Cryptosporidiosis

Not to be confused with Cryptococcus (fungus).
Cryptosporidiosis

Micrograph showing cryptosporidiosis. The cryptosporidium are the small, round bodies in apical vacuoles on the surface of the epithelium. H&E stain. Colonic biopsy.
Classification and external resources
Specialty Infectious disease
ICD-10 A07.2
ICD-9-CM 007.4
DiseasesDB 3221
MedlinePlus 000617
eMedicine med/484
Patient UK Cryptosporidiosis

Cryptosporidiosis, also known as crypto,[1] is a parasitic disease caused by Cryptosporidium, a genus of protozoan parasites in the phylum Apicomplexa. It affects the distal small intestine and can affect the respiratory tract in both immunocompetent (i.e., individuals with a normal functioning immune system) and immunocompromised (e.g., persons with HIV/AIDS) individuals, resulting in watery diarrhea with or without an unexplained cough.[2] In immunocompromised individuals, the symptoms are particularly severe and can be fatal. It is primarily spread through the fecal-oral route, often through contaminated water;[2][3] recent evidence suggests that it can also be transmitted via fomites in respiratory secretions.[2]

Cryptosporidium is the organism most commonly isolated in HIV-positive patients presenting with diarrhea. Despite not being identified until 1976, it is one of the most common waterborne diseases and is found worldwide. The parasite is transmitted by environmentally hardy microbial cysts (oocysts) that, once ingested, exist in the small intestine and result in an infection of intestinal epithelial tissue.

Signs and symptoms

Cryptosporidiosis may occur as an asymptomatic infection, an acute infection (i.e., duration shorter than 2 weeks), recurrent acute infections in which symptoms reappear following a brief period of recovery for up to 30 days, and a chronic infection (i.e., duration longer than 2 weeks) in which symptoms are severe and persistent.[2][4][5][6] It may be fatal in individuals with a severely compromised immune system.[2][4] Symptoms usually appear 5–10 days after infection (range: 2–28 days) and normally last for up to 2 weeks in immunocompetent individuals (i.e., individuals with a normal functioning immune system);[2][4][5] symptoms are usually more severe and persist longer in immunocompromised individuals (e.g., persons with HIV/AIDS).[2][4][5] Following the resolution of diarrhea, symptoms can reoccur after several days or weeks due to reinfection.[4][5][6][7] Based upon one clinical trial, the likelihood of re-infection is high in immunocompetent adults.[7]

In immunocompetent individuals, cryptosporidiosis is primarily localized to the distal small intestine and sometimes the respiratory tract as well.[2][5] In immunocompromised persons, cryptosporidiosis may disseminate to other organs, including the hepatobiliary system, pancreas, upper gastrointestinal tract, and urinary bladder;[2][5] pancreatic and biliary infection can involve acalculous cholecystitis, sclerosing cholangitis, papillary stenosis, or pancreatitis.[5][8]

Intestinal cryptosporidiosis

Common signs and symptoms of intestinal cryptosporidiosis include:

Less common or rare signs and symptoms include:

Respiratory cryptosporidiosis

Symptoms of upper respiratory cryptosporidiosis include:

Symptoms of lower respiratory cryptosporidiosis include:

Cause

Life cycle of Cryptosporidium spp.

Cryptosporidium is a genus of protozoan pathogens which is categorized under the phylum Apicomplexa. Other apicomplexan pathogens include the malaria parasite Plasmodium, and Toxoplasma, the causative agent of toxoplasmosis. A number of Cryptosporidium infect mammals. In humans, the main causes of disease are C. parvum and C. hominis (previously C. parvum genotype 1). C. canis, C. felis, C. meleagridis, and C. muris can also cause disease in humans. Cryptosporidium is capable of completing its life cycle within a single host, resulting in microbial cyst stages that are excreted in feces and are capable of transmission to a new host via the fecal-oral route. Other vectors of disease transmission also exist.[2][9]

The pattern of Cryptosporidium life cycle fits well with that of other intestinal homogeneous coccidian genera of the suborder Eimeriina: macro- and microgamonts develop independently; a microgamont gives rise to numerous male gametes; and oocysts serving for parasites' spreading in the environment. Electron microscopic studies made from the 1970s have shown the intracellular, although extracytoplasmic localization of Cryptosporidium species.

These species possess a number of unusual features:

DNA studies suggest a relationship with the gregarines rather than the coccidia.[10] The taxonomic position of this group has not yet been finally agreed upon.

The genome of Cryptosporidium parvum was sequenced in 2004 and was found to be unusual amongst Eukaryotes in that the mitochondria seem not to contain DNA.[11] A closely related species, C. hominis, also has its genome sequence available.[12] CryptoDB.org is a NIH-funded database that provides access to the Cryptosporidium genomics data sets.

Transmission

Infection is through contaminated material such as earth, water, uncooked or cross-contaminated food that has been in contact with the feces of an infected individual or animal. Contact must then be transferred to the mouth and swallowed. It is especially prevalent amongst those in regular contact with bodies of fresh water including recreational water such as swimming pools. Other potential sources include insufficiently treated water supplies, contaminated food, or exposure to feces.[3] The high resistance of Cryptosporidium oocysts to disinfectants such as chlorine bleach enables them to survive for long periods and still remain infective.[13] Some outbreaks have happened in day care related to diaper changes.[14]

The following groups have an elevated risk of being exposed to Cryptosporidium:[3]

Cases of cryptosporidiosis can occur in a city that does not have a contaminated water supply. In a city with clean water, it may be that cases of cryptosporidiosis have different origins. Testing of water, as well as epidemiological study, are necessary to determine the sources of specific infections. Note that Cryptosporidium typically does not cause serious illness in healthy people. It may chronically sicken some children, as well as adults who are exposed and immunocompromised. A subset of the immunocompromised population is people with AIDS. Some sexual behaviours can transmit the parasite directly.

Life cycle

Cryptosporidium spp. exist as multiple cell types which correspond to different stages in an infection (e.g., a sexual and asexual stage).[1] As an oocyst – a type of hardy, thick-walled spore – it can survive in the environment for months and is resistant to many common disinfectants, particularly chlorine-based disinfectants.[15][16] After being ingested, the oocysts exist in the small intestine. They release sporozoites that attach to the microvilli of the epithelial cells of the small intestine. From there they become trophozoites that reproduce asexually by multiple fission, a process known as schizogony. The trophozoites develop into Type 1 meronts [1] that contain 8 daughter cells.[17]

These daughter cells are Type 1 merozoites, which get released by the meronts. Some of these merozoites can cause autoinfection by attaching to epithelial cells. Others of these merozoites become Type II meronts,[18] which contain 4 Type II merozoites.[17] These merozoites get released and they attach to the epithelial cells. From there they become either macrogamonts or microgamonts.[18] These are the female and male sexual forms, respectively.[17] This stage, when sexual forms arise, is called gametogony.[19]

Zygotes are formed by microgametes from the microgamont penetrating the macrogamonts. The zygotes develop into oocysts of two types.[18] 20% of oocysts have thin walls and so can reinfect the host by rupturing and releasing sporozoites that start the process over again.[17] The thick-walled oocysts are excreted into the environment.[18] The oocysts are mature and infective upon being excreted.[17]

Pathogenesis

The oocysts are ovoid or spherical and measure 5 to 6 micrometers across. When in flotation preparations they appear highly refractile. The oocysts contains up to 4 sporozoites that are bow-shaped.[20]

As few as 2 to 10 oocysts can initiate an infection.[21] The parasite is located in the brush border of the epithelial cells of the small intestine.[22] They are mainly located in the jejunum. When the sporozoites attach the epithelial cells’ membrane envelops them. Thus, they are “intracellular but extracytoplasmic”.[17] The parasite can cause damage to the microvilli where it attaches.[20] The infected human excretes the most oocysts during the first week.[17] Oocysts can be excreted for weeks after the diarrhea subsides from infections by C. parvum or C. hominis;[1] however, immunocompetent individuals with C. muris infections have been observed excreting oocysts for seven months.[23]

The immune system reduces the formation of Type 1 merozoites as well as the number of thin-walled oocysts.[17] This helps prevent autoinfection. B cells do not help with the initial response or the fight to eliminate the parasite.[21]

Diagnosis

There are many diagnostic tests for Cryptosporidium. They include microscopy, staining, and detection of antibodies. Microscopy[1] can help identify oocysts in fecal matter.[22] To increase the chance of finding the oocysts, the diagnostician should inspect at least 3 stool samples.[19] There are several techniques to concentrate either the stool sample or the oocysts. The modified formalin-ethyl acetate (FEA) concentration method concentrates the stool.[20] Both the modified zinc sulfate centrifugal flotation technique and the Sheather’s sugar flotation procedure can concentrate the oocysts by causing them to float.[19] Another form of microscopy is fluorescent microscopy done by staining with auramine.[22]

Other staining techniques include acid-fast staining,[21] which will stain the oocysts red.[20] One type of acid-fast stain is the Kinyoun stain.[16] Giemsa staining can also be performed.[17] Part of the small intestine can be stained with hematoxylin and eosin (H & E), which will show oocysts attached to the epithelial cells.[20]

Detecting antigens is yet another way to diagnose the disease. This can be done with direct fluorescent antibody (DFA) techniques.[1] It can also be achieved through indirect immunofluorescence assay.[19] Enzyme-linked immunosorbent assay (ELISA) also detects antigens.[22]

Polymerase chain reaction (PCR) is another way to diagnose cryptosporidiosis. It can even identify the specific species of Cryptosporidium.[1] If the patient is thought to have biliary cryptosporidiosis, then an appropriate diagnostic technique is ultrasonography. If that returns normal results, the next step would be to perform endoscopic retrograde cholangiopancreatography.[21]

Prevention

Many treatment plants that take raw water from rivers, lakes, and reservoirs for public drinking water production use conventional filtration technologies. This involves a series of processes, including coagulation, flocculation, sedimentation, and filtration. Direct filtration, which is typically used to treat water with low particulate levels, includes coagulation and filtration, but not sedimentation. Other common filtration processes, including slow sand filters, diatomaceous earth filters and membranes will remove 99% of Cryptosporidium.[24] Membranes and bag and cartridge filters remove Cryptosporidium product-specifically.

While Cryptosporidium is highly resistant to chlorine disinfection,[25] with high enough concentrations and contact time, Cryptosporidium will be inactivated by chlorine dioxide and ozone treatment. The required levels of chlorine generally preclude the use of chlorine disinfection as a reliable method to control Cryptosporidium in drinking water. Ultraviolet light treatment at relatively low doses will inactivate Cryptosporidium. Water Research Foundation-funded research originally discovered UV's efficacy in inactivating Cryptosporidium.[26][27]

One of the largest challenges in identifying outbreaks is the ability to identify Cryptosporidium in the laboratory. Real-time monitoring technology is now able to detect Cryptosporidium with online systems, unlike the spot and batch testing methods used in the past.

The most reliable way to decontaminate drinking water that may be contaminated by Cryptosporidium is to boil it.[28][29]

In the US the law requires doctors and labs to report cases of cryptosporidiosis to local or state health departments. These departments then report to the Center for Disease Control and Prevention.[1] The best way to prevent getting and spreading cryptosporidiosis is to have good hygiene and sanitation.[19] An example would be hand-washing.[1] Prevention is through washing hands carefully after going to the bathroom or contacting stool, and before eating. People should avoid contact with animal feces.[22] They should also avoid possibly contaminated food and water.[1] In addition, people should refrain from engaging in sexual activities that can expose them to feces.[19]

Standard water filtration may not be enough to eliminate Cryptosporidium; boiling for at least 1 minute (3 minutes above 6,500 feet (2,000 m) of altitude) will decontaminate it. Heating milk at 71.7 °C (161 °F) for 15 seconds pasteurizes it and can destroy the oocysts' ability to infect.[30] Water can also be made safe by filtering with a filter with pore size not greater than 1 micrometre, or by filters that have been approved for “cyst removal” by NSF International National Sanitation Foundation.[1] Bottled drinking water is less likely to contain Cryptosporidium, especially if the water is from an underground source.[30]

People with cryptosporidiosis should not swim in communal areas because the pathogen can reside in the anal and genital areas and be washed off. They should wait until at least two weeks after diarrhea stops before entering public water sources, since oocysts can still be shed for a while. Also, they should stay away from immunosuppressed people.[1] Immunocompromised people should take care to protect themselves from water in lakes and streams.[21] They should also stay away from animal stools and wash their hands after touching animals. To be safe, they should boil or filter their water. They should also wash and cook their vegetables.[1]

The US CDC notes the recommendation of many public health departments to soak contaminated surfaces for 20 minutes with a 3% hydrogen peroxide (99% kill rate) and then rinse them thoroughly, with the caveat that no disinfectant is guaranteed to be completely effective against Cryptosporidium. However, hydrogen peroxide is more effective than standard bleach solutions.[31]

Treatment

Symptomatic treatment primarily involves fluid rehydration, electrolyte replacement (sodium, potassium, bicarbonate, and glucose), and antimotility agents (e.g., loperamide).[32][33] Supplemental zinc may improve symptoms,[32] particularly in recurrent or persistent infections or in others at risk for zinc deficiency.

Immunocompetent

Immunocompetent individuals with cryptosporidiosis typically suffer a short (i.e., duration of less than 2 weeks) self-limiting course of diarrhea that may require symptomatic treatment and ends with spontaneous recovery; in some circumstances, antiparasitic medication may be required (e.g., recurrent, severe, or persistent symptoms);[7] however reinfection frequently occurs.[7]

As of 2015, nitazoxanide is the only antiparasitic drug treatment with proven efficacy for cryptosporidiosis in immunocompetent individuals;[7][32][33][34] however, it lacks efficacy in severely immunocompromised patients.[34] Certain agents such as paromomycin and azithromycin are sometimes used as well, but they only have partial efficacy.[32]

Immunocompromised

In immunocompromised individuals, such as AIDS patients, cryptosporidiosis resolves slowly or not at all, and frequently causes a particularly severe and persistent form of watery diarrhea coupled with a greatly decreased ability to absorb key nutrients through the intestinal tract. As a result, infected individuals may experience severe dehydration, electrolyte imbalances, malnutrition, wasting, and potentially death. In general, the mortality rate for infected AIDS patients is based on CD4+ marker counts. Patients with CD4+ counts over 180 cells/mm³ recover with supportive hospital care and medication; but, in patients with CD4+ counts below 50 cells/mm³, the effects are usually fatal within 3 to 6 months. During the Milwaukee cryptosporidiosis epidemic (the largest of its kind), 73% of AIDS patients with CD4+ counts lower than 50 cells/mm³ and 36% of those with counts between 50 and 200 cells/mm³ died within the first year of contracting the infection.[35]

The best treatment approach is to improve the immune status in immunodeficient individuals using highly active antiretroviral therapy that includes an HIV protease inhibitor along with continued use of antiparasitic medication.[32][33] Antiparasitic drug treatment for immunocompromised individuals usually involves the combination of nitazoxanide, paromomycin, and azithromycin together;[7][32] these drugs are only partially active in HIV/AIDS patients compared to their effect in immunocompetent persons.[32] A Cochrane Collaboration review recommended that nitazoxanide be considered for use in treatment despite its reduced effectiveness in immunocompromised individuals.[33]

Currently, research is being done in molecular-based immunotherapy. For example, synthetic isoflavone derivates have been shown to fight off Cryptosporidium parvum both in vitro and in animal studies. Derivates of nitazoxanide, known as thiazolides, have also shown promising results in vitro.[36]

Epidemiology

Cryptosporidiosis is found worldwide. It causes 50.8% of water-borne diseases that are attributed to parasites.[16] In developing countries, 8–19% of diarrheal diseases can be attributed to Cryptosporidium.[37] Ten percent of the population in developing countries excretes oocysts. In developed countries, the number is lower at 1–3%. The age group most affected is children from 1 to 9 years old.[21]

As of 2010 it caused about 100,000 deaths down from 220,000 in 1990.[38]

Roughly 30% of adults in the United States are seropositive for cryptosporidiosis, meaning that they contracted the infection at some point in their lives.[7]

History

The organism was first described in 1907 by Tyzzer, who recognised it was a coccidian.

Research

A recombinant Cryptosporidium parvum oocyst surface protein (rCP15/60) vaccine has produced an antibody response in a large group of cows and also antibody response in calves fed rCP15/60-immune colostrum produced by these vaccinated cows . This is very promising. Human Cryptosporidium parvum infections are particularly prevalent and often fatal in neonates in developing countries and to immunocompromised people, such as AIDs patients. To date (2013), there is no commercially available effective vaccine against Cryptosporidium parvum, although passive immunization utilizing different zoite surface (glyco)proteins has showed promise. Developmental stages within the life cycle of the parasite that might act as possible targets for vaccine development. The organism is detected in 65–97% of the surface-water supply in the United States and is resistant to most disinfectants used for treatment of drinking water. Antibodies in the serum of humans and animals infected with Cryptosporidium parvum react with several antigens, one of which is a 15 kDa protein (CP15) located on the surface of the organism. This protein is a good candidate for use as a molecular vaccine because previous studies have shown that a monoclonal antibody to CP15 confers passive immunityto mice. Currently, there is no drug therapy or vaccine that is effective against Cryptosporidium parvum.

Other animals

The most important zoonotic reservoirs are cattle, sheep and goats. In addition, in recent years, cryptosporidiosis has plagued many commercial leopard gecko breeders. Several species of the Cryptosporidium family (C. serpentes and others) are involved, and outside of geckos it has been found in monitor lizards, iguanas and tortoises, as well as several snake species.

Notable cases

Before 2000

2001–2009

2010 and later

See also

References

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  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Sponseller JK, Griffiths JK, Tzipori S (2014). "The evolution of respiratory Cryptosporidiosis: evidence for transmission by inhalation". Clin. Microbiol. Rev. 27 (3): 575–86. doi:10.1128/CMR.00115-13. PMC 4135895. PMID 24982322. Recent evidence indicates that respiratory cryptosporidiosis may occur commonly in immunocompetent children with cryptosporidial diarrhea and unexplained cough. Findings from animal models, human case reports, and a few epidemiological studies suggest that Cryptosporidium may be transmitted via respiratory secretions, in addition to the more recognized fecal-oral route. ... Upper respiratory cryptosporidiosis may cause inflammation of the nasal mucosa, sinuses, larynx, and trachea, accompanied by nasal discharge and voice change (54, 61, 62). Cryptosporidiosis of the lower respiratory tract typically results in productive cough, dyspnea, fever, and hypoxemia (63,–66). ... While fecal-oral transmission is indisputably the major route of infection, transmission via coughing and fomites is also possible in situations of close contact (20). ... Because they lacked gastrointestinal symptoms and oocyst excretion, the latter cases establish the possibility of primary respiratory infection with Cryptosporidium, which may have been acquired by inhalation of expectorated droplets or by contact with fomites. ... This finding suggests that respiratory cryptosporidiosis may occur commonly in immunocompetent individuals.
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  6. 1 2 "Cryptosporidium: Nitazoxanide". United States Centers for Disease Control and Prevention. 20 February 2015. Retrieved 11 January 2016. Healthcare professionals might consider re-testing stool at least 1 week after the last dose of nitazoxanide only if symptoms do not resolve. In such cases, longer courses of treatment might be needed. Persistent symptoms may also represent re-infection
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  8. ↑ Hawkins S, Thomas R, Teasdale C (1987). "Acute pancreatitis: a new finding in cryptosporidium enteritis". Br Med J (Clin Res Ed) 294 (6570): 483–4. doi:10.1136/bmj.294.6570.483-a. PMC 1245527. PMID 3103738.
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  21. 1 2 3 4 5 6 Chen W, Harp JA, Harmsen AG (April 2003). "Cryptosporidium parvum infection in gene-targeted B cell-deficient mice". J. Parasitol. 89 (2): 391–3. doi:10.1645/0022-3395(2003)089[0391:CPIIGB]2.0.CO;2. PMID 12760662.
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  32. 1 2 3 4 5 6 7 Cabada MM; White AC; Venugopalan P; Sureshbabu J (18 August 2015). Bronze MS, ed. "Cryptosporidiosis Treatment & Management". Medscape. WebMD. Retrieved 8 January 2016. Infection may improve with nutritional supplementation, particularly with regimens including zinc or glutamine. ... Nitazoxanide significantly shortens the duration of diarrhea and can decrease the risk of mortality in malnourished children.[22] Trials have also demonstrated efficacy in adults.[26, 27] ... Use of partially active antiparasitic drugs (eg, nitazoxanide or paromomycin combined with azithromycin) should be considered along with initiating antiretroviral therapy. ... Symptomatic therapy includes replacement of fluids, provision of appropriate nutrition, and treatment with antimotility agents. ... Replacement of fluids and electrolytes is the critically important first step in the management of cryptosporidiosis, particularly in patients with large diarrheal losses. Fluids should include sodium, potassium, bicarbonate, and glucose.
  33. 1 2 3 4 Abubakar I, Aliyu SH, Arumugam C, Hunter PR, Usman NK (January 2007). "Prevention and treatment of cryptosporidiosis in immunocompromised patients". Cochrane Database Syst Rev (1): CD004932. doi:10.1002/14651858.CD004932.pub2. PMID 17253532. The results indicate that nitaxozanide reduces the load of parasites and may be useful in immunocompetent individuals. Due to the seriousness of the potential outcomes of cryptosporidiosis, the use of nitaxozanide should be considered in immunocompromised patients. The absence of effective therapy highlights the need to ensure that infection is avoided. ... For HIV-infected persons, highly active antiretroviral therapy (HAART) is the mainstay of preventing and managing cryptosporidiosis. HAART can lead to complete resolution of clinical symptoms and oocysts (Grube 1997; Maggi 2000; Miao 2000). This intervention is not available for HIV patients who are failing HAART or those unable to access HAART in developing countries. Among these immunocompromised persons without the option of an effective treatment for the underlying disease, supportive management, including rehydration therapy, electrolyte replacement, and anti-motility agents will remain the only alternatives for care until better drugs emerge.
  34. 1 2 Sparks H, Nair G, Castellanos-Gonzalez A, White AC (2015). "Treatment of Cryptosporidium: What We Know, Gaps, and the Way Forward". Curr Trop Med Rep 2 (3): 181–187. doi:10.1007/s40475-015-0056-9. PMID 26568906.
  35. ↑ Gilson M.D., Ian; Buggy, Brian P. M.D. (October 1996). "Cryptosporidiosis in Patients with HIV Disease: Is It Safe to Drink the Water?". HIV Newsline (San Francisco General Hospital).
  36. ↑ Gargala G (September 2008). "Drug treatment and novel drug target against Cryptosporidium". Parasite 15 (3): 275–81. doi:10.1051/parasite/2008153275. PMID 18814694.
  37. ↑ Gatei W, Wamae CN, Mbae C; et al. (July 2006). "Cryptosporidiosis: prevalence, genotype analysis, and symptoms associated with infections in children in Kenya". Am. J. Trop. Med. Hyg. 75 (1): 78–82. PMID 16837712.
  38. ↑ Lozano, R (15 December 2012). "Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010.". Lancet 380 (9859): 2095–128. doi:10.1016/S0140-6736(12)61728-0. PMID 23245604.
  39. ↑ Corso P, Kramer M, Blair K, Addiss D, Davis J, Haddix A (2003). "Costs of Illness in the 1993 Waterborne Cryptosporidium Outbreak, Milwaukee, Wisconsin". Emerg Infect Dis 9 (4): 426–31. doi:10.3201/eid0904.020417. PMC 2957981. PMID 12702221.
  40. ↑ "Cryptosporidium". CBC News. 23 June 2004. Archived from the original on 1 March 2011. Retrieved 19 April 2011.
  41. ↑ "Waterborne Cryptosporidiosis Outbreak, North Battleford, Ssaskatchewan, Spring 2001". Public Health Agency of Canada. 15 November 2001. Retrieved 25 January 2008.
  42. ↑ "State Health Department Issues Update on Seneca Lake State Park Gastrointestinal Outbreak". New York State Health Dept. Retrieved 29 September 2006.
  43. ↑ RTÉ News — Galway water now safer than ever — HSE
  44. ↑ Yahoo.com, Cryptosporidium outbreak hits the West
  45. ↑ Northampton Chronicle and Echo
  46. ↑ Anglian Water-lifting of boil notice
  47. ↑ Crypto spreads to private pools — WFAA-TV. Retrieved 13 August 2008.
  48. ↑ Gym closes pool in danger bug alert
  49. ↑ Mawer, Jessica (20 May 2010). "Woree, Gordonvale residents advised to boil drinking water". ABC Online. Retrieved 19 April 2011.
  50. ↑ "Smittskyddsinstitutets arbete med det vattenburna utbrottet av Cryptosporidium i Östersund" (in Swedish). Smittskyddsinstitutet. Retrieved 19 April 2011.
  51. ↑ Sjöö, Patrick (13 December 2010). "Kommunens parasitenkät avslutas". Östersunds-Posten (in Swedish). Retrieved 19 April 2011.
  52. ↑ "Boil water notice after Cryptosporidiosis outbreak in Co Roscommon". RTÉ News. 15 May 2013.
  53. ↑ "13 people treated following Roscommon water pollution". RTÉ News. 17 May 2013.
  54. ↑ Thirst (1998) IMDB

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