Cryptosporidium is a microscopic parasite that can cause a diarrheal disease known as cryptosporidiosis. The infectious stage of this parasite is called an oocyst. These oocysts are hardy, measuring about 3-5 micrometers in diameter, and have a thick, protective outer shell that allows them to survive for extended periods outside a host. When ingested, oocysts initiate the infection within the small intestine.
How Oocysts Spread
Cryptosporidium oocysts primarily spread through the fecal-oral route, transmitted through accidental ingestion of contaminated feces. Waterborne transmission is a pathway, often involving contaminated drinking water or recreational water sources like swimming pools, lakes, and rivers. Agricultural runoff, sewage discharges, and direct deposition from infected humans or animals can introduce oocysts into water supplies. The oocysts’ resistance to common disinfectants, including chlorine, allows them to persist in treated water and cause outbreaks.
Foodborne transmission occurs when food is contaminated with oocysts. This may happen through contact with manure, contaminated soil or water, or direct contamination from infected animals or food handlers. Unwashed produce and unpasteurized milk or cider have been implicated in foodborne outbreaks. Direct contact with infected individuals or animals is another route of transmission. Oocysts are immediately infectious upon excretion, and only a small number are needed to cause infection.
Recognizing and Confirming Infection
Cryptosporidiosis causes symptoms including watery diarrhea, which can be severe, and stomach cramps, nausea, vomiting, and loss of appetite. A low-grade fever and weight loss may also occur. Symptoms appear 2 to 10 days after exposure and can last for one to two weeks in individuals with healthy immune systems. In people with weakened immune systems, the illness can be more severe, prolonged, and potentially life-threatening due to persistent diarrhea and dehydration.
Confirming a Cryptosporidium infection involves laboratory testing of stool samples. Healthcare providers may request multiple samples over several days because the number of parasites in stool can vary. Diagnosis relies on detecting oocysts, antigens, or DNA of the parasite in the stool using specialized laboratory techniques. These tests are important because Cryptosporidium can be difficult to diagnose using standard microscopic methods alone.
Preventing Exposure
Preventing exposure to Cryptosporidium oocysts involves strategies, especially regarding water and hygiene. Avoid swallowing water from public pools, lakes, rivers, or untreated water sources, even if they appear clean. When contamination is suspected, boiling water is an effective method to inactivate oocysts, or using a filter certified to remove Cryptosporidium can provide protection.
Good hygiene practices are also important in preventing the spread of this parasite. Thorough handwashing with soap and water is recommended, especially after using the restroom, changing diapers, or handling animals. Avoid swimming in recreational water if you are experiencing diarrhea, and individuals diagnosed with cryptosporidiosis should stay out of the water for at least two weeks after symptoms resolve to prevent further spread. Cryptosporidium oocysts are highly resistant to chlorine, so standard chlorination levels in pools may not be enough to kill them.
Managing Cryptosporidiosis
Managing cryptosporidiosis focuses on addressing symptoms, especially dehydration caused by diarrhea. Staying well-hydrated by drinking plenty of fluids is important for all infected individuals, especially young children and pregnant women who are more susceptible to rapid fluid loss. For most healthy individuals, cryptosporidiosis is a self-limiting illness that resolves on its own within a few weeks without specific medication.
In cases of severe illness or for individuals with weakened immune systems, medical consultation is necessary. A prescription medication called nitazoxanide is approved for treating cryptosporidiosis in healthy individuals aged one year or older. While nitazoxanide can shorten the duration of diarrhea and improve outcomes, its effectiveness in severely immunocompromised patients is limited, and it may not fully cure the infection in these individuals. For those with compromised immune systems, rebuilding the immune system through appropriate medical therapy can help reduce or eliminate symptoms.