Intestinal parasites are parasites that populate the gastro-intestinal tract in humans and other animals. They can live throughout the body, but most prefer the intestinal wall. Means of exposure include: ingestion of undercooked meat, drinking infected water, and skin absorption. A parasite is an organism that
feeds off another organism, called a host

Host (biology)

In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...

.

The major groups of parasites include protozoans (organisms having only one cell) and parasitic worm

Parasitic worm

Parasitic worms or helminths are a division of eukaryoticparasites that, unlike external parasites such as lice and fleas, live inside their host. They are worm-like organisms that live and feed off living hosts, receiving nourishment and protection while disrupting their hosts' nutrient...

s (helminths). Of these, protozoans, including cryptosporidium

Cryptosporidium

Cryptosporidium is a protozoan that can cause gastro-intestinal illness with diarrhea in humans.Cryptosporidium is the organism most commonly isolated in HIV positive patients presenting with diarrhea...

, microsporidia

Microsporidia

The microsporidia constitute a phylum of spore-forming unicellular parasites. They were once thought to be protists but are now known to be fungi. Loosely 1500 of the probably more than one million species are named now. Microsporidia are restricted to animal hosts, and all major groups of animals...

, and isospora

Isospora

Isospora is a genus of internal parasites classified under Coccidia.It is responsible for the condition isosporiasis.At least 248 species have been described in this genus, but most of them are little studied and it is doubtful whether all should be recognized as distinct species...

, are most common in HIV

HIV

Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

-infected persons. Each of these parasites can infect the digestive tract, and sometimes two or more can cause infection at the same time.

Infection

Parasites can get into the intestine by going through the mouth from uncooked or unwashed food, contaminated water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 or hands, or by skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 contact with larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

 infected soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

.
When the organisms are swallowed, they move into the intestine, where they can reproduce and cause symptoms. Children are particularly susceptible if they are not thoroughly sterilized after coming into contact with infected soil that is present in environments that they may frequently visit such as sandboxes and school playgrounds. People in developing countries are also at particular risk due to drinking water from sources that may be contaminated with parasites that colonize the gastrointestinal tract.

Symptoms

A list of common symptoms:

• Abdominal pain
• Myositis
  Myositis
  Myositis is a general term for inflammation of the muscles. Many such conditions are considered likely to be caused by autoimmune conditions, rather than directly due to infection It is also a documented side effect of the lipid-lowering drugs statins and fibrates.Elevation of creatine kinase in...
  
  
• Constipation
  Constipation
  Constipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation...
  
  
• Anaemia
• Anorexia
  Anorexia (symptom)
  Anorexia is the decreased sensation of appetite...
  
  
• B-12 deficiency
• Rectal hemorrhage
  Rectal hemorrhage
  Rectal hemorrhage refers to bleeding in the rectum. There are many causes of rectal hemorrhage, including hemorrhoids , rectal varices, proctitis , stercal ulcers and infections...
  
  
• Blindness
  Blindness
  Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...
  
  
• Hematochezia
  Hematochezia
  Hematochezia is the passage of fresh blood per anus, usually in or with stools . Hematochezia is commonly associated with lower gastrointestinal bleeding, but may also occur from a brisk upper GI bleed...
  
  
• Hemoptysis
  Hemoptysis
  Hemoptysis or haemoptysis is the expectoration of blood or of blood-stained sputum from the bronchi, larynx, trachea, or lungs Hemoptysis or haemoptysis is the expectoration (coughing up) of blood or of blood-stained sputum from the bronchi, larynx, trachea, or lungs Hemoptysis or haemoptysis ...
  
  
• Dysuria
  Dysuria
  In medicine, specifically urology, dysuria refers to painful urination.Difficult urination is also sometimes described as dysuria.It is one of a constellation of irritative bladder symptoms, which includes urinary frequency and haematuria....
  
  
• Central nervous system impairment
• Chest pain
• Chills
• Chronic fatigue
• Colitis
  Colitis
  In medicine, colitis refers to an inflammation of the colon and is often used to describe an inflammation of the large intestine .Colitides may be acute and self-limited or chronic, i.e...
  
  
• Coughing
• Diarrhea
  Diarrhea
  Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
  
  
• Digestive disturbance
• Dizziness
• Fever
  Fever
  Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
  
  
• Enlargement of various organs
• Headaches
• Vaginitis
  Vaginitis
  Vaginitis is an inflammation of the vagina. It can result in discharge, itching and pain, and is often associated with an irritation or infection of the vulva. It is usually due to infection. The three main kinds of vaginitis are bacterial vaginosis , vaginal candidiasis, and trichomoniasis. A...
  
  
• Jaundice
  Jaundice
  Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...
  
  
• Joint Pain
• Weight loss due to malnutrition
• Weakness
• Immunodeficiency
• Nausea
  Nausea
  Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
  
  /vomiting
  Vomiting
  Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
  
  
• Swelling of facial features
• Sweating
• Insomnia
  Insomnia
  Insomnia is most often defined by an individual's report of sleeping difficulties. While the term is sometimes used in sleep literature to describe a disorder demonstrated by polysomnographic evidence of disturbed sleep, insomnia is often defined as a positive response to either of two questions:...
  
  
• Skin ulcers
• Rectal prolaspe
• Mental problems
• Lung congestion
• Memory loss
• Night sweats
• Muscle spasms
• Hair loss or thinning

In some people, intestinal worms do not cause any symptoms, or the symptoms may come and go. If you have some of these symptoms, it does not necessarily mean that you are infected. These symptoms may also indicate to other diseases.
Common signs and complaints include coughing, cramping, abdominal pain, bloating, flatulence and diarrhea. Some parasites also cause low red blood cell count (anemia), and some travel from the lungs to the intestine, or from the intestine to the lungs and other parts of the body. Many other conditions can result in these symptoms, so laboratory tests are necessary to determine their cause.

In children, irritability and restlessness are commonly reported by parents.

Diagnosis

Due to the wide variety of intestinal parasites, a description of the symptoms rarely are sufficient for diagnosis. Instead, two common tests are used: Stool samples may be collected to search for the parasites, and an adhesive may be applied to the anus in order to search for eggs.

Treatment

Prescription drugs are generally used to eradicate the parasites. Special poisons are tailored to kill one or more common varieties of intestinal parasites. Good hygiene is recommended to avoid reinfection.