Apr 11, 2008 (CIDRAP News) Samples taken from the Alamosa, Colo., water system before it was treated for Salmonella contamination also showed that the water was tainted with two parasites, Giardia and Cryptosporidium.
The results of the tests, conducted by the US Centers for Disease Control and Prevention (CDC), were announced Apr 9 in a statement from city officials. The city said state water control officials took new water samples to confirm that the parasites, both of which can cause diarrheal illnesses, were eliminated from the water when authorities flushed and disinfected the system.
Judy Egbert, Alamosa city clerk, said the high concentration of chlorine that began circulating though 50 miles of the city's pipes starting on Mar 25 should have been enough to kill Giardia and Cryptosporidium, according to an Associated Press (AP) report yesterday. The city's water comes from deep wells and is not normally treated, according to previous reports.
Post-treatment samples to detect Salmonella have already come back negative, city officials said. Alamosa will lift the boil order on local water as soon as tests are negative for parasites, according to the statement from the city. Results are not expected until the weekend at the soonest.
In late March state water officials found Salmonella enterica serotype Typhimurium in Alamosa's water system after dozens of local residents became ill with Salmonella infections. Authorities still aren't sure what the source of the Salmonella was or how it entered the city's water.
As of Apr 8, the number of reported Salmonella infections had risen to 389, with 107 confirmed cases, according to the city's statement. Sixteen patients were hospitalized, but no deaths have been reported.
Giardia and Cryptosporidium in the city's water have not been linked to any reported illnesses, according to the AP report.
Cryptosporidium is a protozoan parasite that is resistant to disinfectants like chlorine and has been linked with waterborne disease outbreaks, the agency said. The infection can be severe in children, the elderly, and immunocompromised people, according to the Environmental Protection Agency.
Giardia, one of the most common causes of waterborne illnesses, produces gastrointestinal symptoms that can lead to weight loss and dehydration, according to the CDC.
Mar 28 CIDRAP News story: "Salmonella type in Colorado water listed; source still sought"
EPA information on Cryptosporidium and other drinking-water contaminants