HEALTH

Human body parasites: the 10 worst ones we never want to encounter

Parasites are some of the most common organisms on Earth. Truly monstrous-looking, when viewed under a microscope, these unicellular or multicellular organisms are capable of creating many problems for the human body.

Many of these parasites are harmless to humans, but there is also a large variety that uses us as hosts, eating and replicating endlessly. Some affect the intestines, others the liver, and even the brain and nervous system. 

Let's take a look at ten of the worst ones we might ever encounter during our lifetime, in different parts of the world.

Wikipedia.org
Human body parasites: the 10 worst ones we never want to encounter
Parasites are some of the most prevalent organisms on earth. Truly monstrous-looking, when viewed under a microscope, these unicellular or multicellular organisms are capable of creating quite a few problems for the human body. Many of these parasites are harmless to humans, but there is also a wide variety that uses us as hosts, eating and replicating endlessly. Some affect the intestines, others the liver, and even reach the brain and nervous system. Let's see what may be 10 of the worst ones we might ever encounter in our lifetime, in different parts of the world.
Di Photo Credit:Content Providers(s): CDC/ Dr. George Healy - This media comes from the Centers for
Entamoeba histolytica
This parasite is extremely widespread throughout the world, but mainly in India and South America, or at any rate in places where hygienic conditions are most precarious. It is a single-celled protozoan that can enter the body either through contaminated food or water. Entamoeba histolytica infections can result in the development of syndromes known by the generic name amebiasis. The most common symptoms of this condition are rectocolitis or amoebic dysentery, hepatic amebiasis (amoebic colliquative hepatitis) or chronic intestinal amebiasis.
Di Izvora - Opera propria, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=5525738
Trichinella
This parasite can enter our bodies through ingestion of raw or undercooked meat. This worm lurks in the small intestine and, once it reaches maturity, makes its way between the membranes to the muscles, where it creates a cyst. Normal symptoms are diarrhea, vomiting and abdominal pain, but in the worst cases it could also cause myocarditis. Also possible in mild cases are heart attacks and kidney inflammation. If nothing else, it is not transmissible from human to human.
By Rjgalindo, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2496706
Tapeworm
The common name for this parasite, one of the best known, is tapeworm. It enters the body through ingestion of beef or pork, or from undercooked freshwater fish. Ingested in the form of a cyst, once hatched it attaches to the intestinal walls causing abdominal pain, diarrhea, nausea, weight loss and even lack of appetite in some cases. Inside the human body it can reach the monstrous length of nine meters.
Di Geoff Gallice from Gainesville, FL, USA - Human botfly, CC BY 2.0, https://commons.wikimedia.org/
Dermatobia hominis
This is a genus of fly, the only known species of oestridae parasitic to humans. Dermatobia eggs are carried by forty different species of vectors, mostly varieties of mosquitoes and flies, and also ticks. The larvae that emerge from the eggs settle in the subcutaneous tissue for an incubation period of 5 to 10 weeks. This parasite causes an infection called cutaneous myiasis, which manifests as itchy and painful furuncles, sores, or swellings.
Di Photo Credit:Content Providers(s): CDC/ Dr. Govinda S. Visvesvara - This media comes from the Cen
Naegleria fowleri
This is one of the most dangerous parasites that can infest the human body, although cases are quite rare. Also called the brain-eating amoeba, it is found in fresh waters around the world, and for entry into the body it uses the nose. Here it reaches the brain and immediately attacks the nervous system. The first symptoms are loss of taste and sense of smell, but in about ten days it can easily lead to death. Primary amoebic meningoencephalitis is the name of the disease that causes this dreadful parasite.
Di Photo Credit:Content Providers(s): CDC/ Steven Glenn; Laboratory & Consultation Division - Th
Babesiosis
It is a single-celled protozoan carried by ticks, and the ailments it causes are similar to those caused by malaria. Its prevalence is almost solely in the mid-west United States. The disease it causes is called babesiosis, a blood disease that causes anemia and small clots that clog smaller blood vessels and thus interfere with the functioning of many organs.
https://commons.wikimedia.org/wiki/File:Giardia_intestinalis_-_trophozoite.jpg
Giardia
This protozoan is widespread throughout the world, present in freshwater infected with faecal material but also in contaminated mountain waters. In most cases it enters by ingestion. Actually, this is not one of the worst parasites: it attacks the small intestine and causes diarrhoea (with foamy faeces rich in fat), epigastric pain, anorexia, nausea and meteorism. In the case of chronification, symptoms are alleviated. However, in most cases, the infected individual remains asymptomatic.
https://commons.m.wikimedia.org/wiki/File:Trypanosoma_brucei_gambiense_-_trypomastigote.jpg
Trypanosoma brucei gambiense
This parasite occurs almost exclusively in equatorial Africa, especially in rural areas, and is transmitted by the bite of the tsetse fly. The disorder it causes is scientifically called African trypanosomiasis, but is much better known as sleeping sickness. Usually, if left untreated, this disorder causes death about three years after the onset of the first symptoms. As a condition that attacks the central nervous system, it causes problems with coordination, changes in behaviour and, above all, sleep disturbances and drowsiness.
Di I, Flukeman, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2245831
Fasciola hepatica
This parasite is a flatworm that mainly affects herbivores, but can also enter the human body following ingestion of raw or undercooked vegetables, perhaps grown with contaminated pesticides. This worm mainly affects the liver, obstructing the biliary tract. The larvae then cause a disorder called fascioliasis, resulting in nausea, vomiting, fever and abdominal enlargement. In severe cases it can also cause jaundice, or even hepatic haematomas, pyogenic abscesses, pancreatitis, stenosis or perforation of the biliary tract. Extra-hepatic manifestations include eosinophilia, pulmonary infiltrates, serous effusions, meningeal syndromes, lymphadenopathy.
Di http://www.dpd.cdc.gov/dpdx/images/ParasiteImages/A-F/Filariasis/Wuchereria_bancrofti_1_DPDX.JPG,
Ancylostoma and genus of the nematodes
The main species, which can also infest humans, as well as dogs and cats, are Necator americanus, found mainly in the American continent and Australia, and Ancylostoma duodenale, widespread in Asia, Africa and southern Europe. In most cases, the parasite enters the body through the skin after contact with infected soil (e.g. walking barefoot on soil with traces of sewage). Subsequently, the larva travels via the bloodstream and becomes larger in volume, going on to infect the blood, lungs and, later, the intestines. The main symptoms are rashes, fever, cough, diarrhoea and anaemia. Fortunately, drug therapy is sufficient to eliminate the infection and the host.
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