Slave Ship

Blurb

Slave Ship is a 1956 short science fiction novel by Frederik Pohl, originally serialized in Galaxy. The scene is a world in the throes of a low-intensity global war, which appears to be an amplified representation of the Vietnam War, 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 religion of Vietnamese origin. On the American side, 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.