Molecular taxonomic methods have identified Cryptosporidium
Molecular taxonomic methods have identified Cryptosporidium hominis (which infects humans) and C. parvum (which infects cattles, humans and other mammals) as the most commonly detected Tozadenant of Cryptosporidium in surface and wastewater (Paziewska et al., 2007; Smith et al., 2006). An additional Cryptosporidium species of animal origin, C. meleagridis is the third most common species following C. hominis and C. parvum, capable of infecting immuno-compromised humans (Silverlas et al., 2012). Furthermore, C. canis, C. felis, C. suis and C. muris are minor species responsible for human infections (Xiao, 2010) with most cases detected in HIV-positive patients and in children (Cama et al., 2007; Llorente et al., 2007; Thompson et al., 2005; Xiao et al., 2004). C. andersoni has been reported worldwide in post-weened beef and dairy cattle (Olson et al., 2004) and has been implicated as a cause of sporadic human cryptosporidiosis in Australia together with C. fayeri (Waldron et al., 2011).
Giardiasis in humans and most other mammals is caused by Giardia duodenalis. At least eight genotypes of G. duodenalis have been identified (assemblages A–H), however among them, not only assemblages A and B infect humans, but also a wide range of mammalian hosts, making them potential zoonoses. A degree of host-related sub-structuring has been identified within assemblage A, i.e. AI appears to mainly infect animals, AII mainly infects humans, and AIII mainly infects wild ruminants. Assemblages C–H appear generally to be restricted to companion animals, livestock, and rodents while assemblage H so far has only been found in seals and a seagull (Feng and Xiao, 2011).
In a previous study, the prevalence of G. duodenalis in humans and dogs in a rural village in Cambodia was 18.3% (40/218) and 10.6% (10/94) as shown by PCR, respectively. Giardia assemblages AII and BIII of Giardia-positive samples were characterized in humans. G. duodenalis assemblages BIII, C and mix infection between C and D of positive-samples were among the dogs (Inpankaew et al., 2014). In Vietnam, molecular epidemiological studies of the species and genotypes of Giardia and Cryptosporidium infecting humans are few. C. parvum human genotype was found in three HIV patients in Vietnam (Gatei et al., 2003). Mostly non-zoonotic isolates of G. duodenalis (assemblage E) were detected in cattle and pigs at 201 farms located in five provinces around Hanoi in Northern Vietnam (Geurden et al., 2008). Nguyen et al. (2013) found 28/193 pig fecal samples in central Vietnam positive for Cryposporidium oocysts with 12 samples characterized as C.suis and two samples as Cryptosporidium pig genotype II based on 18S rRNA and HSP-70 gene sequence analysis. Fecal samples from cattle in central Vietnam were found positive for C. parvum bovine genotype and C. andersoni (Nguyen et al., 2007). The two non-zoonotic species C. ryanae and C. bovis were detected in native beef calves 2–6months old in Dac Lac province, central Vietnam (Nguyen et al., 2012). Investigating the molecular epidemiology of Giardia and Cryptosporidium in environmental samples can provide important information with regard to the potential sources of infection and likely routes of transmission to humans and animals. Thus, the specific aim of the present study was to evaluate the prevalence and concentrations of Cryptosporidium spp. and Giardia spp. in environmental samples including surface water, compost and fresh vegetables in Hanam, Vienam and to assess potential contamination sources using molecular epidemiological tools. Such knowledge would provide data to aid risk assessment and management measures for preventing contamination of food and water with protozoa in Vietnam.
Materials and methods
Results The applications of immunofluorescence microscopy on 134 environmental samples revealed 34 samples (25.4%) positive for Giardia spp. and 47 samples for Cryptosporidium spp. (35.0%) (Table 1). In 25 of these samples (18.7%), co-contamination by both pathogens was found.