Tick paralysis in bison, 1950s. Yearling bison being tended while lying paralysed. Five cows and six of the ten yearlings in this herd became paralysed within one day. All of them recovered. American bison (Bison bison), also known as buffalo, are found in limited numbers as both wildlife and livestock in the USA. Tick paralysis is a disease caused by ticks, but is not caused by a pathogen transmitted in the bite. Instead, it is caused by a neurotoxin that can be produced in a tick's salivary gland after several days of extended feeding. The patient normally recovers after removal of the tick. Photographed in 1951 as part of work by the Rocky Mountain Laboratory in Montana, USA.