Cryptosporidium viatorum from the native Australian swamp rat Rattus lutreolus - An emerging zoonotic pathogen?

Abstract

Cryptosporidium viatorum is a globally distributed pathogenic species of Cryptosporidium that has only ever been recorded from humans, until now. For the first time, we molecularly characterised a novel subtype of C. viatorum (subtype XVbA2G1) from the endemic Australian swamp rat (Rattus lutreolus) using the small subunit of nuclear ribosomal RNA (SSU) gene and then subtyped it using the 60-kilodalton glycoprotein (gp60) gene. In total, faecal samples from 21 swamp rats (three were positive for C. viatorum), three broad toothed rats (Mastacomys fuscus) and two bush rats (Rattus fuscipes) were tested for Cryptosporidium. The long-term, isolated nature of the swamp rat population in Melbourne's drinking water catchment system (where public access is prohibited), the lack of C. viatorum from other mammals and birds living within the vicinity of this system and its genetic distinctiveness in both the SSU and gp60 gene sequences from other species of Cryptosporidium collectively suggest that C. viatorum might be endemic to native rats in Australia. The current state of knowledge of epidemiological surveys of Cryptosporidium of rats and the zoonotic potential are further discussed in light of the finding of C. viatorum. Long-term studies, with the capacity to repetitively sample a variety of hosts in multiple localities, in different seasons and years, will allow for greater insight into the epidemiological patterns and zoonotic potential of rare Cryptosporidium species such as C. viatorum.

Occurrence and genetic characteristics of Cryptosporidium spp. and Enterocytozoon bieneusi in pet red squirrels (Sciurus vulgaris) in China

“…In this study, five different Cryptosporidium species/genotypes were identified, including Cryptosporidium rat genotypes I and II, Cryptosporidium ferret genotype, Cryptosporidium chipmunk genotype III, and C. parvum. Cryptosporidium rat genotypes I and II have been found in brown rats in the Philippines 34 , Nigeria 20 , Australia 35 , and China 22 , even in South Nation River watershed, raw wastewater, and environmental samples in the United Kingdom, Canada, and China [36][37][38] . Cryptosporidium ferret genotype has been found in ferrets and red squirrels in Italy 39 .…”

“…Among them, 11 Cryptosporidium species have been identified in rodents, Cryptosporidium parvum and C. muris are the most common 12 . For E. bieneusi, more than 474 genotypes have been identified based on the internal transcribed spacer (ITS) region of the rRNA gene 13 , and more than 35 genotypes have been determined in rodents 14 . These genotypes can be classified into eleven groups (groups 1-11) by phylogenetic analyses 13 .…”

First report of Cryptosporidium viatorum and Cryptosporidium occultus in humans in China, and of the unique novel C. viatorum subtype XVaA3h

“…KX190061). High genetic identity among C. viatorum subtypes XVaA3a-h may suggest that C. viatorum recently spread from the source population and is now spreading further through global human travel [54]. However, no travel history was reported in our study.…”

“…C. viatorum has since been identified in people from or who travelled to Bangladesh, Barbados, Colombia, Dubai, Ethiopia, Guatemala, India, Kenya, Nepal, Nigeria, Pakistan and Australia [20,23,[45][46][47][48][49][50][51][52][53]. Recently, researchers in Australia and China identified C. viatorum in rats, underlining its zoonotic potential [54,55]. It was also identified in untreated water in China [56].…”

“…However, no travel history was reported in our study. Perhaps animals or contaminated water contribute to the infection, considering the fact that C. viatorum has been identified in animals and water [54][55][56].…”