An outbreak of haemorrhagic septicaemia associated with Pasteurella multocida subsp gallicida in large pig herd.
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Animals↗
Biomedical subjects
A J Frost
Publications and source records attributed to A J Frost.
Molecular studies on avian strains of Pasteurella multocida in Australia.
A collection of 45 strains of Pasteurella multocida was assembled. The strains had been isolated from cases of fowl cholera in eastern Australia over 8 years, and included mainly type A strains. All the strains were examined for plasmids and resistance to 10 antimicrobial agents and most of the strains were examined for restriction fragment length polymorphism. Nine strains were assayed for pathogenicity for mice. Twenty strains yielded no plasmid. Seven contained a single plasmid of 1.3 kbp and 18 contained 2 plasmids, of 2.4 and 7.5 kbp. All the strains were resistant to streptomycin, trimethoprim and lincomycin while one strain was resistant to tetracycline. There was no correlation between plasmid content and resistance to antimicrobial agents. Three strains that lacked plasmids were highly virulent for mice, 6 strains containing plasmids were not. Restriction fragment length polymorphism generated by HpaII allowed the 39 strains that were tested to be divided into 10 groups.
Animals↗
The isolation of Salmonellas from piggery waste water after orthodox pondage treatment.
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Animal Husbandry↗
Susceptibility of porcine ileal enterocytes to the cytotoxin of Serpulina hyodysenteriae and the resolution of the epithelial lesions: an electron microscopic study.
The cytotoxin from Serpulina hyodysenteriae was injected into ileal loops of eight germ-free pigs, and the effects on the villi were observed after 1, 3, and 18 hours of exposure. The mature vacuolated villus enterocytes of the proximal part of the absorptive villi were most susceptible to the lethal effects of the cytotoxin and were extensively exfoliated. The enterocytes at the base of the villi, the goblet cells, and the follicle-associated epithelium of the dome villi, particularly the M cells, were less affected. As the enterocytes were shed, the villi progressively shortened and the basement membrane became extensively folded. The absorptive villi were markedly stunted at 3 hours, and flattened globlet cells predominated at the site of restitution of the lesion. The myofibroblasts were also damaged, apparently subsequent to the exfoliation of the enterocytes. There was no further damage at 18 hours. The absorptive villi were stunted and were devoid of the large interstitial spaces of the normal lamina propria; the enterocytes were generally columnar, and at the apex of each villus there was an accumulation of goblet cells. There was a preponderance of M cells at the apices of the dome villi. Restitution of the lesions was not as rapid as observed in in vitro systems. The changes observed indicated that as the proximal enterocytes of the absorptive villi were shed, the loss of hydrostatic forces in the lamina propria allowed the myofibroblasts to collapse the villi by progressively retracting the basement membrane. This reduced the surface area to be covered during restitution. Resolution of the lesions was still incomplete after 18 hours.
Animals↗
The effects of hedges on spray deposition and on the biological impact of pesticide spray drift.
Two series of drift deposition measurements were carried out at different wind speeds using sodium fluorescein as a tracer dye sprayed over a grass field 6 m upwind of a hedge. Efficient receptors were placed below and above hedge height (1.6 m) between 1 and 20 m downwind from the sprayed area. Receptors below hedge height reflected a sudden decrease in deposition immediately behind the hedge, followed by a gradual increase again up to 15 m, i.e., nine times the height of the hedge. The sheltering effect of a hedge from the biological impact of spray drift was studied by bioassays using tomato and Lychnis flos-cuculi plants for the herbicide MCPA and young Pieris brassicae larvae for the insecticide cypermethrin. These demonstrated that the protection afforded to sensitive species in strong winds may be quite limited, and severe damage may be inflicted over considerable distances. In intermediate cases, a protected zone is followed by a zone of further significant damage before drift depositions cease to have further effect. In some cases, the sheltered zone may extend to a distance where drift deposition, even in the absence of a hedge, has minimal effect.
2-Methyl-4-chlorophenoxyacetic Acid↗
Detection of bacterial antigens in milk samples from clinical cases of bovine mastitis in which culture is negative.
ELISAs to detect antigens against Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae, Streptococcus dysgalactiae and Streptococcus uberis were developed and used on whey samples from quarter milk samples from cases of clinical mastitis in which no bacterial pathogen had been isolated by standard culture techniques. Antigens against one or other of the bacteria listed above were detected in 68 per cent of 84 samples. Fifty-one per cent of the 84 samples contained antigens to E coli. Antigens against one or other of these bacteria were also detected in 51 per cent of 53 quarter milk samples which were negative on culture but had somatic cell counts of more than 500,000 cells/ml. It is suggested that ELISAs for the detection of antigens in quarter milk samples could be a useful adjunct to culture, to determine the infection status of a quarter.
Animals↗
The bactericidal effect of N-acetyl-beta-D-glucosaminidase on bacteria.
The bactericidal activity of N-acetyl-beta-D-glucosaminidase (NAGase) on some of the potential bacterial pathogens of the cow was determined. NAGase treatment significantly decreased the mean log10 number of Actinomyces pyogenes (P less than 0.01) and Staphylococcus aureus (P less than 0.05) after 2 and 4 hours of incubation at 37 degrees C. Similarly NAGase treatment significantly (P less than 0.05) reduced the mean log10 number of Streptococcus agalactiae and Pseudomonas aeruginosa after 4 hours incubation at 37 degrees C. NAGase did not reduce the numbers of Escherichia coli or Enterobacter aerogenes after either 2 or 4 hours incubation. Since NAGase and presumably other lysosomal enzymes are free on normal mucosal surfaces such as the uterus it is suggested that this direct bactericidal activity may be an important component of the normal defense mechanisms.
Acetylglucosaminidase↗
N-acetyl- beta -D-glucosaminidase activity in the endometrial epithelium of the cow's uterus during the oestrous cycle and pregnancy.
The levels of N-acetyl-beta-D-glucosaminidase (NAGase) were measured in the endometrial epithelial tissue of the bovine uterus during the oestrous cycle and during pregnancy. NAGase levels were significantly (P<0.001) higher in the epithelial tissue of the cow's uterus during the luteal phase of the cycle and during pregnancy than during the non-luteal phase. There were significantly (P<0.001) higher mean NAGase values in the epithelial than the subepithelial layers of the uterus in the two cycle phases and in pregnancy. Leucocyte numbers were significantly (P<0.05 and P<0.001) higher in the cows' uteri during the non-luteal phase than during the luteal phase and pregnancy, respectively. It is concluded that the endometrial epithelial layer is significantly active in terms of NAGase release and that this may be related to increased progesterone concentrations. In addition, the epithelial tissue (not leucocytes) appears to be the main contributor to the total NAGase activity in uterine tissue.
Journal Article↗
Effect of mecoprop drift on some plant species of conservation interest when grown in standardized mixtures in microcosms.
There has been an increasing awareness of potential impacts of herbicide drift on to vegetation in nature reserves and field margin habitats adjacent to treated areas. Previous work using single species bioassays has suggested that the effects of a single drift event are confined close to the sprayer (< 10 m). In the present study eight native dicotyledonous species, with and without a perennial grass (Lolium perenne), were grown in standardized microcosms in order to study (1) the effects of herbicide drift where plants were exposed to competition, and (2) the effects of a second spray application. The microcosms were arranged downwind (0-8 m) of a standard agricultural sprayer applying mecoprop at recommended rates. The effects of the herbicide drift on foliar symptoms of plant damage and end-of-season yield were assessed in each of two years. The main conclusions were that (1) growth of Stachys sylvatica and Lolium perenne (where sown) was enhanced near the sprayer and, (2) six other species (Digitalis purpurea, Galium mollugo, Hypericum hirsutum, Lychnis flos-cuculi, Primula veris and Ranunculus acris) showed some evidence of reduction in either performance (assessed non-destructively after a single exposure) or yield after two exposures. Three species (Lychnis flos-cuculi, Primula veris and Ranunculus acris) showed a reduction in flowering performance. Thus, mecoprop drift affected the aesthetic appearance, possibly the fecundity of some species and the balance between species in these microcosm experiments. The implications of these results for the persistence of attractive plant communities in sensitive areas are discussed.
Journal Article↗
Effects of herbicide spray drift on selected species of nature conservation interest: the effects of plant age and surrounding vegetation structure.
There has been increasing awareness of the possible impact of herbicide drift on vegetation in nature reserves and field-margin habitats adjacent to treated areas. However, relatively little is known about the impact of such drift on species typical of these habitats. To investigate this problem a series of bioassay experiments simulating spray drift were carried out with five native plant species of different age placed at different distances up to 4 downwind from a sprayer under standardized conditions. These experiments used three herbicides--glyphosate, MCPA and mecoprop--in three types of surrounding vegetation structure--short, medium-height and tall grassland. Many plants showed symptoms of damage after spraying but showed no significant growth reduction at the end of the season even underneath the sprayer. Where a reduction in yield was found, it occurred close to the sprayer. In general, young plants were more often affected than old ones. Yield promotion occurred for some species between 2 and 4 m downwind of the sprayer (curvilinear response) with unknown ecological consequences. The structure of the surrounding vegetation influenced the response for some species, which indicates that deposition patterns can be complex, and thus there may be difficulty in predicting effects in semi-natural communities from simple deposition models.
Journal Article↗
A cytotoxic haemolysin from Treponema hyodysenteriae--a probable virulence determinant in swine dysentery.
The haemolysin from a virulent strain of Treponema hyodysenteriae was extracted and injected into ligated loops of the ileum and colon of germ-free pigs. It caused severe epithelial damage, especially to the differentiated cells at the tips of the villi in the ileum and the cells in the intercrypt zones of the colon; goblet cells were less affected. The changes in the colon were similar to those seen in natural cases of swine dysentery. The ligated loop offers a means of investigating pathogenic mechanisms and the mode of action of the toxin. This study demonstrated that the haemolysin was a potent cytotoxin for pig enterocytes, and a probable virulence determinant in swine dysentery.
Animals↗
Survey of intramammary infections in ewes on the New England Tableland of New South Wales.
Samples of mammary secretion were collected aseptically from 1093 ewes in 8 separate flocks. Most of the ewes were suckling lambs 4 to 6 weeks old. Standard bacteriological tests were carried out on the samples to identify the organisms involved in intramammary infections. Data on age, breed, lactational status and clinical status of the gland and its secretion were recorded at the time of sampling. The prevalence of intramammary infection was 14% of ewes (8% of glands). There was a tendency for prevalence of intramammary infection to be positively correlated with age of the ewe (two-year-old and six-year-old ewes had, respectively, 4.4% and 14.0% of glands infected). This relationship was highly significant for Border Leicester x Merino ewes. There were also significant differences in infection prevalence between breeds. infected glands had a higher prevalence of clinical abnormalities of udder, teat and secretion than did non-infected glands. Staphylococcus aureus was overwhelmingly the most frequently isolated bacterium being responsible for 40% of all intramammary infections.
Age Factors↗
Assessment of the effects of herbicide spray drift on a range of plant species of conservation interest.
With increasing use of herbicides there has been growing concern that spray drift from treated land will affect vegetation on adjacent nature reserves and other areas of high conservation interest. A preliminary attempt was made to assess this risk by placing a range of native plant species at different distances downwind from standardised drift events and assessing lethal effects and sublethal damage. Five herbicides were tested: asulam, 'Finesse' (chlorsulfuron + metsulfuron-methyl), glyphosate, MCPA and mecoprop. Applications were made at the appropriate time of years for each herbicide (autumn, spring and summer), and at both low and high wind speeds. The maximum safe distance at which no lethal effects were found was 6 m from the sprayer, but for most herbicides the distance was 2 m or less. Generally, damage symptoms were found at greater distances than lethal effects, but in most cases there was rapid recovery by the end of the growing season. These observations are consistent with drift-deposition models, in which the fallout of herbicide droplets has been measured. It is suggested that buffer zones surrounding nature reserves should be in the order of 5-10 m for ground sprayers to minimise the risk of herbicide impacts on these habitats.
Journal Article↗
Pathological changes in the mammary gland and biochemical changes in milk of the goat following oral dosing with leaf of the avocado (Persea americana).
Two varieties of avocado leaves (Persea americana var Guatemalan and var Mexican) were administered to lactating goats. The Mexican variety was without effect. The Guatemalan variety in doses exceeding 20 g fresh leaf per kg bodyweight, produced damage to the mammary gland with decreased milk production. The lesions were characterised by oedema and reddening, with clots in the large ducts. Microscopically, there was widespread degeneration and necrosis of the secretory epithelium, the necrotic cells sloughing into the lumen. There was no significant cellular inflammatory response. Concentrations of antitrypsin in the milk, indicating changes in vascular permeability, increased rapidly 15 h after a single high dose, coinciding with palpable oedema. Concentrations of NAGase, indicating cell damage, increased after 24 h. Goats given multiple doses followed a similar pattern but the initial response was delayed. The toxic principle, and its mode of action in selectively damaging mammary secretory cells, remains to be determined.
Acetylglucosaminidase↗
Induction by endotoxin of the inflammatory response in the lactating and dry bovine mammary gland.
Quarters of three lactating and three dry cows were infused with 10 micrograms endotoxin and the inflammatory response induced in the mammary gland was compared. The response of the dry glands was much less than that shown by the lactating glands. The swelling in the lactating quarters was severe after four hours and declined slowly; in the dry quarters the swelling was mild and transient. Antitrypsin levels, which reflect vascular permeability, were much greater in the lactating quarters, and the somatic cell counts were similarly much higher in the lactating quarters. One dry quarter gave no response other than a slight increase in antitrypsin after four hours.
Animals↗
Adhesion of Staphylococcus aureus and Escherichia coli to bovine udder epithelial cells.
An assay for the adhesion of tritiated thymidine-labelled Staphylococcus aureus and Escherichia coli to bovine mammary ductular epithelial cell lines was developed. The relative adhesion of 15 strains of S. aureus to these cell lines was examined. Four strains did not adhere and the remaining 11 adhered at variable levels. Adhesion to different cell lines was generally similar. Adhesion to freshly collected bovine mammary epithelial cells was significantly greater than that to cells maintained in tissue culture. The system described was demonstrated to be a suitable model for studying adhesion of mastitis-causing organisms to bovine mammary epithelial cells.
Animals↗
Colony morphology of Staphylococcus aureus in serum-soft agar following in vivo and in vitro growth.
Staphylococcus aureus isolated from cases of mastitis in ruminants were grown in vitro and in vivo and subsequently examined for expression of diffuse colony morphology in serum-soft agar. Growth in the bovine mammary gland, but not in the ovine mammary gland or ovine peritoneal cavity, resulted in subsequent expression of diffuse colony morphology.
Agar↗
Distribution of lysosomal enzymes within the non-secretory epithelium of the bovine mammary gland.
The levels of N-acetyl-beta-glucosaminidase (NAGase) and acid phosphatase were analysed in tissue from the teat and lactiferous sinus epithelia of dairy cows at different stages of lactation. Enzyme levels were lower in the epithelia of the teat sinus than of the lactiferous sinus. For both enzymes, levels were highest in tissue from post-partum glands, lowest in those from dry and mid-lactation glands. In involuting glands the levels were high, but not as high as the post-partum glands.
Acetylglucosaminidase↗