Between scaremongering and shrugging – a sober look at a topic rarely discussed openly
People are reluctant to talk about parasites – yet they are not as exotic as many people think. While some consider the topic long settled, others dramatize it. If one looks at what is really known, a quite clear picture emerges.
What exactly are parasites?
Parasites are organisms that thrive at the expense of a host – in humans, mainly worms and tiny single-celled organisms. Worldwide, hundreds of millions of people carry such co-habitants in their intestines, such as roundworms or hookworms. In Germany, Austria, and Switzerland, the situation is different thanks to good hygiene and strict food controls – but "rarer" does not mean "never".
Causes: How one gets infected in the first place
Depending on the parasite, infection occurs quite differently. The most common ways are:
- Contaminated food, water, or hands: If tiny traces of feces land on what we eat or drink, pathogens can enter the body – the most common transmission route worldwide.
- Raw or undercooked meat and fish: Tapeworms and trichinae are found almost exclusively in insufficiently cooked meat or fish.
- Soil and sand: Worm eggs survive well in the soil – for example, in sandboxes, when gardening, or when walking barefoot over contaminated areas.
- Direct human-to-human contact: Pinworms spread through tiny eggs that stick to hands, toys, or laundry – a classic in daycare and elementary school.
- Pets: Fox and dog tapeworms, as well as some single-celled organisms, can also be transmitted by animals.
- Travel: A large proportion of the cases diagnosed here are brought back from holidays and only noticed after returning home.
- Repeated self-infection: With pinworms, one often scratches unconsciously, swallowing eggs again – and the cycle begins anew, no matter how clean one lives otherwise.
Consequences: What an infestation can trigger in the body
How much one notices depends on the parasite, the amount, and one's own immune system. Much goes unnoticed, but some things become clearly noticeable:
- Abdominal problems: Abdominal pain, diarrhea, bloating, or a constant feeling of fullness are the most common reactions of the intestine.
- Nutrient loss: Some worms directly snatch nutrients from food, which can lead to deficiency symptoms in the long run.
- Itching: Typical for pinworms is nocturnal anal itching.
- Fatigue and poor concentration: A mild but persistent infestation can simply manifest as constant exhaustion – without one realizing that parasites are behind it.
- The immune system has more to do: The body constantly fights the invaders in the background, which costs energy.
- In rare cases, other organs: Some parasites migrate beyond the intestine and reach the liver, lungs, or muscles, very rarely even the brain.
- Particularly delicate during pregnancy: Some single-celled organisms, if one gets infected for the first time during pregnancy, can affect the unborn child.
Prevalence: How often does this really occur in the population?
In short: The large, "classic" worms have become rare here thanks to hygiene and meat controls. Other parasites, however, are surprisingly common – but hardly anyone talks about them.
- Toxoplasmosis: According to the Robert Koch Institute, about every second adult in Germany carries this single-celled organism – mostly completely unnoticed, because it usually causes no symptoms.
- Pinworms: They are among the most common worm infections in industrialized countries and mainly affect children of kindergarten and elementary school age – and often the whole family through them.
- Tapeworms and roundworms: Thanks to strict meat controls since the 1930s, these have become rare here – only isolated cases per year.
- Brought back from vacation: The more people travel to tropical regions, the more frequently cases appear that were acquired there and only noticed at home.
- Globally: Globally, intestinal parasites are among the most common infections ever – estimates speak of hundreds of millions affected, especially where clean water and functioning sanitation are lacking.
Why you often don't notice anything about it
One reason why the numbers seem so high is simple: Many infections cause few or no symptoms. A parasite does not have to visibly sicken its host to survive – on the contrary, a "quiet" host is even advantageous for it. This explains why the numbers for toxoplasmosis are so high, even though hardly anyone ever goes through a noticeable illness.
