Cryptosporidium mortiferum n. sp. (Apicomplexa: Cryptosporidiidae), the species causing lethal cryptosporidiosis in Eurasian red squirrels (Sciurus vulgaris)

Authors: TUMOVA, LENKA - University Of South Bohemia; JEZKOVA, JANA - University Of South Bohemia; PREDIGER, JITKA - University Of South Bohemia; HOLUBOVA, NIKOLA - Biology Centre Of The Ascr Of The Czech Republic, Vvi; SAK, BOHUMIL - Biology Centre Of The Ascr Of The Czech Republic, Vvi; KONECNY, ROMAN - University Of South Bohemia; KVETONOVA, DANA - Biology Centre Of The Ascr Of The Czech Republic, Vvi; HLASKOVA, LENKA - Biology Centre Of The Ascr Of The Czech Republic, Vvi; ROST, MICHAEL - University Of South Bohemia; MCEVOY, JOHN - North Dakota State University; XIAO, LIHUA - South China Agricultural University; Santin-Duran, Monica; KVAC, MARTIN - Biology Centre Of The Ascr Of The Czech Republic, Vvi

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2023
Publication Date: 7/15/2023
Citation: Tumova, L., Jezkova, J., Prediger, J., Holubova, N., Sak, B., Konecny, R., Kvetonova, D., Hlaskova, L., Rost, M., Mcevoy, J., Xiao, L., Santin, M., Kvac, M. 2023. Cryptosporidium mortiferum n. sp. (Apicomplexa: Cryptosporidiidae), the species causing lethal cryptosporidiosis in Eurasian red squirrels (Sciurus vulgaris). Microorganisms. 16(1):235. https://doi.org/10.1186/s13071-023-05844-8.
DOI: https://doi.org/10.1186/s13071-023-05844-8

Interpretive Summary: Cryptosporidium is an important causative agent of mild to severe diarrheal diseases in humans and various animals, with worldwide distribution. The genus Cryptosporidium currently comprises 49 species and dozens of genotypes. Molecular characterization of these species and genotypes has revolutionized our understanding of the biological diversity of this genus. Cryptosporidium chipmunk genotype I was first reported as W17 in New York state storm water samples. Later, it was identified in rodent fecal samples from the watershed of the New York City water supply, and it was renamed to chipmunk genotype I. Since then, it has been reported in sporadic human cases in the United States and Europe, and was the source of a small outbreak in Sweden that confirmed the zoonotic transmission of this genotype from a red squirrel to a human. Cryptosporidium chipmunk genotype I is a common parasite in North American tree squirrels that was introduced into Europe with eastern gray squirrels. It poses an infection risk to native European squirrel species, for which infection is fatal, and to humans. The position of chipmunk genotype I within the genus Cryptosporidium is not yet clear due to the lack of described biologic characteristics. To improve identification and thereby the detection, reporting, and understanding of the epidemiology of this genotype the present study was undertaken to obtain morphological, biological, and molecular data so the chipmuck genotype I could be identified as a distinct and valid species. Phylogenic analyses at 6 different genes confirmed that chipmunk genotype I is genetically distinct from other Cryptosporidium spp. Cross-transmission studies found that no detectable infection occurred in chickens and guinea pigs experimentally inoculated with chipmunk genotype I, while infection was demonstrated in laboratory mice, ferrets, gerbils, Eurasian red squirrels, and eastern gray squirrels. While infection in mice, gerbils, ferrets, and eastern gray squirrels was asymptomatic or with mild clinical signs, Eurasian red squirrels developed severe cryptosporidiosis that resulted in host death. Cryptosporidium chipmunk genotype I infection was localized exclusively in the caecum and anterior part of the colon. Based on these differences in genetics, host specificity, and pathogenicity, we propose the name Cryptosporidium mortiferum n. sp. for this parasite previously known as Cryptosporidium chipmunk genotype I. The description of a new Cryptosporidium species will be of interest to other scientists, epidemiologists, , and public health agencies concerned with this widespread parasite.

Technical Abstract: Cryptosporidium spp. are globally distributed parasites that infect epithelial cells in the microvillus border of the gastrointestinal tract of all classes of vertebrates. Cryptosporidium chipmunk genotype I is a common parasite in North American tree squirrels. It was introduced into Europe with eastern gray squirrels and poses an infection risk to native European squirrel species, for which infection is fatal, and to humans. The position of chipmunk genotype I within the genus Cryptosporidium is not yet clear due to the lack of described biologic characteristics. In this study, the biology and genetic variability of different isolates of the chipmunk genotype I were investigated. Phylogenic analyses at the SSU rRNA, actin, HSP70, COWP, TRAP-C1, and gp60 revealed that chipmunk genotype I is genetically distinct from other Cryptosporidium spp. No detectable infection occurred in chickens and guinea pigs experimentally inoculated with chipmunk genotype I, while in laboratory mice, ferrets, gerbils, Eurasian red squirrels and eastern gray squirrels oocysts shedding began between 4 and11 day post infection. While infection in mice, gerbils, ferrets and eastern gray squirrels was asymptomatic or with mild clinical signs, Eurasian red squirrels developed severe cryptosporidiosis that resulted in host death. The rapid onset of clinical signs characterized by severe diarrhea, apathy, loss of appetite, and subsequent death of the individual may explain the sporadic occurrence of this Cryptosporidium in field studies and its concurrent spread in the population of native European squirrels. Oocysts obtained from a naturally infected human, the original inoculum, were 5.64 × 5.37 µm and did not differ in size from oocysts obtained from experimentally infected hosts. Cryptosporidium chipmunk genotype I infection was localized exclusively in the caecum and anterior part of the colon. Based on these differences in genetics, host specificity, and pathogenicity, we propose the name Cryptosporidium mortiferum n. sp. for this parasite previously known as Cryptosporidium chipmunk genotype I.