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What are the symptoms of parasites?

A parasite lives and feeds off other organisms. Intestinal parasites are generally worms that feed off the material in your body. Hookworms, tapeworms, and roundworms are amongst the most common. Symptoms of parasites vary with the type of parasite.

Some intestinal parasites consume your food, leaving you hungry after every meal. Others cause anaemia by feeding off your red blood cells. Some lay eggs that can cause itching and irritability.

Common gastrointestinal symptoms like bloating, gas, diarrhea and constipation might be linked to parasitic infections.

Some of the most common symptoms or parasitic infection include:


Diarrhoea, abdominal cramping, bloating, gas, nausea, fatigue, and weight loss are often sign of giardia. They can also manifest themselves quite quickly.


Similarly symptoms of tapeworms may begin only about 8 weeks after the tapeworms have developed in the intestine. The symptoms include nausea, diarrhoea, constipation, and abdominal pain. Although these can be mild symptoms only. Untreated tapeworms can live for years, and can lead to malnutrition, headaches, blindness, and seizures.

Chronic symptoms of parasites

Chronic signs and symptoms of parasites include loose or fatty stools, IBS or gastritis. A 10 to 20 percent loss in weight, malabsorption of nutrients, fatigue, and depression may come and go over many months if the condition is not treated. Joint pain and allergic reactions, or decreased immune functions are also long term symptoms.

  • Irritable bowel syndrome 
  • Irregular bowel movements
  • Gastritis or indigestion
  • Skin disorders 
  • Joint pain
  • Allergic reaction
  • Decreased immune function 

How do intestinal parasites happen?

Realistically most people get a parasite at some point. That’s because we all encounter contaminated food or drink no matter how careful we are. Overseas travel has risks, so do pets, swimming pools,river and lakes.Typical causes include:

  • Drinking water containing parasites or their eggs

  • Skin contact with contaminated water

  • Skin contact with contaminated soil or sand (barefoot on the beach)

  • Eating foods which are uncooked or undercooked (eg pork)

  • Contact with insects such as lice, fleas, mites, and ticks

  • Airborne viruses and bacteria

  • Contact with contaminated faeces (i.e. ineffectively washed hands after bathroom use)

  • Pets – dogs, cats and other some animals carry tapeworm parasites at certain stages in their life cycle. These can be transferred to humans by an animal licking the face.

Simple precautions

There are simple ways of trying to avoid parasittes. Travellers should be careful about what water they drink. Also when overseas think twice before paddling or swimming in fresh water. If you are in tropical or sub-tropical areas soft fruit and salads that have been hand-washed locally bring risks.  Again in these regions apply insect repellent, and be sure to apply it, once dried if you have had body contact with fresh water.

Wash your hands with soap and water after contact with pets, or after handling raw meat. If you are a pet owner avoid contact with your animal’s mouth.


Conventional medicine uses anti-parasitic drugs to manage infections such as praziquantel and mebendazole. But these drugs can have many uncomfortable side effects which can be almost as bad as the parasitic infection itself, including nausea, vomiting, headaches, weight loss, and insomnia. The damage parasites have caused before treatment will determine if you need additional pharmaceutical intervention, but there are many natural herbs that possess powerful antiparasitic properties. These are great options if you want to take a completely natural approach or want to take something alongside anti-parasitic medications.



The best way to test for intestinal parasites is with a stool test. Once sure of that the symptoms of parasites are evident, doctors tend to run conventional stool tests, however greater accuracy and therefore better diagnosis comes from a comprehensive stool test. If you think that you are showing symptoms of parasites we offer a complete testing and analysis service. Learn more about our approach to testing here.


Types, and individual symptoms of parasites

Blastocystis hominis
(B. Hominis)

.Blastocystis hominis is a common protozoan found throughout the world. It is transmitted via fecal/ oral transmission or by ingestion of contaminated food or water. Patients with B Hominis commonly have fatigue. Some patients will have abdominal pain, nausea, vomiting, diarrhoea, weight loss as well as anorexia, flatus and eosinophilia. B. Hominis shares the typical symptoms of parasites including diarrhoea, crampy abdominal pain, nausea, vomiting. But it also causes low grade fever, gas, malaise and chills. Fecal leukocytes are sometimes seen and B Hominis can cause colitis.

Campylobacter Jejune (C.jejune)

C. jejune infection causes diarrhoea, which can be watery or sticky and can contain blood. Leukocytes (white blood cells) may be found in the stool. Symptoms include: fever, abdominal pain, nausea, headache and muscle pain. The illness usually occurs 2-5 days after ingesting the contaminated food or water. Illness generally lasts 7-10 days, but relapses are not uncommon (about 25% of cases). Most infections are self-limiting and are not treated with antibiotics.

Citrobacter Freundii

Also known as Citrobacter rodentium, this bacterium can cause gastroenteritis. Animal studies have shown that it can cause an intense inflammatory response in the gastro-intestinal tract which can resemble inflammatory bowel disease (Crohn’s, Ulcerative or Microscopic Colitis). Most Citrobacter freundii produce hydrogen sulphide gas which interferes with mitochondrial function and can contribute to colitis.


Dientamoeba Fragilis

Infection with D Fragilis does not necessarily cause obvious symptoms. It can cause diarrhoea and a painful abdomen in some people. Occasionally there may be some blood seen in the stool. It is transmitted via contaminated water or in food containing pinworm egg.

Entamoeba coli

Not to be confused with the bacterium Escherida coli (E Coli – see below), people infected with the Entamoeba Coli protozoa can be symptom-free, or only experience mild diarrhoea. But occasionally this ‘bug’ can cause symptoms beyond the gastro-intestinal tract. Some patients have reported that they felt “strange all over”. Transmission is via contaminated food or water.

Endolimax Nana (E. Nana)

Endolimax Nana is a protozoa with world-wide distribution and commonly considered to be harmless. However infection with E Nana can cause a peripheral arthropathy which is clinically similar to rheumatoid arthritis and which remits when the parasite is eradicated. Intestinal colonisation by E Nana has been seen in patients presenting with chronic fatigue, myalgia, eczema and refractory chronic vaginitis.

Entamoeba Histolytica
(E. Histolytica)

E Histolytica can induce tissue damage, amoebic colitis and liver abscess. Amoebic colitis can be misdiagnosed as ulcerative colitis and can manifest as IBS, rheumatoid arthritis, fibromyalgia, food allergy or multiple chemical sensitivities. Some infections are asymptomatic.

Escherida Coli (E. Coli)

E Coli is a bacterium that colonises dairy and beef cattle, which is why ground beef is the most common infection vehicle. However, raw milk, sausage, roast beef, unchlorinated water, apple cider, and raw vegetables have also been implicated. The STEC strains cause a spectrum of illness. These can present as mild non-bloody diarrhoea, severe bloody diarrhoea (hemorrhagic colitis), and haemolytic uremic syndrome.

Giardia Lamblia

Giardia is associated with abdominal pain, diarrhoea, constipation, bloating, chronic and fatigue. Additionally food allergy and intolerance occur. Giarda can also exacerbate IBS, rheumatoid arthritis, food allergy or multiple chemical sensitivity. Some infections are relatively asymptomatic.


Heliobacter Pylori (H.Pylori)

H Pylori is found in the intestinal tract of mammals and birds. Mode of transmission is usually via the fecal-oral or oral-to-oral route. This bacterium causes chronic gastritis and predisposes to gastric and duodenal ulcers. Increased risk of gastric carcinoma is associated with infection. If you are infected with H. Pylori, you may develop acute gastritis with symptoms of abdominal pain, nausea and vomiting, usually within two weeks of infection. Many patients have recurrent abdominal symptoms (non-ulcer dyspepsia) without ulcer disease. H Pylori is treated conventionally with multi-drug regimens along with antacid medications.


This causes a common type of food poisoning. Symptoms of salmonellosis include diarrhoea, fever, and abdomen cramping. Symptoms develop 12 to 72 hours after infection, and the illness usually lasts 4 to 7 days. Most people recover without treatment. But diarrhoea and dehydration may warrant hospitalisation as it can be severe. Older adults, infants, and those who have impaired immune systems are at highest risk. If you only have diarrhoea, you usually recover completely, although it may be several months before your bowel habits are entirely normal. Most infections are self-limiting and are not treated with antibiotics.

If you are feeling unwell, exhibiting symptoms of parasites, and would like a free 15 minute telephone consultation to get some advice on parasites please book a time here:

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