Application of polymerase chain reaction to detect animals latently infected with agents of malignant catarrhal fever.

Oligonucleotide primers derived from alcelaphine herpesvirus 1 (AHV-1) isolate WC11 DNA, the first identified agent of malignant catarrhal fever (MCF), were used to assay blood lymphocyte DNA using the polymerase chain reaction (PCR). Multiple species of exotic ruminants were examined to determine the suitability of this technique for detecting animals that may be latently infected. To correlate the PCR results with those of serology, serum samples were obtained from each animal concurrently with lymphocyte collection and subjected to an AHV-1 virus-neutralization assay (VNA). A total of 86 MCF-susceptible animals were tested, and the results of the VNA and PCR assays were compared. PCR results were positive for 44 animals. Of these, 13 were positive by VNA. Animals positive by both VNA and PCR were all wildebeest, the asymptomatic carriers of AHV-1, confirming the ability of the primers to amplify AHV-1 sequence. Positive PCR results from species other than wildebeest may represent sequence amplified from viruses related to AHV-1, which may not induce antibodies capable of neutralizing the WC11 isolate used in the VNA. This study demonstrates that PCR is capable of detecting the presence of MCF agents in various populations of captive ruminants prior to the appearance of clinical MCF so that the sources of infection can be more reliably ascertained.