Postcolonial Ecologies of Parasite and Host: Making Parasitism Cosmopolitan

Cycles and circulation: a theme in the history of biology and medicine

We invite systematic consideration of the metaphors of cycles and circulation as a long-term theme in the history of the life and environmental sciences and medicine. Ubiquitous in ancient religious and philosophical traditions, especially in representing the seasons and the motions of celestial bodies, circles once symbolized perfection. Over the centuries cyclic images in western medicine, natural philosophy, natural history and eventually biology gained independence from cosmology and theology and came to depend less on strictly circular forms. As potent 'canonical icons', cycles also interacted with representations of linear and irreversible change, including arrows, arcs, scales, series and trees, as in theories of the Earth and of evolution. In modern times life cycles and reproductive cycles have often been held to characterize life, in some cases especially female life, while human efforts selectively to foster and disrupt these cycles have harnessed their productivity in medicine and agriculture. But strong cyclic metaphors have continued to link physiology and climatology, medicine and economics, and biology and manufacturing, notably through the relations between land, food and population. From the grand nineteenth-century transformations of matter to systems ecology, the circulation of molecules through organic and inorganic compartments has posed the problem of maintaining identity in the face of flux and highlights the seductive ability of cyclic schemes to imply closure where no original state was in fact restored. More concerted attention to cycles and circulation will enrich analyses of the power of metaphors to naturalize understandings of life and their shaping by practical interests and political imaginations.

Introduction: microbes, networks, knowledge-disease ecology and emerging infectious diseases in time of COVID-19

This is an introduction to the topical collection Microbes, Networks, Knowledge: Disease Ecology in the twentieth Century, based on a workshop held at Queen Mary, University London on July 6-7 2016. More than twenty years ago, historian of science and medicine Andrew Mendelsohn asked, "Where did the modern, ecological understanding of epidemic disease come from?" Moving beyond Mendelsohn's answer, this collection of new essays considers the global history of disease ecology in the past century and shows how epidemics and pandemics have made "microbes complex".

'Birth, life, and death of infectious diseases': Charles Nicolle (1866-1936) and the invention of medical ecology in France

In teasing out the diverse origins of our "modern, ecological understanding of epidemic disease" (Mendelsohn, in: Lawrence and Weisz (eds) Greater than the parts: holism in biomedicine, 1920-1950, Oxford University Press, Oxford, 1998), historians have downplayed the importance of parasitology in the development of a natural history perspective on disease. The present article reassesses the significance of parasitology for the "invention" of medical ecology in post-war France. Focussing on the works of microbiologist Charles Nicolle (1866-1936) and on that of physician and zoologist Hervé Harant (1901-1986), I argue that French "medical ecology" was not professionally (or cognitively) insulated from some major trends in parasitology, especially in Tunis where disciplinary borders in the medical sciences collapsed. This argument supports the claim that ecological perspectives of disease developed in colonial context (Anderson in Osiris 19: 39-61, 2004) but I show that parasitologists such as Harant built on the works of medical geographers who had called attention to the dynamic and complex biological relations between health and environment in fashioning the field of medical ecology in the mid-1950s. As the network of scientists who contributed to the global emergence of "disease ecology" is widening, both medical geography and parasitology stand out as relevant sites of inquiries for a broader historical understanding of the multiple "ecological visions" in twentieth-century biomedical sciences.

René Dubos, tuberculosis, and the "ecological facets of virulence"

Reflecting on his scientific career toward the end of his life, the French-educated medical researcher René Dubos presented his flowering as an ecological thinker as a story of linear progression-the inevitable product of the intellectual seeds planted in his youth. But how much store should we set by Dubos's account of his ecological journey? Resisting retrospective biographical readings, this paper seeks to relate the development of Dubos's ecological ideas to his experimental practices and his career as a laboratory researcher. In particular, I focus on Dubos's studies of tuberculosis at the Rockefeller Institute in the period 1944-1956-studies which began with an inquiry into the tubercle bacillus and the physiochemical determinants of virulence, but which soon encompassed a wider investigation of the influence of environmental forces and host-parasite interactions on susceptibility and resistance to infection in animal models. At the same time, through a close reading of Dubos's scientific papers and correspondence, I show how he both drew on and distinguished his ecological ideas from those of other medical researchers such as Theobald Smith, Frank Macfarlane Burnet, and Frank Fenner. However, whereas Burnet and Fenner tended to view ecological interactions at the level of populations, Dubos focused on the interface of hosts and parasites in the physiological environments of individuals. The result was that although Dubos never fully engaged with the science of ecology, he was able to incorporate ecological ideas into his thought and practices, and relate them to his holistic views on health and the natural harmony of man and his environment.

Nowhere to run, rabbit: the cold-war calculus of disease ecology

During the cold war, Frank Fenner (protégé of Macfarlane Burnet and René Dubos) and Francis Ratcliffe (associate of A. J. Nicholson and student of Charles Elton) studied mathematically the coevolution of host resistance and parasite virulence when myxomatosis was unleashed on Australia's rabbit population. Later, Robert May called Fenner the "real hero" of disease ecology for his mathematical modeling of the epidemic. While Ratcliffe came from a tradition of animal ecology, Fenner developed an ecological orientation in World War II through his work on malaria control (with Ratcliffe and Ian Mackerras, among others)-that is, through studies of tropical medicine. This makes Fenner at least a partial exception to other senior disease ecologists in the region, most of whom learned their ecology from examining responses to agricultural challenges and animal husbandry problems in settler colonial society. Here I consider the local ecologies of knowledge in southeastern Australia during this period, and describe the particular cold-war intellectual niche that Fenner and Ratcliffe inhabited.

'Tipping the Balance': Karl Friedrich Meyer, Latent Infections, and the Birth of Modern Ideas of Disease Ecology

The Swiss-born medical researcher Karl Friedrich Meyer (1884-1974) is best known as a 'microbe hunter' who pioneered investigations into diseases at the intersection of animal and human health in California in the 1920s and 1930s. In particular, historians have singled out Meyer's 1931 Ludwig Hektoen Lecture in which he described the animal kingdom as a 'reservoir of disease' as a forerunner of 'one medicine' approaches to emerging zoonoses. In so doing, however, historians risk overlooking Meyer's other intellectual contributions. Developed in a series of papers from the mid-1930s onwards, these were ordered around the concept of latent infections and sought to link microbial behavior to broader bio-ecological, environmental, and social factors that impact hostpathogen interactions. In this respect Meyer-like the comparative pathologist Theobald Smith and the immunologist Frank Macfarlane Burnet-can be seen as a pioneer of modern ideas of disease ecology. However, while Burnet's and Smith's contributions to this scientific field have been widely acknowledged, Meyer's have been largely ignored. Drawing on Meyer's published writings and private correspondence, this paper aims to correct that lacuna while contributing to a reorientation of the historiography of bacteriological epidemiology. In particular I trace Meyer's intellectual exchanges with Smith, Burnet and the animal ecologist Charles Elton, over brucellosis, psittacosis and plague-exchanges that not only showed how environmental and ecological conditions could 'tip the balance' in favor of parasites but which transformed Meyer thinking about resistance to infection and disease.