Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson characterised parasites as "predators that eat prey in units of less than one". Parasites include single-celled protozoans such as the agents of malaria, sleeping sickness, and amoebic dysentery; animals such as hookworms, lice, mosquitoes, and vampire bats; fungi such as honey fungus and the agents of ringworm; and plants such as mistletoe, dodder, and the broomrapes.
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.
Strongyloides stercoralis is a human pathogenic parasitic roundworm causing the disease strongyloidiasis. Its common name in the US is threadworm. In the UK and Australia, however, the term threadworm can also refer to nematodes of the genus Enterobius, otherwise known as pinworms.
Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question but by their way of life. This means it forms a synthesis of other disciplines, and draws on techniques from fields such as cell biology, bioinformatics, biochemistry, molecular biology, immunology, genetics, evolution and ecology.
Anisakis is a genus of parasitic nematodes that have life cycles involving fish and marine mammals. They are infective to humans and cause anisakiasis. People who produce immunoglobulin E in response to this parasite may subsequently have an allergic reaction, including anaphylaxis, after eating fish infected with Anisakis species.
Opisthorchis felineus, the Siberian liver fluke or cat liver fluke, is a trematode parasite that infects the liver in mammals. It was first discovered in 1884 in a cat's liver by Sebastiano Rivolta of Italy. In 1891, Russian parasitologist, Konstantin Nikolaevich Vinogradov (1847–1906) found it in a human, and named the parasite a "Siberian liver fluke". In the 1930s, helminthologist Hans Vogel of Hamburg published an article describing the life cycle of Opisthorchis felineus. Felineus infections may also involve the pancreatic ducts. Diagnosis of Opisthorchis infection is based on microscopic identification of parasite eggs in stool specimens. Safe and effective medication is available to treat Opisthorchis infections. Adequately freezing or cooking fish will kill the parasite.
Dioctophyme renale, commonly referred to as the giant kidney worm, is a parasitic nematode (roundworm) whose mature form is found in the kidneys of mammals. D. renale is distributed worldwide, but is less common in Africa and Oceania. It affects fish-eating mammals, particularly mink and dogs. Human infestation is rare, but results in kidney destruction, usually of one kidney and hence not fatal. A 2019 review listed a total of 37 known human cases of dioctophymiasis in 10 countries with the highest number (22) in China. Upon diagnosis through tissue sampling, the only treatment is surgical excision.
The Anisakidae are a family of intestinal nematodes (roundworms). The larvae of these worms can cause anisakiasis when ingested by humans, in raw or insufficiently cooked fish.
Angiostrongylus cantonensis is a nematode (roundworm) parasite that causes angiostrongyliasis, an infection that is the most common cause of eosinophilic meningitis in Southeast Asia and the Pacific Basin. The nematode commonly resides in the pulmonary arteries of rats, giving it the common name rat lungworm. Snails are the primary intermediate hosts, where larvae develop until they are infectious.
Thelaziasis is the term for infestation with parasitic nematodes of the genus Thelazia. The adults of all Thelazia species discovered so far inhabit the eyes and associated tissues of various mammal and bird hosts, including humans. Thelazia nematodes are often referred to as "eyeworms".
Dirofilaria repens is a filarial nematode that affects dogs and other carnivores such as cats, wolves, coyotes, foxes, and sea lions, as well as muskrats. It is transmitted by mosquitoes. Although humans may become infected as aberrant hosts, the worms fail to reach adulthood while infecting a human body.
Like humans and other animals, fish suffer from diseases and parasites. Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth. If pathogens breach these defences, fish can develop inflammatory responses that increase the flow of blood to infected areas and deliver white blood cells that attempt to destroy the pathogens.
Anisakis simplex, known as the herring worm, is a species of nematode in the genus Anisakis. Like other nematodes, it infects and settles in the organs of marine animals, such as salmon, mackerels and squids. It is commonly found in cold marine waters, such as the Pacific Ocean and Atlantic Ocean.
Gadimyxa atlantica is a species of parasitic myxozoan. Together with G. arctica and G. sphaerica, they infect Gadus morhua and Arctogadus glacialis by developing coelozoically in bisporic plasmodia in their urinary systems. These 3 species' spores exhibit two morphological forms: wide and subspherical, being both types bilaterally symmetrical along the suture line. The wide spores have a mean width ranging from 7.5-10μm, respectively, while the subspherical ones range from 5.3-8μm in mean width. The subspherical forms of Gadimyxa are similar to Ortholinea, differing in the development of the spores and in the arrangement of the polar capsules. Polychaetes Spirorbisspecies act as invertebrate hosts of G. atlantica.
Gadimyxa sphaerica is a species of parasitic myxozoan. Together with G. arctica and G. atlantica, they infect Gadus morhua and Arctogadus glacialis by developing coelozoically in bisporic plasmodia in their urinary systems. These 3 species' spores exhibit two morphological forms: wide and subspherical, being both types bilaterally symmetrical along the suture line. The wide spores have a mean width ranging from 7.5 to 10μm, respectively, while the subspherical ones range from 5.3-8μm in mean width. The subspherical forms of Gadimyxa are similar to Ortholinea, differing in the development of the spores and in the arrangement of the polar capsules.
Ascarophis is a genus of parasitic nematodes, belonging to the family Cystidicolidae. Species of Ascarophis are parasitic as adults in the gastrointestinal tract of marine and estuarine fishes.
Contracaecum is a genus of parasitic nematodes from the family Anisakidae. These nematodes are parasites of warm-blooded, fish eating animals, i.e. mammals and birds, as sexually mature adults. The eggs and the successive stages of their larvae use invertebrates and increasing size classes of fishes as intermediate hosts. It is the only genus in the family Anisakidae which can infect terrestrial, marine and freshwater animals.
Gastropod-borne parasitic diseases (GPDs) are a group of infectious diseases that require a gastropod species to serve as an intermediate host for a parasitic organism that can infect humans upon ingesting the parasite or coming into contact with contaminated water sources. These diseases can cause a range of symptoms, from mild discomfort to severe, life-threatening conditions, with them being prevalent in many parts of the world, particularly in developing regions. Preventive measures such as proper sanitation and hygiene practices, avoiding contact with infected gastropods and cooking or boiling food properly can help to reduce the risk of these diseases.
