The power of parasites

Sheila Moorcroft, Research Director

Last spotted
13 April 2011

Parasites are known to cause a range of dangerous and life threatening diseases; they may also be implicated in schizophrenia. But, it also appears, some parasites may be good for us. A growing body of evidence indicates that a lack of parasites may be implicated in the rise of autoimmune diseases. Understanding the complex ecology of parasites combined with genetic and other physical factors and their role in health is revealing new solutions.

What is changing?

Wikipedia lists 39 parasitic diseases including malaria and sleeping sickness: they are a major blight on many lives. One parasitic disease, toxoplasmosis caused by Toxoplasma gondii, has the power to change rat behaviour by affecting their brains then making them more likely to be caught by cats, which can then also be infected. About 20%-60% of cats around the world are infected.Research now indicates that humans with the parasite could also be vulnerable in unexpected ways. They may be significantly more prone to traffic accidents than those who are not infected. There may also be a strong correlation with the development of schizophrenia.

Auto immune diseases may also be linked to parasites: or rather the lack of them. New research indicates that treating patients suffering from Irritable Bowel Diseases such as Crohn’s or Ulcerative colitis, with a dose of whipworm parasites in a mineral solution may remove the need for surgery and solve the problem by ‘relining’ the gut with protective mucous.

A 2007 study in Argentina indicated a potentially similar benefit for Multiple Sclerosis sufferers. Those patients with eosinophilia caused by intestinal parasites suffered fewer relapses than those without. The modern world’s tendency towards excessive hygiene may play a role in altering our immune responses, and thus increasing risks of developing diseases such as MS.


Why is this important?
Toxiplasma Gondii is present in between 40-60% of the human population. It infects rats and then cats which can pass to other animals and then on to humans. Once there, it can remain dormant or become active: it can never, at present, be eradicated. In pregnant animals or humans it can cause spontaneous abortions or birth defects. Inflammatory Bowel Disease – Crohn’s disease (CD) and Ulcerative colitis (UC), affects growing numbers of people, running into hundreds worldwide. The prevalence in Canada is among the highest in the world ~234/ 100,000 for CD and 194 for UC; in Northern Europe 58 to 157 / 100,000 for UC, 27 to 48 /100,000 for CD.Worldwide about 2.5 million people have MS, with higher concentrations in northern countries – there is some discussion of exposure to sunlight and vitamin D also playing a role here. (See ST Trend Alert Weather and health: D is for Sunshine )

As many as 51 million people worldwide suffer from schizophrenia at any one time, bringing untold suffering to the individual and often family and friends.

This growing body of research indicates that there may be new treatments which reduce suffering even if not bringing a cure and are far less invasive and disruptive than alternatives such as operating or even some of the drug regimes. They almost certainly cost less.

Parasitic infection connections to schizophrenia and other mental illness were suggested many decades ago, but forgotten with the development of psychology. Revisiting old theories can often, when combined with new tools, techniques and understanding, reveal new truths. As our understanding of the wider ecology of parasites and genetics and even blood type – e.g. positive or negative- grows, so we may be able to develop more personalised solutions to these conditions.

After the fears raised by the H1N1 pandemic, and the associated issues of high proximity to animals in some countries, we may see tougher regulations about pet care and control and animal husbandry in future, if stronger links between parasites and significant mental health issues are proven.

Likewise, dirt may be good for us. Cleanliness used to be regarded as next to godliness in Europe: it would appear not to be next to wellness. Our obsession with cleaning, overcoming smells, dirt and germs of every kind may come under attack. More of the right kind of parasites may need to be encouraged.


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