Evaluation of a blocking ELISA using a urease conjugate for the detection of antibodies to pseudorabies virus

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.Facultad de Ciencias Veterinaria

Antigenic behaviour of several Aujeszky's disease viral strains

Desde que la Enfermedad de Aujeszky fue diagnosticada por primera vez en Argentina en 1978, fueron sucediéndose numerosos brotes en diferentes lugares del país. El objetivo de este trabajo fue comparar diferentes cepas del virus de la Pseudorrabia porcina. Para ello utilizamos 5 cepas argentinas (3 aisladas en nuestro laboratorio) y 4 de referencia internacional. Las mismas fueron caracterizadas mediante pruebas físi- co-químicas; sus proteínas comparadas por electroforesis en SDS-PAGE; su antigenicidad fue comparada al evaluar los 9 antisueros producidos en ratas mediante un sistema de virus neutralización cruzada y ELISA indirecto cruzado. Las pruebas físico-químicas permitieron observar pequeñas diferencias de comportamiento de las cepas virales frente a diferentes variables tales como pH, calor, acción de la tripsina, éter y cloroformo, las que en ningún caso aportan datos concluyentes que permitan observar diferencias significativas. El estudio de la movilidad de las proteínas estructurales de los virus en geles de poliacrilamida tampoco arrojó datos de importancia y resultó insuficiente para distinguirlos. El uso de la prueba de virus neutralización cruzada para estudiar su antigenicidad, en cambio, mostró resultados que permitieron comprobar que las cepas argentinas produjeron títulos neutralizantes más elevados que las extranjeras.Since Aujeszky's Disease was first recognized in Argentina in 1978, many outbreaks occurred in different places in our country. Nine Pseudorabies virus strains, 5 Argentine -3 of them isolated in our laboratory- and 4 reference ones, were characterized by physicochemical, SDS-PAGE, virus neutralization and ELISA methods. Using trypsin, heat, ether, chloroform and pH in physicochemical analysis, only small differences were observed, as well as when the viral structural proteins were compared by SDS-PAGE. Cross virus neutralization test using 9 antisera produced in rats, showed that Argentine Pseudorabies virus strains elicited higher antibodies titres than those obtained with reference ones.Facultad de Ciencias Veterinaria

Ensaladas listas para consumo. Análisis de condiciones de higiene y seguridad

Cincuenta ensaladas listas para consumo compradas en mercados de La Plata (Argentina) fueron analizadas microbiológicamente. Se ha encontrado que el 88% tenían un promedio de 540 ufc/g de bacterias coliformes fecales, 64% tenían Escherichia coli. Ningún aislamiento de E.coli O:157H:7 fue logrado. Por otro lado sólo se logró un aislamiento de Listeria monocytogenes tipo 4 (2%). Por consiguiente, el 88% de las ensaladas cortadas frescas no se encontró en condiciones de higiene y seguridad requeridas para el consumo humano.Fifty ready to eat salads bought in markets in La Plata (Argentina) have been microbiologically analyzed. It has been found that 88% had an average of 540 cfu/g faecal coliform bacteria, 64% had Escherichia coli. No isolation of E.coli O:157H:7 was achieved. On the other hand there was only one isolation of Listeria monocytogenes type 4 (2%). Therefore 88 % of fresh cut salad did not meet the health and safety conditions required for human consumption.Facultad de Ciencias Veterinaria

Evaluation of a blocking ELISA using a urease conjugate for the detection of antibodies to pseudorabies virus

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.Facultad de Ciencias Veterinaria

An outbreak of <i>Bordetella bronchiseptica</i> in a Long Evans rat colony

Bordetella brohisseptica es un germen patógeno, el cual debe estar ausente de las colonias de ratas y cobayos de experimentación, ya que puede interferir en los resultados finales cuando se utilizan estos animales para realizar pruebas de diagnóstico, investigación y/o control de calidad. El presente trabajo describe un brote severo de esta enfermedad en una colonia convencional de ratas long Evans. Se estudiaron 18 animales de los cuales 5 presentaban sintomatología respiratoria. Para realizar el diagnóstico se tomaron muestras de tráquea y pulmón y se cultivaron en agar Bordet Gengou, agar sangre agar DHL y caldo PPLO. Se realizó coloración de Gram, pruebas bioquímicas y pruebas serológicas (microaglutinación y aglutinación). Los resultados fueron positivos para Bordetella bronchiseptica. Se concluyó que dada la magnitud de las pérdidas e inconvenientes que produce esta infección en colonias de ratas y cobayos es aconsejable el establecimiento de medidas sanitarias y de controles microbiológicos estrictos en los bioterios.Bordetella bronchiseptica is a pathogen which must be absent in experimental rats and guinea pigs colonies, since it produces interference in the results. This study describes a severe outbreak of this disease in a Long Evans rat colony. Eighteen animals, five of which showed symptoms were studied. For diagnosis, after necropsy, samples of trachea and lungs were cultured in Bordet Gengou Agar, Blood Agar, DHL agar and PPLO broth. Gram stained, biochemical tests and microagglutination and agglutination tests were performed. The results showed a contamination with Bordetella bronchiseptica. This study demonstrates the importance of establishing sanitary procedures and an appropriate quality control program of experimental animals in conventional facilities.Facultad de Ciencias Veterinaria

Isolation of <i>Clostridium piliformis</i> from mice colonies in Argentina

Para el presente estudio se utilizaron 30 ratones BALB/c, provenientes de 6 colonias comerciales positivas para la enfermedad de Tyzzer. Los animales se inmunodeprimieron con cortisona, observándose síntomas de la enfermedad entre los 3 o 4 días posteriores. Se realizó un homogeinato a partir de los hígados e intestinos que presentaban necrosis, el cual se inoculó a ratones SPF de los cuales se reaisló el Clostridium piliformis Para su diagnóstico se usó la prueba de IFA y la morfología de la bacteria se observó con coloración de Giemsa. Mediante esta infección experimental se reaisló CIostridium piliformis, confirmándose su presencia como agente infeccioso en colonias de ratones en Argentina.In this study 30 Balb/c mice from 6 commercial colonies, which were positive for Tyzzer disease (Bacillus piliformis) were immunodepressed with cortisone. Clinical symptoms of the disease were observed between days 3 and 4 after inoculation An homogenate was prepared with necrotic livers and intestines of mice and inoculated i.v. to SPF Balb/c strain from which Clostridium piliformis was isolated. The microorganism was identified by using IFA assay and the morphology by Giemsa staining. The infection with Clostridium piliformis in mice colonies in Argentina, was confirmed.Facultad de Ciencias Veterinaria

Extended phylogeny of the equine arteritis virus sequences including South American sequences

Objective: To perform genetic analysis of the ORF5 of equine arteritis virus (EAV) may provide new insights into the genetic evolution and origin of the Argentinean EAV sequences. Methods: A total of 76 sequences were analyzed by neighbor joining (NJ), maximum parsimony and maximum likelihood algorithms. The analysis of the selective pressures was performed using the Tajima's test. Results: The trees showed similar topologies. Two clades were identified: the first clade was formed by strains isolated mainly from a donkey, whereas the second clade presented four large groups from different geographic regions exclusively from Equus caballus. In this clade, we identified a group formed by South African and another one by South American and European sequences. In the latter, the monophyletic group was formed by seven Argentinean sequences. In the NJ tree, we identified a group formed by six Argentinean sequences. The Tajima's test showed a D value of 1.73663, indicating that the sequences analyzed follow a neutral evolution model. Conclusion: We concluded that the Argentinean sequences have a paraphyletic origin and that the fixation of point mutation might follow the neutral model evolution; however, we identified purifying pressures that may be involved in the differentiation of the EAV sequences.Facultad de Ciencias Veterinaria

Extended phylogeny of the equine arteritis virus sequences including South American sequences

Objective: To perform genetic analysis of the ORF5 of equine arteritis virus (EAV) may provide new insights into the genetic evolution and origin of the Argentinean EAV sequences. Methods: A total of 76 sequences were analyzed by neighbor joining (NJ), maximum parsimony and maximum likelihood algorithms. The analysis of the selective pressures was performed using the Tajima's test. Results: The trees showed similar topologies. Two clades were identified: the first clade was formed by strains isolated mainly from a donkey, whereas the second clade presented four large groups from different geographic regions exclusively from Equus caballus. In this clade, we identified a group formed by South African and another one by South American and European sequences. In the latter, the monophyletic group was formed by seven Argentinean sequences. In the NJ tree, we identified a group formed by six Argentinean sequences. The Tajima's test showed a D value of 1.73663, indicating that the sequences analyzed follow a neutral evolution model. Conclusion: We concluded that the Argentinean sequences have a paraphyletic origin and that the fixation of point mutation might follow the neutral model evolution; however, we identified purifying pressures that may be involved in the differentiation of the EAV sequences.Facultad de Ciencias Veterinaria

Diversity of genomic electropherotypes of naturally occurring equine herpesvirus 1 isolates in Argentina

The genomes of 10 equine herpcsvirus 1 (EHV-I) 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 Bg/II, 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 genotype of Aujeszky's disease viruses isolated in Argentina

Genomes of four Argentine isolates of Aujeszky's disease virus (ADV) (Rio Cuarto/79, Mercedes, Chanar Ladeado-7 and Chanar Ladeado-15) from pigs were characterized and compared with four ADV strains obtained from U.S.A. (Indiana-S), Sweden (Sweden 66), France (Alfort) and Japan (Yamagata-S81) by restriction endonuclbase (RE) analysis. Although three Argentine isolates were classified into type I of BamHI cleavage pattern, one isolate, Mercedes, belonged to type II, according to the classification by Herrmann et al. [6]. Since this type II virus was first isolated in 1981, no outbreak of ADV infection by this type has so far been reported in Argentina. This may imply that the immediate measures by total slaughter of pigs in the farm led successful eradication of the type II ADV infection in Argentina. This report is the first epidemiological study using RE analysis on ADV strains in this country.Facultad de Ciencias Veterinaria