Rhodococcus Equi: Clinical Manifestations, Virulence, and Immunity

The document from 2011 provides an in-depth analysis of Rhodococcus equi infections in foals, emphasizing the bacterium's ability to cause pyogranulomatous pneumonia, which is a major health concern for young foals, with clinical signs typically appearing between 3 and 24 weeks of age. It details the virulence mechanisms of R. equi, particularly the role of the virulence-associated protein A (VapA) and the pathogen's ability to replicate within macrophages by preventing phagosome maturation. The document also explores the immune response to R. equi, noting that specific antibodies and reactive intermediates are crucial for clearing the infection, and that neonatal foals are particularly susceptible due to their immature immune systems. Despite the challenges in vaccine development, the document reports on various immunization strategies, including the potential of DNA vaccines and live-attenuated vaccines, and highlights the need for further research to identify protective antigens and develop an effective vaccine for R. equi pneumonia in foals.