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An intestinal parasite infection is a condition in which a parasite infects the
gastro-intestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
of humans and other animals. Such parasites can live anywhere in the body, but most prefer the intestinal wall. Routes of exposure and infection include ingestion of undercooked meat, drinking infected water, fecal-oral transmission and skin absorption. Some types of helminths and
protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
are classified as intestinal parasites that cause infection—those that reside in the intestines. These infections can damage or sicken the host (humans or other animals). If the intestinal parasite infection is caused by helminths, the infection is called
helminthiasis Helminthiasis, also known as worm infection, is any macroparasitic disease of humans and other animals in which a part of the body is infected with parasitic worms, known as helminths. There are numerous species of these parasites, which are ...
.


Signs and symptoms

Signs and symptoms depend on the type of infection. Intestinal parasites produce a variety of symptoms in those affected, most of which manifest themselves in gastrointestinal complications and general weakness. Gastrointestinal conditions include inflammation of the small and/or
large intestine The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces before being re ...
,
diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...
/
dysentery Dysentery (UK pronunciation: , US: ), historically known as the bloody flux, is a type of gastroenteritis that results in bloody diarrhea. Other symptoms may include fever, abdominal pain, and a feeling of incomplete defecation. Complications ...
,
abdominal pain Abdominal pain, also known as a stomach ache, is a symptom associated with both non-serious and serious medical issues. Common causes of pain in the abdomen include gastroenteritis and irritable bowel syndrome. About 15% of people have a more ...
s, and nausea/ vomiting. These symptoms negatively impact nutritional status, including decreased absorption of micronutrients, loss of appetite, weight loss, and intestinal blood loss that can often result in
anemia Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, t ...
. It may also cause physical and mental disabilities,
delayed growth Child development involves the biological, psychological and emotional changes that occur in human beings between birth and the conclusion of adolescence. Childhood is divided into 3 stages of life which include early childhood, middle childhood, ...
in children, and skin irritation around the anus and vulva.


Cause

The prevalence of intestinal parasites is the highest among children that are living in the poorest communities in developing nations. The most common causes of intestinal parasites are through consumption of contaminated water, infected soil, inadequate sanitation and hygiene, and improper hygiene. Specifically, lack of access to facilities for safe disposal of human waste can result in intestinal parasites and disease. Poor hygiene habits or lacking available hygiene resources, such as hand washing facilities, also negatively impact rates of disease. Parasitic contamination can also occur from eating raw produce, soil-eating behaviour, and low availability of safe drinking water. Parasites can get into the intestines by going through the mouth from uncooked or unwashed food, contaminated water or hands, or by skin contact with larva infected soil; they can also be transferred by the sexual act of
anilingus Anilingus (from the Latin ''anus'' + ''-lingus'', from ''lingere'', "to lick", variantly spelled "analingus") is the oral and anal sex act in which a person stimulates the anus of another by using the mouth, including lips, tongue, or teeth. I ...
in some cases. When the organisms are swallowed, they move into the intestines, where they can reproduce and cause symptoms. Children are particularly susceptible if they are not thoroughly cleaned 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.


Diagnosis

Due to the wide variety of intestinal parasites, a description of the symptoms rarely is sufficient for diagnosis. Instead, medical personnel use one of two common tests: they search stool samples for the parasites, or apply an adhesive to the
anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, de ...
to search for eggs.


Types

Major groups of parasites include protozoans (organisms having only one cell) and parasitic worms (helminths). Of these, protozoans, including
cryptosporidium ''Cryptosporidium'', sometimes informally called crypto, is a genus of apicomplexan parasitic alveolates that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves watery diarrhea (intestinal cryptos ...
,
microsporidia Microsporidia are a group of spore-forming unicellular parasites. These spores contain an extrusion apparatus that has a coiled polar tube ending in an anchoring disc at the apical part of the spore. They were once considered protozoans or pr ...
, and
isospora ''Isospora'' is a genus of internal parasites in the subclass Coccidia. It is responsible for the condition isosporiasis, which causes acute, non-bloody diarrhoea in immunocompromised individuals. Taxonomy At least 248 species were originall ...
, are most common in
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
-infected persons. Each of these parasites can infect the digestive tract, and sometimes two or more can cause infection at the same time.


Prevention

Good hygiene is necessary to avoid reinfection. The Rockefeller Foundation's hookworm campaign in Mexico in the 1920s was extremely effective at eliminating hookworm from humans with the use of
anthelmintic Anthelmintics or antihelminthics are a group of antiparasitic drugs that expel parasitic worms (helminths) and other internal parasites from the body by either stunning or killing them and without causing significant damage to the host. They may ...
s. However, preventative measures were not adequately introduced to the people that were treated. Therefore, the rate of reinfection was extremely high and the project evaluated through any sort of scientific method was a marked failure. More education was needed to inform the people of the importance of wearing shoes, using latrines (better access to sanitation), and good hygiene. Intestinal parasite prevention methods are not isolated to specific geographical areas; however, many of the research-based interventions have primarily taken place in underdeveloped countries and regions, where sanitation is a large concern for spreading disease.Current best practice behaviors that prevent intestinal parasites include: using proper hand washing practices, using correctly-built latrines with ample ventilation, having a piped water source, and wearing shoes. Currently, in some parts of Ethiopia where disease prevalence is high, up to 80% of people in a population lack access to washing facilities. While this is high, 93% did have access to a latrine, but only 29.2% of those latrines had proper construction to decrease parasitic infections. Behavioral interventions have focused on promoting washing, sometimes with soap, in context of education at schools and child care facilities. In recent studies, the best interventions follow a multidisciplinary approach by: * Increasing environmental sanitation to promote hand washing and shoe wearing habits * Educating children at young ages at school and at home Specific evidence-based interventions that may lower disease prevalence include: * Interventions at schools, focusing on the construction of pit latrines (ventilated and improved), providing clean drinking water and educating the students about hygiene * The SAFE (surgery, antibiotics, facial cleanliness, environmental sanitation) strategy to address
trachoma Trachoma is an infectious disease caused by bacterium ''Chlamydia trachomatis''. The infection causes a roughening of the inner surface of the eyelids. This roughening can lead to pain in the eyes, breakdown of the outer surface or cornea of ...
, primarily the facial cleanliness and the environmental sanitation components * Hand-washing with soap at critical times and nail clipping to decrease reinfection rates, although further research is needed to develop and implement similar interventions at scale * Programs combining anthelmintic drug administration with interventions to increase environmental sanitation (such as decreasing fecal contamination)


Treatment

Drugs are frequently used to kill parasites in the host. In earlier times, turpentine was often used for this, but modern drugs do not poison intestinal worms directly. Rather, anthelmintic drugs now inhibit an enzyme that is necessary for the worm to make the substance that prevents the worm from being digested. For example, tapeworms are usually treated with a medicine taken by mouth. The most commonly used medicine for tapeworms is praziquantel.


References


External links

* {{Medicine, state=collapsed Gastrointestinal tract disorders Parasites of animals