typhus: A Review of a Reemerging Flea-Borne Rickettsiosis with Potential for Neurologic Manifestations and Sequalae

Murine typhus is an acute febrile illness caused by Rickettsia typhi, an obligately intracellular Gram-negative coccobacillus. Rats (Rattus species) and their fleas (Xenopsylla cheopis) serve as the reservoir and vector of R. typhi, respectively. Humans become infected when R. typhi-infected flea feces are rubbed into flea bite wounds or onto mucous membranes. The disease is endemic throughout much of the world, especially in tropical and subtropical seaboard regions where rats are common. Murine typhus is reemerging as an important cause of febrile illness in Texas and Southern California, where an alternate transmission cycle likely involves opossums (Didelphis virginiana) and cat fleas (Ctenocephalides felis). Although primarily an undifferentiated febrile illness, a range of neurologic manifestations may occur, especially when treatment is delayed. Serology is the mainstay of diagnostic testing, but confirmation usually requires demonstrating seroconversion or a fourfold increase in antibody titer from acute- and convalescent-phase sera (antibodies are seldom detectable in the first week of illness). Thus, early empiric treatment with doxycycline, the drug of choice, is imperative. The purpose of this review is to highlight murine typhus as an important emerging and reemerging infectious disease, review its neurologic manifestations, and discuss areas in need of further study.