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Cryptosporidiosis

Cryptosporidiosis

Definition

Cryptosporidiosis refers to infection by the sporeforming protozoan known as Cryptosporidia. Protozoa are a group of parasites that infect the human intestine, and include the better known Giardia. Cryptosporidia was first identified in 1976 as a cause of disease in humans.

Description

Cryptosporidia are normally passed in the feces of infected persons and animals in the form of cysts. The cysts can remain in the ground and water for months, and when ingested produce symptoms after maturing in the intestine and the bile ducts. When viewed under the microscope, they appear as small bluish-staining round bodies. Most common sources of infection are other humans, water supplies, or reservoirs. These are contaminated by animals that defecate in these areas. An outbreak in Milwaukee in 1993 in which over 400,000 persons were affected was traced to the city's water supply. Cysts of Cryptosporidia are extremely resistant to the disinfectants that are commonly used in most water treatment plants and are incompletely removed by filtration.

Most persons who experience significant symptoms have an altered immune system, and suffer from diseases such as AIDS and cancer. However, as shown in the Milwaukee outbreak, even those with normal immunity can experience symptoms.

Causes and symptoms

Cysts of Cryptosporidia mature in the intestine and bile ducts within three to five days of ingestion. As noted, large-scale infections from contaminated water supplies has been documented. However, human to human transmission (such as occurs in day care centers or through sexual behavior) is also an important cause.

Many individuals can be infected without any illness, but the major symptom is diarrhea, which is often watery and incapacitating. Dehydration, low-grade fever, nausea, and abdominal cramps are frequent.

In those with a normal immune system, the disease usually lasts about 10 days. For patients with altered immunity (immunocompromised), the story is quite different, with diarrhea becoming chronic, debilitating, and even fatal.

Complications

Dehydration and malnutrition are the most common effects of infection. In about 20% of AIDS patients, bile duct infection also occurs and causes symptoms similar to gallbladder attacks. Eighty percent or more of those with infection of the bile ducts die from the disease. The lungs and pancreas are also sometimes involved. Cryptosporidia are just one cause of the diarrhea wasting syndrome in AIDS, which results in severe weight loss and malnutrition.

Diagnosis

This is based on either finding the characteristic cysts in stool specimens, or on biopsy of an infected organ, such as the intestine.

Treatment

The first aim of treatment is to avoid dehydration. Oral Rehydration Solution (ORS) or intravenous fluids may be needed. Medications used to treat diarrhea by decreasing intestinal motility (Anti-Motility Agents), such as loperamide or diphenoxylate, are also useful, but should only be used with the advice of a physician.

Treatment aimed directly at Cryptosporidia is only partially effective, and rarely eliminates the organism. The medication most commonly used is paromomycin (Humatin), but others are presently under evaluation.

Prognosis

Cryptosporidia rarely cause a serious disease in persons with normal immune systems. Replacement of fluids is all that is usually needed. On the other hand, those with altered immune systems often suffer for months to years. Paramomycin and other drugs have been able to improve symptoms in over half of those treated. Unfortunately, many organisms are resistant, and recurrence is frequent.

Prevention

The best way to prevent cryptosporidiosis is to minimize exposure to cysts from infected humans and animals. Proper hand washing technique, especially in day care centers, is recommended.

Resources

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. http://www.cdc.gov.

OTHER

"Cryptosporidiosis." Centers for Disease Control. http://www.cdc.gov/ncidod/diseases/crypto/crypto.htm.

Vakil, Nimish B., et al. "Biliary Cryptosporidiosis in HIV-Infected People after the Waterborne Outbreak of Cryptosporidiosis in Milwaukee." New England Journal of Medicine Online. http://content.nejm.org.

KEY TERMS

Anti-motility medications Medications such as loperamide (sold as Imodium), dephenoxylate (sold as Lomotil), or medications containing codeine or narcotics that decrease the ability of the intestine to contract. This can worsen the condition of a patient with dysentery or colitis.

Cyst A protective sac that includes either fluid or the cell of an organism. The cyst enables many organisms to survive in the environment for long periods of time without need for food or water.

Immunocompromised A change or alteration of the immune system that normally serves to fight off infections and other illnesses. This can involve changes in antibodies that the body produces (hygogammaglobulinemia), or defect in the cells that partake in the immune response. Diseases such as AIDS and cancer exhibit changes in the body's natural immunity.

Oral Rehydration Solution (ORS) A liquid preparation developed by the World Health Organization that can decrease fluid loss in persons with diarrhea. Originally developed to be prepared with materials available in the home, commercial preparations have recently come into use.

Parasite An organism that lives on or in another and takes nourishment (food and fluids) from that organism.

Protozoa Group of extremely small single cell (unicellular) or acellular organisms that are found in moist soil or water. They tend to exist as parasites, living off other life forms.

Spore A resistant form of certain species of bacteria, protozoa, and other organisms.

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Cryptosporidiosis

CRYPTOSPORIDIOSIS

Cryptosporidium is a genus of protozoan parasites that are infectious to humans and animals. The first reports of human infection with Cryptosporidium were made in 1976; the infection occurs worldwide. Cryptosporidiosis, the enteric disease caused by Cryptosporidium is considered one of the most common parasitic infections in the United States. The largest water-borne outbreak occurred in Milwaukee, Wisconsin, in 1993, when more than 400,000 people were affected. People at highest risk are children less than two years of age, animal handlers, international travelers, homosexual individuals, health care and day-care workers, and the elderly. Cryptosporidiosis infections have been associated with drinking water, recreational water, contaminated food (mainly fruits and vegetables), and direct fecal local contamination.

There are many species of Cryptosporidium, and they infect a wide range of animals. Cryptosporidium parvum is the most common species infecting humans; however, rare cases of C. felis, C. canis, and C. meleagridis infections have been reported in persons with compromised immune systems. There are two main strains of C. parvum, one apparently restricted to humans (anthroponotic), the other infecting animals and humans (zoonotic). C. parvum can also infect humans, cattle, and other domestic animals.

Identification of Cryptosporidium is of both medical and veterinary importance. Cryptosporidium oocysts, the infectious stage of the parasite passed in the feces, predominantly colonize the epithelial cells of the small intestineyet infections have also been found in epithelial cells of both the gastrointestinal and respiratory tract, including the bile ducts, gall bladder, pancreas, stomach, trachea, lungs, and possibly conjunctiva. Asymptomatic infections are common, though the most frequent symptom in humans is diarrhea. Symptoms often wax and wane, but generally remit in fewer than thirty days (with an average of one to two weeks) in most healthy, immunocompetent persons. Symptoms include profuse or watery diarrhea, dehydration, fever, anorexia, nausea, vomiting, stomach cramping, and flatulence. Immunocompromised persons often cannot clear the infection, which significantly contributes to such persons' illness and death.

Transmission routes are fecal-oral, person-to-person, animal-to-person, waterborne, and food-borne. Oocysts of C. parvum are round and 4 to 6 microns in diameter. They are so small that over 10,000 of them would fit on the period at the end of this sentence. The oocysts are highly resistant to chlorine, and to environmental conditions such as frost and heat.

In the laboratory, the most commonly used technique to detect Cryptosporidium oocysts in feces are staining procedures and commercial testing kits. Molecular methods of detection are mainly used as a research tool. Commercial blood tests are not yet available.

Various ways of preventing Cryptosporidium infection include educating the public in personal hygiene, using care in handling animal or human excreta, washing all vegetables and fruits, and avoiding drinking untreated water from lakes, rivers, springs, ponds, or streams. Ways of eliminating oocysts from drinking water are by boiling for one minute or by filter sterilization with either absolute 1.0 micron filters, reverse osmosis filters, or filters that meet NSF (National Sanitation Foundation) standards. Infected food handlers should be removed from work areas, and infected children should be excluded from day-care and recreational water facilities until the infection clears.

There is no established therapy for human cryptosporidiosis. Supportive measures to alleviate symptoms include antidiarrheal medication and management of fluid and electrolyte balance.

Eva M. Kovacs-Nace

Bibliography

American Public Health Association (2000). "Control of Communicable Diseases Manual." 17:134137.

Centers for Disease Control and Prevention (2000). Parasitic PathwaysDrinking Water. Available at http://www.cdc.gov/ncidod/dpd/parasiticpathways/drinkingwater.htm.

MacKenzie, W. R.; Hoxie, N. J.; Proctor, M. E.; Gradus, M. S.; Blair, K. A.; Peterson, D. E.; Kazmierczak, J. J.; Addiss, D. G.; Fox, K. R.; Rose, J. B.; and Davis, J. P. (1994). "A Massive Outbreak in Milwaukee of Cryptosporidium Infection Transmitted Through the Public Water Supply." New England Journal of Medicine 331:161167.

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Cryptosporidiosis

Cryptosporidiosis


Cryptosporidiosis (also referred to as Crypto) is a gastrointestinal illness that results from exposure to the organism Cryptosporidium parvum (C. parvum ). Cryptosporidiosis rose to public attention in the United States in 1993 when more than 100 people died and more than 400,000 people were sickened by Crypto in Milwaukee, Wisconsin.

Cryptosporidiosis is primarily a waterborne illness. People get infected from drinking inadequately treated drinking water, or from swallowing or drinking untreated water from a lake, stream, or swallowing water from a recreational swimming pool. People can become infected with Crypto through contact with the contaminated fecal matter of humans or animals carrying the organism, usually by swallowing food or liquid that has had contact with the contaminated fecal matter. Children at day care centers, day care workers, and health care workers interacting with infected individuals must be vigilant about sanitation to reduce the spread of the organism. Unwashed fruits and vegetables that have been in contact with Cryptoinfected soil have also exposed people to the organism. Cattle and calves contribute significant amounts of Crypto to soils and adjacent water bodies; and wild animals such as elk, deer, bear, and beaver can also carry and spread the organism.

Crypto's symptoms in humans are not unique. They include upset stomach, diarrhea, cramps, weight loss, dehydration, and sometimes fever. Some people do not experience any symptoms. The effects of cryptosporidiosis can be fatal for immunocompromised individuals, including AIDS and cancer patients. Cryptosporidiosis can only be diagnosed by testing a person's stool for the parasite. There is currently no treatment for the illness, which can last several days to a few weeks in healthy individuals.

The organism, C. parvum, is miniscule. It is 3 to 5 microns in size, while the diameter of a human hair is 50 to 200 microns. Giardia lamblia, another significant waterborne parasite, is 5 to 7 microns in size.

Drinking water regulations that went into effect in 1990 focused on the removal and inactivation of Giardia. The threat of Giardia is removed by common water treatment practices, including filtration and disinfection with chlorine. These treatment practices are not as effective against Crypto, which is half the size of Giardia and resistant to disinfection with chlorine. Because drinking water containing Cryptosporidium is difficult to treat, it is important to protect the source of the water against animal waste runoff and other sources of Crypto contamination. Water treatment regulations in effect in 2002 require water utilities to improve treatment plant performance and consistency against Cryptosporidium. The revised drinking water regulations only address exposure from public drinking water sources; they do not address recreational waterborne exposure, or other routes of exposure that tend to be more common.

see also Health, Human; Risk; Water Pollution; Water Treatment.

Bibliography

American Water Works Association. (1990). Water Quality and Treatment: A Handbook of Community Water Supplies, 4th edition. San Francisco: McGraw-Hill.

American Water Works Association and the Society of Civil Engineers. (1998). Water Treatment Plant Design, 3rd edition. San Francisco: McGraw-Hill.

Internet Resource

U.S. Environmental Protection Agency, Office of Water. Available from http://www.epa.gov/safewater.

Julie Hutchins Cairn

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cryptosporidiosis

cryptosporidiosis (krip-toh-sper-id-i-oh-sis) n. an intestinal infection of mammals and birds caused by parasitic protozoa of the genus Cryptosporidium, which is usually transmitted to humans via farm animals. Ingestion of water or milk contaminated with infective oocysts results in severe diarrhoea and abdominal cramps, caused by release of a toxin. Most patients recover in 7–14 days, but the disease can persist in the immunocompromised (including AIDS patients), the elderly, and young children.

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Cryptosporidiosis

Cryptosporidiosis

Introduction

Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues

BIBLIOGRAPHY

Introduction

Cryptosporidiosis (KRIP-toe-spo-rid-ee-OH-sis) is a parasitic infection of the gastrointestinal tract that usually results in diarrhea. It occurs when the parasite Cryptosporidium is ingested due to contact between the mouth and fecal material containing the parasite. In addition to humans, more than 45 species of animals, including common farm animals, can become infected with Cryptosporidium.

There is often no treatment administered in otherwise healthy individuals following diagnosis, although fluid replacement may be necessary following severe diarrhea. Symptoms last around two weeks, and the disease is transmissible even in the absence of symptoms. Infection can be prevented through adhering to hygienic regimes including handwashing, washing or cooking food, boiling water, and avoiding contact with animals.

Outbreaks can occur, especially if drinking water becomes contaminated with the parasite. In this case, it is necessary to filter or boil water to prevent infection.

Disease History, Characteristics, and Transmission

Cryptosporidiosis was first diagnosed in humans in 1976 after a three-year-old girl suffering from vomiting and diarrhea was found to be infected with the parasite Cryptosporidium. The girl's digestive tract contained large amounts of gas in the colon, large amounts of fluid in the small and large bowel, and on further examination, the parasite was found within her digestive tract. Since the initial diagnosis, multiple outbreaks have occurred in the United States, including one significant outbreak transmitted through the Milwaukee, Wisconsin public water system occurred in 1993 during which 403,000 people became infected.

Cryptosporidiosis occurs after ingestion of the parasite Cryptosporidium. This parasite is a one-celled, ball-shaped organism that affects the digestive, biliary, and respiratory systems of other organisms. The parasite lays oocytes, which are egglike structures covered in a protective shell. Oocytes leave an infected organism's body in fecal matter. Oocytes can remain viable for two to six months in a moist environment, and due to their protective outer covering, are highly resistant to chemical disinfectant. Therefore, these parasites are potentially highly infectious.

WORDS TO KNOW

PREVALENCE: The actual number of cases of disease (or injury) that exist in a population.

WATER-BORNE DISEASE: Water-borne disease refers to diseases that are caused by exposure to contaminated water. The exposure can be by drinking the water or having the water come in contact with the body. Examples of waterborne diseases are cholera and typhoid fever.

IN CONTEXT: PERSONAL RESPONSIBILITY AND PROTECTION

The Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Parasitic Diseases recommends that states that “If you are unable to avoid using or drinking water that might be contaminated (with Cryptosporidium parvum), then you can make the water safe to drink by doing one of the following:

  • Heat the water to a rolling boil for at least 1 minute OR use a filter that has an absolute pore size of 1 micron or smaller, or one that has been NSF rated for ‘cyst removal.’
  • Do not rely on chemicals to disinfect water and kill Cryptosporidium. Because it has a thick outer shell, this particular parasite is highly resistant to disinfectants such as chlorine and iodine.”

SOURCE: Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Parasitic Diseases

Ingestion of infected fecal matter results in transmission of the parasite to a new organism. Ingestion of fecal matter occurs when the mouth comes in either direct contact with fecal matter, or in contact with something that has touched fecal matter. The most common means are: not washing hands after using the toilet, handling infected animals, not washing food or cooking food thoroughly, and drinking contaminated water. In addition, swimming pools and spas are common places for infection to occur due to the moist environment, and the resistance of the parasite to chemicals, including pool chlorine. Swallowing pool water infected with the parasite can lead to infection.

Scope and Distribution

Cryptosporidiosis is widespread within the United States, and is also present worldwide. Outbreaks have occurred in over 50 countries worldwide on six continents. The U.S. Food and Drug Administration estimates that about 80% of the American population has had cryptosporidiosis, and its prevalence (the proportion of a population having a particular disease at a given time) is about 2% in North America.

The people most commonly infected by cryptosporidiosis are children younger than two years of age, animal handlers, health care workers, and travelers. While the people most at risk of suffering long term, or even fatal cases of cryptosporidiosis, are those with weak immune systems. Young children are at risk due to the likelihood of them placing infected objects into their mouth, or not washing their hands after using the toilet.

Animal handlers are required to come into contact with animals on a daily basis. If hygienic procedures such as handwashing and washing clothes are not undertaken, transmission can occur between the animals and humans. Animals that can be infected include a range of common farm animals such as cattle and sheep, as well as common pets such as cats, dogs, birds, and fish.

Health care workers usually come into contact with fecal matter on a daily basis, which could potentially result in them becoming infected, particularly if they are caring for patients infected with cryptosporidiosis. To avoid infection, healthcare workers use contact precautions, including handwashing and wearing gloves when anticipating contact with potentially infected feces. People taking care of children may also be exposed to infection during diaper changing, as they are likely to come into contact with fecal matter.

Travelers are at risk as they may travel through areas with differing levels of hygiene in terms of food preparation and water standards. Lower standards may result in food and water harboring the parasite. Therefore, their chances of infection are greater.

People with weak immune systems are most at risk of suffering prolonged or severe symptoms of cryptosporidiosis. Persons with AIDS, who have transplanted organs, or who were born with weakened immune systems are more likely to develop complications from cryptosporidiosis, including severe dehydration and lung infection (pulmonary cryptosporidiosis) that can lead to death.

IN CONTEXT: REAL-WORLD RISKS

Advertising on filters can be deceptive. The Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Parasitic Diseases states that filters with any of the following messages on the package “should be able to remove Crypto” (Cryptosporidium parvum):

  • Reverse-osmosis (with or without NSF testing)
  • Absolute pore size of 1 micron or smaller (with or without NSF testing)
  • Tested and certified by NSF Standard 53 for cyst removal
  • Tested and certified by NSF Standard 53 for cyst reduction

“Filters labeled only with these words may not be designed to remove Crypto:”

  • Nominal pore size of 1 micron or smaller
  • 1-micron filter
  • Effective against Giardia
  • Effective against parasites
  • Carbon filter
  • Water purifier
  • EPA approved - Caution: EPA does not approve or test filters.
  • EPA registered - Caution: EPA does not register filters for Crypto removal
  • Activated carbon
  • Removes chlorine
  • Ultraviolet light
  • Pentiodide resins
  • Water softener

SOURCE: Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Parasitic Diseases

Treatment and Prevention

The most common symptoms of cryptosporidiosis in humans are diarrhea, stomach cramps, nausea, vomiting, slight fever, and weight loss. These symptoms usually appear between two and 10 days after infection, and last up to two weeks, sometimes occurring sporadically during that time. Following recovery, relapses may occur. In some cases, symptoms are not present. However, the infection is still contagious and can be passed on to other humans.

There is no standard cure for cryptosporidiosis, and the symptoms usually disappear after about two weeks. One new drug approved for treating the disease, nitazoxanide, has shown effectiveness in treating the diarrhea associated with cryptosporidiosis in people that are otherwise healthy. Some people also receive relief from antibiotics and from common anti-diarrhea and anti-vomiting medicines. In order to prevent dehydration, fluid and electrolyte replacement may be necessary in some cases. Therefore, persons with Cryptosporidium are encouraged to increase their water intake, and to watch for signs of dehydration, such as dry mouth, headaches, fatigue, joint aches, and decreased skin elasticity.

In order to prevent contracting cryptosproidiosis, contact with fecal matter should be avoided. This may involve washing hands after handling soil, after toileting, or after handling animals. To avoid infection via food, washing with uninfected water, or cooking it thoroughly will remove or kill the parasite. Water is a major source of infection due to the parasite's protective covering against chemicals. Boiling infected water for at least one minute will kill the parasite, and filtering it through filters small enough to prevent the parasite passing will remove the parasite. This water can then be used for all water-related uses such as drinking, washing food, and making ice.

The Western Australian Health Department recommends that infected people remain away from public places, especially public swimming bodies, while exhibiting cryptosporidiosis symptoms to prevent possible infection of other people.

Impacts and Issues

Cryptosporidiosis has the potential to spread rapidly and affect many people in a short amount of time, and infection of a community's drinking source puts the whole community at risk. Before 2001, water treatment in many locations in the United States did not remove the parasite, as chemical treatment usually did not kill them, and filters were too large to prevent them passing. The outbreak in Milwaukee in 1993 resulted in over 400,000 reported cases and remains the single largest outbreak of waterborne disease reported in the United States. More than 100 people, mostly persons with AIDS or elderly persons, died during the outbreak. Estimated monetary costs of the outbreak spiraled to over 95 million dollars, including 30 million dollars of direct medical care costs and 60 million dollars attributed to lost productivity in the Milwaukee workplace. As a result of this outbreak, the U.S. Environmental Protection Agency (EPA) mandated that major U.S. water systems (those relying surface water sources, such as a rivers or lakes, and serving more than 10,000 people) implement new EPA standards by 2001 that strengthened control over microbial contaminants, including Cryptosporidium.

Another notable occurrence occurred in New York in 2005 at a popular water park. The Senaca Lake State Park was found to have two water storage tanks infected with Cryptosporidium. Over 3,800 people reported cryptosporidiosis symptoms.

Cryptosporidiosis disease is a major cause of diarrhea worldwide. Due to differing food and water quality controls over the world, this disease has a large impact on travelers who are unfamiliar with a region's water quality. Travelers are often advised to consider the following precautions to prevent infection: bringing water to a full boil for one minute, avoiding undercooked food, handling or peeling raw food such as fruit themselves, avoiding swimming in freshwater rivers and lakes, and carrying bottled water when unsure of an area's water quality.

Persons with compromised immune systems are often advised to take extra precautions with their drinking water to prevent Cryptosporidium infection, including boiling it, installing point-of-use filters that remove particles one micrometer or less in diameter, or drinking bottled water from protected well or protected spring water sources.

See AlsoAIDS (Acquired Immunodeficiency Syndrome); Contact Precautions; Gastroenteritis (common causes); Handwashing; HIV; Parasitic Diseases; Travel and Infectious Disease; Water-borne Disease.

BIBLIOGRAPHY

Books

Mandell, G.L., J.E. Bennett, and R. Dolin. Principles and Practice of Infectious Diseases, vol. 2. Philadelphia, PA: Elsevier, 2005.

Web Sites

Australian Government. “Cryptosporidiosis.” April, 2006 <http://www.healthinsite.gov.au/topics/Cryptosporidiosis> (accessed Jan. 29, 2007).

Centers for Disease Control and Prevention (CDC). “Cryptosporidium Infection Cryptosporidiosis.” Aug. 19, 2005 <http://www.cdc.gov/ncidod/dpd/parasites/cryptosporidiosis/factsht_cryptosporidiosis.htm> (accessed Jan. 29, 2007). Department of Health, Western Australia.

“Cryptosporidiosis: Environmental Health Guide.” 2006 <http://www.health.wa.gov.au/envirohealth/water/docs/Cryptospordiosis_EH_Guide.pdf> (accessed Jan. 29, 2007).

New York State Department of Health.

“Cryptosporidiosis.” June, 2004 <http://www.health.state.ny.us/diseases/communicable/cryptosporidiosis/fact_sheet.htm> (accessed Jan. 29, 2007).

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