CRYPTOSPORIDIUM PARVUM

Cryptosporidium is a microscopic parasite that causes the diarrheal disease cryptosporidiosis. Both the parasite and the disease are commonly known as "Crypto."

There are many species of Cryptosporidium that infect humans and animals. The parasite is protected by an outer  shell that allows it to survive outside the body for long periods of  time and makes it very tolerant to chlorine disinfection.

While this parasite can be spread in several different ways, water (drinking water and recreational water) is the most common method of transmission. Cryptosporidium is one of the most frequent causes of waterborne disease among humans in the United States.

EPIDEMIOLOGY & RISK FACTORS

Crypto lives in the intestine of infected humans or animals. An infected person or animal sheds Cryptosporidium parasites in the stool. Millions of Crypto parasites can be released in  a bowel movement from an infected human or animal. Shedding begins when  the symptoms begin and can last for weeks after the symptoms (e.g.,  diarrhea) stop. You can become infected after accidentally swallowing  the parasite. Crypto may be found in soil, food, water, or surfaces  that have been contaminated with the feces from infected humans or  animals. Crypto is not spread by contact with blood. Crypto can be  spread:

• By putting something in your mouth or  accidentally swallowing something that has come in contact with the  stool of a person or animal infected with Crypto.

Recreational water can be contaminated with sewage or feces from humans or animals.    

• By swallowing water or beverages contaminated by stool from infected humans or animals.
• By  eating uncooked food contaminated with Crypto. All fruits and  vegetables you plan to eat raw should be thoroughly washed with  uncontaminated water.
• By touching your 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.
• People with greater exposure to contaminated materials are more at risk for infection, such as:    
• 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 who drink from untreated shallow, unprotected wells
• People, including swimmers, who swallow water from contaminated sources
• People who handle infected cattle
• 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. Several community-wide outbreaks of cryptosporidiosis have  been linked to drinking municipal water or recreational water  contaminated with Cryptosporidium.

Cryptosporidium parasites are found in every region of the United States and throughout  the world. Travelers to developing countries may be at greater risk for  infection because of poorer water treatment and food sanitation, but  cryptosporidiosis occurs worldwide. In the United States, an estimated 748,000 cases of cryptosporidiosis occur each year.

Once  infected, people with decreased immunity are most at risk for severe  disease. The risk of developing severe disease may differ depending on  each person's degree of immune suppression.

BIOLOGY

Causal Agent:

Many species of Cryptosporidium exist that infect humans and a wide range of animals. Although Cryptosporidium parvum and Cryptosporidium hominis (formerly known as C. parvum anthroponotic genotype or genotype 1) are the most prevalent species causing disease in humans, infections by C. felis, C. meleagridis, C. canis, and C. muris have also been reported.

Life Cycle:

Sporulated oocysts, containing 4 sporozoites, are excreted by the infected host through feces and possibly other routes such as respiratory secretions. Transmission of Cryptosporidium parvum and C. hominis occurs mainly through contact with contaminated water (e.g., drinking or recreational water). Occasionally food sources, such as chicken salad, may serve as vehicles for transmission. Many outbreaks in the United States have occurred in waterparks, community swimming pools, and day care centers. Zoonotic and anthroponotic transmission of C. parvum and anthroponotic transmission of C. hominisoccur through exposure to infected animals or exposure to water contaminated by feces of infected animals. Following ingestion (and possibly inhalation) by a suitable host, excystation occurs. The sporozoites are released and parasitize epithelial cells of the gastrointestinal tract or other tissues such as the respiratory tract. In these cells, the parasites undergo asexual multiplication (schizogony or merogony) and then sexual multiplication (gametogony) producing microgamonts (male) and macrogamonts (female). Upon fertilization of the macrogamonts by the microgametes, oocystdevelop that sporulate in the infected host. Two different types of oocysts are produced, the thick-walled, which is commonly excreted from the host, and the thin-walled oocyst, which is primarily involved in autoinfection. Oocysts are infective upon excretion, thus permitting direct and immediate fecal-oral transmission.

Life cycle image and information courtesy of DPDx.

DISEASE

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. Other symptoms include:

• Stomach cramps or pain
• Dehydration
• Nausea
• Vomiting
• Fever
• Weight loss

Some people with Crypto will have no symptoms at all.

Symptoms  usually last about 1 to 2 weeks (with a range of a few days to 4 or  more weeks) in persons with healthy immune systems. Occasionally,  people may experience a recurrence of symptoms after a brief period of  recovery before the illness ends. Symptoms can come and go for up to 30  days.  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. People  with weakened immune systems may develop serious, chronic, and  sometimes fatal illness. Examples of people with weakened immune  systems include:

• people with AIDS;
• those with inherited diseases that affect the immune system; and
• cancer and transplant patients who are taking certain immunosuppressive drugs.

The risk of developing severe disease may differ depending on each person's degree of immune suppression.

DIAGNOSIS

Diagnosis of cryptosporidiosis is made by examination of stool samples. Because detection of Cryptosporidium can be difficult, patients may be asked to submit several stool samples  over several days. Most often, stool specimens are examined  microscopically using different techniques (e.g., acid-fast staining,  direct fluorescent antibody [DFA] , and/or enzyme immunoassays for  detection of Cryptosporidium sp. antigens).

Molecular  methods (e.g., polymerase chain reaction – PCR) are increasingly used  in reference diagnostic labs, since they can be used to identify Cryptosporidium spp. at the species level.  Tests for Cryptosporidium are not routinely done in most laboratories; therefore, health care  providers should specifically request testing for this parasite.

PREVENTION AND CONTROL

• Practice good hygiene
• Wash hands with soap and water for at least 20 seconds, rubbing hands together vigorously and scrubbing all surfaces:             
• Before preparing or eating food
• After using the toilet
• After changing diapers or cleaning up a child who has used the toilet
• Before and after tending to someone who is ill with diarrhea
• After handling an animal or animal waste
• At child care facilities
• To reduce the risk of disease transmission, children with diarrhea should be excluded from child care settings until the diarrhea has stopped.
• At recreational water venues (pools, interactive fountains, lakes, ocean)
• Protect others by not swimming if you are experiencing diarrhea (this is essential for children in diapers). If diagnosed with cryptosporidiosis, do not swim for at least 2 weeks after diarrhea stops.
• Shower before entering the water.
• Wash children thoroughly (especially their bottoms) with soap and water after they use the toilet or their diapers are changed and before they enter the water.
• Take children on frequent bathroom breaks and check their diapers often.
• Change diapers in the bathroom, not at the poolside.
• Around animals
• Minimize contact with the feces of all animals, particularly young animals.
• When cleaning up animal feces, wear disposable gloves, and always wash hands when finished.
• Wash hands after any contact with animals or their living areas.
• Wash hands after gardening, even if wearing gloves.
• Immunocompromised persons
• Avoid close contact with any person or animal that has cryptosporidiosis. Cryptosporidiosis can become a life threatening disease for immunocompromised persons.
• Do not handle animal feces because infection can be life threatening for immunocompromised persons.
• Avoid Water That Might Be Contaminated
• You may not be protected in a chlorinated recreational water venue  (for example, swimming pool, water park, water play area, splash pad, spray pad) because Cryptosporidium is chlorine-resistant and can live for days in chlorine-treated water.
• Do not swallow water while swimming in swimming pools, hot tubs, interactive fountains, lakes, rivers, springs, ponds, streams or the ocean.
• Reduce  contamination of treated recreational water venues by having pool operators install in-line secondary disinfection systems (for example, ultraviolet light, ozone) to inactive this chlorine-tolerant parasite.
• Do not drink untreated water from lakes, rivers, springs, ponds, streams, or shallow wells.
• Do not drink inadequately treated water or ice made from water during communitywide outbreaks caused by contaminated drinking water.
• Do not use or drink inadequately treated water or use ice when traveling in countries where the water supply might be unsafe.
• If the safety of drinking water is questionable (for example, outbreak, poor sanitation, lack of water treatment systems):             
• Drink bottled water
• Disinfect it by heating the water to a rolling boil for 1 minute, or
• Use a filter that has been tested and rated by National Safety Foundation (NSF) Standard 53 or NSF Standard 58 for cyst and oocyst reduction; filtered water will need additional treatment to kill or inactivate bacteria and viruses

For more information view the source:Center for Disease Control

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