Animal Waste, Water Quality and Human Health

34Animal Waste, Water Quality and Human Healthstool samples from school children in Thailand found positive for Blastocystis hadsubtypes similar to those found in the water samples, strongly suggesting thatwaterborne transmission had taken place (Leelayoova et al. 2008).Another study implicating water to be a mode of transmission collectedinformation through a detailed questionnaire given to 60 patients diagnosed withB. hominis, living in two localities of the Girardot municipality in Aragua State,Venezuela. It revealed that the affected age group was under ten years of ageand drank water from lid-covered storage containers (Serna et al. 2005).Whether these water containers were contaminated is unknown. In a survey ofpotable water in Egypt, 1% of 840 samples were found to be positive forBlastocystis (Elshazly 2007). Viable cysts have been demonstrated in sewageeffluent in Pakistan (Zaman et al. 1994) and in Scottish and Malaysian sewageand effluents (Suresh et al. 2005). Recently, viable cysts of Blastocystis havebeen isolated from recreational waters for the first time (Suresh et al. 2010).In summary, Blastocystis is widespread in animals (including birds) and inhuman populations and there is increasing evidence, based on modern moleculartyping methods, that many subtypes of Blastocystis can infect a number of hostspecies including humans. The 3–4 µm cysts produced by the organism are robustand appear to be readily transmitted through water. Epidemiological evidencesuggests that boiling and perhaps other treatment of drinking-water are requiredto decrease exposure to the pathogen. Due to these factors they feature among themost common intestinal parasites detected in human stool surveys carried out indeveloping countries in Asia and Latin America. Recent advances in thesensitivity of detection methodologies such as the in vitro culture methodusually used to detect the organism in stools (Suresh & Smith 2004) will greatlyfacilitate stool and water surveys to detect the parasite and allow a betterassessment of the extent of the zoonotic waterborne disease associated withthis pathogen.Schistosoma species RANK 3 Schistosomiasis remains a major public healthproblem in countries where the disease is endemic. There are four species ofblood fluke of the genus Schistosoma that parasitize humans namely,S. mansoni, S. haematobium, S. japonicum and S. mekongi. Globally, it isestimated that more than 200 million individuals are infected with schistosomesand around 800 million more are at risk of infection (Steinmann et al. 2006).Humans are infected when they come in contact with water contaminated withthe infective stage of the parasite. Contamination of water starts when eggs of theparasite from faeces of an infected host reach the water. These eggs give rise tomiracidia which infect the snail intermediate host. The infective form of theparasite, cercariae, develop and are released from the snail. Cercariae can survivefor 24 hours in the water at room temperature and can be carried more than 100