This paper describes the first isolation of equine arteritis virus (EAV) in Argentina. The virus was isolated from the semen of an imported seropositive stallion held in isolation at a breeding farm in Tandil in the Buenos Aires Province. In addition, viral nucleic acid was detected in seminal plasma using the reverse-transcription polymerase chain reaction. The isolated virus was propagated in cell cultures and confirmed as EAV by indirect immunofluorescence and virus neutralisation, using a serum specific for the reference Bucyrus strain of EAV. As far as the authors are aware, this is the first time that EAV has been isolated in South America. The equine industry is very important for Argentina and international movement of horses is very intensive. This finding may have effects on the international trade of horses and semen from Argentina.

The genomes of 10 equine herpesvirus 1 (EHV-1) strains isolated in Argentina from 1979 to 1991, and a Japanese HH1 reference strain were compared by restriction endonuclease analysis. Two restriction enzymes, BamHI and BglII, were used and analysis of the electropherotypes did not show significant differences among isolates obtained from horses with different clinical signs. This suggests that the EHV-1 isolates studied, which circulated in Argentina for more than 10 years, belong to a single genotype.

The genomes of 10 bovine herpesvirus 1 and 5 strains isolated in Argentina from 1989 to 1994, recovered from animals showing different clinical signs, and two reference strains (Los Angeles and A663) were compared by restriction endonuclease analysis. Four restriction enzymes, HindIII, BamHI, EcoRI and PstI, were used and analysis of the restriction patterns used to assign the isolate to either the BHV-1.1, BHV-1.2 or BHV-5 genotype. There was a correlationship between restriction pattern and clinical signs in six out of ten Argentinian isolates.

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We report the nucleotide sequence and genetic diversity of four Equine Arteritis Virus (EAV) ORF 5 and 6 from Argentina isolates, obtained from asymptomatic virus-shedding stallions. Nucleic acid recovered from the isolates were amplified by RT-PCR and sequenced. Nucleotide and deduced amino acid sequences from the Argentine isolates were compared with 17 sequences available from the GenBank. Phylogenetic analysis revealed that the Argentine isolates grouped together in a definite cluster near European strains. Despite the greater genetic variability among ORF 5 from different isolates and strains of EAV, phylogenetic trees based on ORF 5 and 6 are similar. Both trees showed that virus sequences from America and Europe segregate into distinct clades based on sequence analysis of either ORF 5 or 6. This study constitutes the first characterization of Argentine EAV isolates.

Abstract.A blocking enzyme-linked immunosorbent assay (ELISA) using a urease conjugate (U-B-ELISA) was evaluated for screening sera for antibodies to pseudorabies virus under field conditions. A total of 764 serum samples were analyzed by U-B-ELISA. Of these, 264 were evaluated by both virus neutralization and U-B-ELISA, and the results were compared. U-B-ELISA showed 98.5% and 98.9% sensitivity and specificity, respectively. This test combines the sensitivity and specificity of the blocking ELISA format while allowing visual assessment of results.Pseudorabies (Aujeszky's disease) virus (PRV) is a very important pathogen for the swine industry worldwide, and eradication programs for PRV are in progress in many countries. Most if not all of PRV eradication programs are based on the use of differential vaccines and appropriate serodiagnostic techniques. In Argentina, the National Animal Health Service established in 1996 a PRV control program based on serologic detection of infected animals with interdiction of vaccine usage. In accordance with the National PRV control program, the seropositive animals are segregated and/or sent to slaughter. Two serologic techniques are accepted as official by Argentina's animal health authorities: the latex agglutination test 4 and the nondifferential enzymelinked immunosorbent assay (ELISA). 8 The kits for these 2 different tests are imported from other countries, which results in a significant additional surcharge for the performance of PRV serology by diagnostic laboratories in Argentina. Likewise, there are few laboratories in the country that can run the commercially available PRV ELISAs because ELISA plate readers are not readily available. Therefore, the development of serodiagnostic techniques that are reliable, easy to perform, and require minimal equipment are of fundamental importance for the control and eradication of PRV in developing countries such as Argentina. The ELISA is probably the most widely used test for screening of PRV exposure in pig populations. In 1977, indirect ELISAs (IELISAs) for detection of antibodies to PRV were developed in the USA. 8 Since then, a number of reports on the application of ELISA as a serodiagnostic test for PRV have been published. 1,2,10 Most of the ELISA methods use alkaline phosphatase (AP) or horseradish peroxidase (HRPO) antibody conjugates. The evaluation of the results of these tests usually requires the use of an ELISA plate reader. If a urease conjugate is used instead, results can be obtained visually without using specialized equipment. The urea-containing substrate causes a pH shift, which in turn is visualized by the use of bromocresol purple as a pH indicator. In the present study, a blocking ELISA using a urease conjugate (U-B-ELISA) was evaluated for screening sera for antibodies to PRV under field conditions. This test combines the sensitivity and specificity of the blocking ELISA format while allowing visual assessment of results.From the Area of Virology, Faculty of Veterinary Sciences, National University of L...

Summary The demonstration of EHV‐1 antigen in formalin‐fixed and paraffin‐embedded liver tissue sections of aborted foetuses is described. The peroxidase‐antiperoxidase (PAP) technique is easy to perform and compared to the immunofluorescent technique seems to be more useful, especially if slightly autolysed material is being investigated. Zusammenfassung Nachweis von equinem Herpesvirus Typ 1 (EHV‐1) in Gewebeschnitten und in der Zellkultur mit Hilfe der Peroxidase‐Antiperoxidase (PAP)‐Technik Der Nachweis von EHV‐1‐Antigen in formalinfixierten und in Paraffin eingebetteten Lebergewebeschnitten abortierter Foeten wird beschrieben. Die einfach durchzuführende Peroxidase‐Antiperoxidase‐Technik erweist sich dabei gerade bei geringgradig autolytisch verändertem Untersuchungsmaterial der Immunfluoreszenztechnik überlegen.

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