ABSTRACT
Rhodococcus equi is an important cause of bronchopneumonia in 1to 6-month-old foals, being responsible for 3% of horse death in many countries of the world. It is an intracellular microorganism able to survive and to multiply inside macrophages. Three virulence levels have been identified in R. equi, by the presence of virulence associated antigens on the bacteria surface. Virulent strains have a plasmid encoding VapA protein and are isolated from diseased foals and some human patients. Intermediate virulent strains show VapB protein and are commonly found in swine and HIV infected patients. Avirulent strains do not show virulence antigens and are found in the environment and humans. The immature immune system is the major cause of the susceptibility of foals to the R. equi pneumonia. In humans, the infection routes are still unknown, but contact with horses is related with one-third of human infections. Due the clinical importance of the disease, diagnostic methods for early identification in animals are necessary, increasing the chances for treatment. The more common diagnostic methods are microbiologic culture, serologic tests and PCR techniques for 16S rDNA and vapA detection.
KEY WORDS
Rhodococcus equi
; pneumonia; foals; virulence