Canadian journal of comparative medicine and veterinary science最新文献

A successful method for low temperature preservation of bull semen was modified for use with boar semen and resulted in recovery of twenty to fifty per cent motile cells immediately after thawing. Recovered cells did not survive five hours incubation at 37 degrees C. and no pregnancies resulted following insemination of twenty-four sows and gilts with frozen semen.

A number of different SALMONELLA types were recovered from samples of water collected from the containers in which pet turtles were kept for sale to the public in New York City.

Veterinary clinicians can make a significant contribution to the knowledge of the practical value of using alternative treatment methods by conducting clinical trials. By following a logical sequence of steps the clinician can design and participate in a clinical trial in his clinic without interfering with his normal practice. The successive stages of a field trial were presented along with an example to demonstrate the application of the principles involved. These stages are: design and planning, implementation, collection of data, and analysis of data.The veterinary clinician who initiates clinical trials to answer questions plaguing him provides two services to the veterinary profession. First, he helps answer questions facing private practitioners throughout the profession. Second, he can demonstrate that not all research must be done in a laboratory setting isolated from "real world" complications. Seeing the results that can be derived from individual practicing veterinarians participating in clinical trials should act as a stimulus to other veterinarians to logically organize the data coming from their practices.

The agar double-diffusion precipitation test was applied successfully in the demonstration of ASF viral antigen in spleen and liver from swine experimentally infected by the oral route. Positive reactions were obtained with tissues collected as early as 24 hours after the onset of pyrexia and before other clinical manifestation of the disease. Cross-reactions were observed between the various ASF strains used in the study, making the test practical for routine diagnosis in which different strains may be encountered.

African swine fever immunofluorescent conjugates were prepared in swine and used successfully in the demonstration of viral antigen in frozen tissue sections and in inoculated tissue culture cells. Cross reactivity was observed with the six strains used in the inoculation of swine. The high antibody content of the serum of immune swine did not interfere with demonstration of the antigen in frozen tissue sections of certain of their organs. The localisation and extent of antigen varied with the stage of infection. The virus was demonstrated in spleen and other organs as early as after one day of pyrexia and until after death of the animal. A pool of hog cholera and African swine fever conjugates stained with dyes of different colours was used in the localisation of respective antigens in experimental mixed infection.

These studies report on the production of African swine fever antiserum for use in serological tests. The first attempt to obtain antiserum was made by inoculating ASF virus - infected pig blood into the lactiferous sinus of lactating bovines. This failed to result in the development of detectable antibody, but resulted in propagation of the virus over a 14 to 21 day period. In the second attempt use was made of a tissue culture - attenuated virus to produce resistance in normal pigs. Clinical response to inoculation with the attenuated virus was limited to a one day increase of temperature. These pigs were subsequently orally exposed to virulent ASF virus and later challenged by intramuscular injection. The sera were subjected to testing by the modified direct complement-fixation test and the agar gel double-diffusion technique in order to follow the development of antibodies. Some sera were also conjugated with fluorescein isothiocyanate and used for the detection of viral antigen by the fluorescent antibody technique. It was found that inoculation with the attenuated virus brought about the development of low antibody levels in the pigs. This antibody level did not increase following oral exposure. One pig following intramuscular challenge underwent a series of ascending temperature peaks, coinciding with increased complement-fixing titres.

Six strains of African swine fever (ASF) virus were propagated in culture of primary pig kidney (PK) cells. The course of virus growth was followed by means of the fluorescent antibody staining technique. All 6 strains multiplied in the cultures, and 5 of these eventually showed cytopathic effects leading to cell death. Three of the strains were tested for pathogenicity in pigs at various passage levels. Each showed evidence of modification in virulence after a relatively few passages in PK cells. In one case modified virus produced resistance to challenge with homologous virulent virus. All strains rendered the PK cultures capable of hemadsorption of pig erythrocytes.

A successful method for low temperature preservation of bull semen was modified for use with boar semen. Observations were made on the effects of varying cooling rate, equilibration time, freezing rate, glycerol concentration, method of glycerol addition, packaging containers, extender pH and tonicity. Observations indicate that boar semen should be cooled and frozen at a slower rate than bull semen. Within the ranges or methods examined, the other factors had little effect on recovery of motility after freezing.