[Experiments to identify Mycoplasma isolates from cell cultures]. / Opiti za identifitsirane na mikoplazmeni izolati ot kletuchni kulturi.

Identified were various species of Mycoplasma organisms isolated from three continuous cell lines--BHK-21, SPZF, and TT. On the base of cultural, biochemical, and serological investigations the isolates were defined as M. bovirhinis, M. arginini, and A. laidlawii. The bovine sera, used to culture the cell lines were shown to be the basic source of contamination with Mycoplasma organisms. This made it necessary to carry out a preliminary study on each batch of serum for Mycoplasma contamination prior to its use for laboratory and productional needs.

[Creation of an avirulent and immunogenic mutant from the rhinopneumonitis virus]. / Suzdavane na avirulenten i imunogenen mutant ot virusa na rinopnevmonita.

An avirulent immunogenic virus strain mutant of the causative agent of rhinopneumonia was found to cause abortions and respiratory diseases in horses. The mutant was obtained with the use of a virulent strain that induced strongly manifested clinical symptoms of the disease, and was cultured in cell media containing 5-iodine-2-desoxiuridine as an antimetabolite, following a definite pattern. It was found that the mutant completely lost its virulence, however, it retained its immunogenicity. It likewise retained these newly acquired biologic properties with regard to its being stable and irreversible. Animals vaccinated with this mutant did not act as carriers, neither did they shed any virus. The mutant is now used in the production of a vaccine for the practice.

[A method for demonstrating mycoplasmas]. / Metod za dokazvane na mikoplazmi.

Bisbenzimid-marked continuous cell lines were investigated via fluorescent microscopy. The presence of Mycoplasma DNA was demonstrated in the cytoplasm with some of them. The method employed for the demonstration of Mycoplasma contamination is readily applicable, and could be used for control on continuous cell lines.

[Immunogenic properties of foot-and-mouth vaccines]. / Prouchvaniia vurkhu imunogennite kachestva na protivoshapnite vaksini.

Studied were the immunity effect and duration with cattle at different age vaccinated with monovalent, bivalent, and trivalent F. M. D. vaccines. It was found that the various F. M. D. vaccines bring about the building up of immunity varying in terms of effectiveness. Calves vaccinated with a single dose of the vaccine obtained but weak immunity of short duration. However, their immunization with a double dose of the vaccine prevented the outbreak of a homologous infection in up to 80 per cent of the animals. Revaccination was shown to confer a stable and lasting immunity. It was demonstrated that the various types of F. M. D. viruses participating in the F. M. D. vaccines differed in immunogenicity. The latter was better with the viruses of the A type as against that possessed by the remaining viruses. Discussed is the importance of the regular prophylactic immunizations of cattle in the control of the foot-and-mouth disease infection.

[Comparative testing of the quality of foot-and-mouth disease vaccines prepared with different virus inactivators]. / Sravnitelno izpitvane kachestvata na protivoshapni vaksini, prigotveni c razlichni inaktivatori na virusa.

Formalin, glycidaldehyde, and the binary ethyleneimine were tested under laboratory conditions as inactivators of the foot-and-mouth disease virus along with the possibility of using them in the process of vaccine production. Data is presented on the comparative testing for innocuity and immunogenicity for sheep of F. M. D. vaccines produced with such inactivators. Results showed the advantages of the binary ethyleneimine as against formalin and glycidaldehyde as an inactivator of the F. M. D. virus.

[Safety of foot-and-mouth disease vaccines in cell cultures]. / Bezvrednost na protivoshapnite vaksini vurkhu kletuchni kulturi.

Experiments were carried out to test imported and home-produced production and experimental series of foot- and-mouth vaccines in cell cultures. It was found that the primary cell cultures of swine kidney were most appropriate to study the innocuity of the F. M. D. vaccines, which, in terms of sensitivity proved of superior quality as compared to the primary cell cultures of calf kidney and the BHK 21 cells. Comparative investigations have revealed that the most promising method for testing the innocuity of the F. M. D. vaccines is the elution of the antigen from the aluminium hydroxide after Dannacher and coll. The problem is discussed of using cell cultures to check the innocuity of F. M. D. vaccines prior to their release.

[Comparative study of methods for controlling the immunogenicity of rabies vaccines]. / Sravnitelno prouchvane na metodi za kontrolirane imunogennostta na antirabichnite vaksini.

The need for a quantitative evaluation of the immunologic activity of rabies vaccines led to the carrying out of comparative investigations of various methods for controlling their immunogenicity. Three methods were tested: the Bulgarian method with the use of rabbits, which did not make it possible to evaluate the amount of immunogenic power; the Soviet method, which is based on the survival rate of immunized little mice after challenge; and the Habel test, which is based on the principle of immunity challenge and with which the amount of protection is evaluated through comparing the LD50 value of the vaccinated mice with the same value of the control animals. Most appropriate proved to be the Habel test, which was shown to be readily applicable, accessible, and with the use of animals of low price (albino mice) and least time-consuming in the quantitative evaluation rabies vaccine immunogenicity.

[Immunogenic properties of lyophilized vaccine against fowl pox produced on a New Jersey strain of pigeon]. / Prouchvaniia na imunogennite svoistva na liofilizarana vaksina protiv sharka po ptitsite ot guluboviia shcham Niu dzhursi.

Studied was a freeze-dried vaccine against fowl pox, which was produced with the pigeon type of the New Jersey strain and was considered an innocuous and immunogenic biopreparation for birds of all ages. There were neither complications after vaccination via the wing web or through rubbing the leg nor any drop in egg laying. The vaccine stored at 4 degrees C retained its immunogenic properties in the course of one year (the period of observation).

[Histological and ultrastructural changes in calves infected with bovine herpesvirus 2]. / Khistologichni i ultrastrukturni promeni pri teleta, infektsirani s bovid herpesvirus 2.

We studied the hide, neck knots, as well as the liver of calves infected intradermally with strain KOS-Haskovo of Bovid Herpes Virus 2. On the spot of the injection we found necrotic changes in the superficial strata of the epidermis, hydropic distrophy of St. spinosum and also eosinophil intranuclear inclusions in separate epithelial cells. Intranuclear acidophil inclusions were proved also in the macrophages of the lymph knots, whereas in the liver we found a reactive lithic micronecroses. The ontogenic cycle of development took place in the cytoplasm of the infected cell and during this process the nucleocapsid was formed in the nucleus, whereas the virion was formed in the cytoplasm with the membrane elements. It was proved that changes were due to the virus which has a wide range of alteration in the bodies of the calves.

[Biological characteristics of the plaque variants of the swine vesicular disease virus]. / Biologichna kharakteristika na plakovi varianti pri virusa na vezikuloznata bolest po svinete.

The Swine Vesicular Disease virus yields a heterogenic plaque population consisting of large round plaques of 8-10 mm, small uniform plaques with slightly indented contours, measuring 1-3 mm, and single plaques of transient form and size. The reisolates of the large (Lpf) plaques give a population that is similar to the initial virus, while the cloning of the small (Mpf) plaques leads to a homogenic population of such plaques. In vivo, the virus of the large plaques manifests enhanced virulence for swine. On the other hand, the selected small-plaque variant is apathogenic, which makes it possible to produce a live avirulent vaccine.

[Diagnosis of infectious anemia in horses using the Coggins test]. / Diagnostika na infektsioznata anemiia po konete s testa na Coggins.

Coggins' immune diffusion test was modified, and was applied as a screening one in the study of the epizootic status. The positive reactions were characterized by the production of a precipitation line between the antigen and the respective serum that was tested. The appearance of such a line was associated with that formed with the use of the positive control serum, pointing to a reaction of identity. With the weakly positive reactions the ends of the precipitin lines, formed with the use of the positive control serum, were found to deviate slightly toward the site where the antigen had been placed. The specificity of the test was confirmed through biological experiments and clinical, morphological, and hematological investigations.

[Serologic methods for the overall diagnosis of bovine herpes mamillitis]. / Serologichni metodi za kompleksna diagnostika na kherpesniia mamilit po govedata.

Developed were methods of seroneutralization, agar gel precipitation, and complement-fixation test (CFT) for the complex diagnosis of herpes mamillitis of herpes mamillitis in cattle. An agreement was found between the results obtained with the use of each method. Highest sensitivity and specificity possessed the seroneutralization reaction with which a highest percent of positively reacting sera was revealed (18.6). However, the CFT method could preferably be applied in mass investigations as it is more quickly and readily used as a screening test. By means of the agar gel precipitation and CFT methods the antigenic relatedness between Bovid herpesvirus 2 and the remaining representatives of the herpes virus group, and chiefly Human herpes virus 1, could be demonstrated.

[Plaque activity of vaccinal and epizootic Newcastle virus]. / Plakova aktivnost na vaksinni i epizootichni niukiasulski virusi.

The plaque technique is applied to the type differentiation of the Newcastle disease viruses, 0.5 per cent agarose being used as a nutritive overlayer. The epizootic Newcastle disease strains are characterized by a heterogenic plaque population in which the large plaques are prevalent, averaging 3--4 mm, with an irregular round form, an unclearly delineated diffuse edge, and a red center. The vaccinal strains (B1 and K) yield a homogeneous small-plaque population, the plaques themselves being 1--2 mm large, with a regular round shape, a well delineated edge, and a bright center.

[Attempts at specific immunoprophylaxis against herpes mammillitis]. / Opiti za spetsifichna imunoprofilaktika protiv kherpesniia mamilit.

A live cell culture adsorbate vaccine was produced against herpes mammillitis in cattle. Comparative investigations were carried out on the immunogenic properties of four vaccines having different adjuvants--aluminum hydroxide, saponin, arlacell, and Freund's adjuvant. All tested vaccines proved harmless and immunogenic for sensitive cattle, the highest immunogenic effect being produced by the vaccine that contained aluminum hydroxide and Freund's adjuvant. The vaccinated animals reacted to immunization with the formation of specific antibodies that showed a highest titre between the 21st and 28th day following treatment. Immunity was checked through challenge on the 45th day, all immunized heifers being fully protected against Bovid herpesvirus infection 2 infection. When necessary the vaccine can be used successfully in a dose of 3-6 cm3, subcutaneously, in the region of the dewlap.

[Demonstration of the Bovid herpesvirus 2 in cell cultures with the aid of fluorescent antibodies]. / Dokazvane na Bovid herpesvirus 2 v kletuchni kulturi s pomoshta na fluorestsirashti antitela

Used was the immunofluorescence method employing fluorescinisothiocyanate-labeled antibodies against Bovid herpesvirus 2. The localisation and the dynamics of the virus antigen were followed up in cell cultures of calf kidney epithelium. Results showed that there was a specific cytoplastic-nuclear fluorescence in the infected cells. The dynamics of the virus multiplication revealed the presence of a specific antigen by about the 6th hour following the infection of the cells. Discussed is the problem of using the immunofluorescence technique in the differentiation of herpes mammillitis from the rest vesicular diseases of the cow's udder that are similar to one another by clinical picture.

[Experimental infection with bovid herpesvirus 2]. / Eksperimentalna infektsiia s Bovid Herpesvirus 2

An experimental infection with strain KOS/Haskovo of the Bovid Herpesvirus 2, isolated in Bulgaria, was induced in susceptible heifers through intradermal, intranasal, and intravenous application. Regardless of the route of infection clinically the disease manifested itself as an eczema of an urticarial type, accompanied by a febrile reaction, leukopenia, erythropenia, and oligochromemia. Highest titers of virus-neutralizing antibodies were established on the 30th day following infection in the i/v injected animals. All experimentally infected animals remained resistant to a challenge with a homologous virus on the 80th day after they were infected.

[Isolation and identification of a virus causing abortions and stillbirths in swine (Preliminary report)]. / Izolirane i identifitsirane na virus, prichiniavashch aborti i m'rtvi razhdaniia pri svinete (Predvaritelno s'obshchenie)

A virus of the RNA type, having no lipid envelope, acid-fast and stable to heat, was isolated from an aborted fetus and from the kidney of a piglet of a lower viability at birth. It was readily cultured, multiplying quickly in primary cell cultures of pig kidney and in the SPEV cell line, producing a characteristic cytopathic effect. It gave no hemagglutination with human, chicken, and swine erythrocytes. Serologically, it was identified as a swine enterovirus of serotype I, identical with the viruses described as the etiologic agents of SMEDI.

[Plaque characteristics of herpes mamillitis virus (HMV)]. / Plakova kharakteristika na virusa na kherpesniia mamilit (VHM)

The virus of the bovine herpes mammillitis (VHM) produces a homogeneous plaque population. The plaques are either round or have the form of a slightly irregular circle, cized 2--3 mm in diameter, with a semitranslucent center. The microscopic examination of paticular plaques has revealed a necrotic center composed of destroyed cells, and in cases where the gross examination gives a clearly defined ontour there is a band of both normal and destroyed cells. No morphologic differences have been established in plaque formation so far as local strains KOS/H-ovo and DZS and the reference strain TVA are concerned. It has been found that the number of the plaques formed is directly proportional to the concentration of the inoculated virus. The preciseness and specificity of the plaque reduction test has been demonstrated as well. The comparative testing of hydrolysed starch, agarose, agar, and carboxylmethylcellulose for the plaque study of VHM has shown that best results are obtained with the use of starch and agarose, no morphologic variation being established among plaques overlaid with the four tested substances.