Ever since Louis Pasteur saved the French silk industry by identifying a disease affecting silkworms, scientists have focused their attention on smaller and smaller organisms. Once upon a time, the rhinoceros beetle threatened the coconut plantations of Polynesia until scientists discovered the virus that would control it. In more modern times, the first experimental vaccine for HIV was produced using recombinant baculovirus introduced into insect eggs. Meanwhile, soybeans, corn, and cotton are protected from insects by genes from one insecticidal bacterium, Bacillus thuringiensis—and a related strain might hold clues for combating West Nile virus and malaria.

In this book, Elizabeth Davidson shares amazing stories about diseases of insects and other invertebrates important to people—and about the scientists who learned to use those diseases to control pests and create products beneficial to humans. Focusing on insect-microbial interactions crucial to public health, she tells detective stories ranging across global history, from the silkworm farms of nineteenth-century Japan to the research labs of modern America. In these fascinating accounts, Davidson shows us how human health often comes down to a contest of bug against bug. Even habitats seething with bacteria, such as the runoff from cattle farms or sewage treatment plants, are also teeming with invertebrate life—animals that, like ourselves, have ways of fighting infection.

Scientific curiosity about what allows creatures as simple as water fleas to survive in such polluted environments has led to the discovery of chemicals with remarkable properties and potential usefulness to humankind. From diseases of shellfish to parasites of bees, Davidson opens a window on a world most of us never stop to consider—but which matters to all of us more than we might ever imagine. In our present era of pandemic scares, Big Fleas Have Little Fleas is a sweeping historical review that’s as timely as tomorrow’s headlines, showing us that the most exciting discoveries can emerge from the smallest sources.