In the film Conquest of the Planet of the Apes . it was explained that more than 18 years after the end of Escape from the Planet of the Apes , a disease killed the world 's cats and dogs , leaving humans with no pets .
Armando ( Ricardo Montalbán ) explains that in 1983 ( TWENTY years after the end of Escape from the Planet of the Apes , which was set two years ahead of its theatrical release date ) , a disease killed the world 's cats and dogs , leaving humans with no pets .
Conquest of the Planet of the Apes