Cryptosporidiosis Facts

  • Parasitic protozoans cause cryptosporidiosis, a diarrheal disease.
  • Causes of cryptosporidiosis are protozoans (genus Cryptosporidium). At least 15 different species can cause the disease in humans and other animals.
  • Risk factors include poor environmental sanitation, contaminated water supply systems and/or ingestion of contaminated food or water, and close association with infected individuals and items they may handle.
  • Cryptosporidiosis is highly contagious.
  • The incubation period for cryptosporidiosis is about two to 10 days (average is seven days).
  • Symptoms and signs include watery diarrhea, stomach cramps, fever, dehydration, weight loss, lack of appetite, nausea, and vomiting.
  • Medical professionals diagnose the disease by acid-fast staining of stool specimens and by immunoassays.
  • Most individuals with cryptosporidiosis only receive supportive care because most recover without treatment, however, the FDA has approved nitazoxanide to treat the disease.
  • Although the prognosis for cryptosporidiosis is good because it is self-limiting, people with immune system problems may have complications develop.
  • It is possible to reduce the chance of getting cryptosporidiosis by avoiding possibly contaminated food and water, good personal hygiene, and not sharing items touched by an infected individual. Boiling water and foods may prevent exposure to these parasites. There is no commercially available vaccine for this disease.

What Is Cryptosporidiosis?

Cryptosporidiosis is a disease caused by infection of humans and other animals by one or more species of Cryptosporidium protozoans. At least 15 different species of Cryptosporidium can cause the disease in humans and other animals. Cryptosporidium hominis is the only species that uses only humans as a host. The disease causes diarrhea and mainly affects children.

What Causes Cryptosporidiosis?

The causes of cryptosporidiosis are protozoan parasites that reproduce in the epithelial cells lining the distal small intestine tract and, if the host is immunocompromised, parasites may reproduce almost anywhere in the G.I. tract and in the lungs. C. hominis and C. parvum are the two species that mainly infect humans although other species may participate.

Is Cryptosporidiosis Contagious?

Cryptosporidiosis is highly contagious, and many outbreaks can occur from fecal-oral route. Transmission of the infections often are by person-to-person contact. However, humans can get the disease from parasites excreted by humans, animals, and the environment.

Life cycle of Cryptosporidium
Life cycle of Cryptosporidium; image courtesy of the CDC

What Are Risk Factors for Cryptosporidiosis?

Risk factors for cryptosporidiosis include poor environmental sanitation, contaminated public water supply systems, including swimming pools, ingestion of contaminated food, and close human-animal contacts. Unfortunately, Cryptosporidium species can resist chlorination and survive for long periods in the environment. For example, in 1993, Milwaukee, Wis., had a significant outbreak documented to be caused by contamination in the treatment processing of the city's drinking water. Apparently, thousands of citizens developed symptoms. The city health department eventually determined that Cryptosporidium was in the tap water. People had to destroy food and drinks, and the city's population had to boil water and clean all foods. This outbreak was the largest documented waterborne disease in U.S. history.

What Is the Incubation Period for Cryptosporidiosis?

The incubation period ranges from about two to 10 days, with the average being seven days after exposure to the parasite. A few patients may not develop symptoms for as long as 28 days.

What Are Cryptosporidiosis Symptoms and Signs?

The first signs and symptoms of the disease often are watery diarrhea and fever. The patient can develop lack of appetite, stomach cramps, dehydration, weight loss, nausea, and/or vomiting. Symptoms last about five to 10 days but may persist longer in immunosuppressed individuals.

How Do Medical Professionals Diagnose Cryptosporidiosis?

Testing stool samples can diagnose the disease. Most laboratories do not routinely test for Cryptosporidium parasites. However, medical professionals may rarely utilize tests such as acid-fast staining of stool specimens, fluorescent antibody tests, and other immunoassays to diagnose the disease.

What Is the Treatment for Cryptosporidiosis?

Most individuals who have normal, healthy immune systems recover without treatment. However, young children and pregnant women are susceptible to dehydration, which could become life threatening. Consequently, patients need to be well hydrated. Doctors suggest a lactose-free diet to avoid malnutrition since the tips of the villi that process lactose are often lost for the duration of the illness. The FDA approved nitazoxanide for cryptosporidiosis diarrhea. Physicians have prescribed paromomycin and azithromycin used alone and together with some effect. Infected individuals may use over-the-counter treatments to suppress diarrhea and reduce symptoms of fever and nausea. An infectious disease consultant is often helpful in the management of immunosuppressed patients with this disease.

What Is the Prognosis for Cryptosporidiosis?

In healthy individuals, the prognosis is good because the disease is usually self-limiting and does not require special treatment. However, individuals who are immunocompromised (for example, patients with AIDS) have a prognosis that may vary from fair to poor depending upon how they respond to supportive care and treatment. Complications of cryptosporidiosis can be persistent diarrhea, malnutrition, dehydration, respiratory problems, pancreatitis, and gallbladder problems (acalculous cholecystitis). Some patients may have persistent pain in the head, joints, eyes, and may have problems with cognition.

Is It Possible to Prevent Cryptosporidiosis?

It is possible to reduce the chance of getting cryptosporidiosis by maintaining good personal hygiene, avoiding food and drinks that may be contaminated, by not swimming in natural sources of water (especially after heavy downpours), and not sharing linens or towels or other items touched by an infected person. Because Cryptosporidium parasites are resistant to chlorination, health officials recommend boiling water for drinking for prevention of the disease in areas that may have outbreaks. People may use special filters to purify water. Although research is ongoing to develop a vaccine, there is currently no commercially available vaccine for humans.

Cryptosporidiosis Sign


  • Diarrhea is the frequent passage of loose, watery, soft stools with or without abdominal bloating, pressure, and cramps commonly referred to as gas or flatulence.
  • Causes of diarrhea include viral and bacterial infections, as well as parasites, intestinal disorders or diseases, reactions to medications, and food intolerance.
  • The main symptom of diarrhea is watery, liquid stools. In addition, other symptoms of diarrhea include:
    • Stomach cramps
    • Fever
    • Bloating
    • Bowel movement urgency
    • Dehydration
Cabada, M. "Cryptosporidiosis." Aug. 24, 2018. <>.