Until recently the idea that intestinal parasites offer benefits to their hosts would be considered radical. But thanks to new information, that’s all changed.
The change in attitude began when scientists started to notice that wherever worms are eradicated by improved hygiene and medicine, sharp spikes in auto-immune diseases have followed.
Auto-immune diseases on the rise in us and our pets
Auto-immune diseases are those where the body’s immune system starts attacking its own cells. Common examples include type I diabetes (organ attacked is the pancreas), asthma (the lungs), crone’s disease (the intestines), multiple sclerosis (nerve coverings), rheumatoid arthritis (joints), and a wide range of allergies.
Asthma and allergies are epidemic in the world’s richest countries. They began their rise in the 1960s and now affect two to three times as many people as they used to. In the same period multiple sclerosis has nearly tripled and celiac disease has increased more than four-fold. By 2009 type 1 diabetes had also tripled since the middle of the 20th century, and looks set to double again by 2020.
And our pets have suffered similar increases in auto-immune diseases. In dogs for example, the incidence of diabetes has risen from under 2% in 1974 to almost 6% by 1999, increasing another 32% between just 2011 and 2015 (and 16% in cats over the same period). About half of these would be Type 1.
In both people and animals, allergies are also on the rise. In humans the main symptoms of allergy occur in the respiratory system, with animals it tends to be the skin in the form of dermatitis that now affects about one in ten dogs.
How Worms May Prevent Auto-Immune Diseases
Scientists have a theory called “the old friends hypothesis”to explain the protective effect intestinal parasites seem to have against autoimmune diseases. Basically, worms have a natural dampening effect on our immune system. This prevents it over-reacting to their migrations. Over millions of years of evolving together we’ve become dependent on this dampening effect to modulate our immune system and keep it healthy and functional. Wherever modern hygiene deprives us of the immune calming presence of worms, rising autoimmune disease is the result.
Now a new generation of scientists are exploring the possible role of parasites in combatting these diseases. A few intrepid individuals suffering from various maladies have even put the theory to the test by deliberately infecting themselves.
In 2005, Garin Aglietti, a medical school dropout with severe psoriasis, got the ball rolling. He successfully treated himself by swallowing tapeworm cysts harvested from cattle in a Kenyan abattoir. Many other self-medicators soon followed. Since then promising results have come from work on rats, and now there are several studies underway for a variety of autoimmune conditions in people. However, its early days yet. Some of the many types of worms that live in our guts have been found useful for particular conditions and some not, or even harmful.
So where does this leave us as dog lovers?
I’m not advocating that we stop worming our dogs, particularly our puppies and whelping bitches that can present a danger to small children if wormy. However, maybe adopting a more tolerant attitude to the presence of intestinal worms in our non-breeding adult pets is warranted.
Many years ago I travelled around Australia studying the relationship between Aboriginals and their dogs for my PhD research project. I documented the parasite loads in hundreds of dogs and found that it is naturally low in adults (apart from nursing bitches) despite them having never been wormed. The same is normally the case with any healthy creature. Indeed most dogs and people that harbour worms show no ill effects.
The immune system of us and our pets were shaped by the presence of intestinal parasites. New therapies using gut worms may emerge as we develop greater understanding of this relationship.