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author:("varnum, D A")
1.  Observations on Intramammary Infections in First Calf Heifers in Early Lactation 
The Canadian Veterinary Journal  1986;27(3):112-115.
Intramammary infections and mastitis were monitored on four occasions at three-week intervals in 61 first calf heifers in five dairy herds during the first ten weeks of lactation. Of 940 quarter milk samples examined 65% were classed as negative, 10.4% as positive for mastitis (mainly subclinical), 1.8% as group 3 (infection present but no elevation in somatic cell count) and 22.8% as group 4 (elevated somatic cell count). Seventy-seven percent of the infections detected and identified were those due to coagulase-negative staphylococci, the main species being S. hyicus, S. epidermidis, S. simulans and S. hominis. Other infections detected with Corynebacterium pyogenes (three samples), Escherichia coli (one sample), Micrococcus spp. (one sample), S. aureus (two samples) and Streptococci (non-agalactiae) (seven samples).
The geometric mean somatic cell count for 23 quarters infected with coagulase-negative staphylococci was 311 × 103 cells / mL compared to 134 × 103 cells / mL in noninfected adjacent contralateral quarters. The respective figures for% cell volume in Channel 8 (mainly neutrophils) were 10.6% and 3.5%. There was a highly significant association between herd and the proportion of quarter milk samples in the four mastitis categories.
PMCID: PMC1680159  PMID: 17422635
Heifers; mastitis; somatic cell counts
2.  Preliminary observations on the use of latex agglutination test for the detection of mastitis due to Streptococcus agalactiae in cows. 
A commercial latex agglutination test for the detection of Group B streptococcal antigens was used to detect infection due to Streptococcus agalactiae in whey of bovine milk samples. Fifteen out of 17 known infections were detected, but it was necessary to incubate the wheys at 37 degrees C for 18 hours in nine of the samples. It was found that the latex agglutination test could detect Group streptococcal carbohydrate antigens in whey samples from artificially infected quarters from one to four days after failure to detect the organism on culture or after antibiotic therapy of the affected quarter.
PMCID: PMC1255176  PMID: 3527389
3.  Comparison of the API Staph-Ident and DMS Staph Trac micromethods for the identification of coagulase-negative staphylococci. 
Two rapid identification micromethods, the API Staph-Ident and the DMS Staph Trac, were compared for the identification of coagulase-negative staphylococci. Seventy-five isolates, mainly of bovine origin, were used as the test organisms. Species identification and profile numbers assigned to isolates by each system were compared. However, no clear correlation patterns emerged, indicating the two methods were not comparable.
PMCID: PMC1255172  PMID: 3527388
4.  Studies on the immunogenicity of Streptococcus equi vaccines in foals. 
The ability of either formalin-treated or heat-inactivated whole Streptococcus equi cell vaccines or partially purified M-protein of S. equi to give rise to protective antibody levels was studied in Standardbred foals by serological means. Two commercial preparations, i.e. a beta-propiolactone killed whole S. equi cell bacterin and a cell-free extract of S. equi cells were included in the study. The mean passive hemagglutination antibody titers (10 X log2) in sera of foals given either four doses of formalin-treated whole cell vaccine or an initial dose of formalin-treated followed by three doses of heat-inactivated vaccine with or without levamisole were significantly higher two weeks after the final dose. These passive hemagglutination antibody titers were higher in foals given formalin-treated whole cell vaccine (6.7 +/- 1.5) than given commercial bacterin (4.5 +/- 2.1). The passive hemagglutination antibody titers in all the groups decreased at 12 to 16 weeks after fourth dose of the vaccine. Foals given a commercial cell-free extract did not show a significant increase in passive hemagglutination antibody titers even up to four weeks after third dose. A group of six pony foals immunized with partially-purified M protein showed mean passive hemagglutination antibody titers lower than those observed in foals given whole cell vaccines. In a challenge experiment with S. equi, two of six foals vaccinated with partially-purified M-protein and all three controls developed clinical disease. The passive hemagglutination antibody of vaccinated foals increased after challenge, while at 28 days postchallenge the passive hemagglutination antibody titers of vaccinates and recovered controls were similar.
PMCID: PMC1236191  PMID: 4075235
5.  Acridine orange staining for diagnosis of Mycoplasma bovis infection in cow milk. 
Journal of Clinical Microbiology  1984;20(4):624-625.
Mycoplasma organisms were readily recognized in samples of milk or udder secretions from cows with clinical Mycoplasma bovis mastitis when these samples were stained with 0.01% acridine orange at pH 3.0. Samples could be stored at -4 degrees C for several days or subjected to repeated freezing and thawing without loss of staining or fluorescence properties. Use of this procedure in diagnostic laboratories on suspect samples from cows with clinical mastitis could hasten inauguration of control measures against this highly contagious disease by several days; however, definitive diagnosis still requires standard culture methods.
PMCID: PMC271397  PMID: 6208217
6.  The susceptibility of bovine udder quarters colonized with Corynebacterium bovis to experimental infection with Staphylococcus aureus or Streptococcus agalactiae. 
Twenty bovine udder quarters colonized with Corynebacterium bovis SR6 and 20 uncolonized quarters were challenged by inoculation of Staphylococcus aureus Newbould 305 (ATCC 29740) into the teat cistern. The percentage of infection in quarters colonized with C. bovis (50%) was significantly lower than that in controls (100%). By similar challenge no significant difference was observed between the percentage of infection with Streptococcus agalactiae ATCC 27956 in 33 quarters colonized with C. bovis (70%) compared to 33 controls (87.9%). A total of 37 quarters colonized with C. bovis and 37 control quarters were challenged with Staph. aureus Newbould 305 (ATCC 29740) and Maxi (ATCC 27543) and Strep. agalactiae (ATCC 27956) by exposure of the teat orifice. The percentage of teat ducts colonized with C. bovis which became infected with either pathogen was not different from that for controls.
PMCID: PMC1236027  PMID: 6372969
7.  Experimental colonization of the bovine teat duct with Corynebacterium bovis and the effect on milk somatic cell counts. 
Colonization with Corynebacterium bovis was established in 59 of 64 (92%), 58 of 59 (98%) and 19 of 34 (56%) of uninfected bovine mammary quarters following inoculation of 83.3 X 10(4) colony-forming units (CFU) of the organism into the teat cistern, 4.7 X 10(3) CFU 5 mm into the teat duct or by exposure of the teat orifice to a milk culture containing 1.6 X 10(7) CFU/mL respectively. Mean somatic cell counts for foremilk samples from 122 quarters were significantly higher after colonization with C. bovis (145,900/mL) compared to before exposure (130,900/mL).
PMCID: PMC1236026  PMID: 6722643
8.  Fatal mastitis of dairy cows: a retrospective study. 
The necropsy records of dairy cows with mastitis were reviewed from the provincial veterinary laboratory in Guelph (44 cases of mastitis in nine years) and from the Ontario Veterinary College (168 cases in 14 years). Mastitis was considered to be the primary cause of death in 167 of 212 cows (79%). Of these 167 cases of mastitis, Escherichia coli was involved in 107 (64%), Klebsiella sp. in 12 (7%) and Staphylococcus aureus in 11 (7%). Bacteriology was not reported in 22 cases. Coliform mastitis, the most commonly identified type of fatal mastitis, was characterized histologically by the presence of infarcted areas in affected glands and by the lack of demonstrable bacteria, and was thus easily identified from fatal mastitis caused by S. aureus.
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PMCID: PMC1236023  PMID: 6722641
9.  Characterization of strains of Corynebacterium bovis. 
The biochemical and morphological characteristics of 104 strains of Corynebacterium bovis isolated from bovine milk samples and the C. bovis reference strain were found to be uniform. Valuable criteria for identification were presence of catalase and oxidase, production of acid from glucose and fructose and a requirement for enriched basal media. Six strains of human and three strains of bovine origin were found to be inconsistent with the reference strain.
PMCID: PMC1236046  PMID: 6722650
11.  Morphological, biochemical, antigenic, and cytochemical relationships among Haemophilus somnus, Haemophilus agni, Haemophilus haemoglobinophilus, Histophilus ovis, and Actinobacillus seminis. 
Journal of Clinical Microbiology  1983;17(5):728-737.
Morphology, biochemical reactions, pigmentation, antigens, and cell envelope proteins were examined in 12 strains of Haemophilus somnus, Haemophilus agni, Histophilus ovis, and Actinobacillus seminis. All of the strains except A. seminis are related and are considered as a single Haemophilus-Histophilus (HH) group. In immunodiffusion tests, HH group bacteria had at least two antigens common to all members of the group, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that they have similar cell envelope protein profiles. A quantitatively variable yellow pigment with absorption maxima of 430 to 435 nm was present in strains of H. somnus and H. agni. The HH group did not produce catalase and grew only in air containing 10% CO2. Of 10 HH group bacteria, 9 required thiamine monophosphate for growth. A. seminis was distinguished from the HH group by its lack of yellow pigment, production of catalase, growth in air, lack of a thiamine monophosphate requirement, and different cell envelope protein profile. In gel immunodiffusion tests, A. seminis antigens produced two lines of partial identity with the HH group when antiserum against H. somnus was used. Reference strains of Haemophilus influenzae, Actinobacillus lignieresii, and Haemophilus haemoglobinophilus were compared with the test strains. In immunodiffusion tests, a single antigen was found to be common to H. haemoglobinophilus, A. seminis, and the HH group. No similarities between any of the test strains and H. influenzae or A. lignieresii were noted. The close relationship of H. somnus, H. agni, and Histophilus ovis suggests that these unofficially named bacteria may belong to a single taxon.
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PMCID: PMC272733  PMID: 6408118
12.  An observational study of Corynebacterium bovis in selected Ontario dairy herds. 
An observational study of Corynebacterium bovis was conducted in 74 Ontario dairy herds. The levels of infection with C. bovis were 19.9, 36.2 and 85.6% at the quarter, cow and herd level, respectively. Teat disinfection was found to be the variable best able to distinguish between herds with a high or low C. bovis quarter infection rate. Mean total milk somatic cell counts for 1103 quarters and 107 cows infected with only C. bovis ranged between 150,000 and 200,000/mL and were significantly higher than for uninfected quarters or cows. The rate of infection with mastitis pathogens was not significantly different in quarters previously colonized with only C. bovis compared to previously uninfected quarters.
PMCID: PMC1235889  PMID: 6831308
13.  A Survey of Mastitis in Selected Ontario Dairy Herds 
The Canadian Veterinary Journal  1982;23(5):156-159.
A mastitis survey involving 74 Ontario dairy herds was conducted. The prevalence of infection at the quarter level was found to be 4.1% with Streptococcus agalactiae, 4.5% with other streptococcal species and 8.0% with Staphylococcus aureus. Regardless of the infection status, the geometric mean somatic cell count was found to increase with age of the cow but no increase was observed with increasing stage of lactation. The percentage of cows from which a bacterial pathogen was isolated increased with age but not with stage of lactation.
PMCID: PMC1790115  PMID: 17422140
14.  The pulmonary clearance of Pasteurella haemolytica in calves infected with bovine virus diarrhea or Mycoplasma bovis. 
Based on current literature which commonly associates bovine virus diarrhea virus and Mycoplasma bovis with "pneumonic pasteurellosis," an investigation was conducted into the effect of these two pathogens on the capacity of bovine lung to clear inhaled Pasteurella haemolytica. There was no significant effect (p less than 0.05) of either bovine virus diarrhea virus or M. bovis on the mean clearance rate of P. haemolytica, nor did the time interval of three, five or seven days between the first inoculation and exposure to P. haemolytica and adversely affect the lung clearance rates. However, it was found that the left lungs and a higher bacterial retention (p less than 0.05) than the right lungs.
PMCID: PMC1320328  PMID: 7127194
15.  The use of polyethylene intramammary device in protection of the lactating bovine udder against experimental infection with Staphylococcus aureus or Streptococcus agalactiae. 
The susceptibility of lactating bovine udder quarters fitted with a polyethylene intramammary device to infection was investigated. Following experimental challenge with Streptococcus agalactiae or Staphylococcus aureus, the incidence of infection was significantly (p less than 0.05) lower in intramammary device-fitted quarters compared to control quarters. In general, total foremilk and strippings milk somatic cell counts for intramammary device-fitted and control quarters were not significantly (p less than 0.05) different. Differential foremilk and strippings milk somatic cell counts were significantly (p less than 0.05) higher in samples from intramammary device-fitted quarters compared to control quarters.
PMCID: PMC1320321  PMID: 7127192
16.  An Evaluation of a Teat Dip with Dodecyl Benzene Sulfonic Acid in Preventing Bovine Mammary Gland Infection from Experimental Exposure to Streptococcus agalactiae and Staphylococcus aureus 
The effectiveness of a teat dip with dodecyl benzene sulfonic acid (1.94%) for the prevention of intramammary infections was determined in cows experimentally challenged with Streptococcus agalactiae and Staphylococcus aureus. The infection rates with Streptococcus agalactiae and Staphylococcus aureus were 62.5% and 75% in undipped quarters, 12.5% and 21.5% in dipped quarters with a reduction rate of 80% and 71% respectively. The significance of some findings in relation to mastitis control are discussed.
PMCID: PMC1790094  PMID: 17422110
17.  Occurrence of "Haemophilus somnus" in bovine semen and in the prepuce of bulls and steers. 
Haemophilus somnus was isolated from 40 of 79 unprocessed bovine semen samples, 14 of 23 preputial washings of bulls and three of eight preputial washings of steers. The results indicate nonvenereal colonization of the male urogenital tract. It is suggested that dissemination of H. somnus from the urogenital tract may be of significance in the epizootiology of H. somnus associated diseases.
PMCID: PMC1320285  PMID: 7093816
18.  Evaluation of the API 20E system for the identification of gram-negative nonfermenters from animal origin. 
The API 20E system was evaluated on isolates from animals of aerobic nonfermentative and cytochrome oxidase positive Gram-negative rods. An accuracy of identification of 80% (214/268 isolates) was achieved for those organisms included in the 1976-1977 API profile index. Members of the genera Pseudomonas and Acinetobacter were identified with 100% accuracy. Organisms not included in the API profile gave either an unacceptable profile number or were incorrectly identified as Moraxella spp. When the inoculum size was increased there was better identification.
PMCID: PMC1320201  PMID: 7042055
19.  Somatic cell counts, mastitis and milk production in selected Ontario dairy herds. 
Somatic cell counts were performed monthly on bulk tank milk samples for all producers in the Ontario counties of Hastings, Lennox/Addington and Prince Edward throughout 1978 and 1979. Other data were obtained via a structured questionnaire and from the records of the Ontario Milk Marketing Board. Many producers have not adopted practices that have been advocated for the integrated control of mastitis. For example, 43.3% of producers surveyed used single service paper towels, 63.3% regularly used teat dip and 56.5% dry cow therapy. The mean of the average monthly somatic cell count for all producers for 1978 was 621.1 x 10(3) cells/mL. This latter value was used to divide the producers into case (higher than average) and control (lower than average) groups. Control herds averaged 95.9 liters more shipped milk per cow per month than case herds. Milk from control herds averaged 0.22 percentage points higher than case herds for each of average fat and lactose, and 0.16 percentage points higher for protein. The linear regression of monthly shipped milk on the respective monthly bulk tank somatic cell count indicated a loss of 13.26 L/cow/month for each 100,000 increase in somatic cell count.
PMCID: PMC1320186  PMID: 7200385
20.  Lymphocyte stimulation response in horses against phytohaemagglutinin and M protein of Streptococcus equi using whole blood. 
Lymphocyte stimulation was observed in whole equine blood in the presence of phytohaemagglutinin and M protein extracted from a typical strain of Streptococcus equi. Blood samples were collected from several healthy horses and horse and pony foals and cultured in vitro with varying concentrations of phytohaemagglutinin and M protein for several days. Phytohaemagglutinin was found to induce lymphocyte stimulation in these animals. Highest mean stimulation indices in horse foals (49.3 +/- 24.4) and pony foals (54.7 +/- 32.0) were observed with 0.625 and 1.25 micrograms/mL phytohaemagglutinin, respectively, at either 72 or 96 hours of incubation. Significantly higher radioactive counts per minute in horse and pony foals were recorded in blood cultures incubated with 0.625 and 1.25 micrograms/mL phytohaemagglutinin. M protein induced a dose related stimulation response in adult horses. Maximum stimulation indices were observed against 125 micrograms/mL M protein at 96 hours. These stimulation indices were higher in adult horses (40.0 +/- 2.2) than observed in pony foals (14.4 +/- 15.7). Higher stimulation levels in adult horses indicated either nonspecific stimulation against M protein or previous exposure of these animals to S. equi.
PMCID: PMC1320195  PMID: 7074416
21.  The Application of Bulk Tank Somatic Cell Counts to Monitoring Mastitis Levels in Dairy Herds 
The objective of this study was to investigate the feasibility of developing a system whereby measurements taken on bulk tank milk samples could be used to monitor the level of subclinical mastitis in dairy herds.
The variables that were examined were the logarithmically transformed total somatic cell counts and percentages of cell volume in channel 8 (volumes from 89.2 to 178.3 µm3), the presence or absence of Streptococcus agalactiae and various husbandry/management factors including herdsize and the use of teat dips. Each of the use of actual monthly and rolling average bulk tank cell count determinations was investigated.
It was found that the inclusion of all variables resulted in a correct classification of approximately 85% of herds and that no improvement was achieved by the use of rolling as opposed to actual monthly values. The inclusion of various husbandry/management practices improved the percentage correct classification to some extent over that achieved by the sole use of total somatic cell counts and percentages of cell volume in channel 8 when the herds were grouped on the basis of quarter infection rate (<10%, >10%) but not in the case of the cow infection rate categories (<20%, >20%). The use of both total cell counts and percentages of cell volume in channel 8 did not improve the overall predictive value over that achieved by the sole use of percentage of cell volume in channel 8 in the case of the quarter infection rate groupings but did to some extent in the case of the cow infection rate groupings.
When the classification functions were applied prospectively and considering combinations of the two cell count determinations only, it was found that they were able to correctly classify, on the basis of the quarter infection rate groupings, approximately 75% of the study herds. It is concluded that the system described herein has limited application as a basis for selecting problem herds.
PMCID: PMC1320185  PMID: 7042053
22.  Optimal milk penicillin levels for the treatment of experimentally induced mastitis in cows. 
Infection of the mammary gland (mastitis) was produced by infusing ten quarters 2/cow x 5 cows) with Staphylococcus aureus strain 305. Mastitic and normal quarters were then infused with a preparation containing two levels of penicillin G (100,000 and 200,000 IU) in 10 mL of 3% aluminum monostearate and peanut oil. Milk penicillin levels were determined prior to treatment and twice daily for eight milkings after treatment. Normal and mastitic quarters infused with 200,000 IU had higher peak levels than those infused with 100,000 IU. Milk penicillin levels were similar in mastitic and normal quarters for the first three milkings after treatment. However, residues persisted for a longer time in milk from mastitic quarters. Penicillin was not detected in milk from the untreated control quarters nor in serum samples assayed during the experiment. The in vitro penicillin G sensitivity of the udder pathogen (MIC=0.039 and MBC=0.078 IU) was well below the milk penicillin levels for the first five milkings in all cases. However, infection recurred in two of the ten quarters (one receiving 100,000 IU and one receiving 200,000 IU).
PMCID: PMC1320214  PMID: 7340909
23.  Bovine Mastitis: A Survey of Ontario Dairy Producers, 1978 
A survey to assess the knowledge and perception regarding mastitis of 1200 randomly selected Ontario dairy producers was conducted using a mailed questionnaire. Other data were provided by the Ontario Milk Marketing Board and the Dairy Herd Improvement Association.
In general, producers were less aware of subclinical than clinical mastitis and did not appreciate the losses in production associated with it. Approximately 40% of producers were not familiar with mastitis in its subclinical form.
Many producers have not adopted practices that have been advocated for the integrated control of mastitis. For example, 35.5% of producers surveyed used single service paper towels and 38% regularly used teat dips and dry cow antibiotic therapy.
PMCID: PMC1789855  PMID: 7225997
24.  The serological response of foals to vaccination against strangles. 
A group of 100 foals was given either a commercial bacterin or an autogenous vaccine consisting of whole cells and an acid extract of Streptococcus equi. During the study, some of the foals developed clinical strangles. Various sets of sera were collected from these foals prevaccination, during vaccination, postvaccination and postinfection. The serological response of these foals was measured by passive haemagglutination and long chain tests. In foals which remained healthy, the highest titres were reached within one to two months postvaccination with a passive haemagglutination 10 x log2 mean titre of 6.78 and the long chain indices of 4.41. These levels persisted for 120 days postvaccination. Those foals which had clinical strangles exhibited lower passive haemagglutination titres (3.78) at one to two months postimmunization, but rose significantly after recovery. Four ponies immunized with formalinized Str. equi bacterin showed a partial protection against the challenge infection. The passive haemagglutination titres, long chain indices and serum bactericidal activity in these ponies were highest at 35 days postvaccination but did not increase after infection.
PMCID: PMC1320115  PMID: 7272839
25.  Use of total and differential somatic cell counts from composite milk samples to detect mastitis in individual cows. 
The objective of this study was to ascertain the value of variables measured on composite milk samples as predictors of mastitis in individual cows. The standard of comparison was the results obtained from the bacteriological examination of individual quarter foremilk samples. Cows were classified as negative or positive with regard to mastitis on the basis of one quarter sampling only and cows which were impossible to classify in this manner were omitted from subsequent analyses. The variables that were examined were: the presence or absence of specific bacteria, demographic data, and logarithmically transformed total somatic cell counts and percentages of cell volume in channels 7 through 12 of a Coulter Counter. It was found that the inclusion of all variables resulted in correct classification of 95.9% of cows with regard to their mastitis status. Sequential elimination of individual variables or groups of variables in an attempt to simplify the procedure reduced the correct classification to 86.8% when only the log transformation of the total somatic cell count and the demographic data were included. The ability of a function which included the logarithm of the total somatic cell count, the logarithm of the percentage in channel 8 and demographic data, to classify cows was examined in detail and the sensitivity and specificity of the function also discussed. It is also shown that with increasing age the minimum total somatic cell count required to classify a cow as positive increased and possible explanations of this phenomenon are discussed.
PMCID: PMC1320113  PMID: 7272844

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