by Here at Galaxy Diagnostics, we are often asked “Why do symptoms for bartonellosis vary between patients so much?” and “How do I know that my symptoms are related to Bartonella species infection?”
The simple yet frustrating answer for patients and physicians alike is that chronic flea- and tick-borne illnesses are complex and typically do not follow a predictable course. Multiple body systems can be affected, including the brain and heart, resulting in a broad spectrum of symptoms.
Furthermore, the same patient can experience symptoms that affect different parts of the body throughout the course of the infection. The spectrum of symptoms often creates a unique web that is specific to each patient and difficult to untangle.
How can a single species, like Bartonella henselae, cause these harmful symptoms in one patient while another infected person appears to be healthy?
Emerging research on bartonellosis and Lyme borreliosis is increasingly showing the role of the host response in mediating the diverse clinical symptoms that patients present with. The host response is the way the infected individual’s immune system responds to cellular/tissue damage (pathology) caused by a pathogen. Some patients may have a more extreme immune response to the damage, resulting in a higher degree of inflammation and a related set of symptoms. Likewise, immune-deficient patients may experience more symptoms caused by the pathogen.
Factors that affect the host response to a pathogen include:
- Immune status (immunocompetent vs. immunocompromised)
- Genetic variances
- Previous and current immune exposures (pathogens, proteins, etc.)
- General health and well-being (stress, nutritional status, etc.)
For Bartonella henselae, the effect of host immune response was shown in extensive research conducted on HIV patients in the 1990s. Symptoms in immune-deficient patients may be atypical and unexpected. For example, researchers found that HIV patients infected with Bartonella henselae, or cat scratch disease, experienced bacillary angiomatosis and bacillary peliosis at a higher rate than immunocompetent patients.
The host response can continue to cause symptoms after a pathogen is gone. Recently, a study showed that arthritic symptoms persisted in mice infected with Borrelia burgdorferi. The researchers found that the mice developed an irregular immune response that resulted in T-cells targeting joint tissue even after the bacteria were eliminated. This aberrant immune response is like that seen in autoimmune diseases where the body is basically attacking itself.
Other recent research has suggested that measles infection can suppress the immune system for up to three years, leading to other illnesses. Meanwhile, parasitic worms that suppress the immune system may reduce heart disease in some communities. The immune system itself is extraordinarily complex, and identifying these influences is only the start of understanding how it is modulated by different exposures.
Conclusion
The web of influences on the host response is only just beginning to be understood, including the influence of flea and tick-borne pathogens in chronic symptoms. A better understanding of the host response, better genetic and biomarker tools to measure it, and better diagnostic tools to determine exposure and current infection of a wide variety of pathogens is necessary to overcome today’s frustrations and develop personalized treatments that will improve health.
References
Chaplin, D. D. (2010). Overview of the immune response. The Journal of Allergy and Clinical Immunology, 125(2, Suppl 2), S3-S23. doi:10.1016/j.jaci.2009.12.980 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2923430/
Resto-Ruiz, S. et al. (2003). The role of the host immune response in pathogenesis of Bartonella henselae. DNA and Cell Biology, 22(6), 431-440. doi:10.1089/104454903767650694 https://www.liebertpub.com/doi/pdf/10.1089/104454903767650694
Lantos, P. M. et al. (2014). Detection of Bartonella species in the blood of veterinarians and veterinary technicians: A newly recognized occupational hazard? Vector-Borne and Zoonotic Diseases, 14(8), 563-570. doi:10.1089/vbz.2013.1512 https://www.liebertpub.com/doi/abs/10.1089/vbz.2013.1512
Carroll, L. (2018). Malfunctioning immune system may explain chronic Lyme symptoms. Today.com. Retrieved from: https://www.today.com/health/chronic-lyme-may-be-due-malfunctioning-immune-system-t122207
Huber, B. R. (2015). A deadly shadow: Measles may weaken immune system up to three years. Retrieved from: https://www.princeton.edu/news/2015/05/07/deadly-shadow-measles-may-weaken-immune-system-three-years
Gupta, S. (2019). Life lessons from the native tribe with the healthiest hearts in the world. CNN.com. Retrieved from: https://www.cnn.com/2019/04/19/health/bolivia-heart-disease-chasing-life-gupta/index.html
