Update Dec 2020
Is there a connection between Long-Covid and chronically active toxoplasmosis?
This might be the case. Patients often report that first symptoms of toxoplasmosis developed following severe infections or other health problems (see p.166).
In 4/2020 a paper was published indicating 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". So 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.
Conversely, exposure to chronically active toxoplasmosis could 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 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.
On the other hand, the loss of taste and smell and the persistent cough reported by some patients with Long-Covid disease 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 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 Chlamydyphila pneumonia is around 60%. If these become active, a persistent urge to cough is a common symptom (see update July 2020). Concluding it might be, that Long-Covid is not only the result of an effect of the virus itself but also of other pathogens, such as Toxoplasma.