Polymerase Chain Reaction (PCR) is a gene amplification tool that allows detection of tiny pieces of infectious agent genetic material (DNA) in a sample. It is a fast, sensitive and specific way of diagnosing infectious agents. The inventor of the PCR procedure received the Nobel Prize in 1993.

In basic terms, the procedure involves repetitive splitting and rejoining of chains of DNA through heating and cooling cycles. The process encourages the replication of segments of recognizable DNA, which can then be detected.

The most common indications for this test are horses with diarrhea or evidence of respiratory disease.

Samples are taken from the manure or rectum, or the respiratory tract, respectively. Swabs are taken of particular locations within the respiratory tract. Swabs or manure samples are provided to the lab in the case of diarrhea.

The EHV-1 PCR has recently been improved (Gluck Center) and is more reliable for differentiating the mutated strain of EHV-1, which causes neurologic disease from non-neuropathogenic EHV-1

A Strep equi equi PCR has been developed which is highly sensitive and specific in the identification of Strangles. This can be helpful for a quick differentiation in respiratory outbreaks.