Parasites Test

寄生蟲 人畜共通傳染病

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Angiostrongylus cantonensis

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廣東住血線蟲 Angiostrongylus cantonensis Angiostrongylus cantonensis Scientific classification

Kingdom:

Animalia

Phylum:

Nematoda

Class:

Secernentea

Order:

Strongylida

Genus:

Angiostrongylus

Species:

cantonensis

Angiostrongylus cantonensis is a parasitic nematode (roundworm) that causes Angiostrongyliasis, the most common cause of eosiniphilic meningitis in Southeast Asia and the Pacific Basin.[1] It commonly resides in the pulmonary arteries of rats, giving it the nickname the rat lungworm. Snails are the primary intermediate hosts, where larvae develop until they are infective. Humans are incidental hosts, and may become infected through ingestion of larvae in raw or undercooked snails or other vectors, or contaminated water and vegetables. The larvae are then transported via the blood to the central nervous system (CNS), where they are the most common cause of eosiniphilic meningitis, a serious condition that can lead to death or permanent brain and nerve damage.[2] Identified in 1964, Angiostrongyliasis is an infection of increasing public health importance as globalization aids in the geographic spread of the disease.

Infectious agent Angiostrongylus cantonensis is a helminth of the phylum Nematoda, order strongylida, and superfamily metastrongyloidea, but is commonly referred to as the rat lungworm. Nematodes are roundworms characterized by a tough outer cuticle, unsegmented bodies, and a fully developed GI tract. The order Strongylida includes hookworms and lungworms. Metastrongyloidea are characterized as long, slender, threadlike worms that reside in the lungs of the definitive host.[3] Angiostrongylus costaricensis is a closely related worm that causes intestinal Angiostrongyliasis in Central and South America.

Angiostrongylus cantonensis

History of discovery Nematodes suspected to be A. cantonensis were first identified in the cerebrospinal fluid of a patient with eosiniphilic meningitis by Nomura and Lim in Taiwan in 1944. They called the parasite Haemostrongylus ratti, and noted that raw food eaten by the patient may have been contaminated by rats. Their paper, however, was not translated from the original Japanese into English until just after the parasite had been recognized in 1964, so their discovery was not widely recognized. In 1955, Mackerass and Sanders identified the life cycle of the worm in rats, defining snails and slugs as the intermediate host and noting the path of transmission through the blood, brain, and lungs in rats. In 1961, an epidemiological study of eosiniphilc meningitis in humans was conducted by Rosen, Laigret, and Bories, who hypothesized that the parasite causing these infections was carried by fish. However Alicata noted that raw fish was consumed by large numbers of people in Hawaii without apparent consequences, and patients presenting with meningitis symptoms had a history of eating raw snails or prawns in the weeks before presenting with symptoms. This observation along with epidemiology and autopsy of infected brains confirmed A. cantonensis infection in humans as the cause of the majority of eosiniphilic meningitis cases in Southeast Asia and the Pacific Islands.[4]

Clinical presentation in humans In humans, Angiostrongylus is the most common cause of eosiniphilic meningitis.[1] Frequently the infection will resolve without treatment or serious consequences, but in cases with a heavy load of parasites the infection can be so severe it can cause permanent damage to the CNS or death.[5]

Early symptoms Infection first presents with severe abdominal pain, nausea, vomiting, and weakness, which gradually lessens and progresses to fever, and then to CNS symptoms and severe headache and stiffness of the neck.

Severe/CNS infection CNS symptoms begin with mild cognitive impairment and slowed reactions, and in a very sever form often progress to unconsciousness.[2] Patients may present with neuropathic pain early in the infection. Eventually severe infection will lead to ascending weakness, quadriparesis, areflexia, respiratory failure, and muscle atrophy, and will lead to death if not treated. Occasionally patients present with cranial nerve palsies, usually in nerves 7 and 8, and rarely larvae will enter ocular structures.[6] Even with treatment, damage to the CNS may be permanent and result in a variety of negative outcomes depending on the location of the infection, and the patient may suffer chronic pain as a result of infection.[2]

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Angiostrongylus cantonensis

Eye invasion Symptoms of eye invasion include visual impairment, pain, keratitis, and retinal edema. Worms usually appear in the anterior chamber and vitreous and can sometimes be removed surgically. The parasite is rarely seen outside of endemic areas, and in these cases patients generally have a history of travel to an endemic area.

Transmission Transmission of the parasite is usually from eating raw or undercooked snails or other vectors. Infection is also frequent from ingestion of contaminated water or unwashed salad that may contain small snail and slugs, or have been contaminated by them. Therefore it is very important to avoid raw snails, wash and cook vegetables thoroughly, and avoid open water sources that may be contaminated.

Reservoirs Rats are the definitive host and the main reservoir for A. cantonensis, though other small mammals may also become infected. While angiostrongylus can infect humans, humans do not act as reservoirs since the worm cannot reproduce in humans and therefore humans cannot contribute to their life cycle.[5]

Vectors A. cantonensis has many vectors, with the most common being several species of snails, including the giant African land snail (Achatina fulica) in the Pacific islands and snails of the genus Pila in Thailand and Malaysia. The golden apple snail, A. canaliculatus, is the most important vector in areas of China.[2] Freshwater prawns, crabs, or other paratenic, or transport, hosts can also act as vectors.[5]

Incubation period The incubation period in humans is usually from 1 week to 1 month after infection, and can be as long as 47 days.[6] This interval varies, since humans are intermediate hosts and, the life cycle does not continue predictably as it would in a rat.[5]

Morphology A. cantonensis is a nematode roundworm with 3 outer protective collagen layers, and a simple stomal opening or mouth with no lips or buccal cavity leading to a fully developed gastrointestinal tract.[1] Males have a small copulatory bursa at the posterior. Females have a “barber pole” shape down the middle of the body, which is created by the twisting together of the intestine and uterine tubules. The worms are long and slender - males are 15.9-19 mm in length, and females are 21-25 mm in length.[7]

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Angiostrongylus cantonensis

Life cycle The adult form of A. cantonensis resides in the pulmonary arteries of rodents, where it reproduces. After the eggs hatch in the arteries, larvae migrate up the pharynx and are then swallowed again by the rodent and passed in the stool. These first stage larvae then penetrate or are swallowed by snail intermediate hosts, where they transform into second stage larvae and then into third stage infective larvae. Humans and rats acquire the infection when they ingest contaminated snails or paratenic (transport) hosts including prawns, crabs, and frogs, or raw vegetables containing material from these intermediate and paratenic hosts. After passing through the gastrointestinal tract, the worms enter circulation.[6] In rats, the larvae then migrate to the meninges and develop for about a month before migrating to the pulmonary arteries, where they fully develop into adults.[5] Humans are incidental hosts; the larvae cannot reproduce in humans and therefore humans do not contribute to the A. cantonensis life cycle. In humans, the circulating larvae migrate to the meninges, but do not move on to the lungs. Sometimes the larvae will develop into the adult form in the brain and CSF, but they quickly die, inciting the inflammatory reaction that causes symptoms of infection.[5]

Diagnostic tests Diagnosis of Angiostrongyliasis is complicated due to the difficulty of presenting the angiostrongylus larvae themselves, and will usually be made based on the presence of eosiniphilic meningitis and history of exposure to snail hosts. Eosiniphilic meningitis is generally characterized as a meningitis with >10 eosiniphils/μL in the CSF or at least 10% eosiniphils in the total CSF leukocyte count.[6] Occasionally worms found in the cerebrospinal fluid or surgically removed from the eye can be identified in order to diagnose Angiostrongyliasis.

Lumbar puncture Lumbar puncture should always be done is cases of suspected meningitis. In cases of eosiniphilc meningitis it will rarely produce worms even when they are present in the CSF, because they tend to cling to the end of nerves. Larvae are present in the CSF in only 1.9-10% of cases.[2] However, as a case of eosiniphilic meningitis progresses, intracranial pressure and eosiniphil counts should rise. Increased levels of eosinophils in the CSF is a trademark of the eosiniphilic meningitis.[2]

Brain imaging Brain lesions, with invasion of both gray and white matter, can be seen on a CT or MRI. However MRI findings tend to be inconclusive, and usually include nonspecific lesions and ventricular enlargement. Sometimes a hemorrhagic, probably produced by migrating worms, is present and of diagnostic value.

Serology In patients with elevated eosiniphils, serology can be used to confirm a diagnosis of Angiostrongylias rather than infection with another parasite.[1] There are a number of immunoassays that can aid in diagnosis, however serologic testing is available in few labs in the endemic area, and is frequently too non-specific. Some cross reactivity has been

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Angiostrongylus cantonensis reported between A. cantonensis and trichinosis, making diagnosis less specific. The most definitive diagnosis always arises from the identification of larvae found in the CSF or eye, however due to this rarity a clinical diagnosis based on the above tests is most likely.

Management and therapy Treatment of angiostrongyliasis is not well defined, but most strategies include a combination of anti - parasitics to kill the worms, steroids to limit inflammation as the worms die, and pain medication to manage the symptoms of meningitis.

Anti-helminthics Anti-helminthics are often used to kill off the worms, however in some cases this may cause patients to worsen due to toxins released by the dying worms. Albendazole, ivermectin, mebendazol, and pyrantel are all commonly used, though albendazole is usually the drug of choice. Studies have shown that anti-helminthic drugs may shorten the course of the disease and relieve symptoms. Therefore anti-helminthics are generally recommended, but should be administered gradually so as to limit the inflammatory reaction.[2]

Anti-inflammatories Anti-helminthics should generally be paired with corticosteroids in severe infections to limit the inflammatory reaction to the dying parasites. Studies suggest that a two week regimen of a combination of mebedizole and prednisolone significantly shortened the course of the disease and length of associated headaches without observed harmful side effects.[8] Other studies suggest that albendazole may be more favorable, because it may be less like to incite an inflammatory reaction.[9] The Chinese herbal medicine long-dan-xie-gan-tan (LDGXT) has also been shown to have a similar anti inflammatory effect, and in mild cases may be used alone to relieve symptoms while infection resolves itself.[9]

Symptomatic treatment Symptomatic treatment is indicated for symptoms such as nausea, vomiting, headache, and in some cases, chronic pain due to nerve damage or muscle atrophy.

Epidemiology A. cantonensis and its vectors are endemic to Southeast Asia and the Pacific Basin.[1] The infection is becoming increasingly important as globalization allows it to spread to more and more locations, and as more travelers encounter the parasites. The parasites probably travel effectively through rats traveling as stowaways on ships, and through the introduction of snail vectors outside endemic areas. Although mostly found in Asia and the Pacific where asymptomatic infection can be as high as 88%, human cases have been reported in the Caribbean, where as much as 25% of the population may be infected. In the US, cases have been reported Hawaii, which is in the endemic area [5]. The infection is now endemic in wildlife and a few human cases have also been reported in areas where the parasite was not originally endemic, such as New Orleans and Egypt.

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Angiostrongylus cantonensis

Public health and prevention There are many public health strategies that can drastically limit the transmission of A. cantonensis by limiting contact with infected vectors. Vector control may be possible, but has not been very successful in the past. Education to prevent the introduction of rats or snail vectors outside endemic areas is important to limit the spread of the disease.[4] There are no vaccines in development for angiostrongyliasis.

Recommendations for individuals To avoid infection when in endemic areas, travelers should: •  Avoid consumption of uncooked vectors, such as snails and freshwater prawns •  Avoid drinking water from open sources, which may have been contaminated by vectors •  Prevent young children from playing with or eating live snails

External links •  Divisian of Parasitic Diseases [10], Centers for Disease Control and Prevention, Angiostrongylus cantonensis Infection •  Laboratory Identification of Parasites of Public Health Concern [11], Parasites and Health, Angiostrongyliasis •  Laboratory Identification of Parasites of Public Health Concern [12], Angiostrongyliasis Image Library •  MeSH Angiostrongylus+cantonensis [13]

External links [1]  Baheti NN & Sreedharan M et al (2008). "Eosinophilic meningitis and an ocular worm in a patient from Kerala, south India" J. Neurol. Neurosurg. Psychiatry 79 (271). [2]  Hua Li, Feng Xu, Jin-Bao Gu and Xiao-Guang Chen (2008). “Case Report: A Severe Eosinophilic Meningoencephalitis Caused by Infection of Angiostrongylus cantonensis”. Am. J. Trop. Med. Hyg., 79(4): 568–570. [3]  http:/ / www. path. cam. ac. uk/ ~schisto/ helminth_taxonomy/ taxonomy_nematoda. html, Accessed 2/26/09. [4]  JE Alicata (1991). “The Discovery of Angiostrongylus Cantonensis as a Cause of Human Eosiniphilc Meningitis”. Parasitology Today, 7(6): 151-153. [5]  David, John T. and Petri, William A Jr. Markell and Voge’s Medical Parasitology. St. Louis, MO: El Sevier, 2006. [6]  L. Ramirez-Avila (2009). “Eosinophilic Meningitis due to Angiostrongylus and Gnathostoma Species”. Emerging Infections, 48: 322-327. [7]  http:/ / animaldiversity. ummz. umich. edu/ site/ accounts/ information/ Angiostrongylus_cantonensis. html, Accessed 2/26/09 [8]  V Chotmongkol and K Sawadpanitch et al. (2006). “Treatment of Eosiniphilic Meningitis with a Combination of Prednisolone and Mebendazole”. Am. J. Trop. Med. Hyg., 74(6): 1122–1124. [9]  SC Lai, KM Chen, YH Chang and HH Lee (2008). “Comparative efficacies of albendazole and the Chinese herbal medicine long-dan-xie-gan-tan, used alone or in combination, in the treatment of experimental eosinophilic meningitis induced by Angiostrongylus cantonensis”. Annals of Tropical Medicine & Parasitology, 102(2):

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Angiostrongylus cantonensis

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143–150. [10]  http:/ / www. cdc. gov/ ncidod/ dpd/ parasites/ angiostrongylus/ factsht_angiostrongylus. htm [11]  http:/ / www. dpd. cdc. gov/ DPDx/ HTML/ Angiostrongyliasis. htm [12]  http:/ / www. dpd. cdc. gov/ DPDx/ HTML/ ImageLibrary/ Angiostrongyliasis_il. htm [13]  http:/ / www. nlm. nih. gov/ cgi/ mesh/ 2009/ MB_cgi?mode=& term=Angiostrongylus+ cantonensis Source: http:/ / en. wikipedia. org/ w/ index. php? oldid=275110817 Contributors: Addshore, Arcadian, Chamal N, CrackDragon, Dziewczynka, HelloAnnyong, MartinezMD, Selmakhan, Victor Lopes, Viriditas

Achatina fulica East African Land Snail

Conservation status

Least Concern (IUCN 3.1) Scientific classification

Kingdom:

Animalia

Phylum:

Mollusca

Class:

Gastropoda

Order:

Pulmonata

Family:

Achatinidae

Subfamily:

Achatininae

Genus:

Achatina

Species:

A. fulica

Binomial name [1] Achatina fulica (Férussac, 1821)

Achatina fulica

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The East African land snail, or "giant African land snail", scientific name Achatina fulica, is a species of large, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinidae. It is native to East Africa, however the species has been widely introduced to Asia, to the Pacific and Indian Ocean islands, and to the West Indies. Where the snail is seen as a pest, it has been intercepted widely by quarantine officials, and incipient invasions have been successfully eradicated, for instance in the mainland USA.[2] In recent times, the land snails have been kept as pets; however, they are illegal to possess in some countries including the United States[3] . The snails are easy to keep and, when bred in captivity, are unlikely to carry parasites.

Description The adult snails have a height of around 7 cm (2.5 inches), and their length can reach 20 cm (8 inches) or more. The shell has a conical shape, being about twice as high as it is broad. Either clockwise (sinistral) or anti-clockwise (dextral) directions can be observed in the coiling of the shell, although the right-handed (dextral) cone is the more common. The weight of the shell is directly proportional to the weight of the body, and in large individuals proves impervious to predators except for carnivorous snails, which bore through the shell using their radulla, a tongue like organ. Shell colouration is highly variable, and dependent on diet. Typically, brown is the predominant colour and the shell is banded. shell of Achatina fulica

Habitat The East African land snail is native to East Africa, especially Kenya and Tanzania. Its habitat includes most regions of the humid tropics, including many Pacific islands, southern and eastern Asia, and the Caribbean. It is a highly invasive species, and colonies can be formed from a single gravid individual. The species has established itself in temperate climates also, and in many places release into the wild is illegal. The giant snail can now be found in agricultural areas, coastland, natural forest, planted forests, riparian zones, scrub/shrublands, urban areas, and wetlands.

Achatina fulica

Nutrition The Giant East African Snail is a macrophytophagous herbivore; it eats a wide range of plant material, fruit and vegetables. It will sometimes eat sand, very small stones, bones from carcasses and even concrete as calcium sources for its shell. In rare instances the snails will consume each other. In captivity, this species can be fed on grain products such as bread, digestive biscuits and chicken feed. Fruits and vegetables must be washed diligently as the Achatina fulica in Hyderabad, India. snail is very sensitive to any lingering pesticides. In captivity, snails need cuttlebone to aid the growth and strength for their shells. As with all molluscs, they enjoy the yeast in beer, which serves as a growth stimulus.

Reproduction The Giant East African Snail is a simultaneous hermaphrodite; each individual has both testes and ovaries and is capable of producing both sperm and ova. Instances of self fertilisation are rare, occurring only in small populations. Although both snails in a mating pair can simultaneously transfer gametes to each other (bilateral mating), this is dependent on the size difference between the partners. Snails of similar size will reproduce in this way. Two snails of differing sizes will mate unilaterally (one way), with the larger individual acting as a female. This is due to the comparative resource investment associated with the different genders. Like other land snails, these have intriguing mating behaviour, including petting their heads and front parts against each other. Courtship can last up to half an hour, and the actual transfer of gametes can last for two hours. Transferred sperm can be stored within the body for up to two years. The number of eggs per clutch averages around 200. A snail may lay 5-6 clutches per year with a hatching viability of about 90%.

Life cycle Adult size is reached in about six months; after which growth slows but does not ever cease. Life expectancy is commonly five or six years in captivity, but the snails may live for up to ten years. They are active at night and spend the day buried underground. The East African Land Snail is capable of aestivating for up to three years in times of extreme drought, sealing itself into its shell by secretion of a calcerous compound that dries on contact with the air. This is impermeable; the snail will not lose any water during this period.

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Achatina fulica

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Pest control In many places the snail is seen as a pest. Suggested preventative measures include strict quarantine to prevent introduction and further spread. Many methods, including hand collecting and use of molluscicides and flame-throwers, have been tried to eradicate the giant snail. Generally, none of them has been effective except where implemented at the first sign of infestation. In some regions, an effort has been made to promote use of the Giant East African Snail as a food resource, the collecting of the snails for food being seen as a method of controlling them. However, promoting a pest in this way is a controversial measure, as it may encourage the further deliberate spread of the snails. One particularly catastrophic attempt to biologically control this species occurred on South Pacific Islands. Colonies of A. fulica were introduced as a food reserve for the American military during the second world war and they escaped. A carnivorous species was later introduced, but it instead heavily harvested the native Partula, causing the loss of several species within a decade.

Further reading •  Mead, Albert R. 1961. The Giant African Snail: A Problem in Economic Malacology. Univ. Chicago Press, 257 pp. (also available online [4]) •  Global Invasive Species Database [5] •  [http:/ / www. hear. org/ species/ achatina_fulica/ Achatina fulica references] from the Hawaiian Ecosystems at Risk project (HEAR [6]) •  Achatina fulica in Captivity

[7]

External links [1]  [http:/ / www. itis. gov/ servlet/ SingleRpt/ SingleRpt?search_topic=TSN& search_value=76978 Achatina fulica (TSN 76978)]. Integrated Taxonomic Information System. Retrieved on July 6 2007. [2]  PBS "Alien Invasion". Accessed on 6 January 2008 (http:/ / www. pbs. org/ saf/ 1204/ features/ nature. htm) [3]  Should Giant African Land Snails Be Kept as Pets At All? (http:/ / exoticpets. about. com/ cs/ rarespecies/ a/ pestsGALs. htm) [4]  http:/ / www. hear. org/ books/ tgas1961/ [5]  http:/ / www. issg. org/ database/ species/ ecology. asp?si=64& fr=1& sts=sss [6]  http:/ / www. hear. org/ [7]  http:/ / www. petsnails. co. uk/ species/ achatina_fulica. html#start Source: http:/ / en. wikipedia. org/ w/ index. php? oldid=273876402 Contributors: Binary TSO, Chieron, Dentren, Dravecky, Elassint, Gillea2k8, Hordaland, Invertzoo, Iridescent, JForget, Jmgarg1, JustADuck, Lawrencegold, Mike Peel, Mygerardromance, Nashville Monkey, Neutrality, Pedro, Philiptdotcom, Regiomontanus, Ricardo Carneiro Pires, Rjwilmsi, Robin Whittleton, SJP, Sengkang, Snek01, Steven Weston, Techman224, Tim Ross, TravisM, William Pietri, Yosri, 43 anonymous edits

Cryptosporidium parvum

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隱孢子蟲 Cryptosporidium parvum Cryptosporidium parvum

Scientific classification

Kingdom:

Protista

Phylum:

Apicomplexa

Class:

Conoidasida

Subclass:

Coccidiasina

Order:

Eucoccidiorida

Family:

Cryptosporidiidae

Genus:

Cryptosporidium

Species:

C. parvum

Binomial name Cryptosporidium parvum

Cryptosporidium parvum is one of several species that cause cryptosporidiosis, a parasitic disease of the mammalian intestinal tract. Primary symptoms of C. parvum infection are acute, watery, and non-bloody diarrhoea. C. parvum infection is of particular concern in immunocompromised patients, where diarrhea can reach 10-15L per day. Other symptoms may include anorexia, nausea/vomiting and abdominal pain.[1] Infection is caused by ingestion of sporulated oocysts transmitted by the fecal-oral route. In healthy human hosts, the medial infective dose is 132 oocysts.[2] The general C. parvum life cycle is shared by other members of the genus. Invasion of the apical tip of ileal enterocytes by sporozoites and merozoites causes pathology seen in the disease. Infection is generally self-limiting in immunocompetent people. In immunecompromised patients, such as those with AIDS or those undergoing immunosuppressive therapy, infection may not be self-limiting, leading to dehydration and, in severe cases, death.

Cryptosporidium parvum The diagnosis of C. parvum consists of serological tests and microscopic evaluation of oocysts in stools using Kinyoun acid-fast staining. C. parvum is considered to be the most important waterborne pathogen in developed countries. It is resistant to all practical levels of chlorination, surviving for 24hrs at 1000mg/L free chlorine.

Genome The genome of C. parvum (sequenced in 2004[3] ) have a relatively small size and simple organization of 10.4 Mb, which is composed of eight chromosomes ranging from 1.04 to 1.5 Mb. The genome is very compact, and is one of the few organisms without transposable elements. Unlike other apicomplexans, C. parvum has no genes in its plastids or mitochrondria.[3]

Treatment Supportive therapy such as IV fluids is the primary for C. parvum infection. Paromomycin and Nitazoxanide may alleviate some of the diarrheal symptoms, however the latter is contraindicated for AIDS patients. Continuing antiretroviral drugs to boost the immune system may also control infection. Research into other potential drugs and therapeutics targets, as well as vaccine candidates, is ongoing.

Important C.parvum proteins and drug targets Lipid metabolism C. parvum is incapable of de novo lipid synthesis, making its lipid trafficking machinery an important potential therapeutic target. C. parvum possesses multiple oxysterol-binding proteins (OSBPs), and oxysterol related proteins (OSRPs). Only OSBPs are capable of lipid binding, while both contain Pleckstrin homology domains, which function in cell signalling pathways.

Surface glycoproteins C. parvum possesses numerous surface glycoproteins thought to play a role in pathogenesis. An immunodominant >900kDa protein, known as GP900, localizes to the apical end of sporozoites and in micronemes of merozoites. Its high molecular mass is most likely due to heavy post-translational glycosylation. Indeed, the structure of GP900 is similar to that of a family of glycoproteins known as mucins. GP900 is thought to mediate attachment and invasion to host cells. GP900 may also play a role in C. parvum’s resistance to proteolysis by the numerous proteases found in the mammalian gut. In vitro, hyperimmune sera as well as antibodies directed at specific epitopes on the GP900 protein inhibit the invasion of C. parvum sporozoites into MDCK cell monolayers. Additionally, competitive inhibition using native GP900 or purified GP900 fragments reduces cell invasion.[4] Further experiments have confirmed the importance of the mucin-like glycosylations. Lectins directed at GP900 carbohydrate moieties (alpha-N-galactosamine) were able to block adhesion and prevent C. parvum invasion.[5]

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Cryptosporidium parvum C. parvum glycoproteins have the characteristics of attractive vaccine candidates. Many are immunodominant, and antibodies against select domains block invasion of host cells.

External links [1]  ”Cryptosporidiosis.” Laboratory Identification of Parasites of Public Health Concern. CDC. 5 Sept 2007. [2]  DuPont HL, et al. The infectivity of Cryptosporidium parvum in healthy volunteers. N Eng J Med 1995;332:855-9 [3]  Abrahamsen MS, Templeton TJ, et al (2004). "[http:/ / www. sciencemag. org/ cgi/ content/ abstract/ 304/ 5669/ 441 Complete genome sequence of the apicomplexan, Cryptosporidium parvum.]". Science 304 (5669): 441–5. doi: 10.1126/science.1094786 (http:/ / dx. doi. org/ 10. 1126/ science. 1094786). PMID 15044751. http:/ / www. sciencemag. org/ cgi/ content/ abstract/ 304/ 5669/ 441. Retrieved on 2008-05-25. [4]  D.A. Barnes et al. A novel multi-domain mucin-like glycoprotein of Cryptosporidium parvum mediates invasion. Molecular and Biochemical Parasitology 96 (1998) 93-110 [5]  Cevallos, A.M. Mediation of Cryptosporidium parvum infection in vitro by mucin-like glycoproteins defined by a neutralizing monoclonal antibody. Infect Immun. 2000 Sep;68(9):5167-75. Source: http:/ / en. wikipedia. org/ w/ index. php? oldid=274407641 Contributors: AlexShalman, Arcadian, Dirrival, Doseiai2, Fullmetal Ink, Hoya20, Kingdon, MatthewBChambers, Mccready, Megstarrr, Mimihitam, WhatamIdoing, 6 anonymous edits

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License License Version 1.2, November 2002 Copyright (C) 2000,2001,2002 Free Software Foundation, Inc. 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others. This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software. We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law. A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language. A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them. The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none. The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words. A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not "Transparent" is called "Opaque". Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only. The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text. A section "Entitled XYZ" means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as "Acknowledgements", "Dedications", "Endorsements", or "History".) To "Preserve the Title" of such a section when you modify the Document means that it remains a section "Entitled XYZ" according to this definition. The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3. You may also lend copies, under the same conditions stated above, and you may publicly display copies.

3. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects. If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages. If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public. It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version: A.  Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission. B.  List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement. C.  State on the Title page the name of the publisher of the Modified Version, as the publisher. D.  Preserve all the copyright notices of the Document. E.  Add an appropriate copyright notice for your modifications adjacent to the other copyright notices. F.  Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below. G.  Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice. H.  Include an unaltered copy of this License. I.  Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

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License J.

 Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission. K.  For any section Entitled "Acknowledgements" or "Dedications", Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein. L.  Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles. M.  Delete any section Entitled "Endorsements". Such a section may not be included in the Modified Version. N.  Do not retitle any existing section to be Entitled "Endorsements" or to conflict in title with any Invariant Section. O.  Preserve any Warranty Disclaimers. If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles. You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard. You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one. The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers. The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work. In the combination, you must combine any sections Entitled "History" in the various original documents, forming one section Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections Entitled "Endorsements."

6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects. You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document. If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

8. TRANSLATION

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail. If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

10. FUTURE REVISIONS OF THIS LICENSE The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http:/ / www. gnu. org/ copyleft/ . Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

How to use this License for your documents To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page: Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the "with...Texts." line with this: with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation. If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

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