Hemagglutination with rhabdoviruses related to bovine ephemeral fever virus

Three different bovine ephemeral fever group viruses were tested for hemagglutination (HA). One of them, Tortilla Flat virus (CSIRO 368), agglutinated erythrocytes from geese, pigeons, horses, hamsters, mice and guinea-pigs when the concentrated infectious culture fluid was used as a hemagglutinin. The HA was dependent on the pH of phosphate buffered saline used as the erythrocyte diluent when using borate buffered saline (pH 9.0) with 0.4% bovine serum albumin as the antigen diluent. The optimal pH of the phosphate buffer was from 5.2 to 5.8. The HA, however, was not dependent on salt concentration. The incubation temperature did not affect the HA titer significantly. This HA reaction was inhibited by serotype specific antiserum.     

Studies on the epidemiology of bovine parasitic bronchitis.

In the West of Scotland the epidemiology of parasitic bronchitis in grazing calves was studied over a two year period with the aid of tracer calves and herbage examinations for Dictyocaulus viviparus larvae. The observations of both years emphasised the importance of overwintered lungworm larvae as a source of disease. In the first year it was shown that the ingestion and development of these overwintered larvae were, by themselves, directly responsible for severe morbidity, high faecal larval counts and deaths. In the second year it was shown that pasture ungrazed during the winter and spring and from which a hay crop was removed in mid-summer was still capable of producing clinical parasitic bronchitis in susceptible calves within three to four weeks of their introduction in later summer. In both years there was some evidence that the outbreaks appeared to be associated with the sudden availability of infective larvae on the herbage. The possibility that such larvae may have survived for many months in the soil is discussed. Despite the heavy challenge with lungworm larvae experienced by the grazing calves in the first year those vaccinated with lungworm vaccine survived, their clinical signs were mild and of short duration and their faecal larval output was greatly reduced.     

Studies on bovine Breda virus

Diarrheic feces from 21 calves were examined by electron microscopy and 16 contained particles morphologically similar to those of Breda virus. The particles were spherical or elongated, 60-270 nm in greatest dimension and had surface spikes 9-13 nm long. Convalescent serum from a human patient with Breda virus-associated diarrhea reacted with one of the bovine viruses by immune electron microscopy, suggesting a serological resemblance between human and bovine Breda-like viruses. Immune electron-microscopy and immunofluorescence demonstrated that isolates of bovine Breda virus from the U.S.A. were related to the French virus. One of the viruses had a density in sucrose solution of 1.16, similar to the value for Berne virus.     

Studies of bovine Mycoplasma mastitis. 3. Testing of biochemical properties of Mycoplasma strains isolated from 3 stocks

Thirty-two isolates of altered milk samples taken from cows with mastitis on three industrialised dairy cattle units were biochemically tested following five passes through no-inhibitor media, assessment of filtratability through 450-nm-membrane filter, and clone assay. Something between five and ten clones of each of the strains involved were tested for their growth properties both at 22 degrees C and in no-serum media, sensitivity to digitonin and capability of aesculin hydrolysis. TTC reduction (triphenyltetrazolium-chloride), as well as for decomposition of glucose, arginine, and urea. The properties found were characteristic of M. bovis, A. laidlawii, and A. axanthum, and of the family of mycoplasmataceaea in the strains of one of the stocks.     

Studies on the Hemagglutination Phenomenon of Hemagglutinating Encephalomyelitis Virus (HEV) of Pigs

Hemagglutinating encephalomyelitis virus (HEV), unlike other Coronaviruses, readily agglutinates a variety of red blood cells. The reaction differs from that of the Myxovirus/Paramyxovirus groups in several respects. Unlike the Myxoviruses, HEV agglutinated red cells treated with receptor destroying enzyme. No neuraminidase activity was demonstrated with HEV and there was no apparent elution of the virus from agglutinated cells. Mucins and animal sera inhibited the agglutination reaction markedly. Ultra violet light exposure sufficient to destroy infectivity had no effect on hemagglutination. Density gradient studies showed that the hemagglutinin was closely associated with the virus particle.