In Denmark, a high-income country with no mandatory surveillance system of cryptosporidiosis in place, little is known about the clinical importance and epidemiology of Cryptosporidium infections.

Danish Departments of Clinical Microbiology (DCMs) are encouraged to submit samples positive for Cryptosporidium to the national Reference Laboratory at Statens Serum Institut (SSI) for confirmation and typing. Here, samples undergo SSU rRNA and 60-kDa glycoprotein (gp60) gene sequencing in order to identify species and subtypes, allowing for assessment of genetic relatedness and transmission dynamics. Even though an ongoing SARS-CoV-2 pandemic has restricted travel activity, the number of diagnosed cases and submitted samples has increased rapidly in recent years (2021 and 2022). Zoonotic species and subtypes have been found that have not previously been observed in Denmark. This is likely a reflection of the introduction in DCMs of new highly sensitive diagnostic methods and syndromic testing assays with multiple-pathogen panels, resulting in analysis for Cryptosporidium without specific suspicion or request from clinicians. Among recent samples, the first Danish case of Cryptosporidium erinacei has been identified. This case also represents the first case of a new C. erinacei subtype family, XIIIb.

The case was interviewed via telephone by SSI. He provided informed, written consent for publication of information about him and his course of cryptosporidiosis. The case was a middle-aged man who contacted his general practitioner after two weeks with intense stomach aches and three to five daily soft, non-watery stools. He also experienced pronounced exhaustion and intermittent nausea in the absence of fever. Symptoms had begun during his summer holidays and his family members remained asymptomatic throughout the course of his illness. He was requested by his physician to submit a stool sample and was sent home without antimicrobial treatment.

The stool sample was received at the DCM in Region Zealand and examined using a multiplex PCR panel, the QIAstat-Dx Gastrointestinal Panel [1], introduced in this DCM in December 2021. According to the manufacturer, this assay tests for presence of 23 different bacteria, viruses and parasites. The sample was positive only for Cryptosporidium spp. and was sent to SSI where species and subtype determination was performed according to current standards [2,3], uncovering C. erinacei subtype XIIIbA23G1R4 (GenBank acc. no. OQ109275 [SSU rDNA] and OQ128062 [gp60]) as the causative pathogen.

The first published case of a human infection with C. erinacei stems from 2014 and presents an immunocompetent man in his twenties from the Czech Republic [4]. A small number of human infections with C. erinacei have since been observed in different countries (Table 1) [3,5,6]. Most of these cases were observed as part of surveillance activities, and little or no clinical data was available for them. In our neighboring country Sweden, cryptosporidiosis has been a notifiable infection since 2004. Between 2013 and 2014, the Public Health Agency of Sweden received 398 samples from local clinical microbiology laboratories and reported two cases of C. erinacei: one domestically acquired and one imported case [3]. Both cases had diarrhea in the week prior to sampling.