Influence of Parasitic Worm Infections on Allergy Diagnosis in Sub-Saharan Africa

Abstract

Epidemiological studies from Sub-Saharan Africa indicate that allergies are on the rise in this region especially in urban compared to rural areas. This increase has been linked to improved hygiene, lifestyle changes, and lower exposure to pathogens in childhood. Reduced exposure to parasitic worm (helminth) infections and allergy outcomes has been the focus of a number of population studies over the years. Paradoxically, there are parallels in the immune responses to helminths and to allergies. Both conditions are associated with elevated levels of immunoglobulin E, high numbers of T helper 2 cells, eosinophils, and mast cells. These immune parallels have meant that the diagnosis of allergies in parts of the world where helminths are endemic can be hampered. The aim of this review is to examine observations from population studies conducted in Sub-Saharan Africa that demonstrate how helminth infections influence the parameters used to diagnose allergy outcomes in this region. We explore specifically how helminth infections hinder the in vitro diagnosis of allergic sensitization, influence the clinical manifestations of allergy, and also the effect of anthelmintic treatment on allergy outcomes. Advancing our understanding of how helminths influence allergy diagnosis is imperative for the development of improved tools to assess, diagnose, and treat allergic disorders in both helminth-endemic and non-endemic countries worldwide.

AllergoOncology: ultra-low IgE, a potential novel biomarker in cancer—a Position Paper of the European Academy of Allergy and Clinical Immunology (EAACI)

“…Some studies defined IgE values of 100-1000kU/L as "high IgE level", and IgE ≥ 1000 kU/L as "very high" [32][33][34]. Very low or absent IgE levels may be found in patients with allergic rhinitis-, chronic sinusitis-like symptoms and asthma [32,36,37,58] Cannot exclude atopic/allergic or parasitic conditions Biomarker for atopy/allergy [29,44,45,53,55], parasitosis [71][72][73] Might potentially be used as a marker for higher cancer susceptibility [32][33][34] Some patients with normal IgE levels may have higher rates of malignancy [18,20] In general, elevated IgE levels are associated with lower rates and risk for malignancy [17,20,21,142]. Very high and extremely high total serum IgE levels are seen in certain malignancies such as lymphoma [146] and IgE myeloma [147] May be a sensitive and specific marker for CVID (Common Variable Immunodeficiency) when there is high suspicion for primary humoral deficiency [38] Cannot exclude immunodeficiency Elevated IgE levels may raise suspicion for certain immunodeficiencies in appropriate patients (e.g.…”

“…Similarly to the atopic/allergic status, the response to parasitic infections is also associated with the induction of strong Th2 immune responses, leading to eosinophilia, elevated Th2 cytokines and increased serum IgE (e.g. in a cohort of patients with Ascaris infection, total IgE levels reached 13,000 kU/L) [71, 72 ]. Moreover, total IgE levels significantly decrease after treatment for E. histolytica, H. nana or A. lumbricoides [73 ].…”

Phenotypic characteristics and asthma severity in an East African cohort of adults and adolescents with asthma: findings from the African severe asthma project

“…We demonstrate similar findings with a high prevalence of allergic and eosinophilic inflammation that is notably most prominent in severe asthma which was associated with elevated eosinophils and FeNO levels. Interestingly, the prevalence of HIV and the presence of parasitic infection was very low in this cohort, thus ensuring that these potential confounders of eosinophilia did not impact the high prevalence rates noted in the cohort 36. The high rates of allergic sensitisation may be a result of geographical location, as the study sites were in large urban areas where exposure to allergens is higher.…”

Worms: Pernicious parasites or allies against allergies?

“…Allergen‐specific IgE is the defining characteristic of atopy, and in high‐income countries, allergen‐specific IgE strongly correlates with functional allergy measured by SPT reactivity. However, in helminth‐endemic areas (especially rural areas of low socioeconomic status), this relationship often breaks down . Furthermore, multiple epidemiological studies have shown a positive association between antihelminth IgE (ascariasis, schistosomiasis, filariasis) and wheeze and/or atopy .…”

“…Therefore, these cross‐reactive responses have the potential to block clinical responses to allergens like peanut . Further studies are needed to clarify whether high levels of circulating cross‐reactive protein or carbohydrate‐specific IgE are instrumental in inducing or preventing allergic (skin) reactivity …”