Genotyping Cryptosporidium Could Improve Outbreak Prevention, Response

Genotyping and subtyping Cryptosporidium can improve responses to outbreaks and strategies for prevention, according to a recent Morbidity and Mortality Weekly Report from the US Centers for Disease Control and Prevention (CDC).

An examination of Cryptosporidium cases in Nebraska from 2015 to 2017 found C parvum cases associated with animal exposure in rural areas and C hominis cases more commonly found in urban areas.

“Characterizing Cryptosporidium species, genotypes, and subtypes from urban and rural populations can improve outbreak detection and investigation, identify potential sources, and inform prevention strategies,” the report noted.

The report was authored by officials with the Nebraska Department of Health and Human Services; the University of Nebraska—Lincoln, Nebraska; Nebraska Public Health Laboratory; University of Nebraska Medical Center, Omaha; and the Division of Foodborne, Waterborne, and Environmental Diseases, National Center for Emerging and Zoonotic and Infectious Diseases, CDC.

There are about 40 known Cryptosporidium species and genotypes, including about 20 known to infect people, with an estimated 750,000 American affected each year. Nebraska’s predominance of rural, agricultural-based communities makes the state well-suited for studying the disease.

Genotyping was conducted on 149 positive stool specimens submitted to the Nebraska Public Health Laboratory (NPHL) and epidemiologic data was gathered as part of the CDC’s CryptoNet surveillance system. C hominis was identified in 80 (54%) of the cases, and C parvum in 59 (29%). The study also found Cryptosporidium chipmunk, Cryptosporidium felis, Cryptosporidium ubiquitum, Cryptosporidium canis, Cryptosporidium melargridis, and Cryptosporidium skunk genotype. Exposures to animals was reported in 81 cases, including exposure to dogs (40%), cats (32%) and cattle (28%).

Among the cases of C hominis, 11 were associated with 3 outbreaks at multiple childcare facilities. C parvum cases were associated with 2 outbreaks and more likely to be associated with exposure to dogs and cattle. No significant associations with recreational water exposure were noted.

Clusters of C hominis cases may help officials pinpoint an exposure source and guide prevention and response practices, including screening and assessment of symptomatic children in child care facilities.

Limitations of the study included the likelihood of undiagnosed or underreported cases of cryptosporidiosis and the lack of stool samples from animals that may have confirmed the transmission source of some cases.

“Nebraska is continuing to explore ways to improve CryptoNet activities, such as further increasing sample submission to NPHL, increasing timeliness of interviews, conducting sequencing methods in real time rather than retrospectively, and reporting results to public health epidemiologists sooner,” the report noted.

Outbreaks of cryptosporidiosis are most common in summer months and are often linked to recreational water. Between 2009 and 2017, outbreaks increased an average of 13% each year, according to an MMWR report released last summer.

The CDC has offered safety tips for reducing the spread of cryptosporidiosis, including staying out of recreational water if you have diarrhea; showering before entering a pool; giving children frequent bathroom breaks; and checking the disinfectant and pH levels of home pools and hot tubs.