[The spread of enzootic bovine leukemia via the seminal fluid in certain breeds of bulls]. / Razprostranenie na enzootichnata levkoza po govedata sus semennata technost ot niakoi porodi bitsi.

Studied was the occurrence of enzootic bovine leukosis as dependent on the use of semen of leukosis-affected bulls for the artificial insemination of cows and heifers and their offsprings in the F1 generation on 16 farms. Semen was used of a total of 30 bulls of the Holstein-Friesian, American Brown, and European Black-and-white breeds. The agar gel immuno-diffusion test was employed to establish antibodies to the bovine leukosis virus in the sera of the bulls. On 9 farms with 2,997 cows and heifers that were negative for leukosis antibodies a total of 800 female calves (F1) were born. Serologic investigations of both dams and calves, aged 2 to 5 years revealed no leukosis antibodies. On other 7 farms with 1,717 cows and heifers, among which sporadic carriers of BLV-antibodies were discovered, 713 female offsprings (F1) were born. Seventeen (2.38 per cent) out of these responded positively for BLV antibodies. Twenty-two (3.0 percent) of the dams following calving also showed a positive reaction. Over the 1981-1985 period a total of 1,593 female calves were born as the offsprings of 4,714 cattle on all 16 farms. The percent of the positively responding to leukosis was 1.06, resp., 1.38. These results were considered indicative in ruling out the transmission of enzootic bovine leukosis with semen in the artificial insemination of cows and their F1 offsprings.

[Effect of levamisole on the level of antihemagglutinins, serum sialic acid and lysozyme in the aerosol vaccination of chickens against Newcastle disease]. / Vliianie na levamizola vurky nivoto na antikhemaglutininite, serumnata sialova kiselina i lizotsima pri aerozolno vaksinirani sreshtu psevdochuma pileta.

Tested was the effect of the levamisole antihelminthic on the dynamic of anti-hemagglutinins, serum sialic acid, and lysozyme in the process of building active immunity against Newcastle disease following aerosol vaccination. It was found that there was unidirectional correlation of the active immunologic process with the level of serum sialic acid and lysozyme. The use of levamisole in adequate doses, applied opportunely enhanced the unspecific humoral defense of the body, having no direct influence on the quality of actively built specific immunity.

[Comparative studies of blood sera and lactosera by agar gel precipitation (AGP) in enzootic leukemia in cows]. / Sravnitelni prouchvaniia vurkhu kruvni serumi i laktoserumi chrez agar-gel pretspitatsiia (AGP) pri enzootichna levkoza po kravite.

Studied were a total of 70 samples of blood and corresponding lactosera taken from lactating cows that were positive for leukosis on three farms with records for the disease. The lactosera were obtained from the milk samples through treatment in two ways--with calcium chloride and with chymosin. The experiments were carried out with untreated blood sera and with the lactosera obtained in both ways. Parallel to these, blood sera and lactosera were both studied in a concentrated state after being deeply frozen and centrifugated. The agar gel precipitation test (AGPT) was employed. It was concluded that the procedure described was a readily applicable method for laboratory use in the way of establishing enzootic leukosis, making unnecessary the blood sampling on a mass scale as undesirable from an economic and epizootic viewpoint.

[Effect of coccidiostats on the quality of the immune response following the vaccination of chickens against Newcastle disease]. / Vliianie na niakoi koktsidiostatitsi vurkhu kachestvoto na imunniia otgovor sled vaksinatsiia na pileta sreshtu psevdochuma.

An experiment was carried out to test the effect of two coccidiostatica, amprol and monensin, on the level of the Newcastle disease anti-hemagglutinins. The study made use of broiler chickens of a four-line hybrid (Plymouth Rock x Cornish) treated with a Hitchner B vaccine. The drugs were admixed with the feed--amprol at the rate of 0.5 g/kg, and monensin at 1 g/kg throughout the entire experimental period. The level of antibodies was recorded by means of the IH level. Highest titers of anti-hemagglutinins were discovered in the group treated with monensin. The birds of this group had higher liveweight as against the remaining birds.

[Changes in the amount of serum sialic acid in the vaccination of poultry against Newcastle disease]. / Promeni v kolichestvoto na serumnata sialova kiselina pri vaksinatsiia ptitsi sreshtu psevdochuma.

A total of fifty birds of a four-line hybrid (Plymouth X Cornish) were used in an experiment to elucidate the link between the dynamics of serum sialic acid and the level of antihemagglutinins prior to and after vaccination against Newcastle disease (ND). It was found that immediately after vaccination the level of serum sialic acid rose essentially, and persisted at high values in the course of 7-8 days. It came back to the initial level at the time when the ND antihemagglutinins showed a maximum rise, i. e., when the active immunopoietic process was over. It is concluded that the changes in the serum sialic acid may be used tentatively as an adjunct in the evaluation of the immune responsiveness of the animal organism in the course of immunopoiesis following active immunization.

[Production of a polyglobulin preparation against respiratory diseases in calves]. / Poluchavane na poliglobulinov preparat sreshtu respiratornite bolesti po teletata.

On the basis of literature data concerning the production of polyglobulins from animal sera with the employment of appropriate, short term methods, and using the author's personal experience a method was tested for the production of specific polyglobulins against the respiratory complex in calves. A particular scheme was used for the purpose, hyperimmunizing adult cattle with killed vaccines against parainfluenza-3, adenoviruses 1 and 3, and IBR. The hyperimmune serum obtained was further treated by the etanol short term method to produce a high-titer polyglobulin. The preparation was tested in the field in the control of respiratory diseases in calves, showing very good prophylactic effects with an abrupt drop of the morbidity rate. In the case of disease outbreaks among treated animals these responded positively to an effective causal therapy. Thanks to its usability the method is recommended for the practice.

[Agar gel diffusion precipitation and immunoelectrophoresis of the Aujeszky virus]. / Difuzionna pretsipitatsiia v agarov gel i imunoelektroforeza pri virusa na Aueski

Two virulent and two vaccinal virus strains are dealt with. The study has been carried out by means of the diffusion precipitation reaction in agar gel and the immunoelectrophoresis technique using hyperimmune sera obtained from cocks as well as concentrated and purified antigens. It has been demonstrated that the virulent and the vaccinal (latent) strains of Aujeszky's disease virus cannot be differentiated serologically. The complex of antibodies induced by the virulent and the latent strains has proved to contain absolutely identical products. On the basis of the results obtained it is suggested to find some other means (markers) to differentiate the virulent from the latent strains of the virus.

[Study of the effect of some of the vaccination plans applied in Bulgaria against Newcastle disease]. / Prouchvane efekta na niakoi ot prilaganite u nas skhemi na vaksinatsiia sreshtu psevdochumata po ptitsite

Comparative studies were carried out on the effect of the vaccination of broilers against Newcastle disease with La Sota strain through the single application in the drinking water on the 21st day and the newly introduced vaccination at the age of four days, using the spray method, as well as the combined method--spray vaccination on the fourth day and giving the vaccine twice on the 21st day. It was found that the last method confers better immunity and higher immunity against the disease as compared to offering the vaccine only once on the 21st day.

[Study of the symplast-forming activity of terpene and standard strains of Aujeszky's disease virus]. / Prouchvane simplastoobrazuvashtata aktivnost na terenni i etalonni shtamove na virusa na Aueski

Studied were the cellular changes and, more specifically, the production of symplasts as a particular form of manifesting the cytopathic effect of some strains of the Aujezsky's virus. Experiments with eight strains of the virus in tissue cultures confirmed the concept of a number of authors that in given tissue cultures virulent strains show a well pronounced trent toward the formation of symplasts containing numerous nuclei, while the latent strains stimulate the production of sporadic, rounded giant cells with a few nuclei in the aggregated cytoplasm. In the course of the investigations the primary cultures of rabbit kidney proved very suitable to demonstrate the presence of Aujeszky's disease and differentiate latent and virulent strains because of the cultures exceptional receptivity to the Aujeszky virus.

[Use of temperature, trypsin and biological tests for the intraspecies differentiation of local strains of Aujeszky's disease virus]. / Izpolzvane na temperaturen, tripsinov i biologichen test pri v'trevidovoto diferentsirane na terenni shtamove na virusa na Aueski

Studies were carried out with 8 strains of Aujeszky's disease virus using a temperature test (50 degrees C for 1 hour), a trypsin test (0.5 mg per cu. cm at 37 degrees C 1 hour), and a biologic test. The strains were isolated from the brain of dead pigs that have presumably been affected with encephalitis. They proved sensitive when studied with the temperature and the trypsin tests sharply lowering their titer. The viruses isolated from pneumonic foci in the lungs of pigs in which the disease had assumed a chronic course turned out to be considerably more resistant with the use of the two tests. The vaccinal strain MK was shown to be the most resistant in all tests. Comparable results were obtained also with the study of the viruses employing a modified test with young albino mice weighing 7-8 grams. The cerebral inoculation of the viruses aimed in this case at establishing the intracerebral pathogenetic index (IPI). Test rabbits were also used for the same purpose. The virulent strains had correspondingly a shorter incubation period and in rabbits there was a well pronounced clinical course, the IPI value being higher than 1.50. To latent viruses the rabbits responded with a protracted clinical course, and IPI ranged between 0.20 and 0.95.