Endostatin inhibits bradykinin-induced cardiac contraction

.Endogenous fragments of extracellular matrix are known to possess various biological effects. Levels of endostatin, a fragment of collagen type XVIII, increase in certain cardiac diseases, such as cardiac hypertrophy and myocardial infarction. However, the influence of endostatin on cardiac contraction has not been clarified. In the present study, we investigated the effects of endostatin on bradykinin-induced atrial contraction. Isometric contractile force of mouse isolated left atria induced by electrical current pulse was measured. Voltage-dependent calcium current of guinea pig ventricular myocytes was measured by a whole-cell patch-clamp technique. Endostatin (100–1,000 ng/ml) alone treatment had no influence on left atrial contraction. On the other hand, pretreatment with endostatin (300 ng/ml) significantly inhibited bradykinin (1 µM)-induced contraction and voltage-dependent calcium current. These data suggest that endostatin may decrease bradykinin-induced cardiac contraction perhaps through the inhibition of voltage-dependent calcium channel.     

Clinical application of 2.16% hypertonic saline solution to correct the blood sodium concentration in diarrheic calves with hyponatremia

The aim of this study was to examine whether 2.16% hypertonic saline solution (HSS) is useful for the treatment of diarrheic calves with hyponatremia. Eleven of 13 female Holstein calves exhibiting moderate diarrhea and hyponatremia received 1,250 ml of 2.16% HSS over 15 min regardless of body weight. The remaining two calves that were unable to stand and had severe hyponatremia received 2,500 ml of 2.16% HSS intravenously over 30 min. As a result, hyponatremia in all diarrheic calves was significantly improved by the administration of 2.16% HSS from 122.2 ± 7.0 mEq/l at pre to 134.8 ± 3.7 mEq/l at post, which was above the threshold of 132 mEq/l for hyponatremia. Therefore, 2.16% HSS may be useful for hyponatremia in calves with diarrhea.     

Hyperferritinemia is associated with short survival time in dogs with multicentric lymphoma

In the present study, we examined the relationship between serum ferritin concentration before treatment and survival time in dogs with multicentric lymphoma. Eighteen dogs with multicentric lymphoma were enrolled in the study. When the dogs were classified into high and low ferritin groups on the basis of their serum ferritin concentration (3,000 ng/ml cut-off value), the median survival time of dogs with high concentrations (≥3,000 ng/ml, n=7) was 40 days, whereas it was 360 days among dogs with low concentrations (<3,000 ng/ml, n=11). This difference was statistically significant (P=0.001). This finding suggests that the initial high level of serum ferritin indicates short survival time in dogs with multicentric lymphoma. Large-scale research is necessary to confirm this finding.     

Detection of ruminant meat and bone meal in feeds by sandwich ELISA with monoclonal antibodies

A sensitive and reproducible enzyme-linked immunosorbent assay (ELISA) using two monoclonal antibodies directed against a synthetic peptide with an amino-acid sequence related to the C-terminus of bovine myoglobin and the whole molecule of sodium dodecyl sulphate (SDS)-denatured bovine myoglobin was adapted for detecting bovine myoglobin in contaminated feeds. The ELISA employed bovine meat extract of a known myoglobin concentration as a calibration standard and had an limit of detection (LOD) of 3.54 ng/ml and an limit of quantification (LOQ) of 11.0 ng/ml corresponding to 0.022% and 0.067% (wt/wt) bovine meat-and-bone-meal (MBM) mixed in 20-fold-diluted feed extracts, respectively. A cut-off threshold of 20.6 ng/ml bovine myoglobin was set to simplify ELISA and facilitate quick assessment of test results without a tedious calibration process. The ELISA was able to detect bovine MBM in artificially prepared model feeds, mixed botanical feeds, mixed botanical feeds with skimmed milk, fish meal, pork meal and pork/chicken meal at 0.1% (wt/wt). It was also able to detect sheep MBM in test feeds, but showed no reactivity to swine MBM, chicken MBM, skimmed milk or gelatine of bovine origin. The advantages of this method are the quick and easy extraction protocol of proteins from test feeds, using 100 mM sodium sulphide and 0.6% sodium dodecyl sulphate in the extraction solution and the effective detection of bovine and sheep MBM at 0.1% (wt/wt).     

A multicenter case-control study of risk factors for equine protozoal myeloencephalitis

OBJECTIVE: To identify risk factors for equine protozoal myeloencephalitis (EPM) among horses examined at 11 equine referral hospitals. DESIGN: Case-control study. ANIMALS: 183 horses with EPM, 297 horses with neurologic disease other than EPM (neurologic controls), and 168 horses with non-neurologic diseases (non-neurologic controls) examined at 11 equine referral hospitals in the United States. PROCEDURES: A study data form was completed for all horses. Data were compared between the case group and each of the control groups by means of bivariate and multivariate polytomous logistic regression. RESULTS: Relative to neurologic control horses, case horses were more likely to be > or = 2 years old and to have a history of cats residing on the premises. Relative to non-neurologic control horses, case horses were more likely to be used for racing or Western performance. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that cats may play a role in the natural epidemiology of EPM, that the disease is less common among horses < 2 years of age relative to other neurologic diseases, and that horses used for particular types of competition may have an increased risk of developing EPM.     

Bovine respiratory disease: efficacy of different prophylactic treatments in veal calves and antimicrobial resistance of isolated Pasteurellaceae

The present study was conducted to evaluate the efficacy of two prophylactic antibiotic treatments against bovine respiratory disease (BRD) in veal calves. In addition, the antibiotic susceptibilities of isolated Pasteurellaceae were tested. The calves were treated either on the day of arrival by a single administration of tulathromycin (group A, n = 20), by a peroral administration of chlortetracycline, sulphadimidine, and tylosin (group B, n = 20) for seven consecutive days, or were not prophylactically treated (group C, n = 19). On the first day of clinically diagnosed BRD, transtracheal lavage samples were obtained prior to therapeutic treatment and were subsequently cultured. Pasteurellaceae isolates were tested for their susceptibility to 12 antimicrobial agents by the determination of the minimal inhibitory concentrations. During the first 56 d after arrival, different calves in group A and B suffered from one episode of clinically diagnosed BRD while calves of group C experienced two episodes. The average daily weight gain during the same period was significantly lower in group C (0.89 ± 0.04 kg/d) than in the two prophylactically treated groups (1.14 ± 0.05 and 1.15 ± 0.04 kg/d for group A and B, respectively). The improved performance of groups A and B in comparison to group C could be related to a lower incidence of respiratory disorders during the first days after arrival in the prophylactically treated animals. No differences in the clinical efficacy were seen between the two tested prophylactic treatments. The most prevalent bacterial pathogens isolated (n = 79) were Pasteurella multocida (23% of isolated pathogens), Mycoplasma bovis (18%), and Mannheimia varigena (16%). For the isolated Pasteurellaceae, a high resistance pattern was observed to tylosin (83% of the tested P. multocida and 88% of the Mannheimia spp. isolates resistant) and tilmicosin (56% of the tested P. multocida isolates non-sensitive).     

Blood biochemical values in Japanese Black calves in Kagoshima Prefecture,Japan

To obtain blood biochemical basic data of Japanese Black calves in Kagoshima Prefecture, Japan, blood samples were obtained from 582 clinically healthy calves on 27 farms. Calves were divided into three stages: the suckling stage (between 14 and 90 days of age, n=191), the early growing stage (between 91 and 180 days of age, n=200) and the late growing stage (between 181 and 270 days of age, n=191). The mean concentration of total cholesterol, triglyceride, nonesterified fatty acids, calcium and zinc, and the mean activities of γ-glutamyltransferase and alkaine phospatase in the suckling stage were significantly higher than those in the early and late growing stages (P<0.01). The mean concentration of total protein, albumin and globulin increased gradually with growing. The mean concentration of beta-hydroxybutyrate in the suckling stage was below 150 µmol/l, however, it elevated above 400 µmol/l in the early and late growing stages. The mean concentration of copper concentration was above 70 µg/dl in all stages. The mean concentration of zinc was between 90 and 110 µg/dl in all stages. These results suggest that the blood biochemical values of Japanese Black calves vary with growing stages, and the blood parameters obtained in this study are considered useful as indices for health management of Japanese Black calves.     

A globotetraosylceramide (Gb4) receptor-based ELISA for quantitative detection of Shiga toxin 2e

Currently, no simple assays are available for routine quantitative detection of Escherichia coli-produced Shiga toxin 2e (Stx2e) that causes porcine edema disease. Here, we present a novel quantitative detection method for Stx2e based on the measurement of Stx2e binding to the specific globotetraosylceramide (Gb₄) receptor by ELISA (Gb₄-ELISA). No cross-reactivity was found with the other Shiga toxins Stx1 and Stx2, indicating high specificity. When the recombinant Stx2e B subunit (Stx2eB) was used, the absorbance measured by Gb₄-ELISA increased linearly with Stx2eB concentration in the range of 20–2,500 ng/ml. The Gb₄-ELISA method can be easily performed, suggesting that it would be a useful diagnostic tool for porcine edema disease.     

Effect of trehalose supplementation in milk replacer on the incidence of diarrhea and fecal microbiota in preweaned calves

Trehalose, a nonreducing disaccharide consisting of d-glucose with α,α-1,1 linkage, was evaluated as a functional material to improve the gut environment in preweaned calves. In experiment 1, 173 calves were divided into two groups; the trehalose group was fed trehalose at 30 g/animal/d with milk replacer during the suckling period, and the control group was fed nonsupplemented milk replacer. Medication frequency was lower in the trehalose group (P < 0.05). In experiment 2, calves (n = 20) were divided into two groups (control group [n = 10] and trehalose group [n = 10]) based on their body weight and reared under the same feeding regimens as in experiment 1. Fresh feces were collected from individual animals at the beginning of the trial (average age 11 d), 3 wk after trehalose feeding (experimental day 22), and 1 d before weaning, and the fecal score was recorded daily. Fecal samples were analyzed for fermentation parameters and microbiota. The fecal score was significantly lower in the trehalose group than in the control group in the early stage (at an age of 14 to 18 d; P < 0.05) of the suckling period. Calves fed trehalose tended to have a higher proportion of fecal butyrate on day 22 than calves in the control group (P = 0.08). Population sizes of Clostridium spp. were significantly lower (P = 0.036), whereas those of Dialister spp. and Eubacterium spp. tended to be higher in the feces of calves in the trehalose group on day 22 (P = 0.060 and P = 0.083). These observations indicate that trehalose feeding modulated the gut environment and partially contributed to the reduction in medication frequency observed in experiment 1.     

Cardiovascular effects of total intravenous anesthesia using ketamine-medetomidine-propofol (KMP-TIVA) in horses undergoing surgery

Cardiovascular effects of total intravenous anesthesia using ketamine-medetomidine-propofol drug combination (KMP-TIVA) were determined in 5 Thoroughbred horses undergoing surgery. The horses were anesthetized with intravenous administration (IV) of ketamine (2.5 mg/kg) and midazolam (0.04 mg/kg) following premedication with medetomidne (5 µg/kg, IV) and artificially ventilated. Surgical anesthesia was maintained by controlling propofol infusion rate (initially 0.20 mg/kg/min following an IV loading dose of 0.5 mg/kg) and constant rate infusions of ketamine (1 mg/kg/hr) and medetomidine (1.25 µg/kg/hr). The horses were anesthetized for 175 ± 14 min (range from 160 to 197 min). Propofol infusion rates ranged from 0.13 to 0.17 mg/kg/min, and plasma concentration (Cpl) of propofol ranged from 11.4 to 13.3 µg/ml during surgery. Cardiovascular measurements during surgery remained within clinically acceptable ranges in the horses (heart rate: 33 to 37 beats/min, mean arterial blood pressure: 111 to 119 mmHg, cardiac index: 48 to 53 ml/kg/min, stroke volume: 650 to 800 ml/beat and systemic vascular resistance: 311 to 398 dynes/sec/cm⁵). The propofol Cpl declined rapidly after the cessation of propofol infusion and was significantly lower at 10 min (4.5 ± 1.5 µg/ml), extubation (4.0 ± 1.2 µg/ml) and standing (2.4 ± 0.9 µg/ml) compared with the Cpl at the end of propofol administration (11.4 ± 2.7 µg/ml). All the horses recovered uneventfully and stood at 74 ± 28 min after the cessation of anesthesia. KMP-TIVA provided satisfactory quality and control of anesthesia with minimum cardiovascular depression in horses undergoing surgery.     

Effect of hot-iron disbudding on behaviour and plasma cortisol of calves sedated with xylazine

We investigated cortisol and behaviour for the first hour after hot-iron disbudding of calves aged 37 ± 4 days: disbudded after i/m xylazine (n = 10); disbudded after i/m xylazine and regional anaesthesia with lidocaine (n = 10); sham-disbudded after xylazine and lidocaine (n = 11); sham-disbudded after i/m saline and lidocaine (n = 10). Xylazine-treated groups had higher cortisol than saline-treated animals and showed no differences among them at any time. Sham-disbudded calves with xylazine had lower cortisol at 60 min compared with all other times. Xylazine-alone disbudded calves struggled more during the procedure than all other groups. Xylazine-alone disbudded calves showed more ear-flicks at 10, 25 and 40 min and head-shakes at 40 min than all other groups. We conclude that cortisol should not be used as an indicator of pain in disbudded calves while under the sedative effect of xylazine and that some behaviours during and after the procedure are useful in showing that xylazine alone does not control hot-iron disbudding pain.     

Hemato-biochemical changes, disease incidence and live weight gain in individual versus group reared calves fed on different levels of milk and skim milk

A 2 × 3 factorial design was used to study the impact of rearing systems, individual (I) versus group (G) and different levels of milk/skim milk feeding (F1, F2 and F3) on hemato‐biochemical profile, disease incidence and average daily gain of crossbred (Bos indicus × Bos taurus) calves. Six calves were taken in each group on the basis of their birth weight and housed in individual (2.20 × 1.16 m²/calf) or in group pens (2.20 × 1.03 m²/calf). After 3 days of colostrum feeding, calves were allocated to one of three different milk feeding schedules: milk fed up to 8 weeks of age (F1), milk up to 4 weeks followed by 50% replacement by skim milk up to 6 weeks and 100% thereafter (F2) and 100% replacement of milk with skim milk after 4 weeks (F3). Calf starter and cereal green fodders were fed ad libitum from the second week of age and continued for 14 weeks. Parameters on health and disease profiles of calves (disease incidence, duration of illness, response to treatment and recovery) and weekly live weight change were recorded. Calf scour predominated (52.8%), followed by joint ill (25.0%) and respiratory infections (19.4%). The disease incidence was greater (P < 0.01) in individually housed calves (94.4 vs. 55.9%). The management of navel ill required longer recovery (7.01 days) followed by joint ill (4.87 days) and respiratory infection (4.86 days). The average daily gain during 0–14 weeks of age was higher (P < 0.01) in group‐housed calves (433 ± 22 vs. 355 ± 31 g), while the effect of feeding was not significant. Blood samples collected at 4, 8 and 14 weeks of age showed some periodic higher concentrations (but within normal range) of plasma urea and total protein in group housed calves on F2 and F3 feeding schedules in response to high protein intake. Other parameters remained non‐significantly different. Thus, group‐housed calves can be reared successfully with comparatively better performance and less illness than individually housed ones under the present health care and housing management system. However, the system should not be used as a substitute for good management, and frequent observations of calves should be an integral part of any successful rearing program.     

Pharmacokinetics of marbofloxacin after intravenous and intramuscular administration in Hanwoo,Korean native cattle

Pharmacokinetic (PK) parameters of marbofloxacin (MRFX) in Korean cattle, Hanwoo, were determined following its intravenous (i.v.) or intramuscular (i.m.) administration at a dose of 2 mg/kg. Area under the curve (AUC_{0–24 hr}), half-life (t_1/2) and total body clearance (CL_B) of i.v. MRFX were 6.87 hr∙µg/ml, 2.44 hr and 0.29 l/kg∙hr, respectively, and the corresponding values for i.m. administration of MRFX were 5.07 hr∙µg/ml, 2.44 hr and 0.39 l/kg∙hr. The suggested optimal doses of MRFX in Hanwoo cattle, calculated by integration of PK data obtained in the present study and previously reported minimum inhibitory concentration (MIC) for MRFX against susceptible (MIC ≤1 µg/ml) and intermediate (MIC ≤2 µg/ml) pathogenic bacteria, were 2.1 and 4.2 mg/kg/day by i.v. route and 3.9 and 7.8 mg/kg/day by i.m. route.     

Effects of oral orbifloxacin on fecal coliforms in healthy cats: a pilot study

The study objective was to determine the effect of oral orbifloxacin (ORB) on antimicrobial susceptibility and composition of fecal coliforms in cats. Nine cats were randomized to two groups administered a daily oral dose of 2.5 and 5.0 mg ORB/kg for 7 days and a control group (three cats per group). Coliforms were isolated from stool samples and were tested for susceptibilities to ORB and 5 other drugs. ORB concentration in feces was measured using high-performance liquid chromatography (HPLC). The coliforms were undetectable after 2 days of ORB administration, and their number increased in most cats after termination of the administration. Furthermore, only isolates of Escherichia coli were detected in all cats before administration, and those of Citrobacter freundii were detected after termination of the administration. E. coli isolates exhibited high ORB susceptibility [Minimum inhibitory concentration (MIC), ≤0.125 µg/ml] or relatively low susceptibility (MIC, 1−2 µg/ml) with a single gyrA mutation. C. freundii isolates largely exhibited intermediate ORB susceptibility (MIC, 4 µg/ml), in addition to resistance to ampicillin and cefazolin, and harbored qnrB, but not a gyrA mutation. HPLC revealed that the peaks of mean concentration were 61.3 and 141.0 µg/g in groups receiving 2.5 and 5.0 mg/kg, respectively. Our findings suggest that oral ORB may alter the total counts and composition of fecal coliform, but is unlikely to yield highly fluoroquinolone-resistant mutants of E. coli and C. freundii in cats, possibly because of the high drug concentration in feces.     

Evaluation of the isoflurane-sparing effects of lidocaine infusion during umbilical surgery in calves

ObjectiveTo evaluate the isoflurane-sparing effects of lidocaine administered by constant rate infusion (CRI) during umbilical surgery in calves.Study designRandomized ‘blinded’ prospective clinical study.AnimalsThirty calves (mean 4.7 ± SD 2.5 weeks old) undergoing umbilical surgery.MethodsAfter premedication with xylazine (0.1 mg kg^?1, IM), anaesthesia was induced with ketamine (4 mg kg^?1, IV) and maintained with isoflurane in O₂ administered through a circle breathing system. The calves were assigned randomly to receive a bolus of 2 mg kg^?1 lidocaine IV after induction of anaesthesia, followed by CRI of 50 μg kg^?1 minute^?1 (group L, n = 15) or a bolus and CRI of 0.9% sodium chloride (NaCl, group S, n = 15). End-tidal isoflurane was adjusted to achieve adequate depth of anaesthesia. Heart rate, direct arterial blood pressure and body temperature were measured intraoperatively. Groups were compared by t- tests, anova or Mann–Whitney rank sum test as appropriate.ResultsThe end-tidal concentration of isoflurane (median, IQR) was significantly lower in group L [1.0% (0.94–1.1)] compared to group S [1.2% (1.1–1.5)], indicating a 16.7% reduction in anaesthetic requirement during lidocaine CRI. Cardiopulmonary parameters and recovery times did not differ significantly between groups.Conclusion and clinical relevanceLidocaine CRI may be used as a supplement to inhalation anaesthesia during umbilical surgery in calves in countries where such a protocol would be within the legal requirements for veterinary use in food animals. This study did not show any measurable benefit to the calves other than a reduction in isoflurane requirement.     

The effect of antimicrobial treatment and preventive strategies on bovine respiratory disease and genetic relatedness and antimicrobial resistance of Mycoplasma bovis isolates in a western Canadian feedlot

Feedlot calves (n = 3784) were systematically randomized and allocated in a 2 × 2 factorial study to receive metaphylactic oxytetracycline (OTC) on arrival or no antimicrobial, as well as florfenicol once subcutaneously or twice intramuscularly (48 h apart) if diagnosed with bovine respiratory disease (BRD). Calves of different treatment groups were comingled and followed from placement to re-implantation (~100 days). Animals receiving OTC had a reduced risk of BRD, an increased risk of arthritis, and no significant differences in average daily gain, BRD relapse, overall mortality, or BRD mortality. There were no significant differences between treatment protocols. Deep nasal swabs (n = 233) taken at arrival (n = 122), treatment (n = 77), and swabs from lungs and joints at postmortem (n = 34) were cultured for Mycoplasma bovis from 61 animals ill or dying of chronic pneumonia and arthritis and from 61 healthy calves. There was significant variation in diversity among isolates (n = 51) between study years and different cattle. Metaphylaxis or antimicrobial treatment did not affect the diversity of isolates. Except for tilmicosin, isolates were largely susceptible to tested antimicrobials.     

Comparison of levels and duration of detection of antibodies to bovine viral diarrhea virus 1, bovine viral diarrhea virus 2, bovine respiratory syncytial virus,bovine herpesvirus 1, and bovine parainfluenza virus 3 in calves fed maternal colostrum or a colostrum-replacement product

Colostrum-replacement products are an alternative to provide passive immunity to neonatal calves; however, their ability to provide adequate levels of antibodies recognizing respiratory viruses has not been described. The objective of this study was to compare the serum levels of IgG at 2 d of age and the duration of detection of antibodies to bovine viral diarrhea virus 1 (BVDV-1), bovine viral diarrhea virus 2 (BVDV-2), bovine respiratory syncytial virus (BRSV), bovine herpesvirus 1 (BHV-1), and bovine parainfluenza virus 3 (BPIV-3) in calves fed maternal colostrum (MC) or a colostrum replacement (CR) at birth. Forty newborn male Holstein calves were assigned to the CR or the MC group. Group CR (n = 20) received 2 packets of colostrum replacement (100 g of IgG per 470-g packet), while group MC (n = 20) received 3.8 L of maternal colostrum. Blood samples for detection of IgG and virus antibodies were collected from each calf at birth, at 2 and 7 d, and monthly until the calves became seronegative. Calves in the MC group had greater IgG concentrations at 2 d of age. The apparent efficiency of absorption of IgG was greater in the MC group than in the CR group, although the difference was not significant. Calves in the CR group had greater concentrations of BVDV neutralizing antibodies during the first 4 mo of life. The levels of antibodies to BRSV, BHV-1, and BPIV-3 were similar in the 2 groups. The mean time to seronegativity was similar for each virus in the 2 groups; however, greater variation was observed in the antibody levels and in the duration of detection of immunity in the MC group than in the CR group. Thus, the CR product provided calves with more uniform levels and duration of antibodies to common bovine respiratory viruses.     

Antimicrobial resistance in bovine respiratory disease: Auction market- and ranch-raised calves

This study compared changes in prevalence and antimicrobial susceptibility of Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni in feedlot calves derived from the auction market (AUCT; n = 299) and from a single-ranch source (RANCH; n = 300). In the AUCT calves, the prevalence of Mannheimia haemolytica decreased, whereas Histophilus somni increased over the feeding period. The AUCT calves showed an increase in isolates not susceptible to tulathromycin for all bovine respiratory disease (BRD) pathogens, an increase in Pasteurella multocida and Histophilus somni isolates not susceptible to oxytetracycline, and an increase in Pasteurella multocida isolates not susceptible to florfenicol. In the RANCH calves, the prevalence of all 3 BRD pathogens was high at feedlot entry and decreased significantly during the study period. In RANCH calves, there was a significant increase in Pasteurella multocida isolates not susceptible to oxytetracycline, tulathromycin, and florfenicol. Surprisingly, there was a significant decrease in Mannheimia haemolytica isolates that were not susceptible to oxytetracycline, tilmicosin, and tulathromycin.     

Fluoroquinolone Resistance Mechanism of Clinical Isolates and Selected Mutants of Pasteurella multocida from Bovine Respiratory Disease in China

The minimum inhibitory concentrations (MICs), mutation prevention concentrations (MPCs) and contribution of quinolone resistance-determining region (QRDR) mutations to fluoroquinolone (ciprofloxacin, enrofloxacin and orbifloxacin) susceptibility in 23 Pasteurella multocida (Pm) isolates were investigated. Fluoroquinolone-susceptible isolates (MICs ≤0.25 µg/ml, 9 isolates) had no QRDR mutations, and their respective MPCs were low. Fluoroquinolone-intermediate isolates (MICs=0.5 µg/ml, 14 isolates) had QRDR mutations (Asp87 to Asn or Ala84 to Pro in gyrA), and their respective MPCs were high (4–32 µg/ml). First-step mutants (n=5) and laboratory-derived highly resistant fluoroquinolone mutants (n=5) also had QRDR mutations. The MICs of fluoroquinolones for mutant-derived strains were decreased in the presence of efflux inhibitors. The results indicated that the fluoroquinolone resistance of Pm is mainly due to multiple target gene mutations in gyrA and parC and the overexpression of efflux pump genes.     

Resistance to Eimeria zuernii produced after chemotherapy of experimental infection in calves

Nineteen Holstein-Friesian bull calves were inoculated with 2.4 × 10⁶ sporocysts of Eimeria zuernii by stomach tube. The calves were divided into three groups 10 days after infection. The first group (seven calves) was treated with monensin (1 mg/kg body weight daily) from the 10th–20th day after infection; the second group (six calves) with amprolium (10 mg/kg body weight daily) for the same period of time and the third group (six calves) acted as infected controls. Both drugs were effective in preventing clinical signs, in reducing rates of weight gain and in suppressing oocyst production. The calves were reinfected with E. zuernii 35 days after the initial infection. The calves of all three groups were resistant to the second infection with E. zuernii as measured by rates of weight gain, fecal oocyst output and lack of clinical signs.