Cryptosporidium infection

by | Gastrointestinal Health

What is Cryptosporidium?

Cryptosporidium is a microscopic parasite that can infect the intestines and cause gastroenteritis symptoms such as watery diarrhoea, abdominal cramps, nausea and vomiting.


The symptoms of Cryptosporidium infection usually take a week to appear after a person is infected with the parasite, but can appear any time between 2 to 10 days after infection.

Watery diarrhoea is the main symptom, often accompanied by stomach cramps. Other less common symptoms of Cryptosporidium infection are nausea, vomiting, fever, and dehydration.

These symptoms may last one or 2 weeks in a healthy person but may be severe and last much longer in people with immune suppression.


Cryptosporidiosis happens when a person swallows the Cryptosporidium parasite. The parasite travels to the small intestine usually, where it then stays in the walls of the intestine. From here, the parasite multiplies, and large quantities of infectious cells are shed in the person’s faeces.

Cryptosporidium is spread by contamination from the faeces of an infected person or animal.

A person could become infected by accidentally swallowing water while swimming in a pool, water park or spa which is contaminated with Cryptosporidium. Cryptosporidium is resistant to chlorine, so even chlorinated swimming pools can be contaminated.

Outbreaks of Cryptosporidium have occurred in Australia associated with public swimming pools and aquatic facilities, especially in the summer months. Young children are more likely to introduce Cryptosporidium to these facilities due to poorly fitting swim nappies and reduced hygiene.

Eating food or untreated milk contaminated with the parasite is another means of infection, as is touching your mouth after touching something contaminated with Cryptosporidium. Infected animals or people can be a source of infection like this. Any sexual activity that exposes a person to faeces may result in transmission. Pets, farm animals and native animals can all be infected.

Cryptosporidium is a hardy parasite – the cysts can live in the environment for months and are resistant to disinfection. People who have Cryptosporidium are most infectious when they have diarrhoea, but can excrete cells for a few weeks after the symptoms have gone.

cryptosporidium in public swimming pools

Risk factors

People who are immunocompromised are more susceptible to illness and have more severe symptoms from a Cryptosporidium infection than people with a healthy immune system. The infection may also continue for longer than in a healthy person.

Children who attend daycare are at higher risk, as are childcare workers. If your child has cryptosporidiosis, you are at higher risk of getting it.

People who swim in rivers, lakes and pools, and people who drink untreated, unfiltered water, such as campers and backpackers are more at risk. Anyone working with animals is also at higher risk.

Tests and diagnosis

Cryptosporidium infection can be diagnosed from a stool sample. The faecal sample can be treated and examined under the microscope for cysts, or a faecal PCR test can be done. It is much easier to see the cysts early in the infection when the stools are watery than when they are solid.

PCR (polymerase chain reaction) tests work by detecting the genetic material (DNA or RNA) of microorganisms. Some PCR tests can screen for 10 different gastrointestinal bugs in the stool sample, including Salmonella, Giardia, Blastocystis and Cryptosporidium. This is a quick and accurate way of diagnosing what type of bacteria or parasite may be causing the diarrhoea.

Cryptosporidiosis is a notifiable disease in Australia, which means laboratories are required to report any new cases. This allows the Government to identify any outbreaks that occur.


In healthy people, cryptosporidiosis symptoms usually go away without the need for any specific treatment such as antibiotics. Take care to drink plenty of fluids to stay hydrated. Do not take any medicines to prevent diarrhoea or vomiting – unless advised by a doctor.

If a person has a weakened immune system, such as someone with HIV, cancer, or who has had an organ transplant, then the infection may be more severe and go on for longer. Antibiotics have not been shown to help, so treatment focuses on strengthening the person’s immune system. Keeping the person hydrated is important. Sometimes the doctor will prescribe anti-diarrhoea drugs. If a person becomes dehydrated, then oral rehydration solutions (such as Hydralyte or Gastrolyte) or IV fluids may be required.


Generally, healthy people will not have any complications of Cryptosporidium infection. Young children and people who are immunocompromised are more at risk of severe dehydration.

Rarely, in people with severely compromised immune systems, the gallbladder, bile ducts or pancreas may become inflamed.

While cryptosporidiosis isn’t life-threatening in healthy people, complications in people who have weakened immune systems can develop into a serious ongoing illness that can be fatal.

How long will I be infectious for?

A person is infectious as long as they have symptoms of Cryptosporidium, and will still be infectious for a few weeks after the symptoms have ended. You should not handle food for at least 48 hours after the diarrhoea has stopped. If you handle food in your job, you should not return to work until there has been no diarrhoea or vomiting for 48 hours.

The recommended exclusion period for Cryptosporidium is that children should be kept at home and not return to childcare, pre-school or school until there has not been a loose bowel motion for 24 hours.

What type of doctor should I see?

A general practitioner (GP) will be able to help diagnose your illness and order any relevant tests for cryptosporidiosis.


There is no vaccine against Cryptosporidium, so prevention is down to good hygiene measures and taking care to avoid sources of infection.

Always wash your hands with soap and water after using the toilet, changing nappies, helping children with the toilet, and before preparing food and eating. Alcohol-based hand sanitisers are not effective against Cryptosporidium. Wash your hands after handling animals (including pets and farm animals) or their dung and after gardening.

Don’t drink untreated water. Water needs to be boiled or filtered to kill Cryptosporidium – chlorine tablets don’t work. Don’t eat food that has been washed in water that may be contaminated.

Don’t swim in public pools for 2 weeks after your diarrhoea has stopped – you may still be contagious.

Take special care when travelling in countries with reduced sanitation or unsafe water supply.

People who have immune deficiencies should take further precautions by also avoiding pet faeces and children who have diarrhoea.