[Production and titration of a vaccine against the infectious encephalomyelitis of poultry]. / Poluchavane i titrirane na vaksina sreshtu zarazen entsefalomielit po ptitsite.

A vaccine was produced against infectious encephalomyelitis of day-old chicks infected cerebrally with strain Calnek 1143. It is a brain suspension from killed birds that have shown disease symptoms, treated with penicillin and streptomycin and stored at -20 degrees C. Experiments were carried out to titrate the vaccine through determining the minimum infective dose for day-old chicks treated with 0.1 cm3 each of it, orally, as obtained from tenfold dilutions. It was found that birds do not manifest clinically the disease, however, with birds killed 20--25 days following infection there have been characteristic histologic changes speaking of infectious encephalomyelitis. The minimum infective dose of the various batches of vaccine have been found to range from 10(-3) to 10(-5)/cm3. Applied under the conditions of the practice the vaccine has proved harmless, contributing to eradication of the disease on the infected farms.

[Effect of the preparation hydroprot on immunogenesis in birds with Newcastle disease]. / Vliianie na preparata khidroprot vurkhu imunogenezata pri psevdochumata po ptitsite.

Investigations were carried out on the immunogenesis and the serum-protein profile in the treatment of broilers with the protein hydrolysate Hydroprot as well as with Newcastle disease vaccine. The treatment with Hydroprot led to a lower average geometric titer of antibodies--6.4 on the 14th, 6.9 on the 24th, and 6.6 on the 39th day following immunization. Characteristic changes in the serum-protein profile were established--decrease in the total serum-protein, increase in the globulins and particularly in the fractions the peak level of which corresponded to the period of most strongly expressed immunity. The results obtained were associated with the involvement of amino acid synthesis in the immunologic process. They showed that under the effect of the preparation applied there set in enhanced immunogenesis as an expression of changed immune responsiveness.

[Combined vaccination of birds with inactivated and live vaccines]. / Kombinirano vaksinirane na ptitsi s inaktivirani i zhivi vaksini.

Studies were carried out on the immune response of birds-parental forms of broilers--in the combined use of an inactivated vaccine Dessau and a live avirulent vaccine La Sota. The dynamics was followed up till the age of 58 weeks of the changes taking place at an antidody level, and the resistance of the birds after challenging with a virulent virus. After the first immunization with a killed vaccine there was an average geometric titer of 78.65, and the resistance of the birds was low. The revaccination with an inactivated vaccine caused an increase in the amount of antibodies and a rise in the level of resistance. In the immunization with a live La Sota vaccine there was an abrupt rise of the immune titer--214.31 (in the twenty-eighth week), and 207.60 (in the thirty-eighth week). During the following periods there was a gradual drop of the antibody level, however, this was accompanied by a comparatively high resistance of the birds at challenge. The results obtained are in relation to some immunogenic properties of the experimental vaccine Dessau the use of which develops an immunogenic background at which, with a two-fold reimmunization applying a live vaccine La Sota the immunogenesis process is strongly enhanced.

[Properties of the contagious ecthyma virus used for vaccine production]. / Vurkhu niakoi svoistva na virusa na ektima kontagioza, izpolzvan za poluchvane na vaksina

Experiments were carried out to establish the effect of some antibiotics and merthiolate on the vaccinal Phylaxia strain of ecthyma contagiosa. Besides, followed up was the effect of these antibiotics on concomitant microflora that had multipled in the virus suspension. Trials were also made to titrate the vaccinal strain on lambs through scarification. Titration was carried out by the method of Schmidt. Virus dilutions of 10-1 were applied following scarification on the the thighs and fore limbs of two lams. A scarified site was also left without application to check up the effect. Each treatment needed two lambs. It was found that the antibiotics nistatin, kanamycin, oxacillin, tetraolean, oleandomycin, oxitetracyclin and chloramphenicol did not lower the activity of the vaccinal virus Phylaxia. The antibiotics tested at the respective concentrations had no sterilizing effect on the crust media regard to the concomitant bacteria. It is pointed out that the method of virus treatment can be employed to determine the biologic potential of productional batches of ecthyma contagiosa vaccine.