Mouse running activity is lowered by Brucella abortus treatment: a potential model to study chronic fatigue.
Ottenweller, J E, Natelson, B H, Gause, W C et al. · Physiology & behavior · 1998 · DOI
Quick Summary
Researchers infected mice with a killed bacterium to see if it would create a model similar to ME/CFS. The mice immediately stopped running and grooming after infection, then slowly recovered over 2-4 weeks—though some mice recovered faster than others. Interestingly, during recovery, the mice could only run for short periods at first before becoming exhausted, gradually building up their endurance over time.
Why It Matters
This study establishes a potential animal model for investigating the biological mechanisms underlying post-infectious fatigue and reduced exercise tolerance in ME/CFS. Understanding how infection triggers and sustains fatigue at a physiological level could ultimately inform treatment strategies. The observation that gradual exercise capacity recovery mirrors human ME/CFS patterns may enable researchers to test interventions in a living system.
Observed Findings
BA injection caused immediate, large decrease in running activity and loss of grooming behavior
Running and grooming gradually returned to normal levels over 2-4 weeks with substantial individual variation in recovery rate
During recovery, mice initially showed normal running activity immediately after lights-off but stopped running after only 1-2 hours
As recovery progressed, mice gradually increased the duration of their nighttime running bouts
Vehicle (saline) injection produced no changes in running or grooming behavior
Inferred Conclusions
Killed Brucella abortus can induce a behavioral fatigue state in mice that partially recovers over weeks
The pattern of early exercise cessation followed by gradual recovery of exercise duration resembles features of human chronic fatigue
Individual differences in recovery rates suggest variability in response to post-infectious challenge, similar to human ME/CFS heterogeneity
This model may be useful for studying the biological underpinnings of chronic fatigue due to its use of voluntary exertion and measurable recovery
Remaining Questions
What are the specific immune, neurological, or metabolic mechanisms driving the fatigue and gradual recovery in this model?
What This Study Does Not Prove
This study does not prove that Brucella infection causes ME/CFS in humans, nor does it establish that the mechanisms in mice directly translate to human disease pathology. The model demonstrates behavioral fatigue following infection but does not identify the underlying biological cause of post-infectious fatigue. Additionally, findings in highly controlled laboratory mice may not generalize to the complex, heterogeneous presentation of ME/CFS in humans.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
Does this model produce other ME/CFS-like symptoms beyond reduced activity (e.g., cognitive dysfunction, sleep disturbance, post-exertional malaise)?
What factors determine individual differences in recovery rate, and are these relevant to variation in human ME/CFS severity and prognosis?
Do other post-infectious triggers or doses of Brucella produce similar fatigue patterns, or is this response specific to this bacterial strain and dose?