Ovine pulmonary adenocarcinoma be predisposed to OPA. Most affected sheep show signs at 2 to 4 years of age. OPA is not a notifiable disease, and therefore it is difficult to assess its prevalence. OPA was first described in the UK in 1888, and described in detail in South Africa in 1891. The disease was initially known as "jaagsiekte" , a word derived from Afrikaans, meaning "chasing sickness," so called because animals are in respiratory distress as if they are out of breath from being chased. It has also been known as sheep pulmonary adenomatosis and ovine pulmonary carcinoma. OPA has been used
Animal People "Animal People News", which covered current events related to animal issues worldwide. The newspaper was retired in 2014 following a split within the board of directors, and in 2015 Animal People launched a new project, the Animal People Forum, an online magazine and social networking site for people interested in animal rights, welfare, and conservation. Kim Bartlett was hired as editor of "The Animals' Agenda" news magazine in August 1986, where Patrice Greanville was already associate editor. Merritt Clifton had been freelancing for "The Animals' Agenda", and was hired by Bartlett and Greanville as the feature writer in November 1986.