Stein M, Greenberg Z, Boaz M, Handzel ZT, Meshesha MK, Bentwich Z. The Role of Helminth Infection and Environment in the Development of Allergy: A Prospective Study of Newly-Arrived Ethiopian Immigrants in Israel.
PLoS Negl Trop Dis 2016;
10:e0004208. [PMID:
26752538 PMCID:
PMC4709081 DOI:
10.1371/journal.pntd.0004208]
[Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 10/12/2015] [Indexed: 12/23/2022] Open
Abstract
Helminth infection may be protective against allergy and account for the low prevalence of allergy in developing countries. We studied prospectively the prevalence of allergy in Ethiopian immigrants with heavy helminth infection on arrival in Israel, and again after a year of adjustment to an urban industrialized setting, to explore the roles of helminth infection, changed environment and background immunity on the manifestations of allergy. 126 newly arrived Ethiopian immigrants were studied at baseline and 115 after a year of follow up in Israel. Allergic symptoms, Skin prick tests (SPT), Tuberculin (PPD) skin tests, stool and blood samples were obtained for determining parasites, blood IgE and eosinophil levels, respectively. Anti-helminthic therapy was offered to the entire infected individuals, but only 50/108 (46.3%) took the medication. At baseline, there was a significant negative association between helminth infection and allergy, 4/18 (22.2%) of uninfected participants were allergic compared to 7/108 (6.5%) of helminth-infected participants (p = 0.028), as well as between helminth infection and SPT reactivity, 12/18 (66.6%) of uninfected participants compared to 43/108 (39.8%) of helminth-infected participants (p = 0.033). After one year, a significant general increase in allergy and SPT was observed. While only 11/126 (8.7%) were allergic at baseline, 30/115 (26.1%) became allergic at follow-up (p<0.0001), and while 55/126 (43.7%) were SPT+ at baseline, 79/115 (68.7%) became SPT+ at follow-up (p<0.001). A twofold increase in allergen sensitization was also observed after one year in Israel, particularly for dust mites, grasses and olive tree (p<0.001). These results show that: a) Helminth infection is significantly associated with low allergy and low SPT reactivity; b) One year after immigration to Israel, allergy and SPT reactivity increased significantly in all immigrants; c) Higher increases in positive SPT and allergy were observed after a year in the group that remained infected with helminths, even though they had a lowered helminth load; d) The reasons for the increased allergy one year after immigration needs further investigation but probably reflects the combined influence of the decreased helminth load and novel environmental factors.
The role of intestinal parasitic infections in allergy is of great interest since it has been suggested that they suppress the development of allergy. Urbanization has also been claimed to cause allergy because of air pollution and higher exposure to allergens. The present study took advantage of the special opportunity presented by the recent Ethiopian immigration to Israel in order to study this question. A cohort of newly arrived Ethiopian immigrants to Israel, highly infected with parasites, was studied prospectively for the presence of allergy and response to allergens on arrival and after a year of follow up in Israel. The results showed clearly a significant inverse association between the presence of parasitic infections and allergy on arrival, while after a year of living in Israel, accompanied by a lowered parasitic infection load, a general increase of allergy was observed in all immigrant groups, and not only in those that had parasitic infections on arrival. These results lend support to the suppressive effect of intestinal parasites on allergy, but suggest that additional factors, most probably environmental, also play a role in the generation of allergy.
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