Ecology Drives the Worldwide Distribution of Human Diseases

Abstract

Identifying the factors underlying the origin and maintenance of the latitudinal diversity gradient is a central problem in ecology, but no consensus has emerged on which processes might generate this broad pattern. Interestingly, the vast majority of studies exploring the gradient have focused on free-living organisms, ignoring parasitic and infectious disease (PID) species. Here, we address the influence of environmental factors on the biological diversity of human pathogens and their global spatial organization. Using generalized linear multivariate models and Monte Carlo simulations, we conducted a series of comparative analyses to test the hypothesis that human PIDs exhibit the same global patterns of distribution as other taxonomic groups. We found a significant negative relationship between latitude and PID species richness, and a nested spatial organization, i.e., the accumulation of PID species with latitude, over large spatial scales. Additionally, our results show that climatic factors are of primary importance in explaining the link between latitude and the spatial pattern of human pathogens. Based on our findings, we propose that the global latitudinal species diversity gradient might be generated in large part by biotic interactions, providing strong support for the idea that current estimates of species diversity are substantially underestimated. When parasites and pathogens are included, estimates of total species diversity may increase by more than an order of magnitude.

Signatures of strong population differentiation shape extended haplotypes across the human CD28 , CTLA4 , and ICOS costimulatory genes

“…One can envision that new selective influences, appearing after the migration out of Africa, would operate on the extended haplotypes that carried ICOSp.h4 in a subdivided ancestral population (29). Human populations migrating from the predominantly tropical environment of Africa to quite different climates would have faced a very different range of environmental challenges, with a reduced parasitic load at increasing latitudes (30). One may speculate that signatures of adaptation to these varying challenges would be reflected in the pattern of variability at the costimulatory receptor region, because these genes control the intensity and ''flavor'' of immune responses.…”

Gloger's rule in North American Barn Owls

“…Second, animals may be darker in wetter habitats because melanin pigments play a role in thermoregulation, or because heavily pigmented feathers repel water better, allowing the body to dry more rapidly (Heppner 1970, Walsberg et al 1978, Burtt 1981, ClusellaTrullas et al 2008. Third, melanin pigments may protect the integument against ectoparasites (Ruiz- De-Castañeda et al 2012) and bacteria (Burtt andIchida 2004, Goldstein et al 2004) that thrive in warm and humid habitats (Guernier et al 2004). Finally, melanin pigments improve hardness of the feathers and hence protect them against abrasion (Bonser and Witter 1993), which might be more pronounced in warm and humid areas.…”

Economic inequality caused by feedbacks between poverty and the dynamics of a rare tropical disease: the case of Buruli ulcer in sub-Saharan Africa

“…However, more than 1 billion people, most of them in tropical and subtropical countries, continue to suffer a disproportionate burden of disease and poverty [2,3]. Although the global distribution of communicable diseases can be partly explained by a gradient in climatic and biological factors [4,5], there is a growing focus on potential reinforcing feedback mechanisms between ecology, disease and economics, for explaining the distribution of both poverty and disease [6]. Households and individuals need economic resources to reduce their exposure to infectious diseases and to access quality healthcare [7,8].…”