Cryptosporidiosis: causes, symptoms, and prevention

Cryptosporidiosis is a diarrheal disease caused by the parasite Cryptosporidium.
It leads to watery diarrhea, often accompanied by nausea and abdominal cramps. People with weakened immune systems are particularly affected. Transmission usually occurs through contaminated water or food. This article provides important information about cryptosporidiosis to help you better understand what the disease is, how it manifests, how it is transmitted, and what you can do to protect yourself. Our goal is to provide you with reliable and easy-to-understand medical information so you can make informed decisions about your health.

Table of Contents

• What is cryptosporidiosis?
• What symptoms does cryptosporidiosis cause?
• How long does cryptosporidiosis last?
• Who is particularly at risk of cryptosporidiosis?
• How long can cryptosporidium survive?
• How is cryptosporidiosis transmitted?
• How is cryptosporidiosis diagnosed?
• How is cryptosporidiosis treated?
• How can you protect yourself from cryptosporidiosis?
• Summary

What is cryptosporidiosis?

Cryptosporidiosis is a diarrheal disease caused by the parasite Cryptosporidium. These parasites infect the digestive tract of humans and animals and cause watery diarrhea and abdominal cramps, which can be especially dangerous for immunocompromised individuals. Transmission is usually fecal-oral, through contaminated water, food, or infected individuals. Cryptosporidiosis is of particular concern in countries with limited access to clean drinking water, where the parasites can spread rapidly (ECDC, n.d.).

After ingesting Cryptosporidium oocysts, sporozoites are released in the small intestine. These attach to the intestinal cells and begin a reproductive cycle. Thick-walled (about 80%) and thin-walled (about 20%) oocysts are formed in the process. Thick-walled oocysts are excreted in the stool around 5 to 21 days after infection and are highly resistant. Thin-walled oocysts can break open within the intestine, which can lead to reinfection, especially in immunocompromised individuals (RKI, 2019).

What symptoms does cryptosporidiosis cause?

The symptoms of cryptosporidiosis generally affect the gastrointestinal tract and may vary depending on the person's overall health and immune status. Symptoms typically appear 2 to 10 days after infection. The most common symptoms include:

• (Severe) watery diarrhea
• Stomach pain (abdominal cramps)
• Nausea and vomiting
• Loss of appetite
• Low-grade fever
• Weight loss

Sources: Cleveland Clinic, 2022; RKI, 2019

Important: In Germany, cryptosporidiosis is a notifiable disease (but not in the Netherlands) (RKI, 2019).

How long does cryptosporidiosis last?

In immunocompetent individuals, cryptosporidiosis typically lasts 10 to 14 days but may last longer. Symptoms such as diarrhea often resolve after about two weeks. The severity and duration of illness depend on the degree of immune deficiency and can, in extreme cases, lead to death. In immunocompromised individuals, such as those with HIV/AIDS, the infection can cause additional complications, such as inflammation of the bile ducts or pancreas (Mayo Clinic, 2024, RKI, 2019).

Who is particularly at risk of cryptosporidiosis?

Cryptosporidiosis can affect anyone, regardless of age or general health status. However, particularly at risk are:

• Immunocompromised individuals, such as HIV/AIDS patients
• People undergoing immunosuppressive therapy
• Children under the age of five and the elderly
• People living in areas with poor water and food safety due to lack of hygiene
• People in close contact with infected individuals, such as farmers, caregivers, or swimming pool users

Source: Cleveland Clinic, 2022

Cryptosporidium is found worldwide. Various studies in industrialized countries have detected cryptosporidium in the stool of 2–4% of patients with diarrhea. The RKI reported around 2,000 cases in Germany in 2022 (RKI, 2022). However, in so-called developing countries, the prevalence of cryptosporidiosis is significantly higher than in industrialized nations (RKI, 2019).

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How long can cryptosporidium survive?

Cryptosporidium parasites can survive for several weeks in cool and moist environments, and in some cases, even up to two years. Their resistant oocyst shell protects them from drying out and from many disinfectants, which increases their ability to survive under various conditions. They can remain viable on food and surfaces, especially when these are not thoroughly cleaned (Motarjemi, Y., 2013, RKI, 2019).

How is cryptosporidiosis transmitted?

Cryptosporidiosis is primarily transmitted via the fecal-oral route, meaning people become infected by consuming or coming into contact with contaminated food, water, or surfaces. The main transmission routes include:

• Contaminated drinking water
• Contaminated food
• Contaminated objects and surfaces
• Direct contact with an infected person or animals
• Swimming pools or natural recreational waters

Source: RKI, 2019

How is cryptosporidiosis diagnosed?

Cryptosporidiosis is diagnosed by detecting Cryptosporidium oocysts in stool samples, usually using a special staining technique (e.g., Ziehl-Neelsen), with samples collected on three different days. For specific species, immunofluorescence tests and ELISA kits can also be used to detect antigens in the stool. Polymerase chain reaction (PCR) is commonly used for precise species identification. In addition, the diagnosis can be made histologically from endoscopically obtained tissue samples (from the small intestine, and more rarely, the large intestine) (RKI, 2019).

How is cryptosporidiosis treated?

Most people with a healthy immune system recover from cryptosporidiosis without treatment. Therefore, cryptosporidiosis is usually treated symptomatically, mainly by replacing fluids and electrolytes (via oral or intravenous hydration or antidiarrheal medications). Additionally, antiprotozoal agents may be used to inhibit the growth of protozoa like Cryptosporidium in the body (Cleveland Clinic, 2022).

How can you protect yourself from cryptosporidiosis?

Preventing cryptosporidiosis is based on minimizing contact with potential sources of infection and following strict hygiene practices. The following measures can help reduce the risk of infection:

• Safe food handling: Wash fruits and vegetables thoroughly before consumption, especially if they are eaten raw. Ensure that foods are well-cooked to kill any potential parasites.
• Avoid contaminated water: Drink only filtered or boiled water, especially in regions where drinking water safety is questionable. Be cautious when swimming in natural bodies of water such as lakes or rivers, as these are often contaminated with Cryptosporidium oocysts.
• Strict hand hygiene: Wash your hands regularly with soap and water, especially after using the toilet, before eating, and after contact with animals or young children.
• Avoid contact with infected individuals: People with cryptosporidiosis should minimize contact with others—particularly those with weakened immune systems—until symptoms have resolved. Shared surfaces and items should be disinfected regularly. Sexual activity should be avoided for two weeks after symptoms resolve, and condoms should be used.
• Caution around animals: Avoid direct contact with animal feces, particularly from calves and lambs, which are common carriers of the parasite. Wear gloves and wash your hands after working with animals.

Source: Cleveland Clinic, 2022

Summary

Cryptosporidiosis is a parasitic infection of the digestive tract, primarily transmitted through contaminated water or direct contact with infected people or animals. Symptoms range from severe diarrhea to abdominal pain, nausea, and weight loss. People with weakened immune systems, young children, and the elderly are particularly at risk. Diagnosis is typically made through stool examinations, and treatment focuses on fluid replacement and, if necessary, antiparasitic medications. Preventive measures such as strict hand hygiene, safe drinking water, and proper food handling are essential to avoid infection. Awareness of the risks and consistent adherence to hygiene practices can significantly reduce the risk of transmission.