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 welfare in the United States Animal welfare in the United States Animal welfare in the United States relates to the treatment of non-human animals in fields such as agriculture, hunting, medical testing and the domestic ownership of animals. It is distinct from animal conservation. The first known animal welfare laws in North America were regulations against "Tirranny or Crueltie" toward domestic animals included in the 1641 Massachusetts Body of Liberties. Starting in the late 1820s, a number of states passed anti-cruelty statutes. Many of these exempted animals used in experiments, and only twice were they invoked on behalf of animals. The first Humane Societies and