Parasitic intestinal worms are gross, but the average Australian shouldn't be too worried

Parasitic intestinal worms are gross, but the average Australian shouldn't be too worried

Parasitic intestinal worms are gross, but the average Australian shouldn't be too worried

Updated 9 February 2018, 11:10 AEDT

From hookworms you can feel wriggling in your feet to metres-long tapeworms growing in your gut, parasitic worms are truly gross.

From hookworms you can feel wriggling in your feet to 1.5-metre tapeworms being pulled from a man's digestive tract, it's been a rough couple of weeks for people who enjoy exotic beach holidays, sushi or blissful ignorance about the perils of invasive parasites.

So what kinds of parasitic worms should you be worried about? And how likely is the average Australian to pick one up?

There are thousands of varieties of worms that can affect humans, but most of the ones you're likely to come across in Australia are pretty innocuous, says Dr Mark Pearson, who researches parasitic worms at James Cook University.

Part of that is because many problem worms are transmitted via faeces, undercooked meat or contaminated water, which are generally not an issue in Australia.

"We're pretty lucky here in Australia," Dr Pearson said.

"In countries that are underdeveloped, that don't have as good sanitation as we do here, faeces are going to find their way into the environment in some way.

"Here food is adequately cooked and it's not within our culture here to eat those certain types of food [that increase the risk of infestation]."

Your risk of coming across one of the nastier parasites is greater if you travel, particularly to developing countries.

Dr Pearson advises travellers to developing countries to choose well-cooked meat and bottled water or drinks, avoid going barefoot, wash hands after going to the toilet and avoid swimming in waterways that could be contaminated.

But even if you do pick up parasitic worms, whether here or abroad, the majority won't cause you much discomfort, Dr Pearson said.

The only common worm infestation seen in Australia is threadworm or pinworm, which usually occur in children.

As almost anyone who has kids — or has been one — knows, these gross but mostly harmless parasites cause little more than an itchy bottom and irritability and are easily dispatched with a dose of over-the-counter medication.

Dr Pearson says this same medication will get rid of many of the types of worms you could pick up on overseas travel as well, but recommends you talk to your GP if you have concerns.

Dormant for decades

Although rarer, there are areas of Australia that are prone to outbreaks of strongyloidiasis, due to a parasite responsible for making more people sick than malaria worldwide.

Remote Indigenous communities have higher incidences of strongyloidiasis infections, due at least in part to poor sanitation, says Flinders University environmental health researcher Dr Kirstin Ross.

The Strongyloides stercoralis worm that causes the infection usually gains access into your body through the skin coming into contact with contaminated soil or faeces.

Then it makes its way into the bloodstream, to the lungs, where it is coughed up and swallowed, finally taking up residence in the small intestine.

"People get infected for decades and, unless you get treated, you have the infection for a long time," Dr Ross said.

"The symptoms mimic other illnesses, like you get sick in your tummy, so it often goes undetected."

Strongyloidiasis is treatable with medication.

"Communities where they've done mass screening and drug administration seems to be successful, as long as there's good sanitation," she said.

Human-to-human transmission in areas with well maintained plumbing is rare, Dr Ross said, citing studies where Vietnam War veterans lived with the infection for decades but their wives remained unaffected.

The parasite can become life-threatening, however, if your immune system is suppressed, for example if you're undergoing treatment for cancer.

This can allow the worm to move into hyperinfection, where it reproduces rapidly, causing an enormous number of worms that spread throughout the body, carrying gut bacteria into other organs, causing infection.

"When the immune system is suppressed, it allows the worm to multiply to enormous numbers," Dr Ross said.

"It's almost invariably fatal. Once it starts it's almost impossible to treat effectively."

The case of the 10-metre tapeworm

Tales of tapeworms growing to dizzying lengths in people's guts are retold with relish, but are actually very rare, says gastroenterologist Dr Vincent Ho from Western Sydney University.

Choosing saltwater fish, such as salmon and tuna, especially farmed salmon as we have in Australia, over freshwater fish greatly reduces your risk of contracting fish tapeworm, so don't be too scared of your local sushi joint.

"It's very rare, particularly in Australia. There's only one documented case of a type of fish tapeworm in Australia," Dr Ho said.

"But in other countries, particularly in the northern hemisphere, people do get them."

The longest type of tapeworm found in humans can grow to 10 metres and live for 20 years, Dr Ho said.

Possibly more terrifying than a single 10-metre tapeworm is a cyst packed with tapeworm larvae growing near one of your vital organs.

Dr Ho said larvae of the dog tapeworm, or Echinococcus granulosus, could travel in the blood stream to the lungs, liver or even the brain, and form cysts that could get to the size of a tennis ball. This condition is called hydatid disease.

"Obviously it puts pressure on an organ, and if a cyst bursts it can be fatal," he said.

Hydatid disease like this is very rare, and occurrences in Australia are mainly in rural or remote areas where people are in close contact with dogs that have been eating infected animals.

Good hygiene and being careful around dogs are the best ways to avoid the condition, Dr Ho said.

Wash your hands after playing with dogs or anything that could be contaminated with dog poo, don't let dogs lick your face, don't feed them raw meat from animal carcasses such as sheep organs, and worm your dog regularly with a treatment that covers for hydatid tapeworm.