Faecal-oral transmission , where parasites found in the stool of one person end up being swallowed by another person, is the most common mode of transmission of parasitic protozoa and helminths. The initial symptoms tend to be gastrointestinal symptoms like diarrhoea. When parasites invade the red blood cells or organs, the consequences can become more serious. The protozoa giardia, for example, has a classic two-stage life cycle.
In the first stage, called trophozoite, the parasite swims around and consumes nutrients from the small bowel. In the second stage it develops into a non-moving cyst.
Cysts excreted in faeces can contaminate the water supply, and ingesting contaminated food or water results in transmission. Close human to human contact and unsanitary living conditions can promote transmission. Symptoms of giardia can include severe or chronic diarrhoea, abdominal cramps, fatigue, weakness and weight loss. Other important protozoa are the plasmodium species. Plasmodium develop in mosquitoes, and infected mosquitoes transmit the parasite to humans by biting them.
Plasmodium destroys red blood cells which impacts organ function and causes a disease in humans known as malaria. Malaria causes the most deaths of all parasitic diseases. In it was estimated malaria resulted in , deaths globally , most of them young children in sub-Saharan Africa. Read more: How our red blood cells keep evolving to fight malaria.
Giardia lamblia is a flagellated protozoan parasite. It lives and reproduces in the intestine, causing an infection of the small intestine known as giardiasis. When it takes up residence in a human's gut, it results in inflammation and and other damage, reducing the gut's ability to absorb nutrition and causing diarrhoea.
The parasite is highly resistant to water treatment and is known to exist in drinking water. Entamoeba histolytica This single-celled organism causes a disease called amoebiasis. It predominantly infects humans and other primates. It can be found in water , damp environments and in soil, and can contaminate fruits and vegetables.
It spreads through faecal contamination. Other than the malarial parasite, it causes more deaths than any other protozoan. New Scientist investigates some of the most common human parasites and the damaging effects they can have Hookworm Necator americanus This parasitic nematode worm begins life outside the body and is transmitted through contaminated water, or fruits and vegetables. Scabies mite Sarcoptes scabiei var.
Roundworm Ascaris lumbricoides These are the largest of the intestinal nematodes affecting humans, growing to centimetres in length. Flatworm blood fluke Schistosoma mansoni , S. Tapeworm Taenia solium Transmitted through infected food, a tapeworm attaches itself to its victim's intestine with hooks on its "head", or scolex.
Pinworm Enterobius vermicularis Pinworms are a common human parasite, causing enterobiasis. We actually see quite a few cases of them here at Westchester Health. Not restricted to underdeveloped countries, parasites exist around the world and can afflict anyone of any race, gender or socioeconomic status.
They can cause a myriad of symptoms, only a few of which affect the digestive tract, but the good news is that yes, they are treatable. A parasite is any organism that lives and feeds off another organism.
Examples of parasites include:. The embedded flea swells dramatically up to the size of a pea! This infestation resembles a blister with a black dot which is actually the legs, breathing apparatus and reproductive organs of the flea. After several weeks, eggs there may be several hundred begin to be laid and fall to the ground, hatching about three days later and emerging as adults weeks later.
Pain and swelling are common even in single infestation and complications include secondary infections that can cause tetanus and gangrene and loss of nails and toes. Explore further. Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form. For general feedback, use the public comments section below please adhere to guidelines. Your feedback is important to us.
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By using our site, you acknowledge that you have read and understand our Privacy Policy and Terms of Use. Share Twit Share Email. Home Diseases, Conditions, Syndromes. August 28, Maybe not such a great place to go swimming. Credit: Phanatic. Giardia intestinalis Credit: AJC1. Guinea worm. Now on the retreat. Credit: CDC. Filarial worm. Jigger lesions. Credit: Boyznberry.
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