a SLACK Incorporated newspaper
October 1998
--Cryptosporidium
NEW ORLEANS - Recreational waters are a common vehicle for Cryptosporidium outbreaks, and summer and early fall are peak periods for cryptosporidiosis, according to William MacKenzie, MD, of the division of parasitic diseases at the Centers for Disease Control and Prevention (CDC).
"What this tells us is that these peak periods are good times to test for Cryptosporidium if you're a pediatrician or a practitioner seeing kids," MacKenzie said here at the Pediatric Academic Societies' annual meeting. Cryptosporidium is highly resistant to chlorine, so once the organism is in a public pool or water park, for instance, outbreaks can affect thousands of people.
Cryptosporidiosis is most likely a common disease that often goes unreported, according to MacKenzie. The incubation period is generally six to seven days, but can range from one to 14. Watery diarrhea, fatigue and vomiting are the primary symptoms.
"Many practitioners don't realize that Cryptosporidium is not detected during routine stool examination," MacKenzie said, "unless the microscopist is incredibly good and the stool is absolutely loaded with [the organism]." Special testing is required, and only 5% to 10% of clinical laboratories across the country will routinely test for Cryptosporidium when a physician orders a test for ova and parasites.
During a Cryptosporidium outbreak in Minnesota that was associated with children playing in a fountain at the city zoo, 373 cases were reported, 70 of which were laboratory confirmed. Most of the children had diarrhea, fever and vomiting; only 4% had bloody stools. With regard to duration of illness, children represent an immunologically naive population, so their illness is longer, according MacKenzie. The duration of illness in this particular outbreak was seven days, ranging from four to 25 days; 2% were hospitalized. "This is an illness with a lot of vomiting, fever, diarrhea and fatigue, so people tend to think it must be viral, but it's not," said MacKenzie.
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Depending on the age of the population studied, three documented outbreaks offer three different answers concerning secondary transmission of Cryptosporidium. The first outbreak was associated with children in a day care center and indicated that the secondary transmission rate in the home was about 38%. A second outbreak associated with apple cider at an elementary school resulted in a secondary attack rate of 15%. Finally, an outbreak of Cryptosporidiumin drinking water in Wisconsin, where the trackers were primarily adults, resulted in a secondary attack rate of only 5%.
"There's a broad range of secondary attack rates and it mainly depends on the age of the primary case," said MacKenzie. "When you have a child with Cryptosporidium, they are much more likely to transmit it to their household members. Therefore, parents and family members need to be counseled with regard to the importance of hand washing and [protect themselves]."
For your information:
- MacKenzie WR. Cloudy water: Cryptosporidium. Presented at the annual meeting of the Pediatric Academic Societies. May 1-5. New Orleans.
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