Definition
Cryptosporidiosis is a diarrheal disease caused by microscopic parasites, Cryptosporidium, that can live in the intestine of humans and animals and is passed in the stool of an infected person or animal. Both the disease and the parasite are commonly known as “Crypto.” 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 resistant to chlorine-based disinfectants. During the past 2 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.
History
Cryptosporidium was first recognized as a cause of disease in 1976. As methods were developed to analyze stool samples, the protozoa was increasingly reported as the cause of human disease. Crypto was first categorized as a veterinary problem because the majority of the early cases were diagnosed in handlers of such farm animals as cows. 155 species of mammals have been reported to be infected wity Cryptosporidium parvum or C. parvum. Of 15 named species of Cryptosporidium infectious to nonhuman vertebrate hosts C. Baileyi, C. canis, C. felis, C. hominis, C meleagridis, C. muris, and C. parvum have been reported to also infect humans. Humans are the primary hosts for C. hominis, and except for C. parvum, which is widespread in nonhuman hosts and is the most frequently reported zoonotic species, the remaining species have been reported primarily in immuno crompomised humans.
The first widely publicized outbreak of Crytpsporidiosis occurred in 1987 in Carrollton, Georgia, where approximately 13000 people became ill with the disease. The source of the outbreak was traced to a contaminated municipal water system. Six years later, in Milwaukee, Wisconsin, drinking water was again contaminated, causing approximately 400000 people to become ill.
Epidemiology
Prevalence rates reported in large-scale surveys of fecal oocyst excretion generally range from 1-3% in developed countries in Europe and North America. Children, especially those younger than 2 years, appear to have a higher prevalence of infection than do adults.
Cryptosporidiosis is a notifiable disease at the European Union level, and surveillance data are collected through the European Basic Surveillance Network. The crude incidence rate was similar to that in the United States, although considerable differences in the rates of cryptosporidiosis between countries were observed. A pronounced seasonal peak was observed in the autumn season, with 59% of cases reported between August and November. However, Ireland and Spain experienced a peak in spring and summer, respectively. Routine cryptosporidiosis surveillance in northwest England over 17 years revealed that cases predominantly occurred in spring and autumn. There, most infections are caused by C. hominis, while C. parvum is associated with rural areas and animal contact.
In August 2012, an unexpectedly large increase in Cryptosporidium infections occurred in the Netherlands, Germany, England, Wales, and Scotland. In the Netherlands, for instance, 8 medical microbiology laboratories reported the detection of 524 Cryptosporidium -positive fecal samples for weeks 31-42 of that year, compared with 115 in 2010. Reasons behind the increases in these countries were uncertain.
In developing countries, cryptosporidiosis causes approximately 10-15% of cases of acute diarrheal illness. Rates are often higher when molecular tests such as polymerase chain reaction (PCR) are used. In addition, investigations using PCR assays have found Cryptosporidium species in 6% of American travelers to Mexico.
In developing countries, most people are infected as children. For example, studies in Brazil documented an infection rate of 90% for children younger than 5 years who were living in slums.
In persons with AIDS, cryptosporidiosis is more common in developing countries, ranging from 12-48% of persons with AIDS who have diarrhea.
Cycle of cryptosporidiosis
Risk factors
Anyone who comes into contact with contaminated feces runs the risk of contracting Crypto. Children younger than 10 years often get sick with the infection because they’re most likely to swallow swimming water.
Others who are also at increased risk of Crypto include:
- Childcare workers
- Parents of infected children
- Animal handlers
people exposed to untreated drinking water, such as travelers to undeveloped countries and campers or hikers who may drink from streams
Causes of Cryptosporidiosis
Cryptosporidium infection begins when you ingest the one-celled cryptosporidium parasite. Some strains of cryptosporidium may cause more serious disease.
These parasites then travel to your intestinal tract, where they settle into the walls of your intestines. Eventually, more cells are produced and shed in massive quantities into your feces, where they are highly contagious.
You can become infected with cryptosporidia by touching anything that has come in contact with contaminated feces. Methods of infection include:
- Drinking contaminated water that contains cryptosporidium parasites
- Swimming in contaminated water that contains cryptosporidium parasites and accidentally swallowing some of it
- Eating uncooked, contaminated food that contains cryptosporidia
- Touching your hand to your mouth if your hand has been in contact with a contaminated surface or object
- Having close contact with other infected people or animals especially their feces which can allow the parasite to be transmitted from your hands to your mouth
If you have a compromised immune system from HIV/AIDS, you’re more susceptible to illness from cryptosporidium parasites than is a person with a healthy immune system. People with HIV/AIDS can develop severe symptoms and a chronic, persistent form of disease that may be difficult to treat.
Hardy parasites
Cryptosporidium parasites are one of the more common causes of infectious diarrhea in humans. This parasite is difficult to eradicate because it’s resistant to many chlorine-based disinfectants and can’t be effectively removed by many filters. Cryptosporidia can also survive in the environment for many months at varying temperatures, though the parasite can be destroyed by freezing or boiling.
Symptoms of Cryptosporidiosis
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. While the small intestine is the site most commonly affected, Crypto infections could possibly affect other areas of the digestive tract or the respiratory tract.
Complications of Cryptosporidiosis
Complications of cryptosporidium infection include:
- Malnutrition resulting from poor absorption of nutrients from your intestinal tract (malabsorption)
- Severe dehydration
- Significant weight loss (wasting)
- Inflammation of a bile duct — the passage between your liver, gallbladder and small intestine
- Inflammation of your gallbladder, liver or pancreas
Cryptosporidium infection itself isn’t life-threatening. However, if you’ve had a transplant or if you have a weakened immune system, developing complications can be dangerous
Diagnosis and test
You may undergo the following tests to diagnose cryptosporidium infection:
Acid-staining test: The simplest way to diagnose cryptosporidium infection is a method called an acid-staining test, which identifies cryptosporidium under a microscope. To obtain cells for the analysis, your doctor might ask for a stool sample, or in more extreme cases, take a tissue sample (biopsy) from your intestine for the test.
Stool culture: Your doctor might also order a standard stool culture. Although this test cannot detect the presence of cryptosporidium, it may help rule out other bacterial pathogens.
Other tests: Once it’s clear that your infection is caused by cryptosporidium parasites, you may need further testing to check for development of serious complications. For example, checking liver and gallbladder function may determine whether the infection has spread. If you have both AIDS and cryptosporidiosis, a T-cell count which measures the level of a certain white blood cell that’s part of your immune system can help predict the duration of the cryptosporidiosis. A T-cell count under 100 cells per microliter means you’re more likely to have complications.
Treatment and medications
A person with Crypto needs to increase fluid intake to combat the dehydrating effects of severe diarrhea. If dehydration persists or becomes worse, a person may be hospitalized and given intravenous fluids.
Your doctor may prescribe the antidiarrheal drug nitazoxanide, but it’s only effective in people with healthy immune systems. People with weaker immune systems, such as those with HIV, may be given drugs to boost the immune system as a way of fighting the infection.
Prevention of Cryptosporidiosis
Cryptosporidiosis prevention involves adequate sanitation and hand washing, particularly in health care facilities and day care centers and after contact with soil, animals, or infected people. People should not drink or swallow water that could be contaminated, such as that from a swimming pool, stream, or lake or in an area where sanitation is poor.
When public health departments discover a localized outbreak of the disease, they typically advise people to
- Boil drinking water (including water for toothbrushing and food washing)
- Eat only cooked foods
- Avoid unpasteurized milk and juice
Tap water filters that use reverse osmosis or have the words “absolute 1 micron” or “tested and certified by NSF Standard 53 for cyst removal/reduction” are effective. Other types of filters may not be.