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. During September 2015-December 2017, a total of 630 Cryptosporidium-positive stool specimens were reported to public health agencies by clinical laboratories, which most commonly used culture independent diagnostic testing (CIDT) and enzyme immunoassays (EIAs) for detection; among these 630 positive stool specimens, 149 (24%) were sent to the Nebraska Public Health Laboratory (NPHL), and subsequently to CDC, where genotyping was conducted using nested polymerase chain reaction-restriction fragment length polymorphism analysis and DNA sequencing of the 18S rRNA gene and the gp60 gene (3,4). Epidemiologic data on cases with genotyped and subtyped Cryptosporidium stool specimens were exported

High Diversity of Cryptosporidium Species and Subtypes Identified in Cryptosporidiosis Acquired in Sweden and Abroad

“…A few C. parvum outbreaks were included in the present study ( Table 5 ), but even if those patients ( n = 22) are excluded from the dataset, C. parvum remains the dominant species in patients infected in Sweden, at least in the four areas that contributed most of the samples ( Table 1 ). Differences in the geographical distribution of C. parvum and C. hominis , with more C. parvum in rural regions and more C. hominis in urban settings, have been described [ 42 , 43 ], and a similar tendency was seen in our study, where the rural region of Halland had relatively more cases of C. parvum and fewer cases of C. hominis compared with the metropolitan region of Stockholm ( Table 1 ). These differences are often attributed to the closer contact with farm animals in rural areas and more traveling activity for people living in urban areas [ 44 ].…”

“…The most common cause of non- hominis and non- parvum infections acquired in Sweden was Cryptosporidium chipmunk genotype I, which was diagnosed in five adults; four women and one man. Cryptosporidiosis caused by the chipmunk genotype is considered an emerging infection in the US [ 19 , 43 ]. Meanwhile, in Europe, only one human case (from France) has been reported outside Sweden [ 19 ].…”

Molecular characterization of Cryptosporidium isolates from humans in Ontario, Canada

“…Differences in C. parvum and C. hominis geographical distribution exist in some regions, with higher C. hominis in urban centers and C. parvum in rural regions [ 32 , 40 ]. Maier et al [ 41 ] reported that people living in rural areas had twice the odds of having Cryptosporidium than people living in urban settings; however, molecular data were not available to determine the Cryptosporidium spp.…”

An Update on Zoonotic Cryptosporidium Species and Genotypes in Humans

“…In that study, in the three rodent samples analysed, subtypes XIVaA18G2T1a and XIVaA18G2T2 were detected. It was identified in a human in Nebraska [ 37 ] and between 2014 and 2015, chipmunk genotype 1 was identified in five adults (four women and one man) in Sweden and all were typed as XIVaA20G2T1 [ 51 ]. Subsequently, it was identified in sixteen sporadic cases, three outbreak-related cases, and one zoonotic case, as well as in two squirrel samples in Sweden between 2018 and 2019, and subtyping of nineteen humans and two squirrels identified subtype XIVaA20G2T1 in all samples, supporting zoonotic transmission [ 75 ].…”

“…Contact with animals has been identified as a risk factor in many studies [ 34 , 35 , 36 , 37 ]; therefore, zoonotic transmission plays a major role in the epidemiology of cryptosporidiosis [ 1 , 23 , 38 , 39 , 40 , 41 ]. In order to track transmission, multi-locus sequence typing (MLST) tools have been developed, including analysis of the highly polymorphic glycoprotein 60 ( gp60 ) gene, the most commonly used locus [ 31 ].…”