Evidence of Cryptosporidium transmission between cattle and humans in northern New South Wales

Abstract

Cryptosporidium is an enteric parasite of public health significance that causes diarrhoeal illness through faecal oral contamination and via water. Zoonotic transmission is difficult to determine as most species of Cryptosporidium are morphologically identical and can only be differentiated by molecular means. Transmission dynamics of Cryptosporidium in rural populations were investigated through the collection of 196 faecal samples from diarrheic (scouring) calves on 20 farms and 63 faecal samples from humans on 14 of these farms. The overall prevalence of Cryptosporidium in cattle and humans by PCR and sequence analysis of the 18S rRNA was 73.5% (144/196) and 23.8%(15/63) respectively. Three species were identified in cattle; C. parvum, C. bovis and C. ryanae, and from humans, C. parvum and C. bovis. This is only the second report of C. bovis in humans. Subtype analysis at the gp60 locus identified C. parvum subtype IIaA18G3R1 as the most common subtype in calves. Of the seven human C. parvum isolates successfully subtyped, 5 were IIaA18G3R1, one was IIdA18G2 and one isolate had a mix of IIaA18G3R1 and IIdA19G2. These findingssuggest that zoonotic transmission may have occurred but more studies involving extensive sampling of both calves and farm workers are needed for a better understanding of the sources of Cryptosporidium infections in humans from rural areas of Australia.Key Words: Cryptosporidium; calves; outbreak; humans; genotyping; 18S rRNA; gp60; zoonotic transmission. 3 IntroductionCryptosporidium is a protozoan parasite that causes self-limiting diarrhoea in immunocompetent individuals but may be chronic and life-threatening to those that are immunocompromised (Hunter and Nichols, 2002). Humans can acquire Cryptosporidium infections through various transmission routes, such as direct contact with infected persons (person-to-person transmission) or animals (zoonotic transmission) and ingestion of contaminated food (foodborne transmission) and water (waterborne transmission) (Xiao, 2010). The relative importance of the different transmission routes is still unclear as most species of Cryptosporidium are morphologically identical and cannot be differentiated through routine diagnostics in pathology laboratories (which rely on microscopy and rarely perform genotyping). Molecular characterization tools such as PCR and sequence analysis of the 18S ribosomal RNA (rRNA) gene and the hypervariable 60-kDa glycoprotein (gp60) gene, are required to identify species and track transmission (Xiao, 2010;Ng et al., 2008;Ng et al., 2010aNg et al., , 2010b.Of the 23 valid species, C. hominis and C. parvum are responsible for the majority of infections in humans (Xiao, 2010;Ng et al., 2010a). Cryptosporidium hominis is predominately found in humans, whereas C. parvum can be zoonotic in origin. Cattle are considered one of the main reservoir hosts for C. parvum. However, studies worldwide suggest that cattle are infected with at least five Cryptosporidium parasites: C. parvum, C. bovis, C. andersoni, C. ryanae...

Genetic characterization of Cryptosporidium in animal and human isolates from Jordan

“…However, the IIaA19G2R1 subtype is a relatively rare subtype and has previously been described by Xiao et al (2007), Wielinga et al (2008), Ng et al (2012), Rieux et al (2013) and Couto et al (2014) infecting cattle in the North America, The Netherlands, Australia, France and Brazil, respectively and by Nolan et al (2013) in deer in Australia. To the best of our knowledge, this is the first report of this subtype in sheep.…”

Cryptosporidiumspecies in Australian wildlife and domestic animals

“…Recently, C. fayeri, C. andersoni and C. bovis have been identified in individual human cases in NSW (Waldron et al 2010(Waldron et al , 2011aNg et al 2012).…”

Human Cryptosporidiosis Diagnosed in Western Australia: a Mixed Infection with Cryptosporidium meleagridis, the Cryptosporidium Mink Genotype, and an Unknown Cryptosporidium Species

“…There has been one case each of human cryptosporidiosis with C. fayeri, C. andersoni, and C. bovis in Australia (6,8). It is likely that this patient was infected with Cryptosporidium during his travels to PNG through ingestion of contaminated water; however, this cannot be confirmed.…”