Don’t lose your breakfast – these unlikely creatures might be life-saving superheroes

Just mentioning parasites makes people uncomfortable – yet they’re among the most important and influential creatures we share the earth (and our bodies) with. When we think of parasites, we tend to imagine terrifying tiny creatures who squirm in our guts, suck blood and get up to all kinds of shenanigans in unmentionable places.

And over the millennia, parasites have indeed caused immense suffering and even brought down entire empires and nations. Parasitic diseases caused and spread by parasites, and vectors, like ticks, fleas and mosquitoes, remain an immense challenge in terms of global public health.

But as humans and parasites have existed and evolved together for millions of years, the relationship has some grey areas. Today the human microbiome – a complex, diverse community of bacteria, viruses, fungi and others – and all the ways in which they interact both with us and each other – is now widely seen as a key part of maintaining a healthy body, and even mind.

Humans have distinct microbiomes in our mouths, intestines and skin.

So might one receive a prescription for a parasite someday? Scientists are still unravelling the puzzles of parasite impacts on health, but there is growing evidence that while yes, they are ugly, and disgusting, they may offer some health benefits. Here are ten things they do that might possibly make us healthier…

Understanding inflammation and controlling it is fast becoming an important area of healthcare and research. Inflammation is our body’s response to attack – by germs or injury. When we trigger an immune response, we fight back against disease, but many diseases or autoimmune conditions are a result of inflammation gone haywire.

Whipworms and hookworms have both been shown to relieve inflammation and help stabilise the immune system. Hookworms help change the composition of bacteria in the intestines, and a result is lower inflammation.

Allergies away

Billions of people around the world today suffer some form of allergy. And the prevalence and severity of allergies is exploding worldwide. Research into certain allergies has shown that a lack of exposure to a healthy dose of microbes is partly to blame. In non-industrialised, rural and farming societies the incidence of allergies remains very low. This idea, the ‘hygiene hypothesis’ has been around for some time. In the 1970s, a UK scientist, who suffered from severe allergies infected himself with American hookworms and cleared up his allergies. Research today is looking at infecting people suffering from asthma or eczema with worms to see if this helps reduce their symptoms.

One of the biggest looming public health challenges is the evolution of antibiotic resistance in bacteria. The modern world has been made by antibiotics. Before we invented them, a mere scratch or tummy bug could be life-threatening. In evolving ways to sneak around and not be detected by their hosts, parasites have developed a veritable arsenal of complex compounds. Understanding how these evade, hijack or overcome host immune systems offers potential insights that can help us treat certain cancers and autoimmune diseases, and new antibiotics or other therapies.

Detox me

Detoxing diets, cleanses, colonic irrigation and other questionable therapies are one of the latest health fads. Hundreds of ‘therapies’, juices, pills and potions are available online, making all sorts of unsubstantiated claims. The science is clear: our bodies naturally detox using our kidneys and liver. This applies to everyone – even celebrities pushing their dubious products.

Some remarkable research shows that parasites may help accumulate toxins. Tapeworms from the guts of sharks captured in the Persian Gulf had hundreds of times the concentrations of cadmium and lead compared to their hosts. So, the tapeworms here are helping filter out heavy metals, while stealing nutrients from the shark bellies. Note this applies to sharks and no evidence of this from humans – so please don’t reach for the mail-order tapeworms yet!

Biomarkers

One of the most important things in dealing with certain infections is correctly diagnosing them. As parasites can hide deep within certain organs of their host’s bodies for years, even decades, detecting them can prove a challenge. This also applies to wider populations – both people and livestock – how, when and where can we first detect a problem?

Biomarkers, unique molecules or bits of DNA, from blood, saliva, poo or sewage can serve as ways of an early detection and early warning system. Ticks and leeches collect and store information from all the hosts, and pathogens, they feed on. We can use them as a monitoring tool – by catching, squishing, grinding them up and sequencing the DNA, revealing whom they’ve been feeding on. Forewarned is forearmed.

Parasites are the ultimate manipulators. Living in different host organs and tissues, travelling between different species and engaging with specialised cells has seen them evolve a range of sophisticated strategies. Understanding just how parasite secretions manipulate our immune systems offers potential ways to use these molecules to our own advantage. Parasites have also figured out how to deliver these molecules with great precision, maximising their efficiency. Another important biological lesson for us to learn from.

Maggots to the rescue!

Maggots, perhaps the most revolting of creatures, are one of the most helpful of insects. Today, maggots are widely used in hospitals to help cleanse and heal chronic ulcers and festering wounds. Certain ulcers can be very difficult to treat – and pose a great threat to people with conditions like diabetes. Sterilised maggots are placed on the wounds or sores. They feed only on dead flesh, and avoid living tissues, secrete enzymes and slurp up the resulting slurry. Disgusting, yes, but also lifesaving.

Feeding on necrotic tissue they perform a natural debridement, disinfect the wound and stimulate healing. Indeed, in America, 10% of US Army doctors have used maggots and they have been FDA-approved since 2004.

Bring on the leeches

Leeches have been used in Ayurvedic and Eastern medicine for millennia. Today the application of leeches even has its own name: hirudotherapy. Leech saliva is the magic potion here. It contains anti-coagulants that prevent platelets from clumping, vasodilators that keep oxygen-rich blood flowing and a plethora of other useful compounds.

Leeches are used to treat inflammation, osteoarthritis, severe bruising and help ensure skin grafts take hold and heal properly. One miracle of modern medicine is the ability to re-attach severed fingers or ears using microsurgery. Clotting and venous congestion, leading to pooling of blood in vital tissues, is one of the challenges of these operations. Enter the leech and its saliva: prevents clotting, removes excess blood and stimulates capillaries to heal.

Once a parasite is safely ensconced inside the belly, heart, liver or skin of its host, it is in its own interests to keep the host alive. If the host dies, so does the parasite. One remarkable thing is that some parasites extend the lifespan of their hosts. Biologists call this parasite-induced host longevity. Ants that are hosts to a tapeworm, live several times longer than their uninfected peers. This tapeworm parasite even secretes an anti-aging substance. Other parasites castrate or take over their hosts completely, turning them into zombies.

So, they do live longer, but only at the whims of the parasite. Note this research does not apply to humans!

Frenemies

The enemy of my enemy is my friend. This applies to modern geopolitics and nature. Malaria, Lyme disease, and the less well-known bilharzia, chikungunya, dengue and lymphatic filariasis, are all monstrous vector-borne diseases that cause suffering for many hundreds of millions of people.

Controlling vectors historically involved using toxic chemicals, which caused other problems, and lead to the evolution of resistance rendering them ineffective. Today, biological control using parasites is a growing area of research. Insects, including mosquitoes, have their own parasites that impact them in various ways. Researchers are looking into using these parasites of parasites to control the pesky critters.

And finally… one lasting lesson

Mother Nature still has a few tricks up her sleeves. What to do when faced with such a complex, convoluted world? Basically, play in the dirt, eat fruit from the vine, drink from the water fountain, kiss your doggies and don’t fret too much about things. And remember you are never more than a few inches away from a parasite!

Hidden Creatures: Luscious Leeches, Bashful Botflies and the Wondrous, History-Shaping World of Parasites, by Dino Martins (HarperCollins, £22) is published on July 30