Genotyping and Subtyping Cryptosporidium To Identify Risk Factors and Transmission Patterns - Nebraska, 2015-2017

Abstract

Cryptosporidium is an enteric pathogen that is transmitted through animal-to-person or person-to-person contact or through ingestion of contaminated water or food. In the United States, Cryptosporidium affects an estimated 750,000 persons each year; however, only approximately 11,000 cases are reported nationally (1,2). Persons infected with Cryptosporidium typically develop symptoms within 2 to 10 days after exposure. Common symptoms include watery diarrhea, abdominal cramps, nausea, vomiting, or fever, which can last 1 to 2 weeks. Cryptosporidiosis is a nationally notifiable disease in the United States. Nebraska presents a unique setting for the evaluation of this pathogen because, compared with other states, Nebraska has a greater reliance on agriculture and a higher proportion of the population residing and working in rural communities. Cryptosporidium species and subtypes are generally indistinguishable using conventional diagnostic methods. Using molecular characterization, Nebraska evaluated the genetic diversity of Cryptosporidium and found a dichotomy in the distribution of cases of cryptosporidiosis caused by Cryptosporidium parvum and Cryptosporidium hominis among rural and urban settings. Characterizing clusters of C. hominis cases revealed that several child care facilities were affected by the same subtype, suggesting community-wide transmission and indicating a need for effective exclusion policies. Several cases of cryptosporidiosis caused by non-C. parvum or non-C. hominis species and genotypes indicated unique animal exposures that were previously unidentified. This study enhanced epidemiologic data by validating known Cryptosporidium sources, confirming outbreaks, and, through repeat interviews, providing additional information to inform cryptosporidiosis prevention and control efforts.

FIGURE 1

Exposures^,† commonly reported by cryptosporidiosis patients (N = 149) — Nebraska, September 2015–December 2017 * Patients could report multiple exposures. No patient reporting dog exposure reported cattle exposure. ^† Does not include data from follow-up interviews that identified specific dog, squirrel, and skunk exposures not previously mentioned.

FIGURE 2

Distribution of Cryptosporidium parvum and Cryptosporidium hominis cases — Nebraska, September 2015–December 2017 * Placement of symbols within a county is random and does not indicate exact location of cases.