Investigations into the role of carrier animals in the spread of contagious bovine pleuropneumonia.

An attempt was made to transmit contagious bovine pleuropneumonia (CBPP) from 22 animals recovered from artificial infection to healthy animals. Despite close contact and the imposition of a number of stresses no disease was transmitted. An unsuccessful attempt was made to reactivate old CBPP lesions by corticosteroid treatment, and by splenectomy. Four animals recovered from artificial infection did not become reinfected when put in contact with acute disease. Seven animals were reinoculated with Mycoplasmamycoides sub-species mycoides by endobronchial intubation. No clinical disease resulted. It is concluded that sequestra do not break down easily and that it is difficult to reinfect recovered animals. It is suggested that in field outbreaks of obscure origin, investigation should be thorough before it is concluded that an animal with an old sequestrum was responsible.