Slave Ship is a 1956 science fiction novel by Frederik Pohl, initially serialized in Galaxy Science Fiction. The story is set is a world in the throes of a low-intensity global war, which appears to be an amplified representation of the War in Vietnam, in which the U.S. was just beginning to be involved. The plot involves telepathy, speaking to animals, and, in the last few pages, an invasion by extraterrestrials.
The nominal adversaries in the novel are known as "cow-dyes", a corruption of Caodai,a syncretic religion in southern Vietnam. Telepaths, who are used in espionage and other covert activities, are falling victim to "the glotch", a fatal affliction which is believed to be a Caodai bio-weapon, transmitted telepathically.