Reviewed by Saskia Knight, Nutritionist
Last reviewed on January 22, 2025
What is Cryptosporidium?
Cryptosporidium spp. is a group of tiny parasites that can infect the intestines and cause diarrhoea. The term "spp." means "multiple species," so instead of one specific type of parasite, it refers to different kinds of Cryptosporidium.
Cryptosporidium is a microscopic parasite that causes cryptosporidiosis, a diarrhoeal illness. It spreads through contaminated water, food, or contact with infected animals or people. This parasite is highly resilient and can survive in chlorinated water and is one of the most common causes of waterborne gastrointestinal infections globally.
These parasites typically reside in the intestines of the infected hosts and can affect people of all ages but is most prominent in children aged 1-5 and travellers to high-risk areas.
How is it spread?
Cryptosporidium can live in water, food, soil, or on surfaces that have been contaminated with infected faeces.
Cryptosporidium is highly contagious and spreads through faecal-oral transmission, meaning a person becomes infected by ingesting Cryptosporidium oocysts from contaminated sources.
Oocysts are the microscopic, infectious form of the parasite. When ingested via contaminated food or water (for example, due to poor hygiene or contaminated water), these oocysts ‘hatch’, releasing the active form of the parasite in the intestines, leading to infection.
Contaminated water
Recreational water: Swimming pools, hot tubs, lakes, and rivers can become contaminated if infected individuals defecate in the water. Cryptosporidium is highly resistant to chlorine, making it difficult to fully eliminate from treated water or public swimming pools.
Drinking water: Outbreaks have occurred due to contaminated drinking water, particularly in areas with insufficient water treatment. Drinking water risk exposure may be higher in certain areas or countries.
Contaminated food
Cryptosporidium can contaminate fresh produce, particularly if washed with contaminated water or handled by someone with the infection.
Raw or undercooked foods may also become contaminated during food handling if proper hygiene practices are not followed. Cooking food to an internal temperature of above 75°C can kill the parasite.
Person to person contact
Direct contact with an infected person, particularly in settings such as nurseries, care homes, or households, can spread the parasite.
Cryptosporidium can be spread during oral-anal sex with an infected partner.
Cryptosporidium can be excreted in an infected person’s faeces for several weeks, even after symptoms have resolved. This means that individuals can continue to spread the parasite to others, potentially causing further infections.
Animal contact
Contact with infected animals, particularly livestock such as calves, lambs and goats, can transmit Cryptosporidium to humans.
Between January and May 2013 over 130 individuals were affected by a Cryptosporidium outbreak among petting farms in England.
Countries at higher risk
Countries at higher risk: Although Cryptosporidium can be found internationally, certain regions with limited access to clean water and sanitation infrastructure are likely to have a higher incidence of Cryptosporidiosis infections.
What symptoms does It cause?
Symptoms can appear anywhere from 2 – 10 days after encountering the infection. The duration of symptoms can vary depending on several factors, including overall health, gut health, and the strength of the immune system. A weakened immune system may prolong the infection and worsen symptoms. Some people may not experience any symptoms, but in general, symptoms usually last between 2 to 4 weeks.
Common symptoms:
- Watery diarrhoea (can last from days to 2-3 weeks)
- Stomach cramps and pain
- Nausea and vomiting
- Temperature/fever
- Dehydration
- Weight loss
When should you see a doctor?
In immunocompromised individuals, Cryptosporidiosis can trigger severe diarrhoea which can result in malnutrition and may present life threatening complications. Individuals with HIV/AIDS or currently undergoing chemotherapy are most at risk of experiencing complications due to the infection and should seek medical advice when experiencing any of the above symptoms.
How is it diagnosed?
The only way to diagnose an infection is by analysing a stool sample to identify Cryptosporidium oocysts.
However, because oocysts (the ‘eggs’ of the parasite) may not always show up in a single sample, doctors may ask for multiple stool samples over a few days.
Testing for Cryptosporidium
There are several tests that can be used to test for parasites including Cryptosporidium, for example, microscopy staining and antigen testing.
Our preferred method of testing is a stool test which detects the parasite’s DNA in a stool sample and is highly accurate. A stool sample can be done at home and is less evasive.
Our gut parasite test identifies 22 different types of parasites, pathogenic bacteria and viruses via an at-home stool sample test.
Common intestinal parasites such as Cyclospora, Giardia Lamblia and Cryptosporidium can cause many of the same symptoms. To understand if you have a parasite, what the specific parasite is and how to treat it, a test must be conducted to identify the type of parasite.
How is it treated?
Most cases of Cryptosporidium infections resolve on their own within 2–4 weeks without treatment. When treatment is required, it primarily focuses on managing side effects, such as dehydration caused by diarrhoea.
There are a few simple things that can be done to aid in the recovery of an infection:
- Stay hydrated
- Get plenty of rest (particularly whilst you are experiencing symptoms)
- Eat small frequent meals
- Foods high in fibre can help to firm up loose stools
Can Cryptosporidium be prevented?
There are certain practices that can significantly reduce your likelihood of contracting a Cryptosporidium infection, these include.
Ensuring water safety:
Avoid swallowing water while swimming in pools, lakes, or rivers.
Drink from bottled water when travelling abroad or countries where there is an increased risk of parasites.
Ensure food safety hygiene:
Wash fruits and vegetables thoroughly before eating, especially if you are consuming them raw.
Avoid eating raw or undercooked meat, most parasites get destroyed during cooking so ensuring your food is thoroughly cooked can help to prevent infection.
Wash your hands before handling food.
Animal contact:
Wash hands after visiting farms, petting zoos, or handling animals.
General hygiene practices:
Carry hand sanitiser that can be used throughout the day, this can be particularly useful after visiting public spaces, changing a baby’s nappy, or even coming into contact with a someone else who may not have washed their hands.
