Ascaris | |
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Adult female | |
Life cycle inside and outside of the human body of one fairly well described helminth: Ascaris lumbricoides | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Nematoda |
Class: | Chromadorea |
Order: | Ascaridida |
Family: | Ascarididae |
Genus: | Ascaris Linnaeus, 1758 |
Species | |
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Ascaris is a nematode genus of parasitic worms known as the "small intestinal roundworms". [1] One species, Ascaris lumbricoides , affects humans and causes the disease ascariasis. Another species, Ascaris suum , typically infects pigs. Other ascarid genera infect other animals, such as Parascaris equorum , the equine roundworm, and Toxocara and Toxascaris , which infect dogs and cats.
Their eggs are deposited in feces and soil. Plants with the eggs on them infect any organism that consumes them. [2] A. lumbricoides is the largest intestinal roundworm and is the most common helminth infection of humans worldwide. Infestation can cause morbidity by compromising nutritional status, [3] affecting cognitive processes, [4] inducing tissue reactions such as granuloma to larval stages, and by causing intestinal obstruction, which can be fatal.
The body is long, cylindrical, and fusiform (pointed at both the ends). The body wall is composed of cuticle, epidermis and musculature. There is a pseudocoelom. Respiration is by simple diffusion. The nervous system consists of a nerve ring and many longitudinal nerve cords. Reproduction is exclusively sexual, and males are usually shorter than females.
As part of the parasite defense strategy, Ascaris roundworms secrete a series of inhibitors to target digestive and immune-related host proteases, which include pepsin, trypsin, chymotrypsin/elastase, cathepsins, and metallocarboxypeptidases (MCPs). Ascaris species inhibit MCPs by releasing an enzyme known as Ascaris carboxypeptidase inhibitor (ACI). This enzyme binds to the active site of MCP and blocks the cleavage of its own proteins by the host MCP. [5] Similarly, they inhibit trypsin by releasing the protein Ascaris Trypsin Inhibitor (pdb 1ATA). [6]
Ascaris has been present in humans for at least several thousand years, as evidenced by Ascaris eggs found in paleofeces and in the intestines of mummified humans. [7]
A. lumbricoides was originally called Lumbricus teres and was first described in detail by Edward Tyson in 1683. [8] The genus Ascaris was originally described as the genus for Ascaris lumbricoides by Carl Linnaeus in 1758. [9] The morphologically similar Ascaris suum was described from pigs by Johann August Ephraim Goeze in 1782. [9]
Ascaris lumbricoides is a large parasitic roundworm of the genus Ascaris. It is the most common parasitic worm in humans. An estimated 807 million–1.2 billion people are infected with A. lumbricoides worldwide. People living in tropical and subtropical countries are at greater risk of infection. Infection by Ascaris lumbricoides is known as ascariasis.
Trichuris trichiura, Trichocephalus trichiuris or whipworm, is a parasitic roundworm that causes trichuriasis when it infects a human large intestine. It is commonly known as the whipworm which refers to the shape of the worm; it looks like a whip with wider "handles" at the posterior end. The helminth is also known to cause rectal prolapse.
Trichuriasis, also known as whipworm infection, is an infection by the parasitic worm Trichuris trichiura (whipworm). If infection is only with a few worms, there are often no symptoms. In those who are infected with many worms, there may be abdominal pain, fatigue and diarrhea. The diarrhea sometimes contains blood. Infections in children may cause poor intellectual and physical development. Low red blood cell levels may occur due to loss of blood.
Ascariasis is a disease caused by the parasitic roundworm Ascaris lumbricoides. Infections have no symptoms in more than 85% of cases, especially if the number of worms is small. Symptoms increase with the number of worms present and may include shortness of breath and fever in the beginning of the disease. These may be followed by symptoms of abdominal swelling, abdominal pain, and diarrhea. Children are most commonly affected, and in this age group the infection may also cause poor weight gain, malnutrition, and learning problems.
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 broadly classified into tapeworms, flukes, and roundworms. They often live in the gastrointestinal tract of their hosts, but they may also burrow into other organs, where they induce physiological damage.
Ascaris suum, also known as the large roundworm of pig, is a parasitic nematode that causes ascariasis in pigs. While roundworms in pigs and humans are today considered as two species with different hosts, cross-infection between humans and pigs is possible; some researchers have thus argued they are the same species. Ascariasis is associated with contact to pigs and pig manure in Denmark.
Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as schistosomes reside in blood vessels.
Helminthic therapy, an experimental type of immunotherapy, is the treatment of autoimmune diseases and immune disorders by means of deliberate infestation with a helminth or with the eggs of a helminth. Helminths are parasitic worms such as hookworms, whipworms, and threadworms that have evolved to live within a host organism on which they rely for nutrients. The theory behind helminth therapy is that these worms reduce negative immune responses due to their TH2 immune response that downregulates the abnormal T-cell responses recently associated with autoimmune disorders. This therapy ties to the Hygiene hypothesis in that the lack of exposure to bacteria and parasites such as helminths can cause a weaker immune system leading to being more susceptible to autoimmune disease.
Visceral larva migrans (VLM) is a condition in humans caused by the migratory larvae of certain nematodes, humans being a dead-end host, and was first reported in 1952. Nematodes causing such zoonotic infections are Baylisascaris procyonis, Toxocara canis, Toxocara cati, and Ascaris suum. These nematodes can infect but not mature in humans and after migrating through the intestinal wall, travel with the blood stream to various organs where they cause inflammation and damage. Affected organs can include the liver, heart and the CNS. A special variant is ocular larva migrans where usually T. canis larvae travel to the eye.
The soil-transmitted helminths are a group of intestinal parasites belonging to the phylum Nematoda that are transmitted primarily through contaminated soil. They are so called because they have a direct life cycle which requires no intermediate hosts or vectors, and the parasitic infection occurs through faecal contamination of soil, foodstuffs and water supplies. The adult forms are essentially parasites of humans, causing soil-transmitted helminthiasis (STH), but also infect domesticated mammals. The juveniles are the infective forms and they undergo tissue-migratory stages during which they invade vital organs such as lungs and liver. Thus the disease manifestations can be both local and systemic. The geohelminths together present an enormous infection burden on humanity, amounting to 135,000 deaths every year, and persistent infection of more than two billion people.
Antiparasitics are a class of medications which are indicated for the treatment of parasitic diseases, such as those caused by helminths, amoeba, ectoparasites, parasitic fungi, and protozoa, among others. Antiparasitics target the parasitic agents of the infections by destroying them or inhibiting their growth; they are usually effective against a limited number of parasites within a particular class. Antiparasitics are one of the antimicrobial drugs which include antibiotics that target bacteria, and antifungals that target fungi. They may be administered orally, intravenously or topically. Overuse or misuse of antiparasitics can lead to the development of antimicrobial resistance.
Trichuris, often referred to as whipworms or the silent serpent, is a genus of parasitic helminths from the roundworm family Trichuridae. The name whipworm refers to the shape of the worm; they look like whips with wider "handles" at the posterior end.
Subclass Spiruria comprises mostly parasitic secernentean nematodes. In an alternate classification, they are treated as suborder Spirurina, with the orders listed here being ranked as infraorders.
The Ascarididae are a family of the large intestinal roundworms. Members of the family are intestinal parasites, infecting all classes of vertebrates. It includes a number of genera, the most well known of which are:
Ascaricides are drugs to treat ascariasis that is caused by infections with parasitic nematodes (roundworms) of the genus Ascaris. The large roundworm of pigs typically infects pigs while Ascaris lumbricoides affects human populations, typically in sub-tropical and tropical areas with poor sanitation. Ascaricides belong to the group of drugs collectively called anthelmintics which 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.
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 also be called vermifuges or vermicides. Anthelmintics are used to treat people who are infected by helminths, a condition called helminthiasis. These drugs are also used to treat infected animals, particularly small ruminants such as goats and sheep.
Baylisascaris procyonis, also known by the common name raccoon roundworm, is a roundworm nematode, found ubiquitously in raccoons, the definitive hosts. It is named after H. A. Baylis, who studied them in the 1920s–30s, and Greek askaris. Baylisascaris larvae in paratenic hosts can migrate, causing larva migrans. Baylisascariasis as the zoonotic infection of humans is rare, though extremely dangerous due to the ability of the parasite's larvae to migrate into brain tissue and cause damage. Concern for human infection has been increasing over the years due to the urbanization of rural areas, resulting in the increase in proximity and potential human interaction with raccoons.
Zanthoxylum zanthoxyloides, also called Senegal prickly-ash or artar root, is a plant species in the genus Zanthoxylum.
Soil-transmitted helminthiasis is a type of worm infection (helminthiasis) caused by different species of roundworms. It is caused specifically by those worms which are transmitted through soil contaminated with faecal matter and are therefore called soil-transmitted helminths. Three types of soil-transmitted helminthiasis can be distinguished: ascariasis, hookworm infection and whipworm infection. These three types of infection are therefore caused by the large roundworm A. lumbricoides, the hookworms Necator americanus or Ancylostoma duodenale and by the whipworm Trichuris trichiura.
Lani Sue Stephenson was an American parasitologist and nutritionist, "a pioneer in field-based studies on nutrition–parasite interactions".
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