[Detection of enzootic bovine leukemia virus using the syncytium test]. / Prükaz viru enzootické leukózy skotu (BLV) syncytiálním testem (SyT).

BLV detection by the syncytial test was performed in 27 heifers experimentally and naturally infected by the enzootic bovine leukosis virus (BLV). The presence of BLV was demonstrated in 94.7% of the animals. The bovine foetal spleen cells (FBS) were found to be suitable for the syncytial test. Positive animals not reacting to infection by the production of anti-BLV antibodies were identified during the syncytial-test investigation. The importance of this finding for the programme of controlling enzootic bovine leukosis on farms is discussed. As suggested by the results, temporary occurrence of anti-BLV antibodies followed by their disappearance can be observed together with a negative result of the syncytial test in some circumstances. The discussion deals with the problems of the determination of anti-BLV antibodies in milk, and/or milk secretion, by the ELISA method.

[The effectiveness of vaccinating gilts against parvoviruses in a herd with endemic parvovirus infection]. / Ucinnost vakcinace prasnicek proti parvoviróze v chovu endemicky zamoreném parvovirovou infekcí.

An inactivated vaccine against swine parvovirosis with a lipoid adjuvant was tested in a herd infested with parvoviruses. The titre of the haemagglutination-inhibition antibodies was studied at the time of the first pregnancy in two groups of gilts included in the herd at the age of 7.5 months - one group vaccinated, the other left untreated. In the vaccinated group the geometrical means of the titres were significantly higher than in the non-vaccinated group throughout the time of study. The difference in the average number of piglets per litter between the two groups was evaluated after parturition. On an average, the gilts of the vaccinated group had 1.5 more live pigs per litter (P less than 0.05). As also found, when the antibody titre increases by log 10, the number of piglets per litter increases by 1.55. On the basis of the results the vaccination of gilts against swine parvovirosis in endemically infested herds is considered an efficient preventive measure having a high economic effect.

[Immunoenzyme detection of enzootic bovine leukemia viruses (BLV) in cell cultures]. / Imunoenzymatický prukaz viru enzootické leukózy skotu (BLV) v bunecných kulturách.

There is a description of the method of immunoenzymic test used for detection of enzootic bovine leukosis virus (BLV) on the cells of foetal lamb spleen (FLS) permanently producing BLV and on the lymphocytes of infected animals. In both cases (in FLS cells and lymphocytes) the presence of BLV was demonstrated by the immunoperoxidase test. Using the defined serums from the animals after experimental and natural infection, BLV was detected by the above-mentioned test in FLS cells in all cases of the use of positive serums with anti-BLV antibodies. The specificity of the antibodies was also demonstrated in this way. The presence of BLV was analogically detected in the lymphocytes of the infected animals where the infection time was precisely defined. The method of immunoperoxidase test on lymphocytes is recommended in indicated cases for the demonstration of the presence of BLV in infected animals.

Antibodies to new variants of subtype A(H3 N2) influenza virus in pigs.

Following an explosive epidemic of A(H3N2) influenza among the human population of Czechoslovakia in 1983, haemagglutination-inhibiting antibodies (titre range 10-640) against strains A/Texas/77, A/Bangkok/79 and A/Philipines 2/83 were detected in 93% of sera collected from 135 pigs on three farms. Only 6.6% of sera were negative. Anti-neuraminidase antibodies were detected at rates of 81% and 23% in two and one of the herds, respectively. Antibodies against A/RNP were demonstrated by the immunodiffusion test in only one of the herds in 10 out of 45 sera tested. This herd was also found to possess antibodies against both envelope antigens of a human A(H1N1) subtype strain. Haemagglutination-inhibition tests with strains A/Hong Kong/68 (H3 N2), A/sw/Shope 15/31, A/sw/Bavaria 2/77 and A/New Jersey 8/76 (H1 N1) were negative in the sera from all three herds.

Experimental infection of sheep with Bhanja virus.

Seven juvenile sheep were infected subcutaneously (s.c.) or intracerebrally (i.c.) with Bhanja virus. Distinct symptoms of CNS affection (ataxia, pareses) were observed only in the case of i.c. application of a massive dose (10(-7) to 10(9) SMicLD50) of the Bg 336/336 strain. A short-term and low viremia (one to four days p.i.) was ascertained after i.c. infection with a dose of 10(4.7) to 10(9.2) SMicLD50 of the same strain. On the other hand, the high titres of neutralization antibodies were detected even after inoculation of small doses of the virus (e.g. 50 SMicLD50). Unlike the symptomatic response, the immune response of sheep to Bhanja virus is high.

[The present epizootological situation in intensively bred cattle in relation to the morbidity and mortality of calves during their rearing]. / Soucasná epizootologická situace v intenzívních chovech skotu v souvislosti s nemocností a mortalitou telat v prubehu jejich odchovu.

The rise and mass incidence of intestinal and respiratory infections in calves kept in large herds depend on a joint influence of infective agents and numerous endogenous and exogenous factors, mostly with non-specific action. Therefore, purely medical approach fails to provide efficient prevention. Detailed epizootological analysis is needed for taking actual measures; the analysis should concern potential respiratory and intestinal pathogens and should also cover the persistent infections such as IBR, BVD-MD and others. The immunological profile of herd, very unfavorable with the high culling rate, will improve as a result of the introduction of a purpose-oriented vaccination programme, higher level of colostral nutrition, and separate rearing of calves, isolated from the dams, in calf houses managed by the all-in-all-out system.