Jaagsiekte sheep retrovirus Jaagsiekte sheep retrovirus Jaagsiekte sheep retrovirus (JSRV) is a betaretrovirus which is the causative agent of a contagious lung cancer in sheep, called ovine pulmonary adenocarcinoma. JSRV is the virus that is the cause of the contagious lung tumors in sheep called ovine pulmonary adenocarcinoma (OPA). The disease has also been called "jaagsiekte", after the Afrikaans words for "chase" ("jaag") and "sickness" ("siekte"), to describe the respiratory distress observed in an animal out of breath from being chased, indicating the breathing difficulty experienced by infected sheep. Transmission of virus is through aerosol spread between sheep. The exogenous infectious form of
Alternatives to animal testing Medical Experiments that despite the use of microdosing, "animal studies will still be required". Guiding principles for more ethical use of animals in testing are the Three Rs (3Rs) first described by Russell and Burch in 1959. These principles are now followed in many testing establishments worldwide. Cell culture can be an alternative to animal use in some cases. For example, cultured cells have been developed to create monoclonal antibodies; prior to this, production required animals to undergo a procedure likely to cause pain and distress. However, even though cell or tissue culture methods may reduce the number of experiments