Having Stomach Problems? You Might Have Intestinal Parasites

What are Intestinal parasites?

Intestinal parasites reside in the gastro-intestinal tract of human beings as well as animals (the “host”). They stick to the walls of the intestine and get their nourishment from the host’s intake of food.

Intestinal parasitic infections are most commonly caused by poor hygiene and sanitation, both of which are common in poor countries. parasitesWhat causes intestinal parasitic infection?

Parasites enter the intestine through intake of water that is not purified or intake of raw food or through direct contact with infected soil or feces of humans or animals that are already infected with these parasites. Once inside the body, these organisms grow and multiply and can even spread throughout the host’s body, leading to a whole host of unpleasant symptoms. There are several types of parasites including the following:

Protozoa: Protozoa are single-celled microscopic organisms that stay and multiply inside the body, feeding on microorganisms. Common types of protozoa are Giardia and Cryptosporidium which are most commonly ingested by drinking unclean water and often cause diarrhoea in the host.

Worms: Parasitic worms also known as Helminths are small animals and can be seen with naked eyes which enters inside the body through the oral cavity. These are multi-celled organisms that reside both in and outside the body. Typical types of worms are pinworm, tapeworm and thorny-headed worm. These worms hatch their eggs inside the body of infected person and move to other organs in time, disrupting the function of these organs. These worms cause poor nutrient absorption in the host or victim, leading to weakness, malnourishment and disease in the host.

Mites and Lice: Ectoparasites are multi-celled organisms which stay either in or outside the skin but not inside the body. These includes fleas, lice, mites and mosquitos.

How can we diagnose parasitic infections?

We can diagnose parasitic infections by performing certain tests and examinations which include:

  • Endoscopy
  • Blood test
  • Faecal (stool) examination.
  • X-rays, MRI or CAT

What are the common different types of intestinal parasites?

Common intestinal parasitic diseases are infections caused by helminths (worms, e.g. tapeworms, pinworms, roundworms) and protozoa (giardia, cryptosporidium). Common diseases which are caused by parasites include the following:


Also known as beaver fever, giardiasis is a waterborne disease which infects the small intestine and is caused by Giardia lambia (microscopic parasite). Giardiasis is more likely to spread among children through drinking contaminated water from rivers, lakes as well as through intake of soil or food that is contaminated due to inadequate sanitation facilities.

Threadworm or Pinworm Infection

Pinworms are tiny, white pin-shaped worms that live in the human colon and rectum. Infections caused by pinworms are enterobiasis or oxyuriasis. These parasites stay for around two weeks around the anal area and cause anal itching, rashes and pain on the infected skin. They commonly spread through pinworms eggs which are stuck to toilet seats or the clothes of the infected person.

Tapeworm Infection

A tapeworm is a parasite that stays in the gut and, with time, can migrate from the intestine to form cysts in tissues and organs of body. Some people may not experience any symptoms but a few may have stomach ache, nausea, diarrhoea, and change in appetite or weight loss. In some cases it can block the intestine or ducts in the intestine, leading to acute inflammation.


This is an itchy skin disease caused by tiny organisms or mites (Sarcoptes scabiei) which enters the skin or hair follicles to lay eggs and cause itching and tiny red burrows. When the skin is scratched by itching, germs enters the skin causing infection through mites or lice. Scabies usually stays in the armpit, groin, back of elbows or knees.

Blastocystis Infection

This is a single-celled parasite. People with diarrhoea and intestinal problems are more likely to have blastocystis. It lives in the gastrointestinal tract causing problems in the intestine. It spreads through contaminated water and food, causing diarrhoea, weight loss, constipation, and stomach ache. It can be diagnosed through a faecal examination. It stays in the body for years and there their role in causing illnesses is actually unclear.

Dientamoeba Fragills Infection

It is a single celled parasite that typically resides in the large intestine of humans. Some people may not have any symptoms while others are likely to have weight loss, nausea, diarrhoea, loose stools and loss of appetite. It is transmitted through the faecal or oral route and can be diagnosed through stool samples.


This is a disease caused by the round worm Ascaris lumbricoides. The adult worm and larvae can live for 2 to 3 years causing infection, intestinal blockage, loss of appetite, nausea and diarrhoea.


It is a parasitic infection of large intestine caused by amoeba Entamoeba histolytica, a single-celled organism. The infected person may have stomach pain, nausea, loose stool and weight loss.

What are the symptoms and risk factors of parasitic infections?


Infected persons typically experience stomach cramps, nausea, and severe diarrhoea leading to dehydration, bloating and persistent weight loss and abdominal pain. Symptoms usually begin to appear about two weeks after infection while some are asymptomatic. It is usually not dangerous but if untreated the symptoms can last from two weeks to two years in some cases which can cause:

  • Persistent pain in stomach
  • Diarrhoea and dehydration
  • Chronic fatigue
  • Intestinal blockages
  • Anaemia
  • Rashes
  • Muscle cramps
  • Allergies
  • Headache

Children are mostly at risk of developing parasitic infections as they easily come into contact with contaminated soil in school, playgrounds and day-care where there is often a lack of hygiene. In adults, the risk of developing parasitic infections is primarily due to weakened immune systems. These infections tend to be far more prevalent in developing countries which typically have lower levels of sanitation and hygiene. The best defence against parasites is good hygiene and intake of purified water and properly cooked food.