Relationship between Multiple Sclerosis (MS) and Parasites | Ward Dean MD

The relationship between Multiple Sclerosis (MS) and parasites, particularly helminth (worm) parasites, is an area of ongoing research with several intriguing findings:

Hygiene Hypothesis:
This theory suggests that the decrease in parasitic infections due to modern sanitation and hygiene might lead to an increase in autoimmune diseases like MS. Parasitic infections could modulate the immune system, potentially preventing or reducing autoimmune reactions.

Immune Modulation:
Parasites are known to modulate the immune system in ways that can reduce inflammation. Studies have shown that helminths can increase the production of anti-inflammatory cytokines like IL-10 and TGF-beta, which can suppress the immune responses that contribute to MS. This modulation might lead to fewer relapses and slower disease progression in MS patients.

Clinical Observations:
Research has noted that in areas where helminth infections are common, there's a lower incidence of MS. For instance, studies from regions with high parasite prevalence show fewer MS cases compared to areas with better sanitation and lower parasite exposure.

Experimental Studies:
In experimental models, like mice with induced MS (experimental autoimmune encephalomyelitis or EAE), infections with certain parasites or administration of parasite-derived molecules have shown protective effects. Mice infected with Schistosoma mansoni or Trichuris trichiura exhibited reduced disease severity or delayed onset of MS-like symptoms.

Human Studies:
Some human studies have observed that MS patients with concurrent parasitic infections might experience fewer relapses and less progression. One notable study followed MS patients with parasitic infections over several years and found they had fewer MS exacerbations and less MRI activity compared to uninfected MS controls.

Mechanistic Insights:
Parasites can induce regulatory T cells and B cells, which are known to down-regulate immune responses. The presence of these cells might shift the immune system's balance from pro-inflammatory to anti-inflammatory, potentially beneficial in MS.

Therapeutic Potential:
The concept of "helminth therapy" has been explored, where live parasites or their secretory products are used to treat autoimmune conditions. Clinical trials, like the WIRMS (Worms for Immune Regulation of Multiple Sclerosis), have tested the use of hookworms in MS patients with some showing positive outcomes in terms of reduced disease activity.