Cryptosporidiosis

Cryptosporidiosis (often called Crypto) is a diarrheal disease caused by infection with microscopic parasites of the genus Cryptosporidium. During the past two decades, Crypto has become recognized as one of the most common causes of waterborne disease (recreational water and drinking water) in humans in the United States. The parasite is found in every region of the United States and throughout the world. It can infect virtually any age group and has been the cause of several outbreaks of diarrheal illness, including the largest outbreak of any waterborne microbe in the United States since record keeping began in 1920.^[1]

Cryptosporidium parvum oocysts appear as red to purple spheres in this modified acid-fast stain. Source: CDC.

Types

Generally speaking, the illness caused by Cryptosporidium parvum is different in patients who were previously healthy and have normal immune systems (immunocompetent persons), and in patients who have a weakened immune system (immunocompromised). Cryptosporidiosis is a common complicating infection in patients with advanced HIV disease.

Cryptosporidiosis in the Immunocompetent

The typical disease for cryptosporidiosis is self-limiting, that is to say that it improves usually without specific treatment. It usually lasts 1 to 2 weeks and affects mainly the small bowel. Even though symptoms have resolved, the parasite can still be shed in the stool (and spread to others) for a few months.

Cryptosporidiosis in the Immunocompromised

In immunocompromised patients, typically those with HIV/AIDS, cryptosporidiosis is a different, chronic illness. In AIDS, infection is not limited to the intestine, and can involve the liver and biliary system, the lungs, the pancreas, the lymph nodes and the spleen. In other words, it is a much more disseminated illness. In AIDS, the outlook for people with cryptosporidiosis has been poor since the disease is often persistent and causes chronic diarrhea. With the development of new drugs that can improve the immune system in people with HIV infection, however, Cryptosporidiosis is becoming a more manageable illness.

Symptoms

Symptoms of cryptosporidiosis generally begin 2 to 10 days (average 7 days) after becoming infected with the parasite. The most common symptom of cryptosporidiosis is watery diarrhea. The diarrhea can be of varying intensity, from mild symptoms to profuse watery diarrhea which can cause rapid dehydration. Frequently the diarrhea can contain mucus, or slime, but it is rare for it to be bloody.

Other symptoms include:

• Stomach cramps or pain
• Dehydration
• Nausea
• Vomiting
• Fever
• Weight loss from malabsorption of food and nutrients
• Tiredness
• Loss of appetite

Some people with crypto will have no symptoms at all. While the small intestine is the site most commonly affected, Cryptosporidium infections could possibly affect other areas of the digestive tract or the respiratory tract. In cases where the respiratory tract is involved symptoms can include the following:

• Shortness of breath
• Cough
• Wheezing
• Sinusitis

In persons with healthy immune systems, symptoms usually last about 1 to 2 weeks. The symptoms may go in cycles in which people may seem to get better for a few days, then feel worse again before the illness ends.

Even if all the symptoms have resolved, a person may still shed the parasite in the stool for another few months, and spread to other people may occur.

Cause

The life cycle of Cryptosporidium. Crypto begins its life cycle as sporulated oocysts (1) which enter the environment through the feces of the infected host. The infective oocysts reside in food and water (2). Infection occurs when the oocysts are ingested by an animal or person (3). While in the intestines, the oocyst releases sporozoites which invade the epithelial linings of the intestines or the lungs (depending on the method of transmission). Within these cells, the sporozoites undergo schizogony, or asexual reproduction. The sporozoites then enter a sexual reproductive stage. The resulting zygote can develop into: a) a thick-walled oocyst that will exit the host, or b) a thin-walled oocyst which will autoinfect the host. The infectious oocysts are passed through the feces (1) to continue the cycle. Source: CDC

Cryptosporidiosis is caused by microscopic parasites of the genus Cryptosporidium. These parasites live in the intestine of infected humans or animals. Millions of crypto parasites can be released in a bowel movement from an infected human or animal. Consequently, Cryptosporidium is found in soil, food, water, or surfaces that have been contaminated with infected human or animal feces. A person becomes infected by swallowing Cryptosporidium parasites (or rarely by inhaling them). It doesn't take many parasites to cause infection and illness in humans. In one study, healthy volunteers knowingly ingested Cryptosporidium oocysts with 50% becoming infected after ingesting only about 130 oocysts.^[2]

Cryptosporidium organisms vary in their ability to infect and cause disease in humans and animals. They infect all age groups, from children born to infected mothers to the elderly in group homes. Up to 90% of children can show evidence of having been infected with the parasite in some areas of the world.

The most commonly encountered species of Cryptosporidium in humans is C. parvum. How this parasite actually causes diarrhea in the human host is unknown. There does not appear to be any toxin produced that causes the diarrhea, and it is not clear if simply the act of infecting cells in the gut is enough to result in diarrhea. Research is continuing into how disease is produced.

Diagnosis

Diagnosing Crypto can be difficult, since the organism can be hard to identify in clinical specimens. Stool tests are the most commonly used method of diagnosing a cryptosporidial infection. The most common test uses a modified acid-fast stain to look for the parasite in several stool samples taken over a few days.

Tests for crypto are often not done as part of a general diarrhea screen during standard stool tests in most laboratories. Therefore, the physician ordering the test should specifically request testing for the parasite. Finding red and white blood cells in the stool is unusual in cryptosporidiosis, and if they are found, an alternative diagnosis should be considered.

Blood test and other methods such as polymerase chain reaction (PCR) are not used in the diagnosis of the illness, but are used more to track outbreaks and to gain further information on the particular species of the Cryptosporidium.

Treatment

Most people who have healthy immune systems will recover without treatment. Diarrhea can be managed by drinking plenty of fluids to prevent dehydration. Young children and pregnant women may be more susceptible to dehydration. Rapid loss of fluids from diarrhea may be especially life threatening to babies. Anti-diarrheal medicine may help slow down diarrhea.

If treatment is considered necessary, Nitazoxanide has been approved for treatment of diarrhea caused by Cryptosporidium in people with healthy immune systems.

People who are in poor health or who have a weakened immune system are at higher risk for more severe and more prolonged illness. The effectiveness of nitazoxanide in immunosuppressed individuals is unclear. For persons with AIDS, anti-retroviral therapy that improves immune status will also decrease or eliminate symptoms of crypto. However, even if symptoms disappear, cryptosporidiosis is often not curable and the symptoms may return if the immune status worsens.

Prevention

Prevention of cryptosporidiosis can be divided into two categories: primary prevention and secondary prevention. Primary prevention refers to what people who do NOT have the disease can do to prevent getting it. Secondary prevention refers to what people who DO have the disease can do to prevent spreading it. Both are essential.

Primary prevention of cryptosporidiosis

• Practice good hygiene:

1. Wash hands thoroughly and frequently with soap and water.
   1. Wash hands after using the toilet and before handling or eating food (especially for persons with diarrhea).
   2. Wash hands after every diaper change, especially for people who work with diaper-aged children, even those people who wear gloves.
2. Protect others by not swimming if experiencing diarrhea (this is essential for children in diapers).

• Avoid water that might be contaminated:

1. Do not drink untreated water from shallow wells, lakes, rivers, springs, ponds, and streams.
2. Do not drink untreated water during community-wide outbreaks of disease caused by contaminated drinking water.
3. Do not use or consume untreated ice or tap water when traveling in countries where the water supply might be unsafe.

• Do not rely on chemical sanitizers:

People should not rely on chemical "sterilizers" to kill Cryptosporidium. Because it has a thick outer shell, this particular parasite is highly resistant to disinfectants such as chlorine and iodine.

• Avoid food that might be contaminated:

1. Use safe, uncontaminated water to wash all food that is to be eaten raw.
2. After washing vegetables and fruit in safe, uncontaminated water, peel them when planning to eat them raw.
3. Avoid eating uncooked foods when traveling in countries with minimal water treatment and sanitation systems.

• Take extra care when traveling:

People who travel to developing nations may be at a greater risk for Cryptosporidium infection because of poorer water treatment and food sanitation. Warnings about food, drinks, and swimming are even more important when visiting developing countries. Avoid foods and drinks, in particular raw fruits and vegetables, tap water, or ice made from tap water, unpasteurized milk or dairy products, and items purchased from street vendors. These items may be contaminated with Cryptosporidium. Steaming-hot foods, peelable fruits (peeled by the patient), bottled and canned processed drinks, and hot coffee or hot tea are probably safe.

Secondary prevention of Cryptosporidiosis

Cryptosporidium can be very contagious. Infected individuals should follow these guidelines to avoid spreading the disease to others:

1. Washing the hands frequently with soap and water, especially after using the toilet, after changing diapers, and before eating or preparing food.
2. Don't swim in recreational water (pools, hot tubs, lakes rivers, the ocean, etc.) when active cryptosporidiosis is present, as well as for at least 2 weeks after the diarrhea and/or symptoms stop. Cryptosporidium can be passed on in the stool and contaminate water for several weeks after the symptoms of disease have ended. Actual defecation in the water is not necessary to spread illness, such is the risk of contagion; immersion in the water may be enough for contamination to occur. This has resulted in outbreaks of cryptosporidiosis among recreational water users.

Note that chlorinated pools do not necessarily give full protection because Cryptosporidium is chlorine-resistant and can live for days in chlorine-treated swimming pools. Other advice given by the Centers for Disease Control and Prevention (CDC) to reduce spread is:

1. Avoid sexual practices that might result in oral exposure to stool (e.g., oral-anal contact).
2. Avoid close contact with anyone who has a weakened immune system.

Chances of Developing Cryptosporidiosis

Cryptosporidiosis is one of the most common waterborne infections in the world. Recreational water is a common source of infection. Source: CDC

• Children who attend day care centers, including diaper-aged children
• Child care workers
• Parents of infected children
• People who take care of other people with cryptosporidiosis
• International travelers
• Backpackers, hikers, and campers who drink unfiltered, untreated water
• People, including swimmers, who swallow water from contaminated sources
• People who handle infected animals
• People exposed to human feces through sexual contact

Contaminated water may include water that has not been boiled or filtered, as well as contaminated recreational water sources (e.g., swimming pools, lakes, rivers, ponds and streams). Several community-wide outbreaks of cryptosporidiosis have been linked to drinking municipal water or recreational water contaminated with Cryptosporidium.

How Cryptosporidiosis is Spread

Cryptosporidium is usually spread through drinking water. In general it can be spread by:

• putting something in the mouth or accidentally swallowing something that has come in contact with the stool of a person or animal infected with crypto.
• swallowing recreational water contaminated with crypto. Recreational water is water in swimming pools, hot tubs, Jacuzzis, fountains, lakes, rivers, springs, ponds, or streams that can be contaminated with sewage or feces from humans or animals.
• swallowing water or beverages contaminated by stool from infected humans or animals.
• eating uncooked food contaminated with crypto. For this reason the CDC advises people to thoroughly wash all vegetables and fruits they are planning to eat raw with uncontaminated water.
• touching the mouth with contaminated hands. Hands can become contaminated through a variety of activities, such as touching surfaces (e.g., toys, bathroom fixtures, changing tables, diaper pails) that have been contaminated by stool from an infected person, changing diapers, caring for an infected person, and handling an infected cow or calf.

In this podcast, CDC's Dr. Michael Beach discusses the superbug, Cryptosporidium, a common cause of recreational water illness.

Related Problems

Complications of Cryptosporidiosis

Although crypto can infect all people, some groups are more likely to develop more serious illness.

• People with severely weakened immune system, for example patients with AIDS/HIV disease, cancers, recent chemotherapy, organ transplantation, or certain medications.
• Young children and pregnant women are more susceptible to the dehydration resulting from diarrhea and are usually advised to drink plenty of fluids while ill.

In people with weakened immune systems, the parasite can spread in the body to involve organs other than the gastrointestinal tract. Cryptosporidium can cause the following:

• Pancreatitis (inflammation of the pancreas)
• Cholecystitis (inflammation of the gall bladder, mimicking gall stones)
• Hepatitis (inflammation of the liver)
• Reactive arthritis (pain and inflammation of the joints)
• Respiratory problems including cough, shortness of breath, wheezing
• Toxic megacolon (a rare complication)

Research

Current research on cryptosporidiosis is mostly in the following areas:

• Epidemiological investigations of the prevalence of Cryptosporidium in various locales and environments. For example, a recent paper in Emerging Infectious Diseases looked at how many swimming pools had evidence of either Cryptosporidium or another waterborne parasite Giardia. It found a large fraction (8%) were positive for one or both parasites.^[3]
• Cryptosporidiosis in special populations (such as HIV/AIDS).
• New methods for detecting or removing Cryptosporidium oocysts. For example, a group from the University of South Florida recently describes a new assay for Cryptosporidium oocysts.^[4]

Epidemiology

Outbreaks

In 1993 there was a large outbreak of acute watery diarrhea among the residents of Milwaukee, Wisconsin. An estimated 403,000 people had watery diarrhea with over 4,400 requiring hospitalization. The outbreak was the result of heavy rains and snowmelt washing Cryptosporidia oocysts from farm animals into streams and rivers that were a source for the municipal water supply. Standard water treatment procedures at the time were not robust enough to remove the parasite from municipal water. This was the worst outbreak of any waterborne illness in the United States since record keeping began in 1920.^[5]

In 2007, a much smaller outbreak in Idaho and the rocky mountain west sickened hundreds.^[6]

References

1. ↑ Corso PS, Kramer MH, Blair KA, Addiss DG, Davis JP, Haddix AC. Cost of illness in the 1993 Waterborne Cryptosporidium outbreak, Milwaukee, Wisconsin. Emerg Infect Dis. 2003 Apr;9(4):426-31. Abstract | Full Text
2. ↑ DuPont HL, Chappell CL, Sterling CR, Okhuysen PC, Rose JB, Jakubowski W. The infectivity of Cryptosporidium parvum in healthy volunteers. N Engl J Med. 1995 Mar 30;332(13):855-9. Abstract | Full Text
3. ↑ Shields JM, Gleim ER, Beach MJ. Prevalence of Cryptosporidium spp. and Giardia intestinalis in Swimming Pools, Atlanta, Georgia. Emerg Infect Dis. 2008 14(6):948-50. Abstract. | Full Text.
4. ↑ Kramer MF, Vesey G, Look NL, Herbert BR, Simpson-Stroot JM, Lim DV. Development of a Cryptosporidium oocyst assay using an automated fiber optic-based biosensor. J Biol Eng. 2007 Oct 10;1(1):3. Abstract. | Full Text.
5. ↑ MacKenzie WR, Hoxie NJ, Proctor ME, Gradus MS, Blair KA, Peterson DE et al. A massive outbreak in Milwaukee of cryptosporidium infection transmitted through the public water supply. N Engl J Med. 1994 Jul 21;331(3):161-7. Abstract | Full Text.
6. ↑ USA Today: Cryptosporidium outbreak hits the West.

External Links

CDC's Healthy Swimming

Food and Drug Administration's Bad Bug Book: Crypto

For information on choosing a water filter or bottled water, see the CDC fact sheet entitled Preventing Cryptosporidiosis: A Guide to Water Filters and Bottled Water].

Microbe Wiki: Cryptosporidium