The disease went by many names and people told different stories about it. Scientists called it aftosa, or foot-and-mouth disease. The other anglophone term, hoof-and-mouth disease, was more precise: cloven-hoofed animals carrying the virus typically foamed at the mouth, developed painful blisters, and lost weight. Some aborted and a handful – mainly newborn animals – died. US and Mexican officials argued that the disease was a “dread plague” – a terrifying and grave threat to national wellbeing, akin to floods, storms, or earthquakes.1 From 1947 to 1954 a bilateral commission waged a campaign across central Mexico against this dangerous enemy. Many Mexicans regarded the campaign as a farcical and cruel affair. Most animals seemed to recover quickly, and many farmers believed that the disease was simply a version of a mild, familiar illness which they called mal de yerba or mal de boca – grass or mouth sickness. Few had seen anything quite like the anti-aftosa campaign before: brigades of pith-helmeted veterinarians, cowhands, and soldiers who dressed in bizarre heavy rubber overalls, drove through the country in jeeps, personnel carriers, and souped-up former ambulances, traipsed over the sierra on horses or mules, or paddled along rivers in wooden canoes, imposing quarantine, exacting fines, and dousing farms with acrid chemicals. At the start of campaign, they corralled hundreds of thousands of cows, pigs, goats, and sheep and shot them dead. Compared to run-of-the mill robavacas – cattle rustlers – their motives were hard to understand. Unlike Santiago matamoros, Spain’s legendary Moor-slayer, these men seemed menacing but cowardly, even slightly ridiculous – mere matavacas, or cowkillers.2