Parasitic worm
Parasitic worms, also known as helminths,[1] are a polyphyletic group of large macroparasites; adults can generally be seen with the naked eye.
[10] Helminths of importance in the sanitation field are the human parasites, and are classified as Nemathelminthes (nematodes) and Platyhelminthes, depending on whether they possess a round or flattened body, respectively.
This lifetime of several years is a result of their ability to manipulate the immune response of their hosts by secreting immunomodulatory products.
The frequency of egg deposition from an adult helminth is generally daily, and can occur up to six times per day for some Taenia species.
[15] Helminth eggs remain viable for 1–2 months in crops and for many months in soil, fresh water, and sewage, or even for several years in feces, fecal sludge (historically called night soil), and sewage sludge – a period that is much longer compared to other microorganisms.
[31] Scientists are looking for a connection between the prevention and control of parasitic worms and the increase in allergies such as hay-fever in developed countries.
[32] Parasitic worms may be able to damp down the immune system of their host, making it easier for them to live in the intestine without coming under attack.
[citation needed] One study suggests a link between the rising rates of metabolic syndrome in the developed worlds and the largely successful efforts of Westerners to eliminate intestinal parasites.
The work suggests eosinophils (a type of white blood cell) in fat tissue play an important role in preventing insulin resistance by secreting interleukin 4, which in turn switches macrophages into "alternative activation".
In the study, the authors fed rodents a high-fat diet to induce metabolic syndrome, and then injected them with helminths.
[citation needed] Helminth eggs can reach the soil when polluted wastewater, sewage sludge or human waste are used as fertilizer.
Therefore, the risk of using contaminated wastewater and sludge in agricultural fields is a real problem, especially in poor countries, where this practice is prevalent.
[citation needed] Due to this strong shell, helminth eggs or ova remain viable in soil, fresh water and sewage for many months.
[37][38] Therefore, waste stabilization ponds (lagoons), storage basins, constructed wetlands, rapid filtration or upflow anaerobic sludge blanket (UASB) reactors can be used.
[citation needed] Helminth ova can be inactivated in sewage sludge treatment if the temperature is increased over 40 °C or moisture is reduced to less than 5%.
[39] Details about the contact time under these conditions and other related environmental factors are generally not well-defined for every type of helminth egg species.
[43] Ascaris and whipworm that are identified in reusable wastewater systems can cause certain diseases and complications if ingested by humans and pigs.
[45] The presence or absence of viable helminth eggs ("viable" meaning that a larva would be able to hatch from the egg) in a sample of dried fecal matter, compost or fecal sludge is often used to assess the efficiency of diverse wastewater and sludge treatment processes in terms of pathogen removal.
[46] For the purpose of setting treatment standards and reuse legislation, it is important to be able to determine the amount of helminth eggs in an environmental sample with some accuracy.
The detection of viable helminth eggs in samples of wastewater, sludge or fresh feces (as a diagnostic tool for the infection helminthiasis) is not straight forward.
