China 
Africa 
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Published in Jamie Bartram, Rachel Baum, Peter A. Coclanis, David M. Gute, David Kay, Stéphanie McFadyen, Katherine Pond, William Robertson, Michael J. Rouse, Routledge Handbook of Water and Health, 2015
All of the faecal–oral helminths in Table 4.1 are considered geohelminths because they can be present as helminth ova (eggs) in human faecal matter that has been deposited on the ground (Feachem et al., 1983; Baron, 1996). They can persist and remain infectious in moist soils, sometimes for years. After the faecally excreted eggs mature in the soil (in hours, days or weeks, depending on the helminth), human exposure typically occurs by the mature helminth larvae penetrating the skin (by walking barefoot or handling or otherwise coming in contact with faecally contaminated soil) or by ingestion of mature ova on faecally contaminated produce or in faecally contaminated water. The life cycle of the hookworms and roundworms typically involves the movement of the helminth larvae from the skin, through the bloodstream to the heart and lungs and then to the gastrointestinal tract by having been swallowed as larvae that migrated from the lungs to the throat. The hookworm Ancylostoma duodenale can also be transmitted through the ingestion of larvae. Heavy infestations with helminths can cause a range of adverse health effects, including abdominal pain, diarrhea, blood and protein loss, intestinal blockage, rectal prolapse, and impairment of physical and mental development in children. Helminth infections are widespread, especially in the developing world where hygiene and sanitation conditions are poor and there is extensive exposure to human faecal matter from environmental sources (Feachem et al., 1983; Baron, 1996). Although helminth infections are readily treatable, reinfection occurs commonly due to re-exposure from faecally contaminated environmental sources.
Xenobiotic metabolism and transport in Caenorhabditis elegans
Published in Journal of Toxicology and Environmental Health, Part B, 2021
Jessica H. Hartman, Samuel J. Widmayer, Christina M. Bergemann, Dillon E. King, Katherine S. Morton, Riccardo F. Romersi, Laura E. Jameson, Maxwell C. K. Leung, Erik C. Andersen, Stefan Taubert, Joel N. Meyer
Nematodes are incredibly ecologically diverse, either living freely in soils, freshwater, or seawater or as a parasites in plants or animals (De Ley 2006). The chemical exposure of nematodes is as diverse as their natural habitats. It includes organic compounds and minerals in soils (Ekschmitt and Korthals 2006), pesticides used in agriculture (Rich, Dunn, and Noling 2004), as well as defensive compounds secreted by bacteria, fungi, plants, and animals (de Veer, Kemp, and Meeusen 2007; Williamson and Kumar 2006). Some nematodes have evolved to survive desiccation and high salinity in extreme arid environments such as deserts (Treonis and Wall 2005). The panoply of abiotic and biotic stresses has likely contributed to the high abundance and diversity of many of the xenobiotic metabolism and transport-related gene classes discussed above. Even within a single species like C. elegans, the diversity of xenobiotic response genes is far larger than the suite of genes found in the lab-adapted strain N2 (https://www.biorxiv.org/content/10.1101/2020.07.23.218420v1.abstract). The power of C. elegans GWA mapping approaches might be expanded to related self-fertilizing species like Caenorhabditis briggsae and Caenorhabditis tropicalis, when reference genomes are completed and species-wide natural variation has been characterized. Comparative genetics and genomics across these three species will discover conserved Caenorhabditis toxin responses along with species-specific toxin responses. The conserved responses are more likely to be conserved with humans. To further supplement the comparative genetics and genomics approach, natural variation in toxin responses across nematode species beyond Caenorhabditis or even other invertebrate species (e.g., Drosophila melanogaster) need to be studied. The “worm community” has begun in-depth investigations of the biology of multiple related Caenorhabditis species (Elsworth, Wasmuth, and Blaxter 2011; Fitch 2005; Martin et al. 2015). However, the total number of nematode species is estimated at approximately one million (Kiontke and Fitch 2013), and only approximately 30,000 species have been described. A limited number of nematode species important in agriculture, biology, and medicine were also examined and provide a basis for comparison, including Ancylostoma duodenale (hookworm), Brugia malayi (Lymphatic filarial nematode), Meloidogyne incognita (root-knot nematode), and Steinernema carpocapsae (entomopathogenic nematode). As xenobiotic response loci are discovered in additional species, comparative approaches might increase in power and enable connections of discovered genes, pathways, and mechanisms to humans.