RESUMEN
By polymerase chain reaction (PCR) using a pair of primers specific for Salmonella phoE gene a 365-bp specific gene fragment could be amplified from yolk of infertile eggs and dead-in-shell chicken embryos, and from environmental samples. Out of 45 dead-in-shell embryo samples, 20 (44.4%) were found positive for Salmonella DNA by PCR compared to 11 (24.4%) by bacteria isolation. Salmonella DNA could also be detected from infertile eggs, chicken faeces, floor litter and chick fluff, which incidence was higher than that by bacteria isolation.
Asunto(s)
Embrión de Pollo/química , ADN Bacteriano/análisis , Reacción en Cadena de la Polimerasa/veterinaria , Salmonella/genética , Animales , Pollos , Huevos/análisis , Heces/química , Incidencia , Reacción en Cadena de la Polimerasa/métodos , Enfermedades de las Aves de Corral/diagnóstico , Enfermedades de las Aves de Corral/epidemiología , Salmonelosis Animal/diagnóstico , Salmonelosis Animal/epidemiologíaRESUMEN
Bovine embryonic spleen cell cultures were examined to find several factors influencing the specificity, sensitivity and reproducibility of the syncytia infectivity assay of bovine leukemia virus (BLV). The highest sensitivity of the assay were observed when cell sheets of 30 to 50% confluence were inoculated with a stock of BLV, and when cells containing 4 or more nuclei were counted as syncytial cells. Treatment of the cell sheets with a diethylamino-ethyl-dextran solution (25 micrograms/ml) prior to BLV inoculation was found to be essential for the optimal induction of syncytia. Low-passage cultures were found to be more susceptible to the induction of syncytia by BLV than high-passage cultures. Cell-free BLV preparations decreased in syncytia-inducing ability to some extent by the first cycle of freezing (at -70 degrees C) and thawing. No further decrease, however, was caused by repeated cycles of freezing and thawing or by prolonged incuvation at -80 degrees C. The syncytia-inducing activity of BLV was inhibited by all the BLV-precipitating antibody-positive sera originated from both cases of the adult form of bovine leukosis and cases of persistent lymphocytosis. It was not inhibited by the sera of 16 of 17 cattle apparently healthy and negative for BLV-precipitating antibody. These results indicate that the syncytia infectivity assay and syncytia inhibition test are specific for BLV.
Asunto(s)
Efecto Citopatogénico Viral , Virus de la Leucemia Bovina/patogenicidad , Retroviridae/patogenicidad , Animales , Bovinos , Células Cultivadas , Embrión de Mamíferos , Congelación , Bazo , Cultivo de Virus/métodosRESUMEN
A search was made for the presence in vivo of infective bovine leukemia virus (BLV) in secretions and excretions as well as in several tissues from five bulls, three cows and one calf. Two of the bulls and three of the cows were natural tumour cases of enzootic bovine leukosis, another three of the bulls were natural cases of persistent lymphocytosis and the calf was a natural tumour case of juvenile bovine leukosis. BLV infection was confirmed for all cattle, except the juvenile leukosis case, by detection of BLV-specific agar gel immunodiffusion (AGID) antibodies. Cell-free preparations were made from homogenates of lymphocytes, lymph nodes, spleens, livers, intestines, urinary bladders, salivary glands, mammary glands, pools of prostate glands and testicles and feces as well as from plasma, urine and milk, by passing them through 5 micrometers membrane filters. BLV infectivity in these cell-free preparations was examined by syncytia infectivity assay using susceptible cell cultures of bovine or ovine origin. Infective BLV could not be isolated from any of these cell-free preparations of plasma, secretions, excretions and tissues, although it was isolated consistently from the in vitro cultures of viable lymphocytes obtained from BLV-infected cattle. There was no indication of BLV involvement in the case of juvenile bovine leukosis.