Cryptosporidium: this very worrying parasite is invading swimming pools around the world

Virus, Microscope, Infection, Illness
Cryptosporidium: this very worrying parasite is invading swimming pools around the world

Cryptosporidium, a microscopic parasite that grows in swimming pools, is on the rise. It causes a potentially serious diarrhoeal disease.

Epidemics of cryptosporidiosis are booming. The cause: a microscopic unicellular parasite that invades swimming pools. A few dozen of its eggs are enough to infect a human, and a contaminated person can produce several million microscopic eggs, thus spreading the disease.

The parasite grows and lays its eggs in your body

According to the Centers for Disease Control and Prevention (CDC), the number of reported cryptosporidiosis outbreaks in the United States increased by 13% between 2009 and 2017.

"Internationally, it is one of the most important pathogens to be monitored by everyone," says Dr. Joseph Eisenberg, an epidemiologist at the U-M School of Public Health.

"Infection is transmitted by exposure to the parasite in its egg form," says Dr. Vernon Carruthers, professor of microbiology and immunology at U-M Medical School. It usually enters the body when the water in the pool is swallowed. "The parasite then develops inside the infected person, and is then expelled through the stool, where the cycle begins again.

In addition, this parasite is so small that it easily passes through filters, which are designed to eliminate other slightly larger parasites, such as Giardia. Dr. Carruthers invites you to beware of the resistance of these eggs. "They can live for years, if they don't dry up, or if you don't live in an area with a climate that can reach freezing temperatures. The gel can kill them. Not chlorine".

Swimming pools, leisure centres, farms... some places are more at risk

While the majority of cases of cryptosporidiosis are related to swimming pools, 15% of them are caused by proximity to livestock, and 13% by childcare facilities (daycare centres, daycare centres, crèches...). This disease affects the vast majority of children between the ages of one and four, who are more likely to swallow water at the pool. The latter can then transmit the parasite to their entourage.

According to the Anses, irrigated plants and shellfish farms can also be contaminated by contact with infected water. They can then cause food poisoning.

While it is difficult to prevent exposure to the parasite, the CDC provides some recommendations to limit its spread. Among others:

  • Do not allow a child to swim if he or she has diarrhea or is recovering,
  • Take your children to the toilet and check their diapers every hour,
  • Change their diapers in a bathroom or changing area, not by the pool,
  • Change clothes and shower after exposure instead of an animal's habitat - especially if it is a ruminant.

The Anses specifies that Cryptosporidium eggs "remain viable and infectious in water and in[stools] for up to six months at temperatures between 0 and 30°C, and for up to one year in seawater. They cannot multiply in the environment but survive several months in cool and humid conditions.

How to recognize cryptosporidiosis, and what is the risk?

The symptoms of cryptosporidiosis are mainly intestinal. Patients generally have often watery diarrhea, abdominal pain, nausea and vomiting, dehydration, fever and weight loss.

The incubation time of the disease averages seven days, and symptoms generally last eleven to thirteen days. An infected person is contagious from the beginning of symptoms until several weeks after their disappearance.

Complications can occur in people with weaker immune systems - pregnant women, children, the elderly or immunocompromised. In 30% of cases, they can suffer from biliary involvement, which can be fatal.

Patients may also have extra-digestive sequelae, such as joint and eye pain. "This disease can lead to a persistent and intractable situation for these high-risk groups," warns Dr. Carruthers. In addition, it can also lead to the death of children already malnourished.