Field study of bovine coronavirus vaccine enriched with hemagglutinating antigen for winter dysentery in dairy cows

A field study of a vaccine; prepared by solubilizing cells infected with bovine coronavirus, Triton X-100, and mixing with an oil adjuvant, was performed at 9 farms over 4 prefectures. The cattle tested were Holstein dairy cows aged 2 to 10 years. A vaccination group consisted of 157 animals (including 132 pregnant cows) and a non-vaccinated control group consisted of 50 animals. The cows received 2 intramuscular injections of vaccine (2 mL) at 3-week intervals. Vaccinated cows did not develop abnormalities, such as a decrease in milk production volume, and all pregnant animals calved normally. The geometric mean of the hemagglutination inhibition antibody titer was 34.2 before vaccination in test cows. The titer had increased to 105.6, 3 weeks after the 1st injection and peaked at 755.6, 1 month after the 2nd injection. A high antibody titer persisted at 396.0; 241.0; and 201.5, at 3, 6, and 9 months after the 2nd injection, respectively.

This confirms the safety and high antibody-response induced by this prototype vaccine. Therefore, this vaccine may be useful for the prevention of winter dysentery caused by bovine coronavirus infection.

     

Characterization of pseudorabies viruses recently isolated in Japan by restriction endonuclease assay.

A total of 148 Japanese isolates of pseudorabies virus (PrV) collected in 1987 to 1990 were examined for the cleavage patterns of their genomes by a restriction endonuclease (RE) assay using BamHI and KpnI. Basically, there was no large difference in the cleavage patterns of viruses recently isolated in Japan. All of them were considered as belonging to BamHI cleavage pattern type II as well as strain Yamagata-S81 that is the first isolate of PrV in Japan, suggesting that no remarkable variations occurred in PrVs spreading in Japan since the first outbreak in 1981. However, considerable variations that are probably due to the gain and/or loss of cleavage sites, and to the addition and/or deletion of nucleotide sequences were detected in the repeat, conjunction and left end regions of genome. Some of those variations were similar to one another among the viruses isolated in the same geographical areas or farms at the same times, and from the epidemiologically related outbreaks, indicating that the RE assay on PrV genome is one of useful tools for the epidemiological studies on Aujeszky's disease.     

Seroprevalence of Neospora caninum in dairy and beef cattle with reproductive disorders in Japan

Serum samples from 145 dairy and 65 beef cattle with reproductive disorders and 54 normally calving dairy cattle (controls) in Japan were tested for presence of Neospora caninum antibodies by use of an indirect fluorescent antibody test (IFAT, titer 1:200). Overall, seroprevalence of N. caninum was significantly higher (P < 0.001) in dairy cattle (20.0%, 29/145) than in beef cattle (1.5%, 1/65). In cattle which aborted, seroprevalence of N. caninum was significantly higher (P = 0.041) in dairy cattle (26.1%, 23/88, compared with controls (3.7%, 2/54)) than in beef cattle (5.0%, 1/20), indicating that neosporosis might be a more common problem in dairy cattle than in beef cattle in Japan. Seropositive cattle were 9.2 times more likely to abort compared to seronegative cows. Abortions associated with N. caninum seropositivity in this study were most frequently observed in the second trimester, and the mean gestational age of the fetuses aborted from seropositive dams was 5.7 months. In conclusions, N. caninum seems to be causing serious economic losses in the dairy industry in Japan. This is the first report on an objective comparison of seroprevalence of dairy and beef cattle with reproductive disorders in Asia.     

Detection of Salmonella invA by isothermal and chimeric primer-initiated amplification of nucleic acids (ICAN) in Zambia

The isothermal and chimeric primer-initiated amplification of nucleic acids (ICAN) is a new isothermal DNA amplification method composed of exo Bca DNA polymerase, RNaseH and DNA–RNA chimeric primers. We detected invA of Salmonella from chicken carcasses, egg yolk and cattle fecal samples. Fifty-three of 59 isolates were invA-positive in ICAN-chromatostrip detection. The result was consistent with those obtained by standard PCR. Salmonella invA was detected in 12 of 14 carcass rinses by ICAN, while in 7 of 14 rinses by standard PCR. These results indicate that ICAN is an efficient, sensitive and simple system to detect invA of Salmonella species in developing countries such as Zambia.     

Characterization of the neurotoxin produced by isolates associated with avian botulism

Several varieties of birds are affected by type C botulism. We conducted neutralization tests of culture supernatants of isolates from cases of avian botulism. Whereas the toxin produced by isolates derived from mammalian botulism was neutralized only with type C antitoxin, the toxins of all isolates related to avian botulism were neutralized with both type C and D antitoxins. An analysis of nucleotide sequences with several strains revealed that the neurotoxin gene in the isolates from avian botulism comprises two thirds of the type C neurotoxin gene and one third of the type D neurotoxin gene. This indicates that the neurotoxin of avian isolates is a mosaic of type C and D neurotoxins. We prepared three sets of primers to differentiate the gene for the mosaic form from the conserved genes of type C and D neurotoxins. The results of polymerase chain reaction with these primers indicated that all avian botulism-related isolates and specimens possess the gene for the mosaic form of the neurotoxin. The toxins purified from avian and mammalian isolates exhibited the same degree of lethality in mice, but the former showed greater toxicity to chickens than the latter. These results indicate that the mosaic neurotoxin is probably a pathogenic agent causing some forms of avian botulism.     

Characteristics of Staphylococcus intermedius isolates from diseased and healthy dogs

Staphylococcus intermedius isolates from diseased and healthy dogs were examined for production of extracellular enzymes and toxins, and phage patterns. There were no significant differences between the two groups of isolates in the production rates of DNase, protease, lipase, gelatinase, hyaluronidase, hemolysins, protein A, and TSST-1, or in phage patterns. But the production rate of enterotoxins in isolates from diseased dogs was significantly higher than that in isolates from healthy dogs. PFGE analysis was performed with isolates from different body sites in individual dogs. In 3 of 6 healthy dogs, identical PFGE patterns were seen in isolates from the nares, external auditory meatus or skin. The remaining 3 dogs yielded isolates of different patterns. In 4 of 6 diseased dogs, identical patterns were seen in isolates from lesions as well as from the other normal sites.     

Fertility of bitches in which estrus was prevented with implantations of chlormadinone acetate for four years

The recurrence of estrus and fertility after removal of a subcutaneous chlormadinone acetate implant (CMA-I) administered to prevent estrus for 4 years, was investigated in 8 female dogs and the results compared with those for 4 untreated female dogs (control group). The sex hormones present during the estrous cycle were also investigated. There were no significant differences in the estrous cycle after removal of the implant between the CMA-I-treated group and the control group. However, although conception was achieved after mating and no uterine diseases developed in the control group, only 5 (4 dogs, 41.7%) of the 12 cases (6 dogs) in which mating took place at the second to fourth estrus after the removal of CMA-I resulted in pregnancy in the CMA-I-treated group. Furthermore, 6 (75.0%) of the 8 dogs in the CMA-I-treated group developed uterine diseases including pyometra or hydrometra. There were no significant differences in plasma progesterone, LH and prolactin levels between the non-pregnant and pregnant dogs in the CMA-I-treated group or control group. These results suggest that long-term implantation of CMA-I affects fertility after the implant is removed.