Non-pathogenic strains of Aujeszky's disease virus are not reactivated in swine after corticosteroid treatment

The Bartha-K and NIA-4 strain of Aujeszky's disease virus (ADV) were readily isolated from oropharyngeal swabs up to 7 days after intranasal vaccination of young piglets. Neither strain could be reisolated 14 days after starting treatment with 10 mg of the corticosteroid isoflupredone acetate per kg of body weight, administered intramuscularly for 4 consecutive days when pigs were 7-9 months of age. Similar treatment with corticosteroid pigs infected with two virulent ADV strains resulted in the reactivation of infection and recovery of ADV from oropharyngeal swabs. Serum neutralizing antibodies were present in all pigles vaccinated twice (2 week interval) intranasally with the attenuated ADV strains, 4 weeks after primary vaccination. However, these antibodies were no longer detectable in some pigs at 12(NIA-4) and 20(Bartha-K) weeks of age even in undilluted sera. Neutralizing antibodies resulting from infection virulent ADV were always detectable, were higher in titer than those produced by the vaccine strains and did not vary in a clear pattern after corticosteroid treatment. These results indicated that the Bartha-K and NIA-4 strains undergo little or no latency in swine and confirm the latency of virulent strains of ADV

Experimental transmission of bovine leukosis virus by leucocytes recovered from the stable fly Stomoxys calcitrans L

1. Wild stable flies (stomoxys calcitrans) feeding on heifers infected with bovine leukosis virus (BLV) carried viable bovine leucocytes in the midgut and proboscis that, when inoculated by the subcutaneous route into lambs aged 5 to 60 days, elicited the development of antibodies to glycoprotein (gp51) and polipeptide 25 (p25). 2. Antibodies were detected as early as one month later and persisted for an experimental period of 24 or 36 months. Uninoculated control lambs reared to gether with the experimental animals did not acquire the infection, indicating the lack of horizontal transmission. 3. S. calcitrans reared in the laboratory were intermittently allowed to feed on the skin of BLV-infected heifers and on five lambs over a period of 3-10 months. Although some of these lambs were bitten about 500 times, none developed antibodies to BLV (gp51 or p25) over observation periods of 30 or 36 months

Experimental vaccination of rabbits with non-pathogenic strains of Aujeszky's disease virus

1. The Bartha K and NIA-4 strains of Aujeszky's disease virus (ADV) were non-pathogenic for rabbits vaccinated once or twice by nasal instillation or intramuscular injection. Neutralizing antibodies were detected in 68% of the rabbits two weeks after primary vaccination and in al rabbits at challenge. 2. Challenge doses of virulent ADV greater than 10**5.0 median tissue culture infective doses (TCID50) resulted in the death of most vaccinated and all unvaccinated rabbits with typical signs of Aujeszky's disease withing 4 days. ADV was recovered from braim and lung suspensions of vaccinated and unvaccinated rabbits who had died as a result of the challenge. 3. When the challenge dose was reduced to approximately 10**3.0 TCID50, rabbits vaccinated twice survived while al unvaccinated controls died within 3 days

Transmission of bovine leukemia virus through milk ingestion.

Foi utilizada a prova de imunodifusao para detectar a presenca de anticorpos contra a glicoproteina maior (gp 51) do virus da leucemia bovina (VLB), para avaliar o desenvolvimento da infeccao em bezerros alimentados com leite de vacas livres e infectadas com o virus da leucemia. Os bezerros recem-nascidos receberam o colostro das maes durante cinco dias e depois tres litros de leite, diariamente, por periodos que variaram entre 11 e 49 dias. Todos os animais em experimentacao foram sangrados mensalmente ate os oito meses de idade, para acompanhar o aparecimento dos anticorpos como evidencia da infeccao. O VLB foi transmitido a um dos quatro bezerros (25,0%) sem anticorpos maternos, depois da ingestao de leite de vacas infectadas. Como testemunhos foram utilizados tres bezerros sem anticorpos maternos e 10 com anticorpos maternos que nao adquiriram a infeccao pelo VLB, apos a ingestao de leite de vacas nao-infectadas, por periodos similares. Concluiu-se que o VLB e eliminado no leite de vacas infectadas e se constitui numa fonte de infeccao para bezerros recem-nascidos

Prevalencia de anticorpos contra o virus da papilomatose bovina no Estado do Rio de Janeiro. / Bovine papilloma virus antibodies in the State of Rio de Janeiro

Soros de 1174 bovinos, de 10 rebanhos leiteiros do Estado do Rio de Janeiro, foram testados para anticorpos contra o virus de papillomatose bovina, utilizando-se a microprova de imunodifusao em agar. A especificidade das reacoes foi confirmada quando grupos de particulas virais foram observados nas linhas de precipitacao, pela microscopia eletronica. Anticorpos de origem materna foram demonstrados em 18,3% dos bezerros, menores de tres meses de idade, enquanto que anticorpos so foram demonstrados em 2,0% dos bezerros, entre quatro e seis meses de idade. Anticorpos tambem foram demonstrados em 21,5% dos bezerros, entre sete e 12 meses de idade; em 25% dos animais, entre 13 e 18 meses de idade; em 21,2% dis animais, entre 19 e 30 meses de idade; em 23,7% dos animais, entre 31 e 48 meses de idade e em 23,1% dos animais, maiores de 49 meses de idade