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The burden of infectious diseases decreased significantly throughout the 19th Century. Thus, despite increasing trends in the emergence of new infectious diseases in recent decades, their impact in terms of human mortality or morbidity remains low in Western and developed countries. Infectious diseases, however, continue to affect populations in developing countries.

The human species is the most parasitized animal species, with more than 1,400 species of infectious parasites and microbes. Over 60% of these parasitic species are of zoonotic origin, meaning that they originate from other wild or domestic animals.

The planet has entered a new geological era: the Anthropocene. Through its relationship with the planet, the human species has demonstrated its ability to modify major geochemical cycles, the climate and the biosphere. Human health has never been better than today, on average, thanks to improvements in public health that are associated with an increase in the wealth of nations. However, the corollary of this economic performance lies in its environmental impacts. The degradation in function of ecosystems because of agricultural intensification and widespread use of various biocides is cited as a factor that aggravates health risks. Changes and loss of biodiversity affect the epidemiological environment through the emergence or re-emergence of new infectious diseases and also non-communicable. Most ecosystems are considered to be more or less degraded, which increases insecurity and conflict. Human well-being is clearly dependent on good social relationships that are reflected in cognitive and affective ties to the natural habitat and the environment. There clearly exists a link between ecosystem health, well-being and human health.

In “An Essay on the Principle of Population” (1798), Thomas Malthus established one of the first scenarios that linked natural constraints (agricultural production) with demography and economic growth. This essay was an essential contribution not only to the development of economic theories but also to ecological and evolutionary theories with the concept of a limiting capacity within a given environment. The Malthusian view of human demography is at the core of the book by Ehrlich and Ehrlich “The Population Bomb”, which called for active control of births in order to avoid famine, resource depletion and corporate collapse.

Biodiversity is often presented as an essential source of pharmaceutical drugs and molecules in the agrochemical industry. The total number of natural plant products was estimated to be more than 500,000 by Mendelsohn and Balick with only 5,000 species of plants studied for their medical properties out of an estimated 350,000 to 400,000 species. The systematic search for natural products in bacterial microorganisms and filamentous fungi was subsequent to the development of penicillin and the golden age of antibiotic discovery.

Abiotic factors, climatic factors (such as temperature and rainfall) and biotic factors (such as population density and the structure of host communities and reservoirs) are essential variables in the transmission of infectious or parasitic agents.

The Rockefeller Foundation/Lancet Commission report on planetary health (2015) shows how improving human health has been primarily done to the detriment of the environment. The report highlights that global environmental change (including climate change, deforestation, land use change and loss of biodiversity) is a serious threat to human health. It proposes adopting the concept of planetary health, which is based on recognizing that human health depends on natural systems functioning properly. However, upon first inspection, the definitions of health and biodiversity do not show clear links between the two.

This chapter is not intended to be a summary of all the studies that exist on ethics, and even less is it intended to be a crash course on ethics in biodiversity and health. Instead, our aim is to open some avenues for reflection on the ethical implications of research in biodiversity and health. Recent health crises, such as the Ebola epidemic in West Africa, have often led to ethical debates when it comes to health interventions in times of crisis. These interventions tend to rely on forced quarantine or use of new vaccines that have not yet been registered or, for veterinary sanitary crises, on mass slaughter of infected and non-infected domestic or wild animals that are promulgated as a measure to eradicate infectious diseases. On the other hand, calls for “bioethics” or a “global health ethic” are not necessarily unanimous among ethicists.

The 1968 UNESCO Biosphere Conference (in partnership with the FAO, WHO and the UN) was the first intergovernmental conference to consider both human and health ecology from a scientific point of view. Thus, it has a leading role in addressing health issues related to ecological diversity on a global scale. It insists on the need for integrated, planned, multidisciplinary policy action for the use and conservation of natural resources within the framework of international cooperation.

As we have seen, there are many definitions of health and even the One Health approach calls on us to abandon a strictly anthropocentric vision of health in order to consider that health and human well-being depend on the health of all living things and that of the environment in general. Far from being restrictive, this approach calls for a much broader approach to health than just human health.

The common cat tapeworm Hydatigera taeniaeformis is a complex of three morphologically cryptic entities, which can be differentiated genetically. To clarify the biogeography and the host spectrum of the cryptic lineages, 150 specimens of H. taeniaeformis in various definitive and intermediate hosts from Eurasia, Africa and Australia were identified with DNA barcoding using partial mitochondrial cytochrome c oxidase subunit 1 gene sequences and compared with previously published data. Additional phylogenetic analyses of selected isolates were performed using nuclear DNA and mitochondrial genome sequences. Based on molecular data and morphological analysis, Hydatigera kamiyai n. sp. Iwaki is proposed for a cryptic lineage, which is predominantly northern Eurasian and uses mainly arvicoline rodents (voles) and mice of the genus Apodemus as intermediate hosts. Hydatigera taeniaeformis sensu stricto (s.s.) is restricted to murine rodents (rats and mice) as intermediate hosts. It probably originates from Asia but has spread worldwide. Despite remarkable genetic divergence between H. taeniaeformis s.s. and H. kamiyai, interspecific morphological differences are evident only in dimensions of rostellar hooks. The third cryptic lineage is closely related to H. kamiyai, but its taxonomic status remains unresolved due to limited morphological, molecular, biogeographical and ecological data. This Hydatigera sp. is confined to the Mediterranean and its intermediate hosts are unknown. Further studies are needed to classify Hydatigera sp. either as a distinct species or a variant of H. kamiyai. According to previously published limited data, all three entities occur in the Americas, probably due to human-mediated introductions. (C) 2016 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

A growing number of comparative analyses in the field of parasite evolution and ecology have used phylogenetically based comparative methods. However, the comparative approach has not been used much by parasitologists. We present the rationale for the use of phylogenetic information in comparative studies, and we illustrate the use of several phylogenetically based comparative methods with case studies in parasite evolutionary ecology. The independent contrasts method is the most popular one, but presents some problems for studying co-adaptation between host and parasite life traits. The eigenvector method has been recently proposed as a new method to estimate and correct for phylogenetic inertia. We illustrate this method with an investigation of patterns of helminth parasite species richness across mammalian host species. This method seems to perform well in situations where host and parasite phylogenies are not perfectly congruent, but one might still want to correct for the effects of both. Finally, we present a method recently proposed for variation partitioning in a phylogenetic context, i.e. the phylogenetically structured environmental variation.

Schistosoma bovis is a digenean platyhelminth that is responsible for a parasitic disease called schistosomiasis or bilharziasis in bovines. It has a natural wide mollusc intermediate host spectrum and is compatible, experimentally, with a wide range of species. Our working hypothesis is that the Mediterranean Sea and the Sahara were two physical barriers that could have separated the populations of S. bovis in three parts and may have played a role in gene flow. Experimental data were collected from earlier published studies, and the different intermediate host spectra and the mollusc-parasite geographical compatibilities were compared between the North Mediterranean zone, the South Mediterranean zone and the South Saharan zone. From our results, the three major groups of S. bovis populations that could be determined were the Iberian, the Mediterranean and the South Saharan populations. Our tested hypothesis was thus not confirmed concerning the Mediterranean sea barrier but was confirmed with the Saharan one. A paleogeographical scenario of S. bovis is proposed following three major steps from a South Saharan origin to a possible local adaptation of the parasite in the Iberian Peninsula.