Current concepts in the epizootiology, diagnosis, and economic importance of ovine progressive pneumonia in North America: A review

Lentiviruses, a genus of retroviruses, include the agents that cause ovine progressive pneumonia or maedi. Infection is characterized by long incubation periods and insidious, slowly progressive clinical courses resulting in chronic degenerative diseases. The ovine lentiviruses are widespread among sheep in North America, yet their significance to livestock production is currently not well defined. Lentiviruses persist and replicate in the presence of host specific immune responses and cause immune-mediated lesions in several organ systems. Due to this unusual relationship with their host, the diagnosis, control and treatment of these infections is difficult and expensive. Scientific studies on the biology of ovine lentiviruses (OvLV) and their complex relationship with the host are yielding new approaches to the detection of infected animals and methods for study of the epizootiology and control of OvLV-related diseases, We summarize some of the known biological properties of the virus, spectrum of clinical features of the diseases, current concepts of disease pathogenesis, economic importance, and strategies used to diagnose and control OvLV infections. (C) 1998 Elsevier Science B.V.