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Parasite Versus Host: Pathology and Disease
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
The apparent link between infection with certain parasites and a reduction in the severity of certain medical conditions has given rise to what seems oxymoronic—helminth therapy: the deliberate infection of patients with specific intestinal nematodes to alleviate symptoms of certain clinical conditions. To date, most research and treatment has focused on the hookworm Necator americanus and especially on the pig whipworm, Trichuris suis (Figure 5.26). Although the logic of helminth therapy may make sense, clinical trials have provided mixed results. In some cases, individuals have clearly benefited, seeing reducing symptomology for conditions such as inflammatory bowel disease, multiple sclerosis, eczema and hay fever. And although there is a general trend in these trials toward some patient improvement, the data supporting the deliberate infection of individuals to treat medical conditions has not been overly compelling.
Control of Human Intestinal Nematode Infections
Published in Max J. Miller, E. J. Love, Parasitic Diseases: Treatment and Control, 2020
This is a major cause of anemia in tropical countries. The infection is soil-transmitted by infective larvae of Ancylostoma duodenale (“Old World hookworm” or Necator americanus (“New World hookworm”) penetrating the human skin. The adult nematodes are firmly attached to the mucosal wall of the upper jejunum on which they “graze.” Proper disposal of infectious human feces, the wearing of shoes, and other hygienic measures designed to prevent infection have been shown to be capable of eradicating this infection wherever they have been systematically implemented, e.g., in European mines. The deplorable fact that a considerable part of the world population is still suffering from hookworm infection illustrates again how difficult it is to implement this prophylactic strategy on a large scale in tropical developing countries. As with ascariasis, one practical way to control ankylostomiasis and necatoriasis in these countries is chemotherapy. In view of the fact that most patients are likely to also carry several ascaris worms in their gut, this type of periodical mass treatment in endemic tropical areas should be done with a broad-spectrum drug. The beneficial effects of this type of chemotherapy on the growth, morbidity, and mortality of children in particular and on the socio-economic development of large tropical developing areas in general would be enormous.
Infectious diseases (and tropical medicine and sexually transmitted diseases)
Published in Shibley Rahman, Avinash Sharma, A Complete MRCP(UK) Parts 1 and 2 Written Examination Revision Guide, 2018
Shibley Rahman, Avinash Sharma
Severe infection with either Ancylostoma duodenale or Necator americanus may produce pneumonitis (‘Loeffler-like syndrome’) that manifests as cough, fever and malaise. As worms mature in the jejunum, patients may experience diarrhoea, vague abdominal pain, colic and/or nausea.
Dynamics of the bacterial gut microbiota during controlled human infection with Necator americanus larvae
Published in Gut Microbes, 2020
Q. R. Ducarmon, M. A. Hoogerwerf, J. J. Janse, A. R. Geelen, J. P. R. Koopman, R. D. Zwittink, J. J. Goeman, E. J. Kuijper, M. Roestenberg
Helminths such as hookworms can have beneficial effects on auto-immune diseases1,2 such as celiac disease,3,4 but also cause eosinophilic gastroenteritis, anemia and protein loss and are therefore responsible for a high burden of disease in low- and middle-income countries.5 As a part of the human gut microbiome in developing countries with a high rate of hookworm infections, hookworms can exert evolutionary pressure on the bacterial gut ecosystem through intestinal motility, mucin glycosylation, mucus secretion, epithelial damage and worm products.6 For example, several helminths and their products have been shown to increase permeability of monolayers in cell culture.7,8 In addition, worm products can have direct antibacterial activity, thereby having the potential to directly alter the bacterial gut microbiota.9,10 However, the complex interplay between hookworms such as Necator americanus and the bacterial microbiota is largely unknown.
Investigational drug therapies for coeliac disease – where to from here?
Published in Expert Opinion on Investigational Drugs, 2018
James Haridy, Diana Lewis, Evan D. Newnham
The ‘hygiene hypothesis’ postulates the rise in autoimmune and immune-mediated diseases in developed countries is in part related to the reduction in infectious disease exposure, particularly in childhood [52]. Epidemiologic studies suggest that a major factor includes the dramatic reduction in helminth infections [53]. Animal and human models have demonstrated reduced autoantigen-specific responses and attenuated response in both autoimmune liver disease and IBD [54–56]. An initial Phase 2 double-blinded placebo-controlled study of 20 patients infected with necator americanus for 21 weeks did not improve histological or patient-reported outcomes [57]. Immunological data this study was encouraging, displaying suppression of intestinal inflammatory cytokine production and possibly modulating T-helper cell responses [58]. This led to a second non-blinded nor placebo-controlled 52-week study of 12 of the same subjects with lower levels of gluten challenge. The study noted a paradoxical decline in mean TG2 IgA titers upon exposure to 3g of gluten daily, and there was no alteration in villous height to crypt depth ratio in those exposed to 1g gluten daily. Patient-reported outcomes were not significantly improved [59]. It is difficult to draw sufficient conclusions based on current data. However, a further Phase 2 trial is currently underway with necator americanus on a larger sample population.
Historical analysis of inverse correlation between soil-transmitted helminthiasis and pancreatic cancer
Published in Baylor University Medical Center Proceedings, 2021
Soil-transmitted helminths, which include Ancylostoma duodenale and Necator americanus (hookworms), Ascaris lumbricoides (roundworms), Trichuris trichiura (whipworms), and Strongyloides stercoralis (threadworms), are transmitted by eggs passed in the feces of infected humans. In regions that lack adequate sanitation (e.g., widespread open defecation, septic tank overflow), these eggs contaminate soil and freshwater sources. Larvae penetrate the skin of those walking barefoot on contaminated soil. Thus, areas lacking in hygiene and sanitation, proper sewage removal, and treatment systems are commonly endemic to STH.5