top of page

   Update Dec 2020

Dr. med. Uwe Auf der Strasse

Can chronically active toxoplasmosis play a role in Long-Covid ?


This might be possible in some cases.  Patients often report that  first symptoms of Toxoplas-mosis developed following severe infections or other health problems (see p.166).  

In 4/2020 a paper was published which indicates that the activity of the so-called CD-8 cells is crucial for an effective defence against Covid-19 (Liu et al.: Longitudinal characteristics of lymphocyte responses and cytokine profiles in the peripheral blood of SARS-CoV-2 infected patients).    It is precisely these CD-8 cells that are essential for the control of Toxoplasma Gondii (6).

Now, the above mentioned study shows that  "significant decreases in the count of CD-8 T cell number and increase in inflammatory cytokine levels (e.g., IL-6, IL-10) are dynamically correlated with the severity of COVID-19 patients". This way a Covid-19 induced weakening of the CD-8 cells may trigger an increase in the activity of toxoplasmas already present in the organism. This increased activity could continue to cause severe symptoms quite similar to Long-Covid after the Covid infection itself has already been stopped.  Currently I know about 4 patients in whom previously mild Toxoplasmosis symptoms worsened significantly after a Covid-19 infection. The treatment of these patients has been successful.

Conversely, if an immune system has been exhausted by chronically active toxoplasmosis this might  be a factor in a severe course of a Covid-19 infection, because it has been proven that toxoplasmosis can weaken the CD-8 cells significantly (6) and can also cause long-term damage to the CD-4 T-helper cells (Kugler et al.: Systemic toxoplasma infection triggers a long-term defect in the generation and function of naive T lymphocytes), and these CD-4 cells are essential for the effective function of CD-8 cells mentioned above.

Addendum 11/2021: Recently a study by Prof Jaroslav Flegr was published in which he points out a connection between Toxoplasma colonization and strikingly severe courses of Covid-19 infection:  Flegr, J. Toxoplasmosis is a risk factor for acquiring SARS-CoV-2 infection and a severe course of COVID-19 in the Czech and Slovak population: a preregistered exploratory internet cross-sectional study. Parasites Vectors 14, 508 (2021)

Still, in some cases of Long-Covid there are symptoms reported like the loss of taste and smell and the persistent urge to cough that are not typical for chronically active Toxoplasmosis and might be caused by a direct effect of the virus.  In this context, however, one should also bear in mind that a weakened immune system may lose control not only of one pathogen, but also of several.


An immune system may initially be weakened by Covid-19 or another virus, but it can subsequently also lose control over other germs such as toxoplasma, chlamydia, borrelia or herpes viruses. This needs to be considered when diagnosing the resulting lengthy and complex clinical pictures, Therapy can only be successful if the major pathogens are identified and treated accordingly. I would also like to point out that the infection rate with Chlamydophila pneumonia is around 60%. If these become active, numerous symptoms similar to a Long Covid may also occur, including a persistent urge to cough (see update July 2020). Concluding it might be, that Long-Covid is not only the result of an effect of the virus itself but in some cases also the result of the activity of other pathogens, such as Toxoplasma. 

Please read also the documentation of "Case 4" (see "Case Reports"). About this case there is also a video available (see "Media"),  subtitles are being prepared.

bottom of page