Animal Waste, Water Quality and Human Health

Assessing the importance of zoonotic waterborne pathogens 33Yan et al. 2007, Rivera 2008). Human isolates of subtypes 4 and 7 were shown tobe capable of infecting both chickens and rats (Iguchi et al. 2007). Parkar et al.(2007) demonstrated for the first time molecular-based evidence supporting thezoonotic potential of Blastocystis in dogs, possums and primates in anatural setting.Polymerase Chain Reaction (PCR)-based genotype classification using knownsequence-tagged site (STS) primers showed that out of 92 isolates from mammalsand birds roughly two-thirds (67.4%) were identical with human Blastocystishominis isolates (Yoshikawa et al. 2004) and 31.8% (7/22) of isolates fromcattle and pigs (Abe et al. 2003a) and 12 isolates from primates (Abe et al.2003b) examined were zoonotic genotypes of B. hominis. In another study,partial ssu rDNA of Blastocystis isolates from a human, a pig, and a horse wereshown to belong to a common subgroup. Blastocystis isolated from a pig and ahorse in the same study was shown to be monophyletic and have 92 to 94%identity with B. hominis (Thathaisong et al. 2003). Blastocystis isolated fromchicken were also shown to be zoonotic using arbitrary primer PCR (Yoshikawaet al. 1996).A recent study in Spain showed subtypes of Blastocystis obtained fromsymptomatic patients were similar to B. ratti from rats (Domínguez–Márquezet al. 2009). The pathogenic potential of human strains of Blastocystis in rats wasevidenced by significant up regulation of the expression of interferon-γ,interleukin (IL)-12, and tumor necrosis factor alpha, but not IL-6 orgranulocyte-macrophage colony-stimulating factor, in the caecal mucosa at twoand/or three weeks post-infection (Iguchi et al. 2009). The first demonstrationthat cysteine proteases of B. ratti WR1, a zoonotic isolate, could activate IL-8gene expression in human colonic epithelial cells further supports evidence for azoonotic role for Blastocytis isolated from rats (Puthia et al. 2008).Out of the 325 water associated outbreaks of parasitic protozoan diseasereported, North American and European outbreaks accounted for 93% of allreports and nearly two-third of outbreaks occurred in North America. Two ofthese outbreaks were related to Blastocystis (Kourenti et al. 2007).A survey of intestinal parasites among soldiers in Thailand demonstrated 21.9%of stools positive for Blastocystis; parasite incidence was statistically associatedwith the quality of drinking-water (Taamasri et al. 2000). Further evidence ofwaterborne transmission of cysts of Blastocystis was provided by a study where334/904 stool samples from personnel in another Thai army camp were foundto be positive for Blastocystis (Leelayoova et al. 2004). In the study, soldiersthat consumed unboiled water were found to be more commonly infected withthis protozoon (Tuncay et al. 2008; Kitvatanachai et al. 2008). Even morecompelling evidence emerged from a subsequent study, where 18.9% of the 675