Risk factors associated with Cryptosporidium species and genotypes in Tennessee, 2018-2023

Cryptosporidiosis is a leading cause of zoonotic illness. We aimed to describe cryptosporidiosis illnesses in Tennessee by species and molecular subtypes, and explore epidemiological risk factors.

Cryptosporidium is a reportable condition in Tennessee. Cases are investigated and molecular subtyping is performed. Collected data includes patient demographics, risk factors, laboratory results, and Cryptosporidium species and subtype. We described Tennessee residents with cryptosporidiosis during 2018-2023. To explore risk factors, we used binomial probabilities to compare exposure frequencies with the Foodborne Diseases Active Surveillance Network (FoodNet) Population Survey.

During 2018-2023, Tennessee recorded 1174 cryptosporidiosis cases. Of those, 282 (24%) had species information and 214 (18%) had genotype information. Of 802 laboratory-confirmed cases without species information, 664 (83%) did not have a specimen submitted for molecular subtyping. Most frequently identified species were C. parvum (n = 183, 65%) and C. hominis (n = 60, 21%) with most frequently identified subtypes being C. parvum subtypes IIaA15G2R1 (n = 80) and IIaA15G2R2 (n = 15), and C. hominis subtype IfA12G1R5 (n = 15). C. felis (n = 8), C. ubiquitum (n = 5), C. meleagridis (n = 3), C. canis (n = 2), and C. deer mouse subtypes (n = 2) were also identified. Rates were higher for C. parvum in rural counties and C. hominis in urban counties. Persons with C. parvum infections more often reported contact with goats, cows, or sheep compared to the population (39% vs. 6%, P <.001). Persons with C. hominis infections more often reported contact with natural (22% vs. 9%, P =.003) and treated (32% vs. 12%, P <.001) water, and having contact with another person with diarrheal illness (28% vs. 15%, P =.013).

Molecular cryptosporidiosis surveillance can facilitate more detailed understanding of cryptosporidiosis risk factors and prevention measures. To best use this tool, a greater proportion of specimens need to be submitted for molecular subtyping.