How the Cows Turned Mad (review)

Transmissible spongiform encephalopathies—or prion diseases, as they often are called now—are fatal, subacute, degenerative diseases of the nervous system characterized by intracellular vacuoles in neural cells. These afflictions are caused by agents that lack a demonstrable nucleic acid and appear to arise from the abnormal folding of a normal host protein. The saga of these diseases is ripe with controversy and sensationalism. In the 1930s the claim of transmission of scrapie of sheep, the first prion disease, was met with great skepticism. Even after confirmation of transmission, fiery debates persisted for decades as to whether transmission in nature was based on genetics or infectivity.

The first human disease recognized to be a prion disease was kuru. In 1957 Carleton Gajdusek and Vincent Zigas described kuru among the Fore tribe of the Eastern Highlands of New Guinea; it reached an unprecedented epidemic intensity, was shown to be transmitted by ritual cannibalism, and was transmitted to nonhuman primates. The high drama of this disease led to great popular interest, despite its confinement to a distant geographic local and its subsequent disappearance. In 1967 a worldwide dementing illness, Creutzfeldt-Jakob disease, was similarly transmitted. Although we lack clues as to how it is usually induced in nature, a few cases are genetic (but nonetheless transmissible in the laboratory), and some cases have been transmitted by medical caregivers via contaminated neurosurgical tools, by the use of grafts of human dura, and, tragically, by giving growth hormone made from human pituitaries to young people with short stature.

During the 1980s and 1990s evidence grew for the lack of nucleic acid in the replication of prions, and this represented a dramatic affront to the central dogmas of biology. Then in 1985 the epidemic of bovine spongiform encephalopathy, mad cow disease, erupted in the United Kingdom. A massive and unforeseeable contamination of bovine and human food supplies led to hundreds of thousands of cattle deaths. The agent has crossed the species-barrier, and more than a hundred young people in the United Kingdom and small numbers in Europe have died of a variant of Creutzfeldt-Jakob disease. The social, political, and economic impacts of these epidemics have been enormous. The tales of mixed-up genes and infectious agents, of cannibalism, of incubation periods of up to forty years, of growth-hormone tragedies, and of contaminated food of cows and humans have made obvious grist for the tabloid press and sensational journalism.

Despite its title, which has the ring of a Sunday supplement, How the Cows Turned Mad is a thoughtful, accurate, and readable book covering the history of scrapie, kuru, Creutzfeldt-Jakob disease, and bovine spongiform encephalopathy. Maxime Schwartz is a molecular biologist and former head of the Institut Pasteur. He also is director of laboratories of the French agency for food safety. The early chapters trace the French and British farmers' early descriptions of scrapie, the original description of the spongiform changes by a French veterinary pathologist, and the initial transmission of scrapie by two French veterinarians. True to his origins, Schwartz also brings in Pasteur, and the classic controversy between spontaneous generation and microbial replication. A cautionary tale involves one of Pasteur's disciples who debunked a "spontaneous" outbreak of anthrax by showing that the fertilizer put on the farmer's fields the previous year had been made by a large company that included animal corpses in the fertilizer; this episode eerily portends the bone-meal from rendering plants that spread mad cow disease a century later.

The coverage of contemporary personalities in this book is even-handed; the unseemly elevation or vilification of investigators seen in some articles or books on this subject is avoided. A few prime characters are neglected: Shirley and Robert...