What is worm infection in humans?
Many types of worm can cause problems in humans.
In Australia, worms that may infect people include:
These intestinal worms are parasites – they survive by living in another living thing (the host) and getting their food from it.
What are the symptoms of a worm infection?
A person with intestinal worms may not have any symptoms, but threadworms (Enterobius vermicularis), the most common worm infection in Australia, often do cause symptoms.
A person with threadworms (also known as pinworms) may have an itchy bottom or redness and scratch marks around the bottom. A child with threadworms may be irritable, not sleep very well and lose their appetite.
Threadworms (come out of the anus at night to lay their eggs between the buttocks, causing extreme itching. They look like small white threads moving about and may be seen with a torch. The threadworms may also be seen on the surface of the stools (poo) if a person has a heavy infestation.
Other types of worms may not cause any symptoms (for example pork and beef tapeworms or Strongyloides stercoralis) or only cause symptoms a long time after infection (for example dog tapeworm) or if there is heavy infection. Symptoms may include diarrhoea, tiredness and weakness, abdominal pain and weight loss. Some worms cause anaemia.
Once they have entered humans by penetrating the skin, the larvae of some worms, for example dog hookworm (Ancylostoma caninum) or Strongyloides, can migrate under the skin causing diagnostic pink or red curving tracks known as larva migrans or larva currens. The tracks may be raised and cause intense itching. There may be tingling or prickling half an hour after the larvae penetrate the skin.
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How do you get worms?
Threadworms are usually acquired by ingesting the eggs. Humans are the only host of threadworms. The adult worms live in the lower intestine, coming out of the anus at night to lay their eggs. Children with threadworms can get the eggs under their fingernails when scratching their itchy bottoms at night. The eggs can then be spread via bed linen, bathroom fittings and other items, even food. The eggs can survive for around 2 weeks like this on surfaces.
Some other types of worms enter humans when their larvae penetrate the skin, often through bare feet.
Dog hookworms can be caught like this through the skin. This commonly happens by being barefoot outdoors and coming into contact with larval hookworms in soil or sand contaminated with stool from an infected dog.
Strongyloides, a roundworm, also infects humans when its larvae penetrate the skin.
Pork tapeworm (Taenia solium) and beef tapeworm (Taenia saginata) can be acquired from eating undercooked meat containing cysts of the tapeworm larvae. These infections are not common in Australia, and are usually only acquired overseas.
Dog tapeworms (Echinococcus granulosus) are yet another type of tapeworm. They can infect humans who accidentally ingest the tapeworm’s eggs, which are released from dog or dingo stools. The tapeworm sheds segments into the animal’s stool, which then rupture releasing the eggs. The eggs can contaminate a dog’s coat, kennel, and fields and play areas. A person may then ingest an egg and become infected. Patting an infected dog may be enough to get infected.
Dog tapeworm can cause a serious disease in humans, known as hydatid disease.
Dwarf tapeworms (Hymenolepsis nana) are acquired by ingesting dwarf tapeworm eggs or are transmitted between people in areas of poor sanitation and hygiene.
Whipworm (Trichuris trichiura) infection happens if a person ingests the eggs from contact with infected soil, or by eating foods grown in soil that contains whipworm eggs.
How are worms diagnosed?
Threadworms can be diagnosed by a ‘sticky tape test’ available from your doctor. The test detects threadworm eggs that are deposited around the anus at night. It involves using special sticky tape to take a sample first thing in the morning. The sticky tape is pressed onto the area around the anus, causing any threadworm eggs present to stick to the tape. The doctor or a laboratory will examine the tape under the microscope to look for the eggs.
Other types of worms may be diagnosed in the laboratory from a fresh stool sample. For example, tapeworms are diagnosed by finding worm segments or worm eggs in a stool sample. Other worms are diagnosed by the presence of eggs, larvae or the parasites themselves, in the stool sample.
Dog hookworm may be diagnosed by finding the parasite on a gut biopsy specimen. The characteristic rash of larva migrans on the skin can also indicate infection with dog hookworm. If this rash moves very quickly, e.g. 2-10 cm per hour, then it is known as larva currens, and indicates infection with Strongyloides.
Infection with some parasites, for example Strongyloides, may cause eosinophilia, an increase in the type of white blood cells known as eosinophils.
What do intestinal worms look like?
Intestinal worms that infect humans and their larvae vary in appearance and size:
- threadworms — these worms are like tiny white moving threads 2-13 mm long; they are visible to the naked eye
- Strongyloides — the larvae are microscopic in size, but mature into 2-3 mm long worms
- dog hookworm — the eggs may be seen as tiny white eggs in a dog’s faeces; the adult worms are 12-15 mm long and j-shaped (hook shaped), with a large mouth with teeth
- dog tapeworm — this tapeworm has 3-4 segments and is around 6 mm long
- pork and beef tapeworms — these are large and flat, like a ribbon; adult pork tapeworms may reach 2-7 metres in length; adult beef tapeworms may be 4-12 metres long. Tapeworms have a head, a neck and many segments, which may contain eggs
- dwarf tapeworms — these are 2-4 cm long and 1 mm wide
- whipworms — adult worms are around 4 cm in length, with one end that is broad and the other thin, making them look like a whip
What are the treatments for worms?
The treatment for threadworms is worming tablets, which are available from the pharmacy. All the family should be treated, even if they have no symptoms. When taking the medicine, you should also ensure you follow strict hygiene practices to prevent re-infestation.
Other intestinal worm infections are also treated with medicines that kill the parasite without harming the person, such as albendazole, mebendazole, ivermectin and praziquantel. Your doctor or a gastroenterologist will advise on the appropriate medicine and the dose. The worms are then usually passed out of the body.
Hydatid disease, caused by dog tapeworm, is serious and potentially fatal. The cysts may be in the liver, lungs, spleen or kidneys, and rarely the brain. Removal of the cysts requires tricky surgery and medicines.
Can a child with worms go to daycare or school?
Children with worms can still go to daycare or school if they have been treated, unless they have loose bowel motions.
How can you avoid getting worms?
Good hand hygiene and keeping fingernails short is the best way to avoid threadworms.
Aside from threadworms, most worm infections in Australia occur in rural and remote communities, or in travellers returning from overseas. They are more common in tropical or subtropical areas. To avoid these types of worms:
- always wash your hands after gardening and before eating, drinking and smoking
- always wash fruit and vegetables before eating
- cook beef and pork thoroughly
- wear shoes when in areas of moist, sandy soil or that may be contaminated with dog faeces
- wash your hands after handling dogs
- supervise dogs so that they can’t feed on dead stock animals or wild animals
- do not feed offal to your dog
- ensure dogs are regularly de-wormed, with worming tablets
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This information was originally published on healthdirect - Worms in humans.
Last reviewed: November 2021