Between fear-mongering and shrugging shoulders – a sober look at a topic rarely discussed openly
People are reluctant to talk about parasites – yet they are not as exotic as many think. While some consider the topic long settled, others dramatize it. A look at what is truly known reveals a rather clear picture.
What exactly are parasites?
Parasites are organisms that live at the expense of a host – in humans, primarily worms and tiny single-celled organisms. Hundreds of millions of people worldwide harbor such co-inhabitants 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
Depending on the parasite, infection occurs quite differently. The most common ways are:
- Contaminated food, water, or hands: If tiny traces of feces end up 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 heated meat or fish.
- Soil and sand: Worm eggs survive well in the soil – for example, in sandboxes, while gardening, or when walking barefoot over contaminated surfaces.
- Direct human-to-human contact: Pinworms spread through tiny eggs that stick to hands, toys, or laundry – a classic in daycare and elementary schools.
- 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 in our country are acquired on holiday and only noticed after returning home.
- Reinfecting oneself repeatedly: With pinworms, one often unconsciously scratches, swallows eggs again – and the cycle begins anew, no matter how clean one otherwise lives.
Consequences: What an infestation can trigger in the body
How strongly one notices something depends on the parasite, the quantity, 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.
- Nutrients are lost: Some worms directly snatch nutrients from food, which can lead to deficiency symptoms in the long run.
- Itching: Typical with pinworms is nocturnal anal itching.
- Fatigue and poor concentration: A mild but persistent infestation can simply manifest as constant exhaustion – without one even considering 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, and very rarely even the brain.
- Particularly tricky during pregnancy: Some single-celled organisms, if one becomes 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 in our country 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 primarily affect children of kindergarten and elementary school age – and through them often the entire family.
- Tapeworms and roundworms: Thanks to strict meat controls since the 1930s, these have become rare in our country – only isolated cases per year.
- Acquired on holiday: The more people travel to tropical regions, the more frequently cases appear that were acquired there and only noticed at home.
- Globally: Intestinal parasites are among the most common infections worldwide – estimates speak of hundreds of millions of affected people, especially where clean water and functioning sanitation are lacking.
Why you often don't notice anything
One reason why the numbers seem so high is simple: many infections cause few or no symptoms. A parasite does not have to make its host visibly sick to survive – on the contrary, a "quiet" host is even advantageous for it. This explains why the numbers for toxoplasmosis are so high, although hardly anyone ever experiences a noticeable illness.
