A study of swine dysentery by immunofluorescence and histology.

Twenty-six specific-pathogen-free pigs were fed pure cultures of Treponema hyodysenteriae. Five untreated pigs were controls. Distribution of this large spirochete in pigs with swine dysentery was shown by the indirect fluorescent antibody technique. Findings by this method were compared with those from dark-field examination of colonic mucosal scrapings and from tissue sections. The cultures caused mucohemorrhagic colitis which by 10 days after inoculation was indistinguishable from the colitis of swine dysentery. Control pigs remained normal. Pigs killed when spirochetes were first seen in the feces had normal colonic mucosa with only a few spirochetes. At the first sign of diarrhea, however, the colonic mucosa was thicker than normal and had many spirochetes. T. hyodysenteriae was confined to regions of hypertrophy and exudation of the large intestine mucosa throughout the course of disease.     

Truncation of the mRNA cap-binding protein eIF4E is specific for the non-invasive implantation in pigs

The mechanism of implantation is species specific (pig: epitheliochorial, bovine: synepitheliochorial, mouse: hemochorial). Recently, we have shown that proteolytical cleavage of the prototypical 25 kDa mRNA cap-binding protein eIF4E (eukaryotic initiation factor 4E) produces a stable variant with a molecular mass of approximately 23 kDa in porcine endometrium at the time of implantation. Here, we investigate if an eIF4E truncation also takes place in the endometrium of species with other implantation forms. Thus, eIF4E and its repressor protein 4E-BP1 were investigated in porcine, murine and bovine endometrium during the time of implantation. Our results show that eIF4E truncation is specific for the porcine implantation. In bovine and mouse uterine tissue, no cleavage of eIF4E was observed. Whereas no difference of bovine 4E-BP1 was found, in murine samples, increased phosphorylation during implantation was observed. However, porcine samples exhibit an opposite behaviour, the abundance and mainly the phosphorylation of 4E-BP1 decrease. We propose that the translation initiation in the endometrium is differently regulated by the two eIF4E forms with regard to different 4E-BP1 abundance and phosphorylation as well as different eIF4E/4E-BP1 binding dynamic depending on the type of implantation.     

Seroprevalence of psittacine beak and feather disease in wild psittacine birds in New South Wales

SUMMARY A haemagglutination inhibition assay was used to detect antibody to psittacine beak and feather disease virus in sera from wild sulphur crested cockatoos (Cacatua galerita), galahs (Eolophus roseicapillus), short-billed corellas (Cacatua sanguinea), eastern long-billed corellas (Cacatua tenuirostris) and other psittacine birds in New South Wales. The seroprevalence of psittacine beak and feather disease ranged from 41% to 94% in different flocks, indicating infection with the virus is widespread in wild populations.     

Identification of toxigenic Pasteurella multocida in atrophic rhinitis of pigs by in vitro characterisation

Toxigenic strains of Pasteurella multocida were readily differentiated from non-toxigenic strains by an agarose overlay method using bovine turbinate cells or bovine lung cells. Cells which were young and densely confluent were best suited to this assay. The incubation period required to distinguish toxigenic strains was dependent on the confluence of the monolayers, which was affected by the seeding rate, cell passage level and growth time prior to overlay. The agarose overlay method correctly identified 11 of 11 reference strains of Pasteurella multocida, and visible cytotoxic changes were present in the monolayers after 48 to 65 h. Outbreaks of the enzootic form of atrophic rhinitis in 2 New South Wales piggeries were associated with the isolation of toxigenic type D strains of P. multocida.     

The effects of antigenic competition on the efficacy of multivalent footrot vaccines

SUMMARY A multivalent footrot vaccine has been developed, containing pilus antigens produced in recombinant Pseudomonas aeruginosa and representing all nine serogroups of Dichelobacter (Bacteroides) nodosus commonly recognised in the field. The responses of sheep to the multivalent vaccine have been compared with those to monovalent vaccines representing only a single serogroup. Antigenie competition between serogroups occurred in sheep immunised with the multivalent formulation, but high levels of protection were still achieved. The study showed that in multivalent footrot vaccines, antigenic competition is predominantly due to the presence of a family of immunologically-related pilus antigens rather than to interference by extraneous proteins.     

Beyond redundant kill: A fundamental explanation of how insecticide mixtures work for resistance management

The use of insecticide mixtures for resistance management has been a controversial topic for many decades. Here, we provide a reassessment of the fundamental theory of insecticide mixtures. First, we examine how mixtures differ from other strategies. We suggest that the fundamental strategy concept of a mixture is defined by the simultaneous use of insecticides and their overlapping exposure. Second, we provide a simple, illustrative model to show how mixtures affect resistance evolution. Following the existing literature, we identify a role for ‘redundant kill’ acting against resistant individuals, which we link to the overlapping exposure of insecticides. We also identify the occurrence of ‘additional kill’ acting against susceptible individuals, which is the immediate consequence of the simultaneous use of insecticides. Third, we take a basic approach to the comparison of mixtures and other strategies using a simple model. We find that a common comparison of the time to resistance alone leaves the effects of additional kill unaccounted for. Moreover, we demonstrate that different approaches to comparison can lead to different results because of biases that are introduced in the comparison setup. Fourth, still using the same model, we showcase a more sophisticated approach to comparison using optimised strategies. We find that optimised mixtures always perform better than other strategies due to the combination of redundant and additional kill. We suggest that the comparison of optimised strategies is unbiased because each strategy is performing the best that it can. On this basis, in theory (but not necessarily practice), we believe that mixtures are better than other strategies and, through the steps of our argument, we can tie this success back to the fundamental properties (of simultaneous use and overlapping exposure) that distinguish mixtures from other strategy concepts. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Impact of biodiversity-climate futures on primary production and metabolism in a model benthic estuarine system

Background

A territory as a prerequisite for breeding limits the maximum number of breeders in a given area, and thus lowers the proportion of breeders if population size increases. However, some territorially breeding animals can have dramatic density fluctuations and little is known about the change from density-dependent processes to density-independence of breeding during a population increase or an outbreak. We suggest that territoriality, breeding suppression and its break-down can be understood with an incomplete-control model, developed for social breeders and social suppression.

Results

We studied density dependence in an arvicoline species, the bank vole, known as a territorial breeder with cyclic and non-cyclic density fluctuations and periodically high densities in different parts of its range. Our long-term data base from 38 experimental populations in large enclosures in boreal grassland confirms that breeding rates are density-regulated at moderate densities, probably by social suppression of subordinate potential breeders. We conducted an experiment, were we doubled and tripled this moderate density under otherwise the same conditions and measured space use, mortality, reproduction and faecal stress hormone levels (FGM) of adult females. We found that mortality did not differ among the densities, but the regulation of the breeding rate broke down: at double and triple densities all females were breeding, while at the low density the breeding rate was regulated as observed before. Spatial overlap among females increased with density, while a minimum territory size was maintained. Mean stress hormone levels were higher in double and triple densities than at moderate density.

Conclusions

At low and moderate densities, breeding suppression by the dominant breeders, But above a density-threshold (similar to a competition point), the dominance of breeders could not be sustained (incomplete control). In our experiment, this point was reached after territories could not shrink any further, while the number of intruders continued to increase with increasing density. Probably suppression becomes too costly for the dominants, and increasing number of other breeders reduces the effectiveness of threats. In wild populations, crossing this threshold would allow for a rapid density increase or population outbreaks, enabling territorial species to escape density-dependency.     

Administration of recombinant porcine somatotropin (rpST) changes hormone and metabolic status during early pregnancy

The objective of this study was to examine the effects of somatotropin (ST) on porcine reproductive and metabolic statuses during early pregnancy. Four pregnant crossbred gilts received 6 mg of recombinant porcine somatotropin (rpST) daily from days 10 to 27 after artificial insemination while six pregnant gilts served as controls. Blood samples were taken on days 8, 10, 12, 14, 18, 22, and 27 prior to rpST injections (8:00 h) and subsequently at 9:00, 10:00, 12:00, 14:00, 16:00, 18:00, and 20:00 h. On all remaining days of treatment, samples were taken once daily before injections (8:00 h). The samples were assayed for the metabolic hormones: ST, insulin-like growth factor I (IGF-I), insulin, thyroxine (T₄), triiodothyronine (T₃), and cortisol; for metabolites: free fatty acids (FFA) and glucose; and for the reproductive hormones: luteinizing hormone (LH), progesterone, estradiol-17β, estrone sulfate, and prostaglandin F₂. Delivery of rpST daily induced a 20- to 40-fold increase in plasma ST concentrations. Moreover, repeated administration of rpST resulted in a continuous increase in plasma IGF-I concentration (P<0.001), from 191.0±22.3–340.0±15.3 ng/mL 24 h after initial injection to 591.3±46.8 ng/mL after final injections. Mean serum insulin tended to be greater in rpST-treated gilts. Blood concentrations of T₄ were reduced (P<0.05) from day 14 of gestation in treated gilts while T₃ concentrations remained unchanged. Concentrations of both glucose and FFA were greater (P<0.01) and cortisol concentrations were unchanged in treated gilts. Changes in reproductive steroid hormones were minimally affected. Circulating progesterone (P=0.078), and estradiol-17β (P=0.087) concentrations tended to be lower in treated animals. These data show that treatment of pregnant gilts with rpST during early gestation mainly impacts metabolic rather than reproductive status.     

A comparison of anesthetic risk factors and outcomes in light and draft horses

As a result of anatomic and physiologic differences, draft breeds may be at greater risk of developing anesthetic complications. The aim of the study was to evaluate and compare anesthetic management of draft (DR) and light (LT) horses. A case‐matched retrospective study of 371 clinical case records of DR (124 cases) and LT (247 cases) horses presented for general anesthesia between 1991 and 1998 was performed. Data were tabulated and comparisons were made using Student's t‐test (significance p < 0.05). Prior to induction, there were significant differences in mean body weight, rectal temperature, PCV, RBC, and serum TP concentration between DR and LT breeds. There were differences in mean doses of pre‐operative butorphanol (LT 21 µg kg^?1; DR 17 µg kg^?1), induction guaifenesin (LT 99 mg kg^?1; DR 88 mg kg^?1), and intraoperative ketamine (LT 0.35 mg kg^?1; DR 0.56 mg kg^?1) required. There were no significant differences in the mean doses of pre‐operative xylazine, detomidine, or induction barbiturate administered. The mean, average, and maximum concentrations of inspired halothane were significantly higher for DR than for LT horses. Draft horses received 33% less intraoperative IV fluids (8.2 mL kg^?1 hour^?1) than LT horses. Mean anesthetic duration, time to extubation, and standing recovery were not significantly different. Induction complications were not reported for either group. Rates of occurrence of intraoperative bradycardia, hypercarbia, hypoxemia, and metabolic acidosis (SBE, TCO₂, and bicarbonate concentration) did not differ significantly. Average MAP was greater in DR horses, but neither the degree nor the mean duration of hypotension differed between DR and LT horses. Mean PaO₂ was significantly lower in DR (246 mm Hg, 32.8 kPa) than in LT (305 mm Hg, 40.7 kPa) breeds. Draft horses were at greater relative risk of hypoventilation than LT horses. The greater MAP and requirement for halothane and intraoperative ketamine may indicate problems in achieving and maintaining a surgical plane of anesthesia. Draft horses may be at a greater risk of ventilation–perfusion mismatching.