The biodiversity hypothesis and allergic disease: world allergy organization position statement

Abstract

Biodiversity loss and climate change secondary to human activities are now being associated with various adverse health effects. However, less attention is being paid to the effects of biodiversity loss on environmental and commensal (indigenous) microbiotas. Metagenomic and other studies of healthy and diseased individuals reveal that reduced biodiversity and alterations in the composition of the gut and skin microbiota are associated with various inflammatory conditions, including asthma, allergic and inflammatory bowel diseases (IBD), type1 diabetes, and obesity. Altered indigenous microbiota and the general microbial deprivation characterizing the lifestyle of urban people in affluent countries appear to be risk factors for immune dysregulation and impaired tolerance. The risk is further enhanced by physical inactivity and a western diet poor in fresh fruit and vegetables, which may act in synergy with dysbiosis of the gut flora. Studies of immigrants moving from non-affluent to affluent regions indicate that tolerance mechanisms can rapidly become impaired in microbe-poor environments. The data on microbial deprivation and immune dysfunction as they relate to biodiversity loss are evaluated in this Statement of World Allergy Organization (WAO). We propose that biodiversity, the variability among living organisms from all sources are closely related, at both the macro- and micro-levels. Loss of the macrodiversity is associated with shrinking of the microdiversity, which is associated with alterations of the indigenous microbiota. Data on behavioural means to induce tolerance are outlined and a proposal made for a Global Allergy Plan to prevent and reduce the global allergy burden for affected individuals and the societies in which they live.

Figure 1

Two global megatrends in biodiversity and public health. (a) Declining biodiversity (percentage change) since 1970 as measured by two indices. WPSI=Waterbird Population Status Index; LPI=Living Planet Index [14]. (b) Increasing trends in the prevalence of inflammatory civilization diseases, asthma and allergic rhinitis among military conscripts in 1966-2003 [165] as an example (modified from ref. [14]).

Figure 2

Trends in a) prevalence of asthma and allergic rhinitis [165], b) incidence of pediatric inflammatory bowel disease [59], c) incidence of colon and rectum cancer [168], and d) prevalence of coeliac disease and type 1 diabetes [166], e) incidence of Wegener’s granulomatosis [167], and f) incidence of non-Hodgkin’s lymphoma in Finland in 1950-2009 [168].

Figure 3

Tolerance can be endorsed by behavioral means including physical training, consumption of healthy diet and doing activities in natural environments. These things should be included also in secondary prevention together with specific immunotherapy. Unspecific and specific means to endorse tolerance act in synergy. Natural Killer (NK) cells and Natural Killer T (NKT) cells share characteristics of both innate and acquired immunity. SIT=Specific Immunotherapy, SLIT=Specific Oral Immunotherapy.

Figure 4

A variety of age-dependent and organ specific clinical allergic manifestations - which often occur together in the same predisposed individuals - contribute to the growing global allergy burden.

Figure 5

The interactions, “cross-talk” of the three cellular DNA compartments determines human survival.