Rhodococcus equi pnemonia is an insidious disease of foals–by the time one sees clinical signs, the pnemonia can be well advanced. Thus, tests that have greater sensitivity for R. equi are needed because they might permit earlier diagnosis.

Texas A&M researchers have described a test that could detect and quantitate virulent R. equi faster than previous tests. The test is based on a technique called quantitative polymerase chain reaction, or QPCR.

The polymerase chain reaction test (PCR) allows a very small segment of DNA from a specific gene to be copied millions of times, until it can be detected in the sample. The QPCR also allows for a specific gene to be copied out of a biological sample such as tracheobronchial fluid. That gene can be verified as having the DNA of a certain bacterium, and unlike standard PCR, quantified within the sample.

This R. equi QPCR test was found to be highly sensitive for detecting the vapA gene, which codes for “virulence associated protein.” R. equi’s ability to cause disease depends on the presen ce of vapA. The test was highly specific (able to differentiate virulent R. equi from other strains). Results suggest that QPCR is a valuable test for rapid diagnosis of R. equi in foals