Search

One hundred and five bulls from an artificial insemination unit were tested for the presence of Campylobacter fetus subspecies venerealis. The method involved the inoculation of preputial samples into a new transport enrichment medium prior to culture and immunofluorescence tests. Seventeen bulls (16%) were found to be either positive or suspected carriers of C. fetus at one or more sampling times. The average age of these 17 bulls was about two years greater than the average age of all the bulls in the unit. A combined treatment of vaccination and dihydrostreptomycin sulfate injection suppressed or eliminated the organism from carrier bulls. The use of transport enrichment medium has increased our capability and effectiveness to monitor the presence of C. fetus in artificial insemination bulls.

Isolation of transmissible gastroenteritis virus was attempted from segments of jejunum collected from piglets submitted for diagnosis of transmissible gastroenteritis. The virus was isolated more frequently in susceptible piglets than in pig kidney or pig thyroid cells. Practically, both cell systems were equally capable of demonstrating the virus when the tissue suspensions were sonicated. The pig thyroid cells prepared with glands collected from minimal disease pigs were preferred to the pig kidney cells for initial virus isolation because of their ability to respond to transmissible gastroenteritis virus with a progressive cytopathic effect. However, the pig thyroid cells, prepared from pool of glands collected in abattoirs, were often contaminated with parvoviruses and could not be used for diagnostic work. Controlled ultrasound treatments of the inoculum increased the frequency of virus isolation in both cell systems.

A Ficoll-gradient method was applied to isolate lymphocytes from fluids used to flush the uterus and oviducts of superovulated cows. Bovine syncytial virus antigens were demonstrated in 15 of 19 cows by cocultivation of lymphocytes with fetal lamb spleen cells and examining them with direct immunofluorescence. Viral serum antibodies were found in the same 15 of 19 cows as above by the modified direct complement-fixation test. The virus was also detected in one of four uterotubal cell cultures.

Fluorescent conjugates were prepared from the sera of calves immunized with four Vibrio fetus strains and one Vibrio bubulus strain. The fluorescent antibody technique (FAT) was then used to detect vibrio organisms in preputial fluid collected from 67 bulls belonging to a Canadian artificial insemination (AI) unit. The V. fetus conjugates reacted with both V. fetus var venerealis and V. fetus var intestinalis. V. fetus was found in 20 animals (29.9%), 13 of which also harboured V. bubulus. In two cases, the FAT failed to detect V. fetus which was isolated by concurrent bacteriological examinations. It was concluded that the FAT can be a rapid method of detecting some carrier bulls but more reliable results are obtained when a combination of FAT and bacteriological methods is employed. It was found that a single sample giving negative results is inconclusive and additional tests are required before making a final diagnosis. The FAT can also be used to differentiate V. fetus isolates from V. bubulus.

The plaque neutralization, complement fixation, and agar gel precipitin tests were compared by measuring bluetongue virus antibody in 137 serums from experimental animals (cattle and sheep) and suspected field reactors (cattle and deer). In general, the tests agreed well with each other. Plaque neutralization titers began earlier than the other two and went much higher than the complement fixation titers. Plaque neutralization titers usually peaked between two and three weeks after exposure and complement fixation titers from four to six weeks. The greater sensitivity of the plaque neutralization test allowed the detection of all complement fixation and agar gel precipitin reactors whereas occasionally the latter two tests failed to detect plaque neutralization reactors.

Preputial fluid samples were collected from 90 bulls in two Ontario artificial insemination units using a penial glove swab technique previously developed by one of us for use in donor bulls. No Campylobacter fetus organisms were identified from the prepuce or from samples of semen collected at the same time from these bulls. The distal genitalia of 200 bulls were collected at a slaughter house. One isolation of a Campylobacter fetus subspecies venerealis was obtained on a culture from the fornix area of the prepuce of one of these bulls.

A Canadian isolate of porcine parvovirus, isolated from cultured pig thyroid cells, was shown to be antigenically indistinguishable from a British (59e/63) and a German (G10/1) strain when treated by the modified direct complement-fixation, the hemagglutination-inhibition and the fluorescent antibody tests. These tests also revealed that antibodies to parvoviruses were detectable in a large proportion of the conventionally raised pigs in the provinces of Quebec and Ontario. Cell cultures, prepared from tissues collected in a slaughterhouse, were often found to be infected with parvovirus. In cell cultures the infection was demonstrated more effectively by immunofluorescence than by the hemagglutination test.

Complement-fixation (CF) and tube agglutination (TA) tests for demonstration of Vibrio fetus antibodies were conducted on the sera of three groups of ten heifers. One group was vaccinated subcutaneously with a commercial V. fetus var venerealis bacterin and challenged intra-utero, at the external os cervicus one month later; the second was infected only and the third vaccinated only. The vaccinated cattle developed high CF serum titers, but no such increase was observed in animals infected only. A moderate increase in serum antibody titers was demonstrated by the TA test following either infection or vaccination; although titers observed were not higher than those observed in the sera of some apparently normal uninfected animals. The group receiving both vaccine and challenge was the only one in which significant serum antibody titers were demonstrable by the TA test. The sera of these animals also had significant titers in the CF tests. The CF and TA tests detected serum antibodies produced by the parenteral inoculation of V. fetus antigen. These two tests were of limited value in detecting serum antibodies from animals with genital V. fetus var venerealis infection, although the formation of local antibodies was demonstrable by the vaginal mucus agglutination test.

Clinical field cases of equine infectious anemia were studied and the disease was reproduced experimentally in horses. Attempts were made to adapt the complement-fixation test to the detection of antibodies in the serum of infected animals and to the demonstration of antigens in tissue extracts.A moderate complement-fixing antibody response was demonstrated in the serum of horses shortly after primary exposure to the infectious agent. However, this reactivity was of short duration and occurred with normal as well as with infected saline tissue extracts. It was therefore concluded that this reaction was not specific for equine infectious anemia. Possibly it is due to the appearance of auto-tissue antibodies. The value of this reaction in the diagnosis of the infection was limited because of its short duration and absence in chronic infection and following re-exposure to the infectious agent.

The complement-fixation, the serum neutralization tests and the fluorescent-antibody technique were the serological methods applied in this laboratory for the detection of antigens for bovine virus diarrhea (BVD). As observed previously, the modified direct complement-fixation (MDCF) test was required to demonstrate antibodies against virus infections of cattle. At a certain stage of infection, the MDCF test was found to be as accurate and less time-consuming than the serum neutralization test for the detection of antibodies in bovine sera. The modified direct complement-fixing antibodies were detectable in the serum from approximately three weeks up to a few months after infection as compared to several years for the serum neutralization test. Thus, as in most other viral diseases, the MDCF test was of value for detecting recent infections while the serum neutralization test detects both recent and long-standing infections. The fluorescent antibody technique was of value to detect viral antigens of both cytopathogenic and noncytopathogenic strains of BVD in primary fetal kidney cell cultures inoculated with field specimens. In addition, the virus was detected in six of 220 fetuses collected at a local slaughter house for the preparation of primary cell cultures. The length of time required for the detection and identification of specific viral antigens by immunofluorescence was considerably reduced over that of the serum neutralization and virus interference tests.

On August 13, 1968 Canada experienced its first outbreak of anaplasmosis. The initial diagnosis based on hematological and clinical evidence was made by the Provincial Veterinary Laboratory, Winnipeg, Manitoba, and later confirmed in our laboratory by use of the complement-fixation test, hematology, and animal transmission studies. Sixteen herds (1,717 cattle) were examined but the outbreak was found to be localized mainly in one herd of 830 cattle. A low degree of infection was also found in four other herds. None of the remaining 11 herds in the area were infected.The infection was controlled by serological testing, and a slaughter policy. In the four herds with low grade infection, no clinical signs were evident, and serological tests made five and six months after the discovery of the outbreak were negative. In the main herd, the tests were negative at six and nine months. Even though no clinical manifestations of anaplasmosis were detected, surveillance of the animals in the area was continued. Sera from all the cattle were tested 16 months after the initial test. Four reactors were detected in the herd in which the main infection had previously been located. In addition, single borderline reactions were observed in a herd which previously had only one questionable reactor, and in another herd which had heretofore been negative. All of these reactive animals were slaughtered including the two with low grade reactions of doubtful significance. Following the removal of the reactive animals, tests were performed until negative results were obtained twice at six week intervals. The last test was conducted at the end of January 1970, 18 months after the original test.