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Many ME/CFS and Long COVID patients are tested for Borrelia (Lyme) and Coxiella burnetii (Q fever) — but almost never for Bartonella henselae
This cat-associated bacterium is common in urban areas, can remain latent for years, damages the vascular endothelium, suppresses immune function, and its symptoms often mirror ME/CFS. Could it be the hidden driver in a subset of patients?
Over the past years, most persistent infection research in ME/CFS and Long COVID has focused on:
Herpesviruses (EBV, HHV-6, CMV)
Coxiella burnetii (Q fever)
Borrelia burgdorferi (Lyme)
Other tick-borne pathogens (Anaplasma, Babesia, etc.)
However, one bacterium rarely tested for could be playing a much bigger role than we think: Bartonella henselae.
¿Por qué sospechar de Bartonella henselae?
1. Underestimated prevalence
Found worldwide, especially in urban environments.
Seropositivity in the general population: 3–6%.
In people with frequent cat contact: up to 30–40%.
Main vector: the cat flea (Ctenocephalides felis), transmitting the bacteria between cats and to humans via scratches, bites, or saliva entering wounds.
Also documented: transmission via ticks and possibly other insects.
2. Clinical similarity to ME/CFS
Persistent, debilitating fatigue
Migratory musculoskeletal pain
Dysautonomia (POTS, dizziness)
Neurocognitive symptoms: brain fog, memory, and concentration problems
Vascular/skin signs: red or purple striae, angioproliferative lesions
Symptoms often worsen after infections or physical stress
3. Persistence and reactivation capacity
Invades red blood cells and endothelial cells: hides from immune system and many antibiotics.
Can remain latent for years, reactivating with immune suppression, stress, or coinfections.
Promotes chronic vascular inflammation, microclots, and endothelial dysfunction — mechanisms increasingly linked to ME/CFS and Long COVID.
4. Link to a progressive immunovascular syndrome
By damaging the vascular endothelium and reducing capillary function, Bartonella henselae could contribute to a progressive immunovascular syndrome — a process where chronic endothelial injury leads to impaired oxygen/nutrient delivery, tissue hypoxia, and sustained immune dysregulation.
This state of impaired microcirculation + immune suppression could explain why some patients develop gradual worsening, new infections, or reactivation of latent pathogens over time.
5. Interaction with other infections
Can facilitate reactivation of latent viruses (EBV, HHV-6) and other intracellular bacteria.
Bartonella + Borrelia coinfections are common in endemic regions and often produce more severe illness.
6. Potential link with Long COVID
Multiple studies in Long COVID have shown persistent endothelial dysfunction — including microclot formation, capillary rarefaction, and reduced nitric oxide bioavailability.
Bartonella henselae has a strong tropism for endothelial cells, where it can persist intracellularly, alter cell signaling, and trigger chronic inflammation.
Chronic infection can lead to:
Microvascular damage: impaired oxygen/nutrient delivery to tissues.
Pro-coagulant state: microclots similar to those found in Long COVID patients.
Immune dysregulation: facilitating viral reactivations (EBV, HHV-6) already documented in Long COVID.
This overlap raises the possibility that, in some Long COVID patients, Bartonella henselae could be:
A pre-existing infection worsened by SARS-CoV-2–induced immune suppression.
A post-COVID opportunistic activation due to endothelial injury and immune imbalance.
Current diagnostic gap
Most private “vector-borne” panels exclude Bartonella henselae.
Standard antibody tests (IgG/IgM) have low sensitivity in chronic cases.
Best methods:
Enriched culture (BAPGM) + PCR
PCR directly on whole blood or tissue samples
Many patients get false negatives and the infection is never even suspected.
Hypothesis
In people with ME/CFS or post-infectious Long COVID, especially if:
They live(d) in urban areas with high cat populations
Had frequent cat contact before illness onset
Experienced persistent or unexplained skin infections in the past
Present vascular, neurological, and long-term fatigue symptoms
…chronic Bartonella henselae could be the trigger or a key perpetuating factor, potentially driving a progressive immunovascular decline over years.
Call to the community
I’d like to know if anyone here:
Has ever been tested for Bartonella henselae (and which method was used)
Has a history of frequent cat contact before illness onset
Has experienced similar symptoms and been diagnosed with coinfections
I believe Bartonella henselae is an unexplored but potentially revealing avenue for a subgroup of ME/CFS patients — especially those with vascular symptoms and evidence of immune suppression over time.
References & further reading
This cat-associated bacterium is common in urban areas, can remain latent for years, damages the vascular endothelium, suppresses immune function, and its symptoms often mirror ME/CFS. Could it be the hidden driver in a subset of patients?
Over the past years, most persistent infection research in ME/CFS and Long COVID has focused on:
Herpesviruses (EBV, HHV-6, CMV)
Coxiella burnetii (Q fever)
Borrelia burgdorferi (Lyme)
Other tick-borne pathogens (Anaplasma, Babesia, etc.)
However, one bacterium rarely tested for could be playing a much bigger role than we think: Bartonella henselae.
¿Por qué sospechar de Bartonella henselae?
1. Underestimated prevalence
Found worldwide, especially in urban environments.
Seropositivity in the general population: 3–6%.
In people with frequent cat contact: up to 30–40%.
Main vector: the cat flea (Ctenocephalides felis), transmitting the bacteria between cats and to humans via scratches, bites, or saliva entering wounds.
Also documented: transmission via ticks and possibly other insects.
2. Clinical similarity to ME/CFS
Persistent, debilitating fatigue
Migratory musculoskeletal pain
Dysautonomia (POTS, dizziness)
Neurocognitive symptoms: brain fog, memory, and concentration problems
Vascular/skin signs: red or purple striae, angioproliferative lesions
Symptoms often worsen after infections or physical stress
3. Persistence and reactivation capacity
Invades red blood cells and endothelial cells: hides from immune system and many antibiotics.
Can remain latent for years, reactivating with immune suppression, stress, or coinfections.
Promotes chronic vascular inflammation, microclots, and endothelial dysfunction — mechanisms increasingly linked to ME/CFS and Long COVID.
4. Link to a progressive immunovascular syndrome
By damaging the vascular endothelium and reducing capillary function, Bartonella henselae could contribute to a progressive immunovascular syndrome — a process where chronic endothelial injury leads to impaired oxygen/nutrient delivery, tissue hypoxia, and sustained immune dysregulation.
This state of impaired microcirculation + immune suppression could explain why some patients develop gradual worsening, new infections, or reactivation of latent pathogens over time.
5. Interaction with other infections
Can facilitate reactivation of latent viruses (EBV, HHV-6) and other intracellular bacteria.
Bartonella + Borrelia coinfections are common in endemic regions and often produce more severe illness.
6. Potential link with Long COVID
Multiple studies in Long COVID have shown persistent endothelial dysfunction — including microclot formation, capillary rarefaction, and reduced nitric oxide bioavailability.
Bartonella henselae has a strong tropism for endothelial cells, where it can persist intracellularly, alter cell signaling, and trigger chronic inflammation.
Chronic infection can lead to:
Microvascular damage: impaired oxygen/nutrient delivery to tissues.
Pro-coagulant state: microclots similar to those found in Long COVID patients.
Immune dysregulation: facilitating viral reactivations (EBV, HHV-6) already documented in Long COVID.
This overlap raises the possibility that, in some Long COVID patients, Bartonella henselae could be:
A pre-existing infection worsened by SARS-CoV-2–induced immune suppression.
A post-COVID opportunistic activation due to endothelial injury and immune imbalance.
Current diagnostic gap
Most private “vector-borne” panels exclude Bartonella henselae.
Standard antibody tests (IgG/IgM) have low sensitivity in chronic cases.
Best methods:
Enriched culture (BAPGM) + PCR
PCR directly on whole blood or tissue samples
Many patients get false negatives and the infection is never even suspected.
Hypothesis
In people with ME/CFS or post-infectious Long COVID, especially if:
They live(d) in urban areas with high cat populations
Had frequent cat contact before illness onset
Experienced persistent or unexplained skin infections in the past
Present vascular, neurological, and long-term fatigue symptoms
…chronic Bartonella henselae could be the trigger or a key perpetuating factor, potentially driving a progressive immunovascular decline over years.
Call to the community
I’d like to know if anyone here:
Has ever been tested for Bartonella henselae (and which method was used)
Has a history of frequent cat contact before illness onset
Has experienced similar symptoms and been diagnosed with coinfections
I believe Bartonella henselae is an unexplored but potentially revealing avenue for a subgroup of ME/CFS patients — especially those with vascular symptoms and evidence of immune suppression over time.
References & further reading
- Maggi RG, Mozayeni BR, Pultorak EL, Hegarty BC, Bradley JM, Correa M, Breitschwerdt EB.
Bartonella spp. bacteremia and rheumatic symptoms in patients from Lyme disease–endemic region. Emerg Infect Dis. 2012;18(5):783–791.
https://pmc.ncbi.nlm.nih.gov/articles/PMC3358077/ - Breitschwerdt EB, et al.
Bartonella spp. bacteremia and subsequent arthropathy in a previously healthy individual. Parasit Vectors. 2014;7:111.
https://parasitesandvectors.biomedcentral.com/articles/10.1186/1756-3305-7-111 - Maggi RG, et al.
Challenges in the diagnosis of Bartonella infections in humans and animals. Diagnostics. 2022;12(1):125.
https://www.mdpi.com/2075-4418/12/1/125 - Kempf VA, et al.
Pathogenesis of Bartonella infections: The role of the endothelium. Trends Microbiol. 2001;9(6):279–285.
https://doi.org/10.1016/S0966-842X(01)02037-5 - Breitschwerdt EB.
Bartonellosis: One Health perspectives for an emerging infectious disease. ILAR J. 2014;55(1):46–58.
https://doi.org/10.1093/ilar/ilu015
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