Cryptonet: The Next Frontier in Cryptosporidiosis Surveillance

BACKGROUND: In the United States, an estimated 748,000 cryptosporidiosis cases occur annually, and Cryptosporidium is the leading cause of waterborne disease outbreaks. Like other enteric pathogens, Cryptosporidium can be transmitted via multiple modes: ingestion of contaminated water and food or contact with infected persons or animals. CryptoNet is a surveillance system which will integrate traditional and molecular data to better understand the transmission of Cryptosporidium and the epidemiology of cryptosporidiosis in the United States. 

METHODS: As a Cryptosporidium molecular typing laboratory, CDC primarily receives outbreak-associated Cryptosporidium specimens to differentiate clusters of illness caused by different Cryptosporidium species and identify outbreaks associated with rare subtypes. CryptoNet represents an extension of CDC’s ongoing laboratory work in support of states with an overarching objective of fully integrated molecular surveillance; that is, subtyping data (single gene or whole genome sequencing [WGS]) with accompanying epidemiologic data on all cases of cryptosporidiosis notified by states to NNDSS (National Notifiable Diseases Surveillance System). To support development of CryptoNet, tiers of laboratory capacity (e.g., specimen submission to CDC versus in-house typing) and epidemiology capacity (e.g., reporting epidemiologic data to CDC for each outbreak-associated specimen using a standard investigation form versus transfer of data to CDC for each case reported to NNDSS) were defined. These tiers delineate support needed to develop capacity in the states.  Monthly calls and ongoing training and support help states advance to the higher tiers.    

RESULTS: In 2015, seven states were funded to participate in CryptoNet.  These states range in laboratory and epidemiology capacity to conduct integrated molecular surveillance for cryptosporidiosis.  Four states have no laboratory capacity to type Cryptosporidium in house and their staff will receive training at CDC to start in-house typing; one state is working to implement WGS.  The CryptoNet investigation form captures epidemiologic exposure data and was developed using previously defined variables that are collected nationally for cases of cryptosporidiosis. Two states are piloting

CONCLUSIONS: CryptoNet will change how we conduct surveillance for cryptosporidiosis in the United States, by improving how we investigate cases, detect outbreaks (e.g., epidemiologically linking seemingly unrelated cases of illness), and differentiate separate outbreaks from apparently larger outbreaks caused by common subtypes.  Integrated molecular surveillance for cryptosporidiosis will increase our understanding of the epidemiology of cryptosporidiosis in the United States, allowing the development of targeted, evidence-based prevention strategies to reduce cryptosporidiosis incidence.