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  • br Impact on the health

    2018-10-22


    Impact on the health of humans and other animals — an opportunistic pathogen Cryptosporidium is a significant cause of diarrhoeal disease, principally in humans and livestock throughout the world. The clinical impact of the parasite is greatest in hosts whose rna helicase is suboptimal as it is in infants and young livestock, the elderly, or those impaired by disease or stress (Checkley et al., 2014; Fletcher et al., 2012; Thompson et al., 2005). In terms of control, there are different priorities in developed and developing countries. In the former, the need is for effective diagnosis and treatment for individuals and livestock, and the prevention of food and waterborne transmission, the latter being a significant economic issue for water utilities. In the developing world, the need is to lessen the burden of disease in those most at risk of infection, particularly children (Hotez et al., 2015; Savioli et al., 2006). Cryptosporidium has gone through two phases of emergence as a cause of intractable diarrhoea and mortality. The first phase was during the AIDS crisis of the 1980s, the second is current and is likely to have a longer-term impact. Cryptosporidium is now recognised as a major contributor to diarrhoeal morbidity and mortality in children in the developing world, particularly Africa and South East Asia (Global Enterics Multisite Study (GEMS)1 and rna helicase Mal-ED2 epidemiological studies) (Kotloff et al., 2013; Mbae et al., 2013). These studies suggest that Cryptosporidium may be responsible for a significant number of cases of moderate-to-severe diarrhoea in children under two living in these regions. Although nitazoxanide is used to treat Cryptosporidium infections its efficacy in those most at-risk, malnourished children and the immunocompromised, is limited (Checkley et al., 2014). The lack of therapeutic interventions is exacerbated by the lack of prophylactic measures including a vaccine, as well as the fact that people in the developing world where infection with Cryptosporidium is frequent, are commonly infected with several other species of intestinal and systemic parasites (Thompson and Smith, 2011). More serious in the long term in such populations is the emerging spectre of HIV. HIV-positive children in Tanzania were found to be almost eight times more likely to have Cryptosporidium than those who were HIV-negative (Tellevik et al., 2015). A study among Kenyan children also found this association (Mbae et al., 2013) and Tumwine et al. (2005) found that HIV-positive Ugandan children with persistent diarrhoea were 18 times more likely to have Cryptosporidium than those who were HIV-negative.
    Problems of detection — molecular tools a revelation In the clinical laboratory, whether dealing with samples from humans, domestic animals, or wildlife, there continues to be a need for rapid, sensitive and specific diagnostic tools that can guide appropriate therapy (Fletcher et al., 2012; Smith et al., 2006). Current laboratory methods that rely on microscopic examination of faecal samples for detecting Cryptosporidium oocysts have suffered from the problem of distinguishing the parasite from other faecal components of similar size and shape such as yeasts and algae. A number of staining techniques have been developed. Some such as those using malachite green provide reliable and consistent results, but many others suffer from problems of sensitivity, specificity, and variable results between laboratories (Elliot et al., 1999). However, microscopy cannot differentiate between the oocysts of C. hominis, zoonotic species, and the many other species and genotypes of Cryptosporidium since they are all morphologically indistinguishable in terms of size and it is only the larger oocysts of C. andersoni and C. muris that can be reliably distinguished from Cryptosporidium of public health significance (Smith et al., 2007). Even when combined with immunofluorescence, microscopy is relatively insensitive and prone to ‘operator variability’. In contrast, a molecular approach offers greater sensitivity and specificity than traditional diagnostics reliant on microscopy.