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Biomedical subjects

D W Morck

Publications and source records attributed to D W Morck.

At least 37 records · Page 2Linked to original sources
PubMed1997

Lipopolysaccharide induced acute red eye and corneal ulcers.

Using a new animal model, the aims of this study were to assess the role played by purified lipopolysaccharide (LPS) and neutrophils in the pathogenesis of acute red-eye reactions (ARE) and corneal ulcers. In addition, IL-1 alpha was assessed for its implications in the formation of corneal ulcers. Following corneal abrasion, eyes of rabbits underwent single or double exposures to various doses of LPS from Pseudomonas aeruginosa or Serratia marcescens. This protocol induced ARE symptoms, and their severity depended on the dosage, number of LPS exposures, and type of LPS used (LPS from S. marcescens showing highest virulence). Corneal ulcers were induced by delivering a high dose of Serratia LPS (100 micrograms) followed by a low dose (10 micrograms). Histopathological examination revealed that both ARE and corneal ulceration were associated with prominent neutrophil infiltration. In addition, many lymphocytes and other monocytic cells infiltrated ulcerated ocular tissue. Tear fluids obtained from ulcerated eyes contained high concentrations of a protein recognized by anti-rabbit IL-1 alpha antibodies as demonstrated by immunoblotting studies. The results indicate that LPS can induce ARE and corneal ulceration in the absence of any live bacteria. Moreover, the findings implicate the accumulation of neutrophils and IL-1 alpha-related proteins in the pathogenesis of ARE and corneal ulcers.

Animals↗
PubMed1997

Giardia and Cryptosporidium in Canadian farm animals.

Giardia intestinalis and Cryptosporidium spp. are commonly identified intestinal pathogens in humans and animals. In light of the clinical disease, production losses and zoonotic potential of both Giardia and Cryptosporidium infections, a study was undertaken to investigate the prevalence of these parasites in cattle, sheep, pigs and horses in Canadian farms at different geographical locations. A total of 104 cattle, 89 sheep, 236 pigs and 35 horses were sampled from 15 different Canadian geographical locations. Fecal samples were examined after concentration and immunofluorescent staining. Giardia and Cryptosporidium were present in cattle and sheep in six out of six sites sampled. In cattle the overall prevalence was 29% for Giardia and 20% for Cryptosporidium. Giardia was identified in 38% of sheep while 23% of sheep were positive for Cryptosporidium. Giardia and Cryptosporidium were identified in four out of six hog operations with an overall prevalence of 9% for Giardia and 11% for Cryptosporidium. All horse sampling locations (4/4) were positive for Giardia with 20% of animals infected. Cryptosporidium was identified in three out of four sampling sites with a prevalence of 17%. The prevalence of Giardia and Cryptosporidium was greater in calves and lambs compared to adults. This study demonstrates that both Giardia and Cryptosporidium appear to be prevalent in farm livestock.

Animals↗
PubMed1997

Efficacy of fenbendazole for treatment of giardiasis in calves.

OBJECTIVE: To determine efficacy of fenbendazole for treatment of giardiasis in calves. ANIMALS: Twenty male and 15 female Holstein calves (100 to 180 kg), naturally infected with Giardia sp. PROCEDURE: In vitro fenbendazole susceptibility and resistance development was determined for a ruminant Giardia isolate by use of an adherence assay. Calves were treated as follows: group 1, a single administration of 5 mg of fenbendazole/kg of body weight; group 2, a single administration of 10 mg of fenbendazole/kg; group 3, 5 mg of fenbendazole/kg, every 24 hours for 3 days; group 4, 10 mg of fenbendazole/kg, every 24 hours for 3 days; group 5, 20 mg of fenbendazole/kg, every 24 hours for 3 days; group 6, 0.833 mg of fenbendazole/kg, every 24 hours for 6 days; and group 7, saline solution. Fecal Giardia cysts were counted on days -3 through -1 and 1 through 7, 9, 11, 13, 21, and 28 by use of sucrose gradient concentration and staining with a fluorescent monoclonal antibody. RESULTS: The 50% adherence inhibition concentration was 0.024 +/- 0.002 microgram/ml, and resistance could not be detected after 5 weeks of continuous culture at sublethal concentration of fenbendazole (0.01 microgram/kg). Fenbendazole was 100% effective in eliminating cysts from the feces within 6 days for calves in treatment groups 2-6. Reinfection was observed in some calves within the 28-day study period. CONCLUSIONS: Fenbendazole is effective in the elimination of Giardia infections in calves, but repeat treatments may be required in reinfected animals. CLINICAL RELEVANCE: Fenbendazole is an effective and economical treatment for Giardia-associated diarrhea and growth rate reduction in calves.

Animals↗
PubMed1997

Treatment of experimentally induced pneumonic pasteurellosis of young calves with tilmicosin.

Twenty four (24) healthy male Holstein calves (< 70 kg) were each experimentally infected by intrabronchial inoculation of 4.0 x 10(9) viable cells of Pasteurella haemolytica-AI (B122) at Time = 0 h. At 1 h following inoculation animals received either: 1) Sham treatment with sterile 0.85% saline SC (n = 12); or 2) a single injection of 10 mg tilmicosin per kg body weight (n = 12). Calves that were non-infected and tilmicosin-treated were also included for determining tilmicosin concentrations in serum and lung tissue at 1, 2, 4, 6, 8, 24, 48, and 72 h (n = 3-per time). In the infected calves, response to therapy was monitored clinically. Serum samples were collected for determination of tilmicosin concentrations using HPLC. Any animal becoming seriously ill was humanely killed. Complete necropsy examinations were performed on all animals and included gross pathologic changes, bacteriologic analysis, histopathology, and determination of pulmonary concentrations of tilmicosin. Tilmicosin treated animals responded significantly better to therapy than saline-treated control calves. Clinical assessment of calves during the study indicated that tilmicosin-treated calves had significantly improved by T = 8 h compared to satine-treated animals (P < 0.05). At necropsy tilmicosin-treated calves had significantly less severe gross and histological lesions (P < 0.05) of the pulmonary tissue. Of the 12 saline-treated calves, 92% (11/12) had Pasteurella haemolytica-A1 in lung tissue, while of the tilmicosin-treated calves 0% (0/12) cultured positive for P. haemolytica. Mean (+/- standard error) serum tilmicosin concentrations in infected calves peaked at 1 h post-injection (1.10 +/- 0.06 micrograms/mL) and rapidly decreased to 0.20 +/- 0.03 microgram/mL, well below the MIC of 0.50 microgram/mL for P. haemolytica-A1 (B122), by 12 h. These serum concentrations were very similar to serum concentrations of tilmicosin in non-infected tilmicosin-treated calves. Lung tissue concentrations of the antibiotic were comparatively high, even at 72 h post-infection (6.50 +/- 0.75 ppm). Lung tissue concentrations at 72 h were significantly higher in experimentally infected calves than in non-infected tilmicosin-treated animals (P < 0.05). These data demonstrate that tilmicosin was effective in treating experimentally-induced pneumonic pasteurellosis as determined by alleviation of clinical signs, pathological findings at post mortem, and presence of viable bacteria from the lung. Concentrations substantially above MIC for P. haemolytica were present in lung tissue even at 72 h following a single subcutaneous injection of 10 mg tilmicosin per kg body weight.

Animals↗
PubMed1997

Giardia and Cryptosporidium in dairy calves in British Columbia.

A study was undertaken to determine the prevalence of Giardia infections in dairy calves and to compare Giardia and Cryptosporidium infections in calves of different ages. Fresh fecal samples were collected from 386 male and female Holstein calves (newborn to 24 wk) in 20 dairies located in the lower Fraser river valley area of British Columbia. Giardia intestinalis, Cryptosporidium parvum, and Cryptosporidium muris were enumerated in each sample after concentration by sucrose gradient centrifugation and immunofluorescent staining. Giardia was identified at all farm locations. The overall prevalence of Giardia in calves was 73% with a geometric mean cyst count of 1180 cysts per gram of feces (CI, 41 to 5014). Cryptosporidium parvum and C. muris were identified in 80% and 40% of the farms, respectively. The prevalence of C. parvum was 59%, and the geometric mean for oocysts was 457 oocysts per gram of feces (CI, 18 to 160). The prevalence of C. muris was only 2% and the mean oocyst counts were 54 oocysts per gram of feces. Giardiasis was not age dependent, and approximately 80% of the calves from 2 to 24 wk were infected. In contrast, C. parvum infections were predominant in calves 2 to 4 wk, while C. muris was demonstrated in calves older than 4 wk. Fourty-seven percent of calves with diarrhea had high numbers of Giardia cysts in their feces. Giardia infections are highly prevalent in dairy calves and should be considered in animals with diarrhea or failure to thrive.

Animals↗
PubMed1997

Preliminary data on the efficacy of a Giardia vaccine in puppies.

Twenty puppies were vaccinated with a trophozoite-derived Giardia vaccine on day 0 and boosted on day 21 (Group 1); 10 control puppies received only saline (Group 2). Both groups were experimentally infected on day 35 with 1 x 10(6) Giardia duodenalis trophozoites by intraduodenal injection. Immunization provided protection to experimental Giardia infection.

Analysis of Variance↗
PubMed1996

Effect of salinomycin on giardiasis and coccidiosis in growing lambs.

An experiment was undertaken to determine the effect of salinomycin on Giardia in vitro and on Giardia and coccidia in growing lambs. Concentrations of salinomycin above (3.9 micrograms/mL) reduced the adherence (index of viability) of Giardia S2 trophozoites by more than 50%. This strain did not develop resistance after repeated exposure to sublethal concentrations of salinomycin. Five of 40 lambs escaped natural infection by Giardia, and these were inoculated with > or = 500,000 cysts. Giardiasis (presence of cysts in feces) was confirmed in all lambs before commencement of the experiment. Coccidiosis (presence of oocysts) developed by natural exposure. Lambs were assigned randomly to diets containing 0, 4, 10, or 16 ppm of salinomycin. Giardia cyst and coccidia oocyst excretions were determined on 6 d during the first week and weekly thereafter. Giardia cysts were detected at each sampling date in all treatments (highest release, 2.3 x 10(6) cysts/g feces). The number of Giardia cysts shed in feces was not affected (P > .05) by salinomycin but did decline (P < .05) with time. Average infection rates remained above 50% until d 41 of the experiment and declined linearly (P < .05) with salinomycin concentration and time. The number of coccidia oocysts in feces was low (highest release, 6.8 x 10(4) oocysts/g feces), but shedding occurred in 38 of the 40 lambs. Treatment with salinomycin had a cubic effect (P < .05) on coccidia oocyst excretion, and no oocysts were detected beyond d 28. Treatment effect on average daily gain (P < .002), dry matter intake (P < .02), and final live weight (P < .07) was cubic, whereas carcass weight (P < .003) and dressing percentage (P < .08) were linearly affected by salinomycin concentration. Although a beneficial effect of 10 ppm salinomycin on lamb performance was apparent, the development of natural resistance makes it difficult to attribute this response to the control of coccidiosis or giardiasis.

Administration, Oral↗
PubMed1996

Use of tilmicosin for treatment of pasteurellosis in rabbits.

OBJECTIVES: To determine tilmicosin concentrations in serum and tissues of rabbits given a single dose of 25 mg of tilmicosin/kg of body weight. To examine the effects of tilmicosin treatment (25 mg/kg, s.c.) in rabbits with pasteurellosis. PROCEDURE: After receipt of tilmicosin, healthy New Zealand White female rabbits (n = 3 at each time) were euthanatized at 2, 4, 8, 24, 48, and 72 hours for collection of blood samples and tissue specimens; 4 rabbits served as untreated controls. Rabbits (male and female) with pasteurellosis (n = 42) also were treated. Tilmicosin concentration was determined in serum, lung, and uterine tissues. Rabbits with pasteurellosis were treated with tilmicosin. Response was monitored, using bacteriologic culturing and antibiotic resistance and susceptibility testing, and by scoring clinical signs of disease. RESULTS: Serum tilmicosin concentration reached 1.91 +/- 0.18 micrograms/ml after 2 hours, decreased to 0.77 +/- 0.07 microgram/ml by 8 hours, and was below minimum inhibitory concentrations for Pasteurella multocida at 24 hours. Terminal half-life in serum was 5.97 hours. Lung and uterus concentrations were 14.43 +/- 1.34 and 11.57 +/- 0.09 ppm at 2 hours, and were 5.10 +/- 1.05 and 8.87 +/- 1.66 ppm at 24 hours, respectively. 69% (29/42) of rabbits with pasteurellosis responded favorably in 3 days. Second treatment was required in 31% (13/42), and 5 of these rabbits had clinical signs on day 6; 2 of these 5 had improved. Treatment success rate was 93% (39/42). Of the rabbits that were culture positive on day 0, 35% (6/ 17) remained positive on day 3. 1 of 6 rabbits was culture positive on day 6. CONCLUSION: Tilmicosin (25 mg/kg, s.c.) was an effective treatment for pasteurellosis in New Zealand White rabbits. CLINICAL RELEVANCE: Tilmicosin treatment of pasteurellosis in rabbits is useful in research rabbits and in those destined for meat production. A single dose of antibiotic minimizes stress-associated handling.

Animals↗
PubMed1996

The efficacy of a Giardia lamblia vaccine in kittens.

Twenty kittens were vaccinated with a Giardia lamblia vaccine prepared on a commercial scale on day 0 and boosted on day 21 (group 1); while 10 kittens received only saline (group 2). These kittens were challenged on day 35 with 10(6) Giardia lamblia trophozoites by a surgical intraduodenal injection. Three control kittens were not vaccinated and not challenged (group 3). Following challenge, Giardia vaccinated kittens had significantly fewer days in which abnormal stools were observed and reduced food intake occurred compared to saline injected animals. The rate of weight gain between group 1 and group 2 animals was not different in the prechallenge period (day 0 to day 35), but vaccinated animals had a significantly higher weight gain in the postchallenge period (P < 0.05). On day 56, all vaccinated animals were not passing cysts in their feces, while 40% of saline injected kittens had Giardia cysts in their feces. In vaccinated kittens, cysts were never demonstrated in 45% of the animals, while cysts were detected in 90% of the saline injected kittens. Viability of the cysts in vaccinated kittens was 38% while the cysts viability in saline injected kittens was 99%. On postmortem examination, trophozoites could be detected in 5% of vaccinated kittens and 60% of saline injected kittens. Vaccination produced an elevated Giardia specific serum IgG and IgA response prior to challenge and throughout the postinfection period. The Giardia infection in the saline injected group did not induce an elevated specific serum response. Giardia vaccination of kittens provides protection in kittens from an experimental challenge by reducing or eliminating intestinal trophozoites and fecal cyst excretion.

Aging↗
PubMed1995

Efficacy of sustained release ciprofloxacin microspheres against device-associated Pseudomonas aeruginosa biofilm infection in a rabbit peritoneal model.

The relative effectiveness of a poly(L-lactic acid) ciprofloxacin hydrochloride (CIP) microsphere formulation (250-425 microns) against peritoneal implanted biofilm of Pseudomonas aeruginosa was investigated in a rabbit model. Correlations between in-vivo CIP pharmacokinetics in peritoneal dialysate and serum after intraperitoneal administration, in-vivo cell counts and rabbit survival rate were obtained. Dialysate and serum concentrations after 12 h (C12h) were greater than those obtained with free drug whereas maximum serum concentrations (Cmax) were lower and the time to reach Cmax(tmax) was longer. A silastic implant device pre-colonised with P. aeruginosa for 2 days was implanted in the rabbit peritoneum, and dialysate with or without drug or microspheres was administered via a catheter. Rabbits receiving no antibiotic and those receiving free drug (10 mg in dialysate) died of peritonitis and septicaemia, whereas all rabbits given CIP microspheres recovered completely from infection. The viable count of P. aeruginosa was markedly reduced or eliminated from the catheter, the device and the peritoneal wall in CIP microsphere-treated rabbits but not in rabbits treated with free drug, as determined from histological and scanning electronmicroscopic evidence. These results demonstrate that sustained release of antibiotics at biofilm eradication concentrations (BEC) is required to treat biofilm infections associated with peritoneal implanted devices.

Absorption↗
PubMed1995

Effects of giardiasis on production in a domestic ruminant (lamb) model.

OBJECTIVE: To examine the effects of giardiasis on production and carcass quality, using growing lambs as a domestic ruminant model. DESIGN: Randomized block. ANIMALS: Giardia-free lambs: 23 in infected group, 24 in control group. PROCEDURE: Six-week-old, specific-pathogen-free lambs were infected with Giardia trophozoites; control lambs received saline solution. Clinical signs of infection, body weight, and feed intake were determined for 10 weeks. Carcass weight and quality were determined at slaughter weight of 45 kg. RESULTS: Giardia infection persisted from weeks 7 to 16. For 5 weeks after challenge exposure, abnormal feces were more frequently observed in infected lambs. Giardia infection was associated with a decrease in rate of weight gain and impairment in feed efficiency. Time to reach slaughter weight was extended in infected lambs, and the carcass weight of Giardia-infected lambs was lower than that of control lambs. CONCLUSION: Giardiasis has a negative effect on domestic ruminant production. CLINICAL RELEVANCE: Giardiasis in domestic ruminants is an economically important disease, thus necessitating control or elimination of the infection.

Analysis of Variance↗
PubMed1994

The parasympatholytic effects of atropine sulfate and glycopyrrolate in rats and rabbits.

Nine groups of rats (n = 5 per group) received an intramuscular (IM) injection of one of the following drugs or drug combinations: saline, atropine (0.05 mg/kg), glycopyrrolate (0.5 mg/kg), ketamine:xylazine (85:15 mg/kg), ketamine:detomidine (60:10 mg/kg), atropine:ketamine:xylazine (0.05: 85:15 mg/kg), glycopyrrolate: ketamine:xylazine (0.5:85:15 mg/kg), atropine:ketamine:detomidine (0.05: 60:10 mg/kg) or glycopyrrolate: ketamine:detomidine (0.5:60:10). Similarly six groups of rabbits (n = 5) received an IM injection of either saline, atropine (0.2 mg/kg), atropine (2 mg/kg), glycopyrrolate (0.1 mg/kg), ketamine:xylazine (35:10 mg/kg) or glycopyrrolate:ketamine:xylazine (0.1:35:10 mg/kg). In rats, atropine sulfate (0.05 mg/kg) and glycopyrrolate (0.5 mg/kg) produced an increase in heart rate for 30 and 240 min, respectively. In rabbits atropine sulfate at either 0.2 or 2.0 mg/kg did not induce a significant increase in heart rate, but glycopyrrolate (0.1 mg/kg) elevated the heart rate above saline treated animals for over 50 min. Both atropine and glycopyrrolate provided protection against a decrease in heart rate in rats anesthetized with ketamine: xylazine (85:15 mg/kg) or ketamine: detomidine (60:10 mg/kg); however, glycopyrrolate was significantly more effective in maintaining the heart rate within the normal range. Glycopprrolate also prevented a decrease in heart rate in rabbits anesthetized with ketamine:xylazine (35:5 mg/kg). Neither glycopyrrolate nor atropine influenced respiration rate, core body temperature or systolic blood pressure when used alone or when combined with the injectable anesthetic. Glycopyrrolate is an effective anticholinergic agent in rabbits and rodents and more useful as a preanesthetic agent than atropine sulfate in these animals.

Animals↗
PubMed1994

Experimental evaluation of a commercial footrot vaccine against native Canadian strains of Dichelobacter nodosus.

Two serotypes of the anaerobic bacterium Dichelobacter nodosus were used to experimentally infect young sheep resulting in infectious pododermatitis or footrot characteristic of the natural disease in sheep. The specific serotypes of D. nodosus were reisolated from the feet and identified using immunofluorescent microscopy of hoof scrapings. Prior immunization of sheep with a commercially available bacterin containing whole cell preparations of ten strains of D. nodosus resulted in serum IgG reactive to a serotype of D. nodosus common to the vaccine. Immunization also produced serum IgG reactive to a serotype of D. nodosus not incorporated in the vaccine. A less severe infection occurred in the immunized sheep than in the controls regardless of the serotype of bacteria used to infect them. Clinical lameness and lesion severity were milder in sheep infected with the serotype of D. nodosus common to the vaccine. Western blot analysis of sera from convalescent sheep showed cross-reactive antibodies to nonfimbrial cell surface proteins, as well as bacterial lipopolysaccharide. Such cross-reactivity may explain the partial protection seen in animals infected with a serotype distinctive from the ones in the vaccine. Despite the historical emphasis of fimbrial immunogens in ovine footrot this study using a new model of experimental ovine footrot suggests other surface antigens may also be important in protective immunity.

Animals↗
PubMed1993

Therapeutic efficacy of fleroxacin for eliminating catheter-associated urinary tract infection in a rabbit model.

The efficacy of fleroxacin as therapy for experimentally induced catheter-associated urinary tract infection (CAUTI) was examined. A rabbit model of CAUTI using a closed urinary catheter drainage system and the mutant strain of Escherichia coli (WE 6933) were used to examine three dosage regimens (30 mg/kg q8h i.v.; 20 mg/kg q8h i.v.; and 10 mg/kg q8h++i.v.) of fleroxacin administered intravenously for 4 days. Quantitative bacterial counts, urinary concentrations of fleroxacin and desmethylferoxacin, histopathologic changes, and electron microscopic evaluation of catheter-associated biofilm and mucosal biofilm were performed. The results indicated that the bacterial biofilm on the urinary catheter could be eliminated by fleroxacin at 30 mg/kg q8h i.v. and 20 mg/kg q8h i.v. Fleroxacin concentrations in urine exceeded the levels necessary to destroy E. coli. Viable bacteria were eliminated with the third regimen (10 mg/kg q8h i.v.), but electron microscopy demonstrated remnants of bacterial biofilm. Histopathologic changes were significantly reduced in all fleroxacin-treated rabbits, and scanning electron microscopy showed deterioration of the bacterial biofilm on the surface of the Foley catheter in treated animals. These data suggest that fleroxacin may be useful for treating catheter-related infections because these therapeutic dosages limited ascending infections of the urethra and bladder, eliminated catheter-associated biofilms, and killed planktonic bacteria in urine.

Animals↗
PubMed1993

Prophylactic efficacy of tilmicosin for bovine respiratory tract disease.

The prophylactic administration of injectable tilmicosin for pneumonia in weaned beef calves was investigated in 1,806 animals. Comparisons were made among calves receiving an "on-arrival" injection of tilmicosin, calves receiving a single injection of long-acting oxytetracycline, and calves receiving no prophylaxis. Morbidity and mortality attributable to pneumonia, morbidity and mortality attributable to all causes, and case fatality were significantly lower in the group of calves that received tilmicosin, compared with calves that received long-acting oxytetracycline and calves that received no prophylactic antibiotic. Mean time to initial pneumonia treatment was significantly extended in calves that received prophylaxis, compared with those that received no antibiotic on arrival at the feedlot. Calves that received tilmicosin gained significantly more weight than calves that received oxytetracycline. Calves that were not treated for pneumonia during the trial period gained significantly more weight than did those calves that were treated for pneumonia regardless of experimental group. The majority of mortalities were attributable to fibrinous pneumonia (31/34). Important bacterial isolates (Pasteurella spp, Haemophilus somnus, Actinomyces pyogenes) obtained at necropsy did not have resistance to tilmicosin in association with administration of tilmicosin as prophylaxis for pneumonia. However, bacterial resistance to trimethoprim/sulfonamide and to oxytetracycline were commonly found in these postmortem isolates.

Animals↗
PubMed1993

A porcine model of Staphylococcus epidermidis catheter-associated infection.

The suitability of using catheterized, partially nephrectomized (uremic) pigs to study catheter-associated infection in peritoneal dialysis was investigated. In some pigs, an inoculum of 10(9) cfu of Staphylococcus epidermidis ATCC 35984 was deposited around the catheter exit site and the organism was allowed to colonize over 21 days. The strain was recoverable from tissues and catheter samples at various locations along the catheter tract from inoculated pigs at postmortem examination. Uninoculated control catheters were colonized to a significantly lesser degree and by various other staphylococcal species. Immune response by inoculated pigs toward catheter-associated bacteria was indicated by a significant increase in serum antistaphylococcal IgG concentration and an increased percentage of peripheral polymorphonuclear leukocytes. Uremia had no significant effect on serologic response. Immunoblotting against S. epidermidis lysostaphin-extracted proteins showed that although incubation with inoculated group antisera produced more intense banding and reacted to a wider range of protein than did antisera from uninoculated controls, common antigenic proteins among the groups were found.

Animals↗