What is it about ?
In general, the worms nest in the intestine and live there as parasites, that is, they feed to the detriment of the good health of the infected person. There are also worms that can settle in different tissues outside the intestine (= extra-intestinal), such as muscles, liver, brain, eyes, bladder, etc. This is technically called extra-intestinal helminthiasis or verminosis.
There are several kinds that we classify according to their shape: roundworms (nematodes), fluke and tapeworms. Humans can become infected through the mouth by eating contaminated food, by penetration through the skin and by insect bites. Human to human contamination is not possible except for pork tapeworm.
Where and how often do they occur?
Most worm infections (also called helminthic infections) occur in (sub) tropical regions. In Europe, there are not many serious infections with worms. On the other hand, in Africa, South America and Asia, there are many serious infections. A significant percentage of the population is infected in some areas. In Belgium, these infections are observed mainly in travelers returning from one of these countries.
How to recognize them?
Roundworms (nematodes)
Trichinosis
The trichinosis is spread by eating raw or smoked meat. This helminthic infection is accompanied, among other things, by fever and muscle pain.
Filariasis
The filariasis or worms are transmitted by the bite of mosquitoes and flies.
- Lymphatic filariasis begins with repeated inflammation of the lymph vessels and nodes. The lymph nodes are swollen, and because the lymph vessels are blocked, swelling of the leg, arm, or scrotum may occur (elephantiasis).
- Onchocerciasis or river blindness is characterized by swelling under the skin and itching. In these swellings huge numbers of larvae develop, which spread through the tissues. Due to the inflammatory response to the larvae in the eyes, the infected person slowly becomes blind.
- People with loiasis suffer from a lot of itching. Sometimes an adult worm can be seen in the conjunctiva of the eye, earning it its nickname “African eye worm”.
Flatworms (moats)
Schistosomiasis
The larva of the schistosome flatworm penetrates through the skin when the person comes into contact with contaminated fresh water (for example by swimming). The risk of infection is greater in stagnant water, such as reservoirs, but contamination is just as possible in rivers. This infection is called schistosomiasis.
- Schistosoma haematobium mainly causes symptoms of the urinary tract, such as blood in the urine (hematuria), pain when passing urine (dysuria), and frequent small amounts of urine (pollakiuria).
- Schistosoma mansoni and japonicum mainly cause problems with the gastrointestinal system. In the acute phase, the patient develops symptoms that resemble the flu. Usually, these symptoms go away on their own after a few weeks. After 3 to 6 months, the infection becomes chronic. In this case, the main symptoms are fatigue, stomach pain, bloody diarrhea and enlargement of the liver and spleen, which can lead to swelling of the stomach.
Liver fluke
Diseases related to liver fluke are transmitted by eating
- Aquatic vegetables (mainly watercress), and sometimes also from drinking contaminated water, eating contaminated raw mutton or goat meat, or chewing on blades of grass that have been in contact with feces animals (Fasciola hepatica),
- Raw or partially cooked fish (Clonorchis sinensis and Opistorchis).
They can be accompanied by swelling of the liver and jaundice.
Lonely worms
Echinococcosis and cysticercosis are two infections caused by tapeworms. They are transmitted through animal feces.
- In case of’echinococcosis, the worm is usually in the liver, but often does not cause symptoms.
- In case of cysticercosis, the worm can be found in the brain and can cause epilepsy and other central nervous system symptoms, such as paralysis.
How is the diagnosis made?
Finding eggs or worms in the stool, urine or blood can make a diagnosis. A blood test can also determine the antibodies directed against the worm. On ultrasound or CT scan, cysts are sometimes visible in the tissue, but this is usually a coincidence finding.
What can you do ?
The main thing is prevention. When traveling to countries where helminthic infections are common, you should only eat well-cooked or fried meat or fish. Drink only bottled water and when filled, always check that the cap is still sealed before opening it for consumption. Do not swim in lakes or ponds. Use insect repellents and sleep under a mosquito net.
What can your doctor do?
Treatment consists of medication. Sometimes you have to repeat the treatment after a few weeks, because the first dose only eliminated the worms, not the eggs.
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