From a genomic library previously constructed from a lymphoblastoid cell line (LCL) propagated from a bovine case of sheep-associated malignant catarrhal fever (SA-MCF), caused by ovine herpesvirus-2 (OHV-2), several OHV-2 clones were identified and characterised by hybridisation using probes from the unique region of the Alcelaphine herpesvirus-1 (AVH-1) genome. Nucleotide sequence from one clone was generated and the predicted amino acid sequence was found to contain regions of homology with the 140 and 160 kDa tegument proteins of Epstein-Barr virus and herpesvirus saimiri respectively. Oligonucleotide primers were constructed and a polymerase chain reaction (PCR) test was developed for the detection of OHV-2 viral DNA. Amplified product was identified by restriction with RsaI and BmyI. The primers were highly specific for OHV-2 DNA with a limit of detection of 6.4 pg of genomic DNA derived from the parent LCL. This was estimated to correspond to one diploid bovine cell. The PCR was successfully applied to detect OHV-2 DNA in peripheral blood leucocytes (pbl) from clinical cases of SA-MCF and normal sheep.

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Analysis of the genomic DNAs of chlamydial isolates from sheep, cattle, and pigs was performed by Southern blot hybridization and by restriction endonuclease (RE) profiling of DNA amplified by PCR. The hybridization probes were derived from whole genomic DNA, the major outer membrane protein (MOMP) gene, the 16s rRNA gene, and an avian Chlamydia psittaci isolate plasmid. The PCR analysis used targets in the MOMP gene, the 16s rRNA gene, and the 60-kDa cysteine-rich protein gene. Together, the results showed that although there was considerable heterogeneity in the DNA sequence in the MOMP gene region, all the isolates had the same underlying total genomic RE profiles and yielded identical RE profiles for the rRNA and 60-kDa-protein gene regions. Most of the isolates were found to hybridize with the plasmid probe. Comparison of the MOMP sequence of one of the isolates (P787) with that of a known Chlamydia pecorum strain together with the results of the RE analyses allowed the conclusion that the isolates should all be classified within this new species.The genus chlamydia has recently been expanded, largely because of the application of measurements of genomic relatedness to discriminate further the various chlamydial species and types. Currently, there are four species recognized, Chlamydia trachomatis, C. psittaci, C. pneumoniae, and the newest grouping of ruminant strains proposed by Fukushi and Hirai and called C. pecorum (10, 12). Recent multistrain comparisons of the gene sequences of the major outer membrane protein (MOMP) yield phylogenetic trees which support these four species groupings (4, 22,40). However, DNA homology measurements (5, 9) indicate that the species C. trachomatis and C. psittaci could be subdivided further if it is accepted that at least 70% sequence homology is necessary for isolates to be considered as belonging to the same species (20).An important aspect of any taxonomic system is that it should be based on criteria which can easily be applied in a standard fashion by all laboratories and which will allow accurate and rapid identification of isolates. The biological and immunological methods which have been used to identify species and subspecies types of Chlamydia are time-consuming, require considerable skill and experience, and are limited by the problems of generating and standardizing serological reagents. Recently, methods based on identifying variations in DNA sequences, usually through the use of restriction endonuclease (RE) analysis, have been applied to the problem of species and strain identification. When a chlamydia] isolate has been cultured, these methods can be applied either at the whole-genome level (9, 27) or to subgenomic fragments by Southern blotting (11, 18,42). However, a substantial advance has come with the use of the PCR (33), which can be used both to detect the presence of chlamydiae in clinical samples by the amplification of specific chlamydial genes and to identify the chlamydial species and type by analysis of sequence variation in the amplified pro...

A polymerase chain reaction test for the detection of ovine herpesvirus-2 (OHV-2) DNA was used to identify sites of OHV-2 infection in peri-natal lambs and in adult sheep. OHV-2 was detected in the nasal secretions from all lambs within a period of two months following birth. Subsequently, OHV-2 DNA was identified in a number of epithelial tissues including the cornea, turbinates and pharynx. In addition, OHV-2 DNA was detected exclusively in B-lymphocytes from six of ten adult sheep tested. An infection cycle for OHV-2 in sheep is proposed which bears similarities with the gammaherpesviruses Epstein-Barr virus and mouse herpesvirus-68.

The major outer membrane protein (MOMP) gene from an ovine abortion strain of Chlamydia psittaci (S26/3) has been cloned and sequenced. The gene shows the features of other chlamydial MOMPs but comparison with the previously reported sequence for the ovine abortion isolate A22/M has revealed substantial sequence divergence which is clustered into the same four intramolecular regions as the sequence variation found between C. trachomatis serovars. Subsequent restriction enzyme analysis of A22/M DNA has shown that it has an avian‐type genomic profile and thus the comparison is between types rather than between Strains.