Pliny the Elder [1st century CE] (Natural History, Book 11, 40): There is an animal belonging to the same season that always lives with its head fixed in the blood of a host, and consequently goes on swelling, as it is the only animal that has no vent for its food: with gorging to excess it bursts, so dying of its very nutriment. This creature never grows in cart horses but occurs frequently in oxen and occasionally in dogs, in which all creatures breed, whereas this alone occurs in sheep and goats. - [Rackham translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Worms 9.21): The tick engulas is a worm that has its name from its nature. For, as Pliny says, it is an animal that has its head always in blood, and constantly sucking it swells up so that it bursts in the middle; for it does not have a vent for superfluous food. By some it is called a 'wild louse' [pediculus silvestris]; some, however, call it a tick [theca = caeca, tick]. In cattle - that is, the ox - they are never born; but they are in wolves, and frequently in dogs. - [Badke translation/paraphrase]