Intestinal Parasites

Overview

Intestinal parasites are tiny living things that live in your gut (intestines). Some are worms you can sometimes see, like threadworms or tapeworms. Others are so small you need a microscope to see them, like Giardia. They get into your body through food, water, dirty hands, or soil, and they feed off your body or the food you eat. Many cause only mild symptoms, and most can be cleared up with treatment.

Yes. Some intestinal parasites, like threadworms, are very common, especially in children. Others, like Giardia or roundworm, are more common in parts of the world with poor sanitation and safe water supplies, but they can affect anyone, anywhere.

Anyone can get intestinal parasites. Children are affected most often because they put things in their mouths and may not wash hands well. Other groups at higher risk include people who travel to areas with limited clean water, people living in crowded or poor housing, people with weakened immune systems, and people who handle animals or soil.

Symptoms

Common symptoms

• Tummy pain or cramping
• Diarrhoea, which may be watery or greasy
• Gas, bloating, and burping
• Feeling sick or being sick
• Itching around the bottom, often worse at night (a classic sign of threadworms)
• Seeing small white worms in your poo or on your bedding
• Losing weight without trying, or poor appetite
• Feeling tired, weak, or short of breath (sometimes a sign of low iron)
• Poor sleep and irritability, especially with itchy bottoms

Symptoms in children

• An itchy bottom, especially at night, which can lead to scratching and broken sleep
• Being irritable or tearful, or finding it hard to concentrate at school
• Poor appetite, tummy aches, and slow weight gain or growth
• Occasional bedwetting in a child who was previously dry
• Visible tiny worms in the poo or around the bottom

Symptoms in older adults

• Diarrhoea that leads to dehydration more quickly, causing dizziness, confusion, or falls
• Feeling very tired or weak, sometimes linked to low iron levels
• Poor appetite and weight loss, which can be more serious in frail people
• Symptoms that last longer or are harder to shake off, especially if the immune system is weaker

Causes

Main causes

• Swallowing parasite eggs or tiny eggs from dirty hands, unwashed food, or contaminated water
• Drinking or swimming in water that contains parasites, such as streams, lakes, or poorly treated water
• Eating raw or undercooked meat, fish, or shellfish that contains parasites
• Walking barefoot on soil contaminated with certain worm larvae, which can burrow through the skin
• Threadworms spread easily from the bottom to the mouth, often through scratching and then touching food, toys, or bedding
• Contact with infected animals or their poo, and touching soil or surfaces where pets have been

Risk factors

• Young children in nurseries, schools, or playgroups where outbreaks happen
• Travel or living in areas with limited clean water and sanitation
• Poor hand hygiene, or sharing towels, bedding, and utensils
• Crowded living conditions
• A weakened immune system from illness or certain treatments
• Close contact with pets, farm animals, or livestock
• Eating raw or undercooked food, or unwashed fruit and vegetables
• Swimming in lakes, rivers, or pools that may be contaminated

When to see a doctor

See a doctor urgently if:

• Blood or lots of mucus in your poo
• Severe or ongoing tummy pain
• Signs of dehydration, such as feeling very thirsty, dark urine, or feeling faint
• A high fever with diarrhoea or vomiting
• Vomiting so much you cannot keep fluids down
• Any of the emergency symptoms listed above

Book a routine appointment if:

• An itchy bottom that lasts more than a few days, or worms you can see
• Diarrhoea that lasts more than a week or keeps coming back
• Tummy pain, bloating, or gas that will not settle
• Losing weight without trying
• Feeling unusually tired, or being told you are low in iron
• You have been somewhere with unsafe water and started feeling unwell afterwards

Diagnosis

Your doctor will ask about your symptoms, where you have travelled, what you have eaten, and whether anyone else at home has the same problems. Then they will usually ask for a stool (poo) sample to look for parasites or their eggs under a microscope. For threadworms, they may instead suggest a simple tape test at home, or sometimes the diagnosis is made just from the symptoms.

Tests that may be done

• Stool sample: you collect a small amount of poo in a container and send it to the lab. You may need to give more than one sample on different days
• Sticky tape test: a piece of clear tape is pressed gently against the skin around the bottom, usually in the morning, and checked for tiny eggs
• Blood tests: to check for low iron, low vitamin levels, or signs of infection
• Occasionally, a small sample of the gut lining taken during a camera test (endoscopy or colonoscopy), usually only if other tests are unclear

What to expect at your appointment

Getting tested is simple and private. You will be given a clean pot and clear instructions. Lab results usually take a few days. In the meantime, keep drinking fluids and washing your hands often. If your child has an itchy bottom, checking at night with a torch can help your doctor, as threadworms are easiest to spot then.

Treatment

Treatment depends on the type of parasite. Many are cleared with a short course of medicine that kills the parasite, prescribed by a doctor. Alongside medicine, good hydration and careful hygiene matter a lot, because they stop the infection spreading and help you feel better faster.

Self-care at home

• Drink plenty of fluids. Rehydration drinks from a pharmacy can help if you have diarrhoea
• Wash your hands with soap and warm water after using the toilet and before preparing or eating food
• Keep fingernails short and clean, and try not to scratch the bottom area
• Shower or wash the bottom area each morning to remove eggs
• Change and wash bedding, towels, and underwear on a hot wash, especially during threadworm treatment
• Wash fruit and vegetables well, and avoid untreated water while you recover
• Stay off work, school, or nursery until your doctor says it is safe to return, especially if you work with food or children

Medical treatments

Your doctor may prescribe medicines that kill the parasite in your gut. For threadworms, treatment is usually given to everyone in the household at the same time, and a second dose is often needed a couple of weeks later to catch any newly hatched worms. Some infections need a longer course. If you are low in iron or vitamins, your doctor may also recommend supplements. Always follow your doctor's or pharmacist's instructions, and finish any course you are given. Do not use leftover medicine or someone else's medicine.

When is surgery considered?

Surgery is rarely needed. In unusual cases, a very heavy worm infection can block the bowel, or a parasite can cause problems in the liver or gallbladder, and an operation or a procedure may be needed. Your medical team will explain this clearly if it applies to you.

Living with this condition

Most people feel better within days of starting treatment. In the meantime, rest, keep fluids up, and keep hands and surfaces clean so the infection does not pass to others. It helps to tell close contacts, such as a school or nursery, if your child has threadworms, so everyone can be treated and reinfection is less likely.

Lifestyle tips

• Make handwashing a family routine, especially after the toilet and before meals
• Keep toothbrushes, towels, and cups separate while someone is being treated
• Wash bedding and nightwear regularly on a hot wash
• Avoid sharing baths or swimming pools until treatment is finished, if your doctor advises this
• Check and treat pets for worms as advised by your vet

Diet and exercise

Eat small, gentle meals if your tummy is upset, and drink often. Plain foods like rice, toast, and bananas can be easier to manage. Avoid heavy, greasy, or very spicy food until you feel better. Once your energy returns, gentle activity like walking is fine, but take it easy while you are recovering and dehydrated. Ask your doctor if you need extra vitamins, iron, or dietary advice because of weight loss.

Mental health and emotional wellbeing

It is very common to feel embarrassed, worried, or squeamish about parasites, especially if a child is affected. These feelings usually settle once treatment starts and symptoms improve. Talk to your doctor if worry, poor sleep, or low mood is affecting daily life. If you ever have thoughts of harming yourself and feel you cannot keep safe, contact your local emergency number or a crisis line in your country straight away.

Prevention

You cannot always prevent parasites, but you can greatly lower the risk. The most important step is washing your hands well with soap and warm water after using the toilet, after touching animals, and before eating or preparing food. Washing fruit and vegetables, drinking safe water, cooking meat and fish thoroughly, and wearing shoes outdoors in high-risk areas also help a lot.

Vaccines

There are no routine vaccines for people against intestinal parasites. Some vaccines exist for animals, such as livestock, and your vet can advise on protecting pets and farm animals.

Screening programmes

There is no routine screening for intestinal parasites in healthy people. Testing may be offered in certain situations, such as after travel to a high-risk area, when symptoms suggest infection, or as part of public health checks in some settings. Ask your doctor or local health service if you think you need a test.

Complications

If left untreated

• Ongoing diarrhoea and dehydration
• Low iron (anaemia) causing tiredness, breathlessness, and poor concentration
• Poor growth or weight gain in children
• Malnutrition and general weakness
• In rare cases, a heavy worm infection can block the bowel
• Rarely, parasites can affect the liver, gallbladder, or other organs
• Spread to other people in the household, school, or workplace

Long-term outlook

The outlook is good. Most intestinal parasites are found quickly and cleared with a short course of treatment, and many people feel better within days. Even when symptoms are unpleasant, serious problems are uncommon, and treatment is straightforward. If symptoms do not settle, or come back, let your doctor know so they can check again and adjust the plan.

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