Including louse-borne Bartonella quintana as a nationally notifiable disease: a step towards health equity

Bartonella quintana is a louse-borne, gram-negative intracellular bacterium responsible for a spectrum of illnesses including chronic bacteraemia, bacillary angiomatosis, and fatal endocarditis, predominantly in low-resource settings.¹ Historically known as the cause of trench fever during World War I, it remains closely associated with poverty, overcrowding, and inadequate access to hygiene.¹ Contemporary outbreaks have been documented in over 40 countries, particularly among populations experiencing homelessness or those living in refugee camps in low- and middle-income countries (LMICs).² When testing is available, B. quintana has been identified as a leading cause of endocarditis and febrile illness in LMICs.^3,4 Recently, novel transmission routes and emerging foci of B. quintana infection have been reported; transplant donor-derived transmission has been documented in multiple countries, and an increasing number of Indigenous communities have reported cases of endocarditis.^5,6

B. quintana is a culture-negative bacterium that evades detection by standard bacterial culture, necessitating specialised serologic and molecular methods for identification.¹ It's chronic and often subclinical bacteraemia can ultimately lead to infective endocarditis, frequently presenting with heart failure and embolic phenomena rather than fever.² Despite treatment, B. quintana endocarditis has a global case fatality rate of 10%, with substantial delays from infection to diagnosis and care.² While only 167 cases of B. quintana endocarditis have been reported worldwide, this figure is considered to be a substantial underestimate, given that many cases occur in settings with limited access to diagnostic testing.²

In Canada, B. quintana incidence is increasing. The majority of Canada's 33 molecularly-confirmed cases were diagnosed in the past three years.⁷ Notably, six Indigenous communities with inadequate access to housing and water have reported transmission, and a donor-derived outbreak in Alberta among organ transplant recipients revealed undetected spread among underhoused populations in Edmonton.⁵ B. quintana has also been detected in Canadian body lice, underscoring its entrenchment among socioeconomically marginalized individuals.⁸

As there is no centralised data on B. quintana, the 33 reported cases are believed to represent only a small fraction of infections. Most identified cases (26/33) have manifested as endocarditis—deemed to be a rare but severe presentation.¹ Individuals experiencing homelessness are often excluded from valve replacement surgery due to social instability, concomitant substance use disorders, and the heightened risk of valve reinfection. Structural barriers and systemic bias further restrict access to this diagnostic and therapeutic procedure. Molecular testing on blood specimens may be falsely negative compared to testing valve tissue.⁷ Numerous B. quintana infections may be excluded from national statistics as they are diagnosed by serology alone, which cannot confirm the diagnosis, or through hospital-based sequencing, independent of public health laboratories. Importantly, B. quintana has no known animal reservoir in Canada, meaning each case reflects direct human-to-human transmission. Seroprevalence studies show approximately 15% exposure rates in affected communities.⁹

Despite meeting the criteria for a nationally notifiable disease (NND), B. quintana is not currently included in Canada's NND list, nor that of any other jurisdiction (Table 1).¹⁰ The neglect of B. quintana likely has a multifactorial explanation: B. quintana is difficult to diagnose, it causes prolonged periods of subclinical disease that may evolve to catastrophic endovascular complications, and it disproportionately affects populations experiencing socio-economic marginalization. Canadian Notifiable Disease Surveillance System uses a standardized scoring system to determine inclusion (Table 1 and Appendix 1). B. quintana scores 28—is similar to many existing NNDs such as Verotoxigenic E. coli (score: 28), salmonellosis (score: 26) and plague (score: 29). This score likely underrepresents its public health significance due to the exclusion of health equity from assessment metrics. Key drivers of its high score include preventability via louse control, severity, shifting epidemiology, and the necessity for a coordinated public health response (Table 1).

Table 1.

Bartonella quintana as a nationally notifiable disease.

Criterion	Justification
1. Public Health Prevention & Regulation	Preventable through notification and early treatment. Recognition is delayed without surveillance.
2. 5-Year Average Incidence	Estimated at 0.016/100,000 based on PCR-confirmed cases, likely an underestimation.
3. Severity	Associated with 10% case fatality for endocarditis; long-term disability common. Overall fatality lower across all syndromes.
4. Communicability	Medium; requires close contact due to louse vector. Environmental persistence unclear.
5. Outbreak Potential	Seroprevalence data suggest potential for outbreaks in at-risk populations (e.g., unhoused communities).
6. Socioeconomic Burden	High treatment costs due to valve surgery and ICU care. Many patients sustain permanent disability.
7. Preventability	Effective control via hygiene (access to laundry and showers), and treatment of bacteremia exists. Limited data on efficacy of prevention measures.
8. Risk Perception	Medium to high, driven by media attention and associations with marginalized populations.
9. Public Health Response Need	As no animal reservoir, each case implies ongoing community transmission; follow-up is warranted to prevent fatal outcomes.
10. Changing Epidemiology	Dramatic increase in cases and positivity rates in past five years.

Please see Appendix 1, for expanded criteria, scoring system, score and detailed justification with additional references.

The NND list is the only mechanism for mandatory laboratory reporting. Thus, inclusion of B. quintana as an NND would enable centralized surveillance, harmonized diagnostic criteria, and improved awareness among healthcare providers. If linked to public health interventions, it may also facilitate early detection and treatment before progression to endocarditis, thereby reducing morbidity, mortality, and healthcare costs associated with complex surgical interventions and prolonged hospital stays. Surveillance could also be non-invasively expanded by incorporating lice screening into existing vector surveillance programs. Laboratory-based reporting of molecularly confirmed cases would involve minimal administrative burden and pose no personal risk to staff.

Crucially, recognizing B. quintana as an NND is an issue of health equity. The bacterium disproportionately affects populations experiencing homelessness and Indigenous populations in Canada, who often face barriers to hygiene due to systemic underinvestment in water infrastructure and are overrepresented among homeless populations due to colonial legacies of marginalization. Without alternative surveillance mechanisms, NND designation is the most feasible path to understanding the true prevalence of B. quintana, identifying at-risk populations, and initiating targeted prevention and control measures. Elevating B. quintana to nationally notifiable status is a necessary public health intervention grounded in equity and the human right to water and sanitation.

Contributors

CB: Conceptualization, Writing-Original Draft, Editing, Project administration.

DLH: Writing Second Draft, Editing.

HC: Conceptualization, Writing-Second Draft, Editing.

Declaration of interests

Carl Boodman's salary is supported by University of Manitoba's Clinical Investigator Program (Canada) and Canadian Institutes of Health Research (CIHR fellowship, MFE 194076). Carl Boodman's work on B. quintana is supported by the bilateral research cooperation grant; The Research Foundation–Flanders (FWO) and Fonds de Recherche du Québec (FRQ).