Cryptosporodium outbreak in Indiana
A health alert from the ever informative Morbidity and Mortality Weekly Report, the main infectious disease reporting publication of the Centers for Disease Control: “Outbreak of Cryptosporidiosis Associated with a Firefighting Response.” On June 6, 2011, 34 firefighters from Indiana and Michigan responded to a barn fire near the Michigan-Indiana border. Of those 34 firefighters, 20 of them reported gastrointestinal illness within 2 weeks of the fire, and one illness was severe enough to warrant hospitalization.
Cryptosporodiosis is a gastrointestinally acquired disease, caused by the protozoan pathogen Cryptosporodium parvum. Infections due to C. parvum occur at high frequency in the United States, however most infections are only noted in livestock and poultry, with most human infections being asymptomatic. The only human population where C. parvum infections have been significantly noted are in those who are immunocompromised, and indeed disease due to this organism is used as an AIDS-defining illness and can be used to facilitate a diagnosis for HIV infection.
The link between livestock and human infection greatly facilitated identification of the source of this outbreak. During the fire call, firefighters used local hydrant water and water drawn from an onsite swimming pond to extinguish the fire. Presumably, contaminated water was aerosolized during the event, which in turn led to the widespread infection of the firefighters. Fortunately, infection by Cryptosporodium does not typically lead to serious disease outside of an immunocompromised host, and in all cases in this outbreak the disease resolved itself without intervention. Subsequent recommendations by the local Michigan Department of Health were primarily to the farmer where the fire occurred, recommending that the family boil their well water, and to discontinue swimming in the pond.
Well water can be a source of fecally-transmitted microorganisms, however most wells are drilled sufficiently deep enough to diminish this risk, and additionally water is typically treated with some degree of chlorination to further reduce microorganisms. In the case of Cryptosporidium, standard chlorination treatments are not effective, as the cysts are extremely resistant to chemical disinfection and most anti-protozoan antibiotics are also poorly effective.