Transfer of a rifampicin-resistant Escherichia coli strain among feedlot cattle

AIMS

To determine the incidence of transfer of a naturally occurring rifampicin-resistant strain of Escherichia coli (RREC) among cattle in a research feedlot.

METHODS AND RESULTS

During three separate experiments, steers in three different pens were orally inoculated with RREC originally isolated from bovine faeces. Faecal swabs were performed on all steers in the feedlot at approximately 5 week intervals thereafter. Faecal grab samples were collected from steers in the inoculated and the immediately adjacent pens for up to 4 months. In all three experiments, the inoculated steers and penmates shed RREC within 48 h, and then shed intermittently throughout the sampling periods. Transfer of RREC to steers in an adjacent pen was confirmed only during the first experiment, but never to those in non-adjacent pens. All recovered RREC isolates were compared with the inoculated strain using multiple methods indicating that all RREC isolates were descendants of the original inoculated strain.

CONCLUSIONS

Detection of the RREC strain on the pen floor and within the animal handling system, but not in the feed troughs or water bowls, suggests faecal-oral to be the primary mode of transmission among animals.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results suggest that in the absence of selective pressure, antibiotic-resistant bacteria may persist in cattle for a short duration but widespread transfer among cattle in a feedlot environment may be an exception rather than the norm. Modifications to feedlot management are discussed.

Biology of Cryptosporidium parvum in pigs: from weaning to market

Cryptosporidium parvum is commonly identified as infecting domestic livestock and humans. Prevalence of C. parvum in pigs has been reported, however, the duration and infection pattern of naturally acquired Cryptosporidium infections in pigs has not been reported. This study was undertaken to investigate the age of oocyst shedding and duration of natural Cryptosporidium parvum infections in pigs from weaning to market weight. Fecal samples were collected from weaned Yorkshire-Landrace piglets (n=33) twice per week until Cryptosporidium oocysts were detected. Upon oocyst detection, fecal samples were collected three times per week and pigs were monitored throughout the study for diarrhea and examined after concentration and immunofluroescent staining. Cryptosporidium isolates were genotyped by polymerase chain reaction to amplify the HSP70 gene which was subsequently sequence analyzed. All 33 pigs shed oocysts some time during the study. The mean age of initial oocyst detection was 45.2 days post-weaning with the mean duration of infection 28.7 days. Mean number of Cryptosporidium oocysts was low and declined to zero prior to study completion. Episodes of diarrhea were not associated with oocyst excretion. Genetic sequences were obtained for 10 of the pigs. All of the 10 isolates aligned as the Cryptosporidium parvum 'pig' genotype. This study demonstrates that the age and duration of oocyst shedding in pigs infected with C. parvum porcine genotype is different from other livestock species.

Prevalence and genotyping of Giardia duodenalis from beef calves in Alberta, Canada

Giardia infections in domestic cattle has come under increasing scrutiny owing to the potential contamination of surface and ground waters through manure distribution on fields and pasture runoff. The objective of the study was to determine the prevalence and genotypes of Giardia duodenalis in beef calves in major beef cow calf farms in Alberta, Canada. Fecal samples were collected from beef calves aged 2-10 weeks at nine farms in Alberta. Samples were examined for the presence of G. duodenalis cysts by immunofluorescent staining. Giardia cysts were found in 168 of the 495 fecal samples examined, with prevalence ranging from 7 to 60% among farms. Genotypic analysis of positive isolates utilizing PCR and sequencing of a 292 bp fragment of the 16S-rRNA locus, revealed the hoofed livestock genotype in 41 of the 42 isolates. One isolate was identical to the Assemblage A genotype. The results of this study demonstrate that beef calves in this area are primarily infected with the livestock genotype which is thought to be specific to artiodactyl hosts and non-infective to humans. This suggests that the Giardia carried by beef cattle may be a minimal zoonotic threat.

Measuring individual free-choice protein supplement consumption by wintering beef cattle

Free-choice supplements provide protein, trace minerals, vitamins, salt and chemotherapeutic agents to cattle. For optimal benefit, a supplement should be consumed on a regular basis and at levels that do not vary significantly on a day-to-day basis. Many factors affect variability in supplement intake such as palatability of the supplement, competition between animals and the ease with which the supplement may be consumed. The aim of this study was to evaluate the differences between a solid molasses-block supplement and a liquid-molasses supplement with respect to intake and the associated behaviors (attendance, duration, and intake rate). Using a cross-over design, 34 pregnant cows weighing 720 ± 11kg were randomly allocated to two separate groups (n = 17 for each group) and evaluated for two 3-wk periods (24 February to 16 March 1999 and 25 March to 14 April 1999), using both forms of the supplement. The individual intake was recorded by way of an electronic feeding system, which made use of an electromagnetic field around the feeder in conjunction with electronic identification (EID) tags, which registered each animal’s unique eight-digit number. Cows fed the liquid supplement visited the feeder more often (P < 0.05) when compared to those fed the block supplement. The mean dry matter intake did not differ between the supplements (349 g head-1 for the block and 330 g head-1 for the liquid), but there were significantly larger deviations in intake for the block supplement than the liquid (P < 0.05) indicating more uniformity in daily intake with the liquid supplement. In almost all cases the liquid supplement was consumed at a faster rate (P < 0.05) and significantly less time (P < 0.05) was spent at the feeder. Free-choice administration of additives in liquid supplements, as compared to blocks, may result in a more frequent and less variable intake. Key words: Protein, intake, supplement, cattle, behavior

Prevalence of Giardia and Cryptosporidium andersoni and their effects on performance in feedlot beef cattle

Sixty individually housed Charolais crossbred steers originating from one ranch source had a 12-d (days 0–12) adaptation period in their pens to adjust to their ration and surroundings, followed by two consecutive backgrounding periods (85.5% roughage, 12% concentrate rations) with durations of 84 d (days 13–97) and 63 d (days 98–153), respectively. Steers had a 21-d adaptation period (days 154–174), followed by a 77-d (days 175–257) finishing period (20% roughage, 75% concentrate ration). Fecal samples and animal weights were collected from each steer every 28 d initially, then every 21 d during a test duration of 257 d. Feed weigh-backs were performed weekly for each steer. Fecal samples were processed, and Giardia duodenalis cysts and Cryptosporidium andersoni oocysts were counted. ADG, DMI and FE were calculated for each of the periods (Backgrounding Period 1, Backgrounding Period 2, Finishing Period 3 and Overall). Overall prevalence of C. andersoni and G. duodenalis was 85 and 82%, respectively. There was a decrease (P < 0.05) in the percentage of G. duodenalis infected steers from day 132 to the completion of the trial. The percentage of C. andersoni infected steers decreased (P < 0.05) from day 97 to the completion of the trial (day 257). Shedding of G. duodenalis cysts and C. andersoni oocysts in the feces was intermittent throughout the trial period. A comparison between the ADG, DMI and FE of G. duodenalis infected and non-infected steers demonstrated no overall differences (P > 0.05). A similar comparison between C. andersoni infected and non-infected steers showed no overall difference (P > 0.05) with the exception of a lower (P < 0.05) DMI for infected steers. The degree of Giardia or C. andersoni infection observed in the present study did not effect DMI, ADG or FE of feedlot steers. Key words: Giardia, Cryptosporidium andersoni, feedlot performance, cattle

Giardia duodenalis trophozoites isolated from a parrot (Cacatua galerita) colonize the small intestinal tracts of domestic kittens and lambs

This study examines the ability of Giardia duodenalis trophozoites, isolated from a wild bird, to colonize the intestinal tracts of companion animals (kittens) and domestic ruminants (lambs). Trophozoites colonized the intestinal tracts of intraduodenally inoculated animals as demonstrated by increasing parasite burdens within the duodenum and jejunum and by fecal passage of cysts within 4 days post-inoculation. The pathogenesis of the trophozoites was further investigated in kittens. In these animals, infection significantly reduced jejunal brush border microvillous length and density, which resulted in a loss of overall epithelial brush border surface area. This injury was associated with the production of diarrhea in four of five infected kittens. These findings indicate that some bird species may carry G. duodenalis that represent a possible health threat to companion animals and livestock. Our results describe the first successful colonization of avian-derived G. duodenalis trophozoites in the small intestines of domestic kittens and lambs.

Successful in vitro cultivation of Cryptosporidium andersoni: evidence for the existence of novel extracellular stages in the life cycle and implications for the classification of Cryptosporidium

The present study describes the complete development of all life cycle stages of Cryptosporidium andersoni in the HCT-8 cell line. The in vitro cultivation protocols were the same as those used for the successful growth of all life cycle stages of Cryptosporidium parvum (Int. J. Parasitol. 31 (2001) 1048). Under these culture conditions, C. andersoni grew and proliferated rapidly with the completion of the entire life cycle within 72h post-infection. The developmental stages of C. andersoni are larger than those of C. parvum enabling easier identification of life cycle stages including a previously unrecognised extracellular stage. The presence of this extracellular stage was further confirmed following its isolation from the faeces of infected cattle using a laser microdissection technique. This stage was present in large numbers and some of them were seen undergoing syzgy. Extraction of DNA from the extracellular stage, followed by polymerase chain reaction-restriction fragment length polymorphism and sequencing of the 18S rDNA confirmed that this is a stage in the life cycle of C. andersoni. In vitro, extracellular stages were always observed moving over the HCT-8 cells infected with C. andersoni. Comparative observations with C. parvum also confirmed the presence of extracellular stages. Extracellular stages were recovered from in vitro culture after 5 days post-infection with the cattle genotype of C. parvum and from infected mice. At least two morphologically different stages (stages one and two) were purified from mice after 72h of infection. The presence and morphological characterisation of extracellular developmental stages in the life cycle of Cryptosporidium confirms its relationship to gregarines and provides important implications for our understanding of the taxonomic and phylogenetic affinities of the genus Cryptosporidium. The growth of C. andersoni in cell culture now provides a means of studying its development, metabolism, and behaviour as well as testing its response to different therapeutic agents.

Characterization of Biofilm Formation by Xylella fastidiosa In Vitro

Xylella fastidiosa colonizes the xylem of various host plants, causing economically important diseases such as Pierce's disease in grapevine and citrus variegated chlorosis (CVC) in sweet oranges. The aggregative nature of this bacterium has been extensively documented in the plant xylem and the insect's foregut. Structured communities of microbial aggregates enclosed in a self-produced polymeric matrix and attached to a surface are defined as biofilms. In this study, we characterized biofilm formation by X. fastidiosa through the use of a novel in vitro assay for studying biofilm growth in a potential mimic system of what might occur in planta. We used wood, a xylem rich material, as a surface for bacterial attachment and biofilm formation, under shear force. We demonstrated that X. fastidiosa strains isolated from various hosts formed biofilm on wood in this in vitro assay. Different biofilm morphology was detected, which seems to vary according to the strain tested and microenvironmental conditions analyzed. We observed that strains from different hosts could be grouped according to three parameters: biofilm morphology, the ability to form clumps in liquid culture, and the ability to attach to glass surfaces. We hypothesize that biofilm formation is likely a major virulence factor in diseases related to X. fastidiosa, bringing a new perspective for disease treatment.

Prevalence of Giardia and Cryptosporidium and characterization of Cryptosporidium spp. isolated from wildlife, human, and agricultural sources in the North Saskatchewan River Basin in Alberta, Canada

The environmental distribution of Giardia spp. and Cryptosporidium spp. is dependent upon human, agricultural, and wildlife sources. The significance of each source with regard to the presence of parasites in the environment is unknown. This 2-year study examined parasite prevalence in human sewage influent, wildlife, and agricultural sources associated with the North Saskatchewan River Basin in Alberta, Canada. Fecal samples were collected from cow-calf, dairy, and hog operations in the watershed area. Sewage-treatment facilities were sampled bimonthly during the 2-year study, and wildlife scat was collected at locations along tributaries of the North Saskatchewan River. All samples were analyzed for the presence of Giardia and Cryptosporidium, using sucrose-gradient separation followed by immunofluorescent microscopy. Giardia and Cryptosporidium were detected in all three sources. The lowest prevalence of both Giardia (3.28%) and Cryptosporidium (0.94%) was found in wildlife, with 6 of 19 species testing positive. Sewage influent had the highest prevalence of Giardia (48.80%) and Cryptosporidium parvum-like oocysts (5.42%); however, the concentration of both parasites was minimal compared with the concentration detected in cattle feces. Cow-calf sources contained the highest concentration of Giardia (mean 5800/g feces, P < 0.01), and dairy sources contained the highest concentration of C. parvum-like oocysts (mean 295/g feces, P < 0.01). Although prevalence and concentration are higher in cattle feces than in sewage, the Giardia and Cryptosporidium in animal manure do not have direct access to water draining into the North Saskatchewan River. PCR-based characterization of rDNA from isolates of Cryptosporidium collected from Alberta human, pig, calf, mature steer, dog, cat, and beaver hosts revealed distinct genetic differences that may reflect host specificity.

The use of a Giardia vaccine as an immunotherapeutic agent in dogs

Dogs (n = 13), which had failed to be cured of giardiosis following chemotherapeutic measures, were treated with a Giardia vaccine (2-3 injections). Clinical signs resolved between 16 and 42 days postvaccination and cessation of fecal cyst shedding was between 21 and 70 days. Vaccination is a potential method of treating giardiosis in dogs.

Characterization of biofilm growth and biocide susceptibility testing of Mycobacterium phlei using the MBEC assay system

The importance of non-tuberculosis mycobacterial biofilm species in medicine, industry and the environment has recently gained attention. Our objectives were to characterize biofilm growth of Mycobacterium phlei M4, as a model of rapidly growing mycobacteria using the minimal biofilm eradication concentration (MBEC) and to compare biocide susceptibility of planktonic and biofilm organisms. Scanning electron microscopy was also carried out to observe biofilm morphology. With the exception of Sporicidin and Virkon the minimum bactericidal concentration values for all biocides tested were lower than the MBEC values. The MBEC assay system was seen to produce multiple and reproducible biofilms of M. phlei and to be a useful tool for susceptibility studies.

The pig as a model for excisional skin wound healing: characterization of the molecular and cellular biology, and bacteriology of the healing process

A pig model of wound healing was developed by excision of 2-cm-diameter full thickness skin in young Yorkshire pigs. The results indicated that wound re-epithelialization in this animal model took an average of 20 days. Analysis of cellular change was assessed by use of DNA quantification and determination of apoptotic cells in tissue sections. The results indicate that RNA and DNA contents paralleled each other throughout the healing process, and observed changes in the pattern of RNA and DNA content of the scar tissues were consistent with cell loss due to apoptosis in this model. Expression of mRNA for relevant genes was assessed by use of semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis, using porcine specific primer sets and RNA isolated from normal skin and specimens obtained at various times after wounding. The mRNA values for tumor necrosis factor-alpha (TNF-alpha), connective tissue growth factor (CTGF), insulin-like growth factor II (IGF-II), and decorin were significantly high at specific times after wounding, but mRNA values for the transcription factors (c-fos and c-jun) were significantly decreased. Quantitative bacteriologic results indicated that the total bacterial count in this animal model reached 10(9) colony-forming units (CFU)/g, with the highest value at post-wounding day 7, and Pseudomonas aeruginosa and Staphylocococci aureus were the most common bacteria detected in this model. Further definition of this model should identify unique points in the healing process, and such information could lead to development of therapeutic interventions to improve skin wound healing.

Xenoinfection of nonhuman primates by feline immunodeficiency virus

New viral infections in humans usually result from viruses that have been transmitted from other species as zoonoses. For example, it is accepted widely that human immunodeficiency virus (HIV) is the result of the propagation and adaptation of a simian immunodeficiency virus (SIV) from nonhuman primates to man [1]. Previously, we reported productive infection of primary human cells in vitro by feline immunodeficiency virus (FIV) [2], a lentivirus that causes an immunodeficiency syndrome in cats similar to HIV in humans [3]. The present study extends these findings by demonstrating that cynomolgus macaques (Macaca fasicularis) infected with FIV exhibited clinical signs, including depletion of CD4+ cells and weight loss, that are consistent with FIV infection. The development of an antibody response to FIV gag-encoded proteins and detection of virus-specific sequences in sera, blood-derived cells, and necropsied tissue accompanied these changes. Moreover, the reactivation of FIV replication from latently infected cells was observed after stimulation in vitro with phorbol esters and in vivo with tetanus toxoid. The proposed use of lentiviruses in human gene therapy [4, 5] and of nonhuman cells and organs in xenotransplantation [6] has raised concerns about zoonoses as potential sources of new human pathogens. Therefore, the study of FIV infection of primate cells may provide insight into the principles underlying retroviral xenoinfections.

Molecular and cell biology of skin wound healing in a pig model

To define the pattern of change at the molecular and cellular levels during the healing of excisional skin wounds in the skeletally immature pig, mRNA levels for relevant molecules were assessed by semiquantitative RT-PCR using porcine specific primer sets and RNA isolated from normal skin and samples at various time post-wounding. Analysis of cellular change was assessed by DNA quantification and histology of tissue sections. The results demonstrated that the changes in the pattern of RNA and DNA content of the scar tissue were consistent with the observed increasing cellularity. The mRNA levels for collagen I, III, HSP47, IL-1, TGF-beta, MMP-1, -2 and -9, TIMP-1, -2, and-4, PAI-1, versican were significantly elevated during healing; levels for biglycan and fibromodulin were not significantly altered; and the mRNA levels for TIMP-3 were depressed. These findings suggest that skin wound healing is a series of complex matrix-cell interactions that involve cellular migration and inflammation, followed by proliferation of fibroblasts with new collagen synthesis, and lastly tissue remodeling of the scar.

Studies on the use of Yucca schidigera to control giardiosis

The potential anti-giardial activity of a powdered preparation of Yucca schidigera (yucca powder) was investigated in vitro, in a modified adherence inhibition assay, and in vivo, by enumeration of trophozoites (intestinal) or cysts (fecal) in experimentally infected gerbils and lambs receiving oral doses of whole or butanol-extracted yucca powder. Yucca powder, butanol-, acetone- and chloroform-extracted powder, and the butanol-insoluble fraction of the powder were required in concentrations of 22, 15, 62, 135 and 250 microg/ml, respectively, to reduce in vitro trophozoite adherence by 50%. Ethyl ether extract exhibited no anti-giardial activity. Virtually no trophozoites were tolerant of butanol extract at >or=90 microg/ml. Butanol extract at 1500 microg/ml exerted effects on trophozoites similar to the nitroimidazole, metronidazole, at 40 microg/ml during a 27-h incubation. Reducing trophozoite adherence to 50% of the controls required 5-10h of exposure to butanol extract or metronidazole. Oral administration of butanol extract (6.1mg) or metronidazole (1mg) once daily for 3 days reduced the number of trophozoites in the small intestine of infected gerbils, significantly (P<0.05) in the jejunum and ileum, and numerically (P>0.05) in the duodenum (n=8). Oral dosing of 50mg of butanol extract in eight doses over 3 days reduced (P<0.05) trophozoites in the duodenum and jejunum, and eliminated them from the ileum. Including 4.5% (w/w) yucca powder in the diet did not alter Giardia trophozoite recovery from the duodenum or jejunum of infected gerbils, but trophozoite reduction (P=0.051) was observed in the ileum (n=9). Jejunum gut loop data were inconclusive, possibly due to insufficient duration of exposure of trophozoites to butanol extract. Compared to controls (0g yucca powder per day) lambs receiving 10g of yucca powder per day in their diet shed fewer (P<0.05) Giardia cysts in their feces after 5, 9, 12 and 19 days of treatment, but a corresponding decline in the prevalence of infection was not observed (n=10). After 26 days, Giardia infections persisted in 90% of the lambs in both treatment groups. At the dosing levels studied in vivo, yucca powder did not affect the extent of cyst shedding by experimentally infected lambs, but further purification and concentration of the saponin fraction from Y. schidigera may provide the anti-giardial effects observed in vitro and in dosing trials.

Individual intake and antiparasitic efficacy of free choice mineral and fenbendazole in range calves

The current study was conducted to assess the feasibility of fenbendazole (FB) administration to steers in a free choice mineral supplement. Provision of free choice FB reduces the need for handling of animals as well as decreases the level of animal parasitism. Two separate trials were conducted using 400 +/- 19 kg Holstein steers (n=14 and 17) during the months of July and August. Each steer was tagged with a unique electronic identification (EID) ear tag and randomly allocated into one of two groups. The tags worked in conjunction with a mineral feeder equipped with a load cell by registering the steer's EID number every time the animal entered the electromagnetic field. Individual daily mineral intake and feeding times were determined over two 8-day periods of non-medicated mineral (no FB), separated by a 14-day period of medicated mineral (0.55% FB). Fecal samples were collected at the beginning and end of each trial period and were analyzed for gastrointestinal nematode eggs and Giardia cyst. There was a consistently high level of attendance for the entire experimental period, with the exception of the first six days of the adaptation period. There were three preferential times for visiting the mineral feeder, approximately 07:00, 12:00 and 18:00 h. Individual daily mineral and FB intake was 229 +/- 27.21 g/day and 2 +/- 0.14 mg/kg BW/day, respectively, for the 14-day drug delivery period. The levels of fecal nematode eggs and Giardia cysts decreased significantly (<0.01) between pre- and post-sampling, with reductions of 92% for nematode eggs and 85% for Giardia cysts. Free choice medication for the control of gastrointestinal parasites is potentially effective, provided that the appropriate drug concentration, adaptation period, intake level and duration of treatment is utilized.

The heart of the matter: an essay about the effects of managed care on family therapy with children

This essay is based on a pilot study that examined the effects of managed care on the treatment of children and families, with special attention to community mental health. We embarked on the pilot study to test the accuracy and generalizability of our impression that family therapy and other systemic practices have been marginalized in ordinary clinics and agencies, and to understand the reasons why. We interviewed managed care providers, researchers, family therapy trainers, and clinicians in the Northeast. Our findings led to seven themes that support our impression that, even though there is a consensus about the need for coordinated family-based services, there is a disconnection between state policies, contractual requirements and what is actually occurring at the implementation level. This study suggests that our knowledge of human systems may be in danger of being disqualified and lost, with damaging consequences for the care of children. Yet, as systemic thinkers and practitioners, it is our belief that ethical and effective treatment need not be at odds with care that is cost-efficient. The direction of our future research will be to study whether the involvement of all stakeholders at all levels of planning and training leads to systemic family-based practices that consistently save costs and provide high-quality care.

Giardiasis in dairy calves: effects of fenbendazole treatment on intestinal structure and function

Twelve Giardia duodenalis-infected Holstein dairy calves were allocated into a treatment (n=6) and placebo group (n=6) according to pre-study faecal cyst counts. Calves in the treatment group received an oral dose of 5 mg/kg fenbendazole once daily for 3 days, while placebo calves received a sterile saline solution. Calves were euthanised 7 days following the initiation of treatment and intestinal were collected and prepared for trophozoite quantitation, histology, electron microscopy, and disaccharidase assays. In all calves treated with fenbendazole, intestinal trophozoites were below detection limits, while in saline-treated calves, trophozoites were observed in all intestinal segments. Histologically, no significant difference was observed between treatment groups with respect to intestinal villus height or crypt depth. However, a significant decline in the number of intraepithelial lymphocytes (IEL) was observed in fenbendazole-treated calves when compared with placebo-treated calves in the duodenum (13.9+/-1.2 vs. 17.0+/-1.1 IEL/100 enterocytes) and jejunum (21.6+/-0.8 vs. 30.7+/-1.0 IEL/100 enterocytes). In addition, measurements from TEM micrographs demonstrated a significant increase in microvillus surface area in the jejunum of fenbendazole-treated calves compared with saline-treated calves (31.2+/-10.2 vs. 22.8+/-7.6 microm(2)). This increase in microvillus surface area was also associated with an increase in jejunal maltase activity in fenbendazole-treated calves compared with calves treated with saline. These results demonstrate that fenbendazole is an effective treatment for giardiasis in calves. fenbendazole treatment eliminated Giardia trophozoites from the small intestine of calves resulting in increased microvillus surface area and greater intestinal enzyme activity. This study also demonstrates that the pathogenesis of giardiasis in calves is similar to that observed in humans and laboratory animals, and provides further evidence that Giardia is a pathogen of cattle with potential economic importance.

Individual intake of mineral and molasses supplements by cows, heifers and calves

In two pastures, two multiplex radio frequency (RF) mineral feeders (GrowSafe Systems Ltd.) equipped with load cells were used to monitor feeder attendance and individual intake of mineral by 33 and 36 cow-calf pairs individually identified by RF transponders. A visit was defined as a return to the feeder after a 5-min absence. In exp. 1, attendance of cows and calves at the feeder and intake of mineral were monitored over 13 d. Sodium chloride was included in the mineral at 9.8% (low salt, LS) on days 1 to 6, and at 22.5% (high salt, HS) on days 7 to 13. Percentages of cows and calves that visited the feeder were similar between LS (60.9% and 21.7% respectively) and HS (62.3% and 24.6%). Number of visits (P > 0.05) and daily mineral intake (P < 0.1) were reduced in cows fed HS as compared with LS. Cows had more visits (P < 0.001) and consumed more mineral (P < 0.001) than did calves. In exp. 2, HS as is (control, C) or formulated to contain 0.468% fenbendazole (FB) was provided for 6 d to 36 and 32 cow-calf pairs in adjacent pastures. All of the cows and 93.8% of the calves attended the FB feeder; whereas only 77.8% of the cows and 33.3% of the calves attended the feeder containing C. Fenbendazole increased visits per day (P < 0.05) by both cows and calves. Intakes of FB and C did not differ, but cows consumed more (P < 0.001) mineral than did calves. In exp. 3, variability in intake of protein-molasses blocks by cows and heifers was examined. Intake differed by animal (P < 0.01), but was similar between cows and heifers. Individual average intake was 445 g d−1 with a range of 0 to 1650 g d−1. These experiments demonstrate that universal and uniform consumption of an additive in mineral or molasses supplements by individuals in a herd cannot be assumed. Key words: Free-choice mineral, molasses, individual intake, cow, calf, fenbendazole

Rat model of experimentally induced abacterial prostatitis

BACKGROUND

An experimental model in rats was developed to investigate the significance of mucosal integrity in abacterial prostatitis.

METHODS

Ethanol was instilled into the ventral prostates of male rats to reduce mucosal integrity; dinitrobenzenesulfonic acid (DNBS) was added as an irritant to induce inflammation. Controls received no treatment, ethanol only, DNBS only, or a suspension of bacteria. After various time points, rats were sacrificed, and their prostates were assayed for gross morphology, histological appearance, and cytokine levels.

RESULTS

Prostates subjected to ethanol plus DNBS showed significant inflammation, most notably after 12, 24, and 48 hr. Inflammation judged by gross and histological observations and interleukin-1beta levels correlated well at these times. Rats given only ethanol, DNBS, or no treatment, acting as negative controls, displayed little or no inflammation; rats given a bacterial suspension, acting as positive controls, showed inflammation consistent with past studies. Cytokine assays revealed raised interleukin-1beta levels in this model, while tumor necrosis factor-alpha remained at a basal level.

CONCLUSIONS

The loss of an intact mucosal surface in the prostate resulted in inflammation caused by an irritant. Interleukin-1beta appears to play a role in this inflammation, while tumor necrosis factor-alpha does not.

A CD-1 mouse model of infection with Staphylococcus aureus: Influence of gender on infection with MRSA and MSSA isolates

Staphylococcus aureus is an important pathogen of humans and other animals, causing bacteremia, abscessation, toxemia, and other infectious diseases. An animal model using CD-1 mice was developed to study the pathogenesis of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA). When inoculated into the CD-1 mouse model, it was shown that both MSSA isolates, (HR 78 and CSA-1) and MRSA isolates (MRSA 456 and MRSA 457) led to chronic infection of the kidney. Female CD-1 mice inoculated with MRSA 456 proved to be more susceptible to infection and mortality than their male counterparts. Castrated mice became more susceptible to infection than intact male mice, suggesting a hormonal involvement in the infection process.Key words: Staphylococcus aureus, animal model, gender, MSSA, MRSA.

A CD-1 mouse model of infection with Staphylococcus aureus: influence of gender on infection with MRSA and MSSA isolates

Staphylococcus aureus is an important pathogen of humans and other animals, causing bacteremia, abscessation, toxemia, and other infectious diseases. An animal model using CD-1 mice was developed to study the pathogenesis of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA). When inoculated into the CD-1 mouse model, it was shown that both MSSA isolates, (HR 78 and CSA-1) and MRSA isolates (MRSA 456 and MRSA 457) led to chronic infection of the kidney. Female CD-1 mice inoculated with MRSA 456 proved to be more susceptible to infection and mortality than their male counterparts. Castrated mice became more susceptible to infection than intact male mice, suggesting a hormonal involvement in the infection process.

The effect of stanozolol on 15nitrogen retention in the dog

The objective of the study was to determine the influence of either oral or intramuscular administration of stanozolol on nitrogen retention in dogs by using a non-invasive 15N-amino acid tracer technique. Ten healthy, intact, adult male sled dogs received either stanozolol tablets, 2 mg/dog PO, q12h, for 25 days (Group 1, n = 5) or an intramuscular injection of 25 mg of stanozolol on Days 7, 14, 21, and 28 (Group 2, n = 5). A 15N amino acid (5.27 mmol) was infused intravenously into each dog on Day 0 (before stanozolol treatment) and on Day 31 (after stanozolol treatment). Urine was collected by catheterization from each animal 3 times daily for 3 consecutive days. The 15N-urea enrichment in urine was determined by high-resolution mass spectrometry and the total amount of urea in the urine was determined. Both oral and injectable stanozolol resulted in significant (P < 0.05) increases in amino acid nitrogen retention compared to pretreatment values. Oral stanozolol increased nitrogen retention from 29.2 +/- 8.2% to 50.3 +/- 9.2%, while stanozolol injection increased nitrogen retention from 26.6 +/- 9.9% to 67.0 +/- 7.5%. The response to intramuscular administration was significantly greater than the response to the oral dosing regime. Stanozolol increases amino acid nitrogen retention in dogs, as has been previously observed in rats. This action of stanozolol may be beneficial in dogs under stress of surgical trauma and chronic disease.

Electronic identification: Applications in beef production and research

Individual identification of beef cattle is not new to the Canadian beef industry, as traceback systems played a pivotal role in the eradication of bovine tuberculosis in the 1940s and 1950s and brucellosis in the 1970s and 1980s. Recent concerns over animal health (e.g., bovine spongiform encephaolopathy), export markets, product consistency, meat quality (e.g., tenderness, marbling) and safety (e.g., Escherichia. coli 0157:H7, Salmonella spp.) make reestablishment of a traceback system a logical approach to assuring consumer confidence in Canadian beef. Originally, simple Kurl-lockTM ear tags with a unique number were used to trace individuals back to their herd of origin. Although useful for addressing disease concerns, this system did not lend itself to compiling additional information (e.g., growth performance, animal health, breeding programs, carcass quality) for use in management or marketing decisions. More sophisticated electronic identification systems can readily interface with computers and make information management an even more pivotal component of beef production. Several electronic identification systems (e.g., bar codes, radio frequency identification, read–write systems) are being assessed for their effectiveness for identifying individual cattle under production conditions. In research applications, this technology has the potential for individual animals to become the experimental unit under group housing conditions. By combining electronic identification technology with devices that measure physiological (e.g., temperature, pH, body weight, feed intake) parameters, researchers will be able to collect data in natural production environments that were previously only obtainable under controlled experimental conditions with a limited number of animals. Key words: Electronic identification, beef, traceback, radio frequency identification

Is prophylactic ciprofloxacin effective in delaying biliary stent blockage?

BACKGROUND

Late stent blockage is a major complication of endoscopic stent insertion for malignant obstructive jaundice. Stents block as a result of bacterial infection and biofilm formation. We report a randomized but unblinded study using an animal model to evaluate the effect of prophylactic ciprofloxacin, which selectively suppresses gram-negative bacteria, in an attempt to prolong stent patency.

METHOD

Ten adult cats underwent surgical implantation of 5F polyethylene stents through common bile duct strictures created around the choledochotomy, with the tip of the stent left in the duodenum. Five animals received intravenous ciprofloxacin perioperatively and were then maintained on oral ciprofloxacin 25 mg twice daily. Control cats were not given antibiotics. The animals were sacrificed when signs of biliary obstruction or cholangitis persisted for more than 3 days or at the end of the 16-week study period. Stents were removed and examined for patency. In addition, the stents were cultured to recover the adherent bacteria.

RESULTS

All control animals developed stent blockage within 4 weeks. Two ciprofloxacin-treated cats developed stent blockage at 21 and 42 days, respectively, whereas the other 3 cats had patent stents for the entire study period. There was a significant difference between the median stent patency of 112 days for the ciprofloxacin group versus 16 days for the control group (p < 0.02). Bacteriologic cultures showed that the bile and blocked stents from the control group had predominantly gram-negative bacteria, whereas the bile and stents of the ciprofloxacin group had gram-positive and anaerobic bacteria, with an absence of gram-negative bacteria (p < 0.01).

CONCLUSION

Ciprofloxacin prophylaxis eliminates gram-negative bacterial infection in bile and minimizes sludge formation and may have a potential benefit in delaying stent blockage.