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1.
On seven dairy farms an attempt was made to control lungworm disease in calves by turnout on a pasture grazed earlier by cows, followed by a move to aftermath and ivermectin treatment 2 months later. Transmission of lungworm was observed on all farms. Lungworm disease occurred on four farms at treatment. Coughing re-occurred on three of these farms in some animals 2 months later. Owing to poor performance between turnout and treatment, weight gain was below the norm on the farm with the highest infections and most severe respiratory signs. On the other farms respiratory signs did not result in poor weight gain. Gastrointestinal nematode infections remained low on all farms. The conclusion is that this dose and move scheme cannot be recommended for the control of lungworm.  相似文献   

2.
The ability of fenbendazole slow release bolus (Panacur SR Bolus, Hoechst) to control gastrointestinal parasitism in calves during their first grazing season at pasture was evaluated in two field trials. The infection level on both investigated farms was low and the control animals did not develop parasitic gastroenteritis. However, it was possible to demonstrate significant differences in the parasitological and biochemical parameters between the control and treated groups during the grazing season. Faecal egg counts and blood pepsinogen levels in the control cattle at both trials sites were significantly higher than those of the bolus-treated cattle.  相似文献   

3.
Each of 10 set-stocked calves was given a fenbendazole sustained-release intraruminal bolus at turnout for the control of parasitic bronchitis while a group of 10 similar calves was left untreated. The respiratory rates of the control calves were not greatly increased during the grazing season, but persistent coughing was evident from early July when they all had patent lungworm infections. Only occasional coughing was reported from the bolus-treated calves except for a transient increase in its frequency in late September. In mid-August, one of the treated calves was passing lungworm larvae and when they were housed six of the 10 had patent infections. In August tracer calves picked up an average of 23.5 lungworms per day from the control paddock but only 2.1 from the paddock grazed by the treated calves. In September the corresponding figures were 7.6 and 19.2 lungworms per day, respectively, from the control and 'treated' paddocks. After housing, the post mortem worm counts after an experimental challenge with Dictyocaulus viviparus larvae were reduced by 99.2 and 98.7 per cent (P < 0.0001), respectively, for the control and bolus-treated calves in comparison with weight-matched parasite-naive calves. Thus, despite a relatively low level of challenge during the grazing season, the treated animals had developed a considerable degree of protective immunity.  相似文献   

4.
Two groups of second grazing season cattle, which had been treated with an ivermectin-sustained-release bolus (ISRB) in their first grazing season, were monitored during consecutive years (1995 and 1996) on the same second grazing season pasture. In the preceding year (1994), this pasture had been grazed by yearlings that had not received chemoprophylaxis in their first grazing season. The objectives of the study were, firstly, to investigate whether the chemoprophylactic-treated yearlings were less resistant to gastrointestinal nematodes upon subsequent exposure, and hence excreted more strongyle eggs compared to the control yearlings; secondly, whether an increased susceptibility of the previously treated animals resulted in a yearly increase of the pasture infestation on the second grazing season pasture; and finally, whether this affected the second year weight gain of the animals. In 1996, the yearlings that had been chemoprophylactic-treated in 1995 excreted higher numbers of nematode eggs, compared to the previously 'untreated' yearlings. In addition, the proportion of Cooperia larvae was markedly higher in the faecal cultures from the chemoprophylactic treated-animals, suggesting a negative effect of preventive treatment with an ISRB on the acquired resistance of the animals. However, there was no evidence that the slightly higher egg output in the previously treated yearlings had an effect on the larval contamination of the second grazing season pasture. A significant yearly decrease in the second season average daily weight gains was observed, but it could not be inferred from the results of the parasitological parameters that the differences in second year growth were caused by different levels of resilience between chemoprophylactic-treated and -untreated animals. As the study covered three consecutive second grazing seasons, an effect of differences between years (e.g. in weather conditions or grass growth) on the results cannot be excluded.  相似文献   

5.
OBJECTIVE: To evaluate clearance of the vaccine strain, immunologic responses, and potential shedding of Brucella abortus strain RB51 organisms after vaccination of bison calves. ANIMALS: Fourteen 7-month-old female bison calves. PROCEDURE: 10 bison calves were vaccinated SC with 1.22 x 10(10) colony-forming units of B abortus strain RB51. Four bison calves were vaccinated SC with 0.15M NaCl solution. Rectal, vaginal, nasal, and ocular swab specimens were obtained to evaluate potential shedding by vaccinated bison. The superficial cervical lymph node was biopsied to evaluate clearance of the vaccine strain. Lymphocyte proliferative responses to strain RB51 bacteria were evaluated in lymph node cells obtained from biopsy specimens and also in peripheral blood mononuclear cells. RESULTS: Strain RB51 was recovered from superficial cervical lymph nodes of vaccinates examined 6, 12, and 18 weeks after vaccination (4/4, 3/4, and 1/4, respectively) but not in vaccinates examined at 24 weeks (0/3) after vaccination or nonvaccinates examined at all sample collection times (n = 1 bison/sample period). Serologic, immunologic, and bacterial culture techniques failed to reveal shedding of strain RB51 by vaccinates or infection of nonvaccinated bison. Lymphocyte proliferative responses were evident in lymph node cells and blood mononuclear cells from strain RB51-vaccinated bison beginning 12 weeks after vaccination. CONCLUSION: Strain RB51 was cleared from bison by 18 to 24 weeks after vaccination. Bison vaccinated with strain RB51 did not shed the vaccine strain to nonvaccinated bison housed in close proximity. Strain RB51 did not induce antibody responses in bison that would interfere with brucellosis surveillance tests, but did stimulate cell-mediated immunity.  相似文献   

6.
The effect of three intraruminal sustained-release devices (SRD) against Dictyocaulus viviparus infection was tested in five groups of six calves. Group 1 served as untreated controls, and groups 2, 3 and 4 were dosed with a levamisole SRD, a fenbendazole SRD, and an ivermectin SRD, respectively. Group 5 was vaccinated against lungworm and received a levamisole SRD. The calves were turned out on May 28 and the devices given seven days later. All the calves received trickle infections with a total of 200 lungworm larvae between 9 and 34 days after turnout. They were housed on October 28, challenged with 5000 lungworm larvae and slaughtered three weeks later. No clinical signs of parasitic bronchitis were observed during the study. The treated groups gained significantly more weight (P < 0.05) than the controls, but did not differ among themselves. Larvae were first detected in the faeces of the control group between 25 and 32 days after the first infection, and had a group mean of 21 larvae per gram (lpg) after 60 to 80 days, after which the lpg gradually decreased. In group 2, larvae were detected near the end of the grazing season and never exceeded a group mean of 1.5 lpg. In group 3, a very low larval output was observed after housing (group mean 0.1 lpg). Groups 4 and 5 never became patent. The results of an ELISA followed the pattern of larval output; optical densities above the cut-off value were recorded in groups 1, 2 and 3. On the basis of worm recoveries after challenge, group 1 was immune. Group 4 had significantly more lungworms than group 2. There were no significant differences in worm numbers between groups 2, 3 and 5, but the worms in group 5 were retarded in growth (P < 0.05).  相似文献   

7.
Various parameter estimates were assessed at housing in calves that had been exposed to gastrointestinal nematodes during a first grazing season. The analysis involved 41 groups of first grazing season (FGS) calves on 15 different farms in Belgium and comprised groups that had received chemoprophylactic treatment and untreated controls. Serum pepsinogen levels gave the clearest division between chemoprophylactic-treated calf groups (all were <2.6 U tyr), and untreated calf groups in which sub-clinical (range: 2.0-4.1 U tyr) and clinical infections (range 3.7-6.3 U tyr) occurred. There was also a tight relationship between individual pepsinogen values and adult Ostertagia burdens obtained at slaughter. In chemoprophylactic-treated groups there was a significant negative relationship between mean serum pepsinogen levels at housing and the proportion of the grazing season covered by different chemoprophylactic systems. Although only limited data on crude adult Ostertagia antigen ELISA were available, a good relationship between optical densities and estimated exposure was also found. The parasitological parameters, faecal egg counts and pasture Ostertagia larval counts at housing, and weight gain per day, gave less clear divisions among the three categories (chemoprophylaxis, sub-clinical and clinical). Distinguishing how much exposure a calf group has experienced during a first grazing season could help in designing more appropriate control measures for the FGS calves in the next year, assuring good protection and at the same time allowing sufficient exposure for the development of acquired immunity to Ostertagia, and for this serum pepsinogen is recommended.  相似文献   

8.
Twelve calves aged 6-10 months, and 12 calves aged 10-16 months were turned out onto a permanent pasture known to have been contaminated with oocysts of Eimeria alabamensis during the previous year. Two days after turnout, six of the older calves and six of the younger were each treated with one bolus per 200 kg bodyweight containing 1.6 g baquiloprim and 14.4 g sulphadimidine. The other 12 calves were left untreated. The excretion of Eimeria oocysts, the faecal dry matter and the weight gain of treated and untreated calves within each age group were compared during the first 3 weeks on pasture to assess the efficacy of the bolus in preventing E. alabamensis coccidiosis. All the older of the untreated calves and four of the younger developed gruel-like to watery diarrhoea 4-7 days after turnout. The faecal consistency of the treated calves remained firm and they lost significantly less weight than the control calves during the first 13 days on pasture. The treated calves also excreted significantly fewer oocysts during the first 20 days of grazing; their oocyst excretion remained low during days 8-10 when all but one of the diarrhoeic control calves excreted more than 850,000 oocysts per gram faeces (OPG). Starting on days 12 to 14 the oocyst excretion of 8 of the treated calves increased to 20,000-65,000 OPG and of 2 calves to 210,000-240,000 OPG. There was no difference in oocyst output between treated and untreated calves from the fourth week of grazing and no difference in weight gain among the younger calves. In the older calves there was a tendency for the untreated calves to gain more weight than treated calves.  相似文献   

9.
Empirical analysis of the profitability of moderate grazing are presented based on sample dairy farms in Pennsylvania and New York. Net income per cow was higher for dairy farms that employed moderate intensive grazing than for dairy farms that employed extensive grazing. Income appeared to be adequate for family living expenses, but moderate intensive grazing could not be considered a high profit system. Detailed analyses of dairy farms that employed moderate and extensive grazing in northern Pennsylvania indicated that returns to management and owner equity were higher for pasture enterprises than for corn silage or hay enterprises. Positive dairy profits were related to lower feed costs. Milk production was lower on farms that employed moderate grazing than on farms that employed extensive grazing. Logit regression analysis characterized farms that employed moderate intensive grazing as oriented toward dairy rather than toward crop production; these farms had lower culling rates and a greater dependence on milk sales as a share of total sales. The reduced use of fertilizers and chemicals suggests that moderate grazing had environmentally sustainable features.  相似文献   

10.
The influence of chemoprophylaxis with an ivermectin sustained-release bolus in the first grazing season on the resistance of cattle to gastrointestinal nematodes during the following grazing season was investigated. In 1993 and 1994 dairy replacement calves were either given one bolus at the start of their first grazing season or left untreated. The two groups were grazed separately on a pasture that was divided into two similar sized paddocks. Faecal egg counts, serum pepsinogen and antibody levels were measured to evaluate host-parasite contact. Pasture infection levels were estimated by pasture larval counts and worm counts in tracer calves. After winter housing the animals were monitored during their second grazing season on a pasture that was also divided into two similar sized paddocks. Acquired resistance to gastrointestinal nematodes was evaluated by faecal egg counts and weight gains. Again, pasture infection levels were determined and pepsinogen and antibody levels were measured. During the first grazing seasons gastrointestinal nematode infections were controlled very effectively by the bolus, as shown by the greater weight gains, the negligible faecal egg counts and the low serum pepsinogen and antibody levels in the treated calves. In contrast, all parameters showed extensive parasite-host contact in the untreated animals. The efficient prophylaxis in the treated groups resulted in low levels of larval contamination on the paddocks grazed by the treated animals, compared to moderate infection levels at the end of both first grazing seasons on the paddocks grazed by the untreated animals. During the second grazing seasons (1994 and 1995) the faecal egg output was low in all groups. Although in the previously treated animals faecal egg counts were consistently higher, the differences were minimal, resulting in comparable levels of larval contamination on both paddocks. Serum pepsinogen and antibody levels were not significantly different between the groups and indicated a similar level of larval uptake on both paddocks. No negative effect of the previous chemoprophylaxis on the clinical condition and the weight gain of the second season grazing animals was observed.  相似文献   

11.
We studied the early immunity induced by a live glycoprotein E (gE) negative bovine herpesvirus 1 (BHV1) marker vaccine. Three groups of specific-pathogen-free calves were either not vaccinated, or vaccinated two days or two hours before the introduction of a calf that was intranasally infected with wild-type BHV1 the day before. We quantified the shedding of gE-negative vaccine virus and of wild-type virus, using a double-staining immunoassay. In calves vaccinated two hours before the introduction of the infected calf, the shedding of wild-type virus was reduced, compared with that of the unvaccinated control calves. The shedding of wild-type virus was most significantly reduced in the calves that were vaccinated two days before: only very small amounts of wild-type virus were isolated. Wild-type virus was not detected at all in the samples from one of the five calves of that group. Furthermore, this calf was the only one in which we did not detect antibodies against gE. Hence, intranasal vaccination with a live gE-negative vaccine induced early immunity against a BHV1 contact infection. This suggests that this vaccine can be used efficaciously in the early stages of a BHV1 outbreak.  相似文献   

12.
An immunoprophylaxis program for R. equi infection of foals has been established on a number of thoroughbred breeding farms in Argentina over the past 4 years. Nearly 800 mares annually were immunized subcutaneously during the last 2 months of pregnancy with 2-3 doses of a vaccine containing soluble antigens of R. equi, including the virulence associated protein (VapA) and 'equi factors' exoenzymes. The mortality from R. equi pneumonia in the foals from vaccinated dams dropped from an average of 3% in the 5 years before the vaccination program was initiated to an average of 1.2% in the 4 years during which the program was applied (P < 0.02). On 3 farms, an additional 380 foals of vaccinated dams annually over 3 years also received at 25 days of age 600-1200 ml of hyperimmune plasma from donors immunized with this vaccine, and as well at 4 days of age in foals with poor transfer of R. equi antibodies from their dams. The average foal mortality because of R. equi in the 380 foals annually to which hyperimmune plasma was administered dropped from 5.8% on these 3 farms to 0.2% (P < 0.05). Active vaccination of foals of unvaccinated mares on an enzootic farm at 20, 30, and 40 days of age did not protect them from mortality due to R. equi pneumonia. Serology was done by complement fixation and an agar gel immunodiffusion (AGID) tests using antigens prepared in the same manner as the vaccine antigens. The immune responses among hyperimmune plasma donors varied considerably as did the responses of vaccinated mares. Of 1117 serum samples with normal post suckling gammaglobulin levels (> 600 mg%) collected at 2 days of age from foals of vaccinated mares, 36% showed a negative or weak positive AGID reaction, while the remainder had positive to strongly positive reactions.  相似文献   

13.
In this study potential vaccine candidate immunogens were identified and evaluated in a vaccine challenge trial. Calves vaccinated with a partially purified fraction of Psoroptes ovis-soluble proteins had 8 of 14 calves free of palpable lesions 8 wk after a challenge infestation. A self-grooming behavioral response elicited by a pruritic immediate-type allergic reaction was believed to be an effector in protecting the vaccinated calves from a clinical P. ovis infestation.  相似文献   

14.
A critical issue has been the observation that vaccination of children with a formalin-inactivated respiratory syncytial virus (RSV) vaccine is associated with disease enhancement. We have taken advantage of bovine RSV and our experience with this disease in calves to develop a natural model that parallels human disease. Using formalin-inactivated bovine RSV vaccine calves were either sham-vaccinated/infected, vaccinated/infected, or vaccinated/sham-infected and their clinical signs, pulmonary function, and histological lung lesions quantitatively scored. Interestingly there was significantly greater disease in vaccinated/infected calves and histological lesions in calves were similar to those of affected children. Finally, we note that vaccination did not induce neutralizing antibodies, but IgG antibodies were detected by ELISA. Our model of RSV enhanced disease is important because it provides quantifiable evidence of disease severity that can be applied to evaluate the mechanisms of immunopathology and the safety of candidate RSV vaccines.  相似文献   

15.
This study was designed to evaluate changes in calf and heifer management in a sample of Pennsylvania dairy farms in conjunction with a statewide extension program on dairy replacements. The extension program reached dairy farmers in addition to individuals in agribusiness, veterinarians, and others who have frequent contact with dairy farmers through a multiplicity of information channels. An extensive survey was conducted during the 1st yr of the project on 329 commercial dairy farms throughout Pennsylvania. The same farms were contacted 2.5 to 3 yr later for comparison. Most (84.7%) of the farmers in the original random sample learned new information about calf and heifer management during this time, and 77.3% reported that they received all or part of this new information from extension. Sources of information most often used by the farmers in this study were dairy magazines, extension newsletters, and meetings organized either through extension or agribusiness. Adoption by farmers of many of the targeted practices specific to calving management, preweaned calves, and health management increased over this period.  相似文献   

16.
An outbreak of ovine listerial meningo-encephalitis on sheep farms in eastern Gippsland, Victoria, during winter and spring 1978, is recorded. Cases were confirmed by histology of brain or by culture of Listeria monocytogenes from sheep on 21 farms. The morbidity rate in affected flocks ranged from 0.2% to 8.0%, and the case fatality rate was almost 100%. The peak incidence of disease followed a period of continuous heavy rain and flooding of grazing pasture, and the majority of affected flocks were located on poorly drained coastal sandy soil. There was evidence of concurrent debilitating disease in many of the cases submitted for laboratory confirmation of listeriosis.  相似文献   

17.
Research on the prevention of gastrointestinal nematode infections of cattle has mainly concentrated on comparing a specific chemoprophylactic treatment system to an untreated control group on a particular farm. Here, the results from analysis of 85 studies involving over 2000 first grazing season (FGS) calves put onto pasture for at least 4 months from late spring/early summer over a 26-year period in 13 countries in Western Europe are presented. Both control and chemoprophylactic treated FGS calf groups were considered. All chemoprophylactic systems (slow- and pulse-release boli, strategic treatments) were given early in the grazing season. Two general infection levels emerged--'sub-clinical' (32 studies) and 'clinical' (53 studies). The 'sub-clinical' infections were characterised by no clinical symptoms of parasitic gastroenteritis (PGE) being observed in the control groups. Mean faecal egg counts in the 'clinical' control groups were significantly higher than those for 'sub-clinical' control groups for almost the entire season with overall peaks of 275 and 100 EPG respectively. Maximum pasture larval counts were also significantly higher in the 'clinical' control groups with 44% of 'clinical' pastures > 10,000 L3 kg(-1) dry herbage by the end of the FGS, compared to only 15% of 'sub-clinical' pastures. There was a significant positive relationship between log transformed worm burdens from tracers put onto pastures for 2 weeks and the corresponding pasture larval count. No evidence of density dependence in tracer worm burden was observed. Weight gains in the 'clinical' control groups (375 g/day) were significantly lower than those of the 'sub-clinical' control groups (530 g/day). No symptoms of PGE were observed in any of the chemoprophylactic treated groups, but in those studies with an outbreak of PGE in the control group, the treated groups had significantly higher faecal egg and pasture larval counts than treated groups in 'sub-clinical' studies. The overall weight gain in chemoprophylactic treated calves in 'clinical' studies (600 g/day) was significantly lower than the chemoprophylactic treated calves in 'sub-clinical' studies (690 g/day), and was not significantly different from the weight gain of control calves in 'sub-clinical' studies. These results indicate that on heavily infected pastures, chemoprophylaxis will prevent PGE, but calves will still suffer production losses.  相似文献   

18.
Between 1959 and 1996, research was performed to change a vaccine against babesiosis in Australia and to improve it as actual or threatened untoward field responses became apparent. The most significant change occurred in 1964 with the traditionally used carriers of Babesia being replaced as vaccine donors by acutely infected splenectomised calves. This ensured the infectivity of the vaccine and was fortuitously associated with a reduction in the virulence of Babesia bovis in vaccine. Since then, more than 27 million doses of highly infective vaccine have been supplied from the laboratory at Wacol near Brisbane. This vaccine reduced serious losses from babesiosis in vaccinated cattle in Australia to very low levels and has now gained acceptance worldwide. Research to ensure the continuing effectiveness of the vaccine has proved to be essential.  相似文献   

19.
Four studies were conducted to a similar experimental design in the U.S. to evaluate the effectiveness of doramectin injectable administered to yearling stocker cattle in the control of gastrointestinal nematodiasis over the subsequent grazing period. Studies were conducted in Wisconsin (WI) and Arkansas (AR) during the summer season. The other two studies were conducted in Georgia (GA) and Mississippi (MS) during the winter/spring season. Doramectin was compared with both ivermectin injectable and ivermectin pour-on in the WI study, with ivermectin injectable alone in the GA study and with ivermectin pour-on alone in the other two studies. At each study site, an area of permanent pasture previously grazed by parasitized animals was subdivided by fencing into equal pasture units each with its own water supply. A treatment designation (non-medicated control, doramectin injectable, ivermectin injectable or ivermectin pour-on) was randomly assigned to each pasture unit. Weaned beef calves with confirmed gastrointestinal nematode infections were randomly allotted to a pasture unit and corresponding treatment group. Each treatment group consisted of three replicates of seven animals per pasture unit (total 21 animals) in the WI study, three replicates of four or six animals per pasture unit (total 16 animals) in the AR study, five replicates of six animals per pasture unit (total 30 animals) in the GA study and three replicates of 12 animals per pasture unit (total 36 animals) in the MS study. Treatments were 1% doramectin injectable solution, 1% ivermectin injectable solution, 0.5% ivermectin pour-on solution or non-medicated controls. The injectables were administered at a dose of 1 ml/50 kg body weight (200 micrograms doramectin or ivermectin/kg) by subcutaneous injection in the neck. Ivermectin pour-on solution was administered topically at a dose of 1 ml/10 kg body weight (500 micrograms ivermectin/kg). After receiving their prescribed treatment, animals were placed on their designated pasture unit where they remained for the entire grazing period (84-140 days). Fecal nematode egg counts and body weights were monitored at predetermined intervals throughout each study. Doramectin treatment reduced pretreatment egg counts by between 95 and 100% by 21 days post-treatment. Subsequent rises in egg output from exposure to infective pastures were delayed by two to four weeks resulting in substantial reductions in total egg deposition over the grazing period and, therefore, potential pasture recontamination. Doramectin treatment resulted in substantial average daily weight gain advantages (0.152-0.272 kg) over the grazing season compared to non-medicated controls. Advantages were statistically significant (P < 0.05) in three of the four studies. There were no significant differences (P > 0.05) in average daily gain between the doramectin and ivermectin injectable or ivermectin pour-on treated groups.  相似文献   

20.
Currently, overall vaccination coverage against measles among infants ranges between 77% and 89% in Switzerland. Experience in other countries has shown that this level of vaccination is not sufficient to prevent measles outbreaks, especially among schoolchildren. During 1992 surveillance for measles outbreaks in closed populations was conducted in the Canton of Berne. Outbreaks were investigated for vaccine efficacy. Two measles outbreaks in schoolchildren were observed during the study period. In 2 Bernese suburban schools 6 measles cases in children (median age 12.5 years) occurred over a period of 37 days. One of the cases had been vaccinated. Vaccination rate in the healthy control children was 89.7%. Estimated vaccine efficacy was 97.7% (95% confidence interval [CI]: 68%, 99%). The second outbreak occurred in a rural region and comprised 21 measles cases (median age 7.5 years) within 43 days. 10 (47.6%) of the cases attended the same school. None of the cases had been vaccinated. Of the healthy control children 82.6% had received measles vaccine. Estimated vaccine efficacy was 100% (CI: 87%, 100%). These two measles outbreaks were due to failure to vaccinate rather than low vaccine efficacy. Surveillance for measles cases is currently not sufficient for the detection of measles outbreaks in our population. Laboratory confirmation of measles, especially in vaccinated persons, has become more important in a time of relatively low measles incidence.  相似文献   

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