parasites

What to Know About Cryptosporidiosis, or the “Pool Parasite”

The Centers for Disease Control and Prevention (CDC) recently issued an advisory for cryptosporidiosis, calling the pathogen Cryptosporidium the number one cause of outbreaks of water-associated diarrhea and the third leading cause of diarrhea tied to animal contact in the United States.1

Commonly dubbed the “swimming pool parasite,” Cryptosporidium has been associated with 444 cryptosporidiosis outbreaks and 7465 cases reported in 40 US states and Puerto Rico from 2009 to 2017.1 Notably, the number of reported cryptosporidiosis outbreaks has increased by about 13% each year since 2009, according to the CDC.1

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Although cryptosporidiosis is self-limiting in most people who are immunocompetent, it can be life-threatening to individuals who are immunocompromised, said Joseph Eisenberg, PhD, MPH, chair and professor of Epidemiology and professor of Global Public Health at the University of Michigan School of Public Health in Ann Arbor, Michigan.

“In 1993, there was a huge waterborne outbreak in Milwaukee that infected over 400,000 people.2 About 50 people died, and almost all of those who died were HIV-positive,” Dr Eisenberg told Consultant360. “Cyptosporidiosis was one of the original AIDS-defining conditions3, and this outbreak was one of several factors that helped put Cryptosporidium on the map.”

Cryptosporidiosis became less of a front-and-center issue after the advent of combination antiretroviral therapy (ART) in the late 1990s, which has led to significantly fewer deaths among HIV-positive individuals in general, said Dr Eisenberg. However, over the past decade, Cryptosporidium has reemerged as possibly the leading enteric pathogen causing infant mortality due to diarrheal disease worldwide, he added.

“Unlike many of the more prevalent viruses for which people can develop long-term immunity, infection with Cryptosporidium does not confer long-term immunity,” Dr Eisenberg told Consultant360.

Cryptosporidiosis can affect people of all ages, but it is most likely to be spread in venues like swimming pools by children, especially infants who are not toilet-trained. Cryptosporidium is resistant to chlorine, making pools an easy vessel for the pathogen to spread to others.

Zoonotic strains of Cryptosporidium, such as Cryptosporidium bovine, can also be spread in petting zoos – another popular summer activity for young children.

Discussing the risks of cryptosporidiosis with patients and parents of young children is important, especially during the summer, when activities like swimming are most common, said Dr Eisenberg. To help prevent its spread, the CDC recommends:1

  • Individuals who are ill with diarrhea should not swim or attend child care.
  • Individuals who come into contact with animals should wash their hands afterwards.


“Awareness among physicians about the rise of cryptosporidiosis is important, and reporting mechanisms for outbreaks allow physicians to know when and where Cryptosporidium outbreaks are on the rise,” said Dr Eisenberg. “Awareness of trends and outbreaks can definitely help keep the rising incidence of Cryptosporidium on physicians’ radar, especially if they encounter cases in their own practice.”

Although preventive measures on an individual level can be difficult due to the nature of cryptosporidiosis, physicians and related providers can also advise patients to swim in pools that are well managed, added Dr Eisenberg. “Generally, a pool that is better managed is going to be a safer pool to use. Physicians can encourage patients to check with pool staff about their pool sanitation and management procedures as a precautionary measure,” he told Consultant360.

Cryptosporidiosis can be diagnosed via laboratory analysis, using different techniques such as acid-fast staining, direct fluorescent antibody, and/or enzyme immunoassays, according to the CDC.4

In patients who are immunocompetent, symptoms typically last 1 to 2 weeks, and most patients will recover without treatment.5 Symptoms of cryptosporidiosis typically include watery diarrhea, as well as stomach cramps or pain, dehydration, nausea, vomiting, fever, and/or weight loss, but some patients may not experience any symptoms.5 The FDA approved nitazoxanide for the treatment of diarrhea caused by Cryptosporidium among immunocompetent individuals aged 1 year or older.6

Although ART can typically decrease or eliminate symptoms of cryptosporidiosis in HIV-positive patients, additional monitoring may be needed for this patient population, as well as other immunocompromised populations, such as patients with inherited immune-mediated diseases, patients with cancer, and transplant patients who are treated with certain immunosuppressive medications.5,6

—Christina Vogt

References:

1. Gharpure R, Perez A, Miller AD, et al. Cryptosporidiosis outbreaks — United States, 2009–2017. MMWR Morb Mortal Wkly Rep. 2019:68(25);568-572. http://dx.doi.org/10.15585/mmwr.mm6825a3.

2. Mac Kenzie WR, Hoxie NJ, Proctor ME, et al. A massive outbreak in Milwaukee of Cryptosporidium infection transmitted through the public water supply. N Engl J Med. 1994; 331:161-167. doi:10.1056/NEJM199407213310304.

3. O’Connor RM, Shaffie R, Kang G, Ward HD. Cryptosporidiosis in patients with HIV/AIDS. AIDS. 2011;25(5):549-560. doi:10.1097/QAD.0b013e3283437e88.

4. Diagnosis & detection. Parasites – Cryptosporidium (also known as “Crypto”). Centers for Disease Control and Prevention. Page last reviewed December 2, 2016. Accessed July 16, 2019. https://www.cdc.gov/parasites/crypto/diagnosis.html.

5. Illness & symptoms. Parasites – Cryptosporidium (also known as “Crypto”). Centers for Disease Control and Prevention. Page last reviewed August 16, 2017. Accessed July 16, 2019. https://www.cdc.gov/parasites/crypto/illness.html.

6. Treatment. Parasites – Cryptosporidium (also known as “Crypto”). Centers for Disease Control and Prevention. Page last reviewed August 16, 2017. Accessed July 16, 2019. https://www.cdc.gov/parasites/crypto/treatment.html.