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1.
Groups of 10-12 Romney and Merino wethers were challenged simultaneously with homologous experimental footrot infection after having received the second of 2 doses of Bacteroides nodosus (strain 198) vaccine 0, 4, 8, 12, 16 and 20 weeks previously. Inoculations were carried out 28 days apart and unvaccinated sheep of both breeds were challenged as controls. Most Romneys that had been vaccinated up to 16 weeks prior to challenge were resistant to footrot whereas 8 of 10 controls were susceptible. This resistance was lost by about 20 weeks after vaccination. By contrast, protection against challenge in vaccinated Merinos lasted only about 4-5 weeks, although residual benefits of vaccination were apparent after longer intervals from the reduced number and severity of foot lesions among vaccinates compared with controls. Agglutinin titres, which did not differ markedly after similar intervals between Romneys and Merinos, reached maximum levels between 4 and 8 weeks after the second vaccine dose and subsequently declined. Although peak titres were generally recorded at the time of maximum protection in Merinos, the relationship between agglutinin levels and resistance in the Romneys was ill-defined.  相似文献   

2.
The distribution of 12 Class I ovine lymphocyte antigens (OLA) was examined in 4 flocks of sheep vaccinated against and/or challenged with Bacteroides nodosus, the transmitting agent of footrot. In a flock of 47 Corriedales in New Zealand, which had been specially bred for resistance to footrot, a higher frequency (70.2%) of OLA type SY6 was found compared with 42.9% in 49 unselected Corriedale sheep (P = 0.001). The serum antibody response of 12 selected Corriedale ewes was compared with that of 12 unselected ewes of the same age after vaccination with a multivalent footrot vaccine and the selected ewes had significantly (P = 0.01) higher agglutinin titres than the unselected ewes, 7 weeks after vaccination. In 3 trials involving 108, 120 and 135 Australian Merinos in Victoria, SYlb was associated with a reduction in the number of feet affected with severe footrot (P = 0.05, P = 0.01, P = 0.02) and in 2 of the trials there was a relationship between SY6 and high vaccinal agglutinin titres. This SY6 effect was evident in the first trial 31 days after primary vaccination (P = 0.05) and again 20 days later after secondary vaccination (P = 0.01). In the second trial, when the sheep were vaccinated 49 days after challenge, an association was again found between SY6 and high agglutinin titres (P = 0.05) after primary but not after secondary vaccination. Exposure of 157 vaccinated Merino rams to B. nodosus during a footrot outbreak in New South Wales also showed an association between low infection and SY6 and SYlb.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

3.
Successful protection against lumpy jaw disease in a colony of captive wallabies (Macropus eugenii) was induced by vaccination with a commercial ovine footrot vaccine. No mortalities attributable to lumpy jaw were observed in 69 vaccinated animals while six of 42 unvaccinated control wallabies died of the disease. Vaccinated animals exhibited significant increases in antibody titres to Bacteroides nodosus after the first and second doses of vaccine. Titres were measured by an enzyme-linked immunosorbent assay.  相似文献   

4.
The immune responses of sheep to single and double doses of commercially available louping-ill virus vaccine were examined. The susceptibility to challenge of sheep which had been vaccinated but showed a poor response was also investigated. Two injections of vaccine were required to provoke an adequate antibody response and maximum titres were obtained when there was an interval of two to eight weeks between injections. After challenge, viraemia could not be detected in animals with an antibody titre of 20 although increase in the concentration of humoral antibodies indicated that infection had occurred. Vaccinated but seronegative sheep and vaccinated animals with an antibody titre of 10 were also clinically resistant to the challenge, although circulation of virus was demonstrated. That vaccination had sensitised those animals to viral antigen was evident from the reduced viraemias, the early rise in humoral antibody titres and subsequent protection afforded compared to unvaccinated control animals. Thus, animals with minimal antibody titres after vaccination are protected, but it is recommended that vaccines eliciting the highest possible antibody responses will be the most useful under field conditions.  相似文献   

5.
In a field experiment on irrigated pasture, sheep of several breeds were vaccinated twice, subcutaneously, in the upper neck, with Bacteroides nodosus vaccine containing either depiliated cells (DC vaccine), or whole, piliated cells (WC vaccine) and the responses were measured over the following 14 weeks. DC vaccine was as effective as WC vaccine in protecting against the development of foot-rot under conditions of moderate challenge, although the WC vaccine induced significantly higher pilus agglutinating antibody titres. Foot-rot developed in significantly more vaccinated Merinos (Peppin and Saxon strains) than in Romney Marsh, Dorset Horn or Border Leicester breeds. Agglutinating antibody titres after WC vaccination were significantly lower in the Peppin Merino than in the other sheep for the first 6 weeks, while after DC vaccination the titres remained elevated longer in the Border Leicester and Saxon Merino and were significantly higher from 6 weeks onwards. Reactions at the inoculation sites were generally larger in the British breeds than in the Merinos and among the former the reactions were largest, most numerous and most frequently discharged their contents in the Dorset Horn. Bodyweight gains in all vaccinated sheep were initially reduced, compared with controls, but the differences were no longer significant after the eighth week.  相似文献   

6.
Highly pilate (P) or non-pilate (NP) cells of Bacteroides nodosus were compounded into oil emulsion (O) either with or without prior absorption onto alum (A). The abilities of these four preparations (referred to as PAO, NPAO, PO and NPO vaccines) to stimulate antibody production and to protect sheep from foot rot were compared. Two injections of PAO vaccine protected sheep against homologous challenge 12 weeks after the second dose by PO, NPO and NPAO vaccines were less effective. Sheep were protected against homologous challenge for 14 weeks after a single dose of PAO vaccine and for 22 weeks after three doses; an ameliorative effect was still evident 40 weeks after the third dose. Protection against challenge with two heterologous strains was demonstrated at six weeks after three doses of vaccine. A numerical system of scoring the lesions also confirmed that foot rot in vaccinated sheep challenged outside the 'protective' period of the vaccine was somewhat less severe than in controls. PAO vaccine induced much higher and more persistent titres of agglutinins than the other vaccines tested. There was a relationship between agglutinin titres and resistance to homologous challenge.  相似文献   

7.
The relationship between the serological classification system for serogroup B and for serogroup H of Bacteroides nodosus and cross-protection between subgroups within these serogroups was examined. Protection against ovine footrot following vaccination was achieved against other subgroup strains provided sufficient cross-reactive antibody was induced by shared pilus antigens. Within serogroup B, better cross-protection against one subgroup was obtained with a pili vaccine than a whole cell vaccine which correlated with higher pilus antibody titres induced by the former. For serogroup H, a lack of cross-protection and serological reactivity between subgroups was demonstrated, which indicates that the prototype strain of subgroup H2 should be designated a new serogroup.  相似文献   

8.
Groups of sheep were immunised twice with one or other of six vaccines consisting of purified pili from Bacteroides nodosus at three dose levels (10, 38 and 154 micrograms) and emulsified with either complete (CFA) or incomplete Freund's adjuvant (IFA). Beginning one month after vaccination the sheep were homologously challenged on irrigated pasture, with naturally transmitted foot rot for a period of 26 weeks. Statistical analyses of the number of feet per sheep with severe foot rot demonstrated that there was a significant effect of vaccinal dose but neither an adjuvant effect nor an interaction between dose and adjuvant. Similar conclusions were reached when the titres of antipilus agglutinins in the serum were analysed. By both criteria the responses to doses of 154 and 38 micrograms of pili were significantly better than to 10 micrograms, but not significantly different from each other. The IFA vaccines caused less reaction at the sites of injection than the CFA vaccines and within the former the vaccines containing 10 and 38 micrograms pilus produced less reaction than those containing 154 micrograms. Hence a vaccine containing 38 micrograms of purified pili in IFA is nearly optimal for homologous protection against severe foot rot and is acceptable in terms of the reaction at the injection site.  相似文献   

9.
An outbreak of virulent footrot was investigated in a flock of 605 Merino cross-bred sheep in Bhutan. Conventional control methods in the preceding eight years had reduced its prevalence from 36-79% in different components of the flock to about 15% overall. Only one serogroup (B) of Dichelobacter nodosus was identified among 40 isolates cultured from affected sheep. A vaccine prepared from this strain was used in a pilot trial to compare the response of 14 treated and 14 untreated sheep. All affected, vaccinated animals in this trial healed quickly and were protected against re-infection while additional cases developed among untreated sheep during a period favourable for the spread of footrot. The serogroup B vaccine was administered to the whole flock for two successive years. No other footrot treatment was given during these or subsequent years. The whole flock was examined three times, foot by foot, for two years and twice yearly for another two years. When vaccination began there were 88 affected sheep in the flock, an affected sheep being defined as an animal with a foot-score of 2 or greater in one or more feet. There were neither affected sheep in the flock 30 days after the first dose of vaccine nor were any identified in later inspections. Virulent footrot, originating from the farm under investigation, persisted in neighbouring village flocks during this period. It was concluded that whole flock specific D. nodosus vaccination made a major contribution to the elimination of all clinical signs of footrot from the flock of 605 sheep where the condition had previously persisted for 10 years.  相似文献   

10.
Programmes based on the identification and treatment of cases and the culling of animals refractory to treatment had failed to eradicate virulent footrot from two districts in the western region of Nepal. From 1993 to 1996 vaccination against two endemic virulent strains of Dichelobacter nodosus was tested for its potential to contribute to the eradication of footrot from the region. Only sheep and goats which had been free of signs of footrot at three inspections at monthly intervals before their annual migration to alpine pastures were eligible for inclusion. From November 1992, the treatment of cases identified during inspections included the injection of specific vaccine. Successfully treated cases migrated with their flocks but were excluded from the vaccine trial. Non-responding cases were culled. Forty combined flocks of sheep and goats (approximately 9500 animals) were used initially to compare three vaccination regimens. Eleven flocks (sheep and goats) were treated with two doses of specific vaccine (group A), nine (sheep and goats) were treated with commercial vaccine followed by specific vaccine (group B) and 10 (sheep and goats) were treated with two doses of commercial vaccine (group C) in March to April 1993 before the annual migration; 10 flocks (sheep and goats) remained unvaccinated (group D). Only sheep and goats free of signs of footrot were allowed to migrate. Nevertheless, virulent footrot recurred in many flocks three months later. However, its prevalence was significantly lower in group A than in the other three groups combined. Groups A, B and C then received the specific vaccine before their migrations in 1994 to 1996; group D remained unvaccinated. The annual programme of inspection and identification and treatment of cases continued for seven years, but the vaccinations ceased after four years. There was no recurrence of virulent footrot after November 1993. After the first season the virulent strains of D nodosus used in the specific vaccine could no longer be isolated, although antigenically distinct, benign strains of the organism persisted in cases of benign footrot.  相似文献   

11.
Toxoplasma gondii infection was established in sheep seven days (acute infection) or 28 days (chronic infection) before they were given enzootic abortion (EAE) vaccine alone or simultaneously with louping-ill (LI) vaccine. Uninfected controls received the same vaccination schedule. The serological response of acute toxoplasma-infected sheep to initial LI vaccination was significantly depressed but after revaccination four weeks later these sheep demonstrated a response equal to that of the revaccinated controls. Infected sheep also gave a significantly poorer response to EAE vaccine than control animals, the effect being more marked in those with chronic infection. Revaccination evoked no clear response in any group but on three of five sampling days antibody titres of controls were significantly higher than those of infected sheep.  相似文献   

12.
SUMMARY: Clinical and serological responses were monitored in sheep following experimental challenge with footrot and subsequent vaccination with an homologous rDNA pilus vaccine. Twenty-two clinical indicators of footrot were identified to describe differences between feet, between sheep, between flocks, and over time. All eleven between-sheep indicators were significantly correlated with each other (0.47 to 0.96). However, analyses of liability on a underlying scale showed that those indicators with several categories, such as the number of feet affected or underrun, were most useful: the data strongly indicated that increasing grades of severity reflect a single underlying variable. The proportion of sheep affected and/or underrun (i.c.e. prevalence) was the most suitable indicator of flock differences. Repeatability of footrot scores over time was relatively low (0.36 to 0.56 prior to vaccination; 0.02 to 0.30 after vaccination), highlighting the need for repeat observations to describe differences in footrot over time. A need was shown to incorporate spontaneous or induced healing following vaccination in scoring systems for footrot. Serological assays detected an increase in antibody titres during infection, but antibody titres were not sufficiently correlated with clinical indicators (0.34 to 0.61) to justify their use as indicators of footrot. K-agglutination titres were moderately to highly correlated with Pili ELISA assays (0.69 to 0.86), but the two types of assay are not interchangeable. On balance, K-agglutination is the most appropriate measurement of antibody response for all types of footrot studies. This set of initial analyses has shown large phenotypic variation in all important footrot indicators. Subsequent studies will investigate the extent to which there is genetic variation in these indicators, with the aim of determining the feasibility of incorporating resistance to footrot into breeding programmes. The traits defined and described in this paper from the basis of a large scale investigation into genetic and phenotypic aspects of resistance to footrot. ZUSAMMENFASSUNG: Krankheitsresistenz bei Merinos. I. Moderhinkeresistenz nach experimenteller Infektion und Impfung mit homologer rDNA-pilus vaccine Klinische und serologische Reaktionen wurden nach experimenteller Infektion von Schafen mit Moderhinke und folgender Impfung mit homologer rDNA-pilus vaccine verfolgt. 22 klinische Symptome wurden identifiziert um Unterschiede zwischen Fü?en, zwischen Schafen, Herden und Zeitspannen zu beschreiben. Alle elf "zwischen Schaf" Symptome waren signifikant miteinander korreliert (0,47 bis 0.96). Die Analysen der Liabilit?t auf zugrundeliegender Skala zeigt allerdings, da? Symptome mit mehreren Kategorien, wie etwa Zahl der befallenen Fü?e, am nützlichsten waren: Die Daten weisen darauf hin, da? steigende Erkrankungsgrade eine zugrundeliegende Variable wiedergeben. Der Anteil der befallenen Schafe und/oder lose Klauen gaben am besten Herdendifferenzen wieder. Wiederholbarkeit von Moderhinke über einen Zeitraum war relativ niedrig (0,36 bis 0,56 vor der Vaccination; 0,02 bis 0,30 nachher), wodurch Notwendigkeit wiederholter Beobachtungen der Moderhinke deutlich wird. Notwendigkeit zur Berücksichtigung spontaner oder medikament?s verursachter Heilung nach Impfung in dem Beurteilungssysteme für Moderhinke ist gegeben. Serologisch konnte ein Anstieg von Antik?rperspiegel w?hrend der Infektion festgestellt werden, doch waren diese nicht hinreichend eng mit klinischen Symptomen verbunden (0,34 bis 0,61), um sie als Moderhinkemerkmale betrachten zu k?nnen. K-Agglutinationsspiegel waren m??ig bis stark mit Pili ELISA-Werten korreliert (0,69 bis 0,86), doch waren die beiden nicht auswechselbar. Insgesamt erscheint K-Agglutination das beste Ma? der Antik?rperreaktion in allen Arten von Moderhinkeuntersuchungen zu sein. Diese anf?nglichen Analysen zeigten gro?e ph?notypische Variabilit?t in allen wichtigen Moderhinkesymptomen. Folgende Studien werden das Ausma? genetischer Ursachen dieser Symptome untersuchen mit dem Ziel, Moderhinkeresistenz in Zuchtprogrammen zu berücksichtigen. Die in dieser Arbeit definierten und beschriebenen Merkmale bilden die Basis einer gr??eren Untersuchung über genetische und ph?notypische Aspekte der Moderhinkeresistenz.  相似文献   

13.
The immune response and protection from challenge afforded to adult pigeons by four different vaccination schedules were assessed. Intravenous challenge with a field pigeon isolate was done four weeks after the second of two doses of vaccine given four weeks apart. Little difference in protection was seen between two 0.25 ml and two 0.5 ml doses of oil emulsion vaccine, although the latter produced a slightly higher immune response. In both cases one of 10 challenged pigeons became sick and died. One dose of Newcastle disease virus B1 live vaccine followed four weeks later by 0.5 ml oil emulsion vaccine gave a comparable immune response to two 0.25 ml doses of oil emulsion but only six birds survived challenge. Two doses of Newcastle disease virus B1 vaccine gave a poor immune response and little protection from challenge; all 10 birds became sick and eight died. Assessment of the onset of protection following one dose of either 0.5 ml oil emulsion vaccine or Newcastle disease virus B1 indicated some partial protection in the latter group as early as five days after vaccination. Both groups showed protection at 10 days but by 21 days, although protection was sustained in the oil emulsion group, birds receiving live vaccine were fully susceptible. Measurement of the duration of protection in pigeons given two 0.5 ml doses of oil emulsion vaccine indicated that protection had begun to wane by 40 weeks after the first dose.  相似文献   

14.
A total of 156 chickens in two villages in Malawi were marked and sampled. One hundred and fifteen of these were vaccinated against Newcastle disease immediately after blood sampling, using the V4 heat-resistant strain applied by eye-drop in one village and the inactivated Newcavac vaccine in the other village. A second blood sample was collected 4 weeks after vaccination. The samples were examined using an indirect ELISA test kit. The titre group median ranged from 2 to 3 before vaccination. Both vaccines led to a positive immune response. Newcavac induced higher and more homogeneous titres compared with the V4 vaccine. There was also an increase in the median of the control group where V4 live vaccine had been applied. The differences between the median titres induced by V4, Newcavac and controls were statistically significant.  相似文献   

15.
The immunogenicity of a sonicated extract (SE) and of outer membrane proteins (OMP) of Salmonella enteritidis was tested in birds of about 8 weeks of age. The dose, route of vaccination and the adjuvant used varied in different groups of birds. Two vaccine doses with or without adjuvant were given parenterally or orally 3 weeks apart. OMP vaccines gave significantly higher antibody titres than SE vaccines, as indicated by ELISA. The vaccines adjuvanted with oil produced higher antibody titres than those without any adjuvant. A dose of 1 mg of vaccine produced higher antibody titres than 0.5 mg of vaccine. Adjuvanted vaccine given subcutaneously elicited higher antibody responses than oral vaccines given without adjuvant. The birds were challenged with virulent S. enteritidis organisms at the end of the second week after a booster dose. None of the birds given 1 mg of OMP vaccine subcutaneously shed the organisms when tested by culturing cloacal swabs, although a few birds vaccinated with 0.5 mg of OMP vaccine did so. In general, adjuvanted OMP vaccines gave better protection than SE vaccines.  相似文献   

16.
Footrot and contagious ovine digital dermatitis (CODD) are common causes of foot disease of sheep in the UK. The study reported here is a split flock randomised treatment trial undertaken on a group of 748 fattening lambs on a UK sheep farm affected by CODD and footrot. The sheep were randomly assigned to one of two treatment protocols. In protocol A, all sheep were given two doses of footrot vaccine (Footvax, MSD), plus targeted antibiotic therapy (long-acting amoxicillin, Betamox LA, Norbrook Pharmaceuticals) to sheep with foot lesions likely to be associated with a bacterial infection. In protocol B, the sheep only received targeted antibiotic therapy. Sheep were re-examined and foot lesions recorded five and nine weeks later. New infection rates in the footrot vaccinated group were lower compared with the vaccinated group for both CODD (18.2 per cent compared with 26.4 per cent, P=0.014) and footrot (12.55 per cent compared with 27.5 per cent, P<0.001). Recovery rates were unaffected for CODD (80.46 per cent compared with 70.97 per cent, P=0.14) but higher for footrot (92.09 per cent compared with 81.54 per cent, P=0.005) in sheep which received the vaccine. On this farm, a footrot vaccine efficacy of 62 per cent was identified against footrot and 32 per cent against CODD infection. An association between a sheep having footrot at visit 1 and subsequently acquiring CODD was identified (odds ratio [OR] 3.83, 95 per cent CI 2.61 to 5.62, P<0.001). These results suggest a role for infection with Dichelobacter nodosus in the aetiopathogenesis of CODD on this farm.  相似文献   

17.
The experiments with sheep and young cattle were carried out to test the immunizing efficacy of inactivated adjuvant vaccine against Aujeszky's disease. The vaccine application at doses of 1 ml and 2 ml to lambs at the age of eight to ten months caused the neutralizing antibody production with a significant rise of titres after revaccination. A survival of infection induced with a dose of 10(5.5) TKID50 of virulent virus was recorded in 62.5% of once vaccinated animals and in 87.5% of twice vaccinated animals. When applying different doses of vaccines (from 1 to 10 ml) to young cattle, the antibody reaction level was directly dependent on the inoculum quantity. The double inoculation of animals with vaccines of 2 ml and 5 ml caused the neutralizing antibody production at titres of 1:35, or 1:46. The animals, immunized with the live or inactivated IBR-vaccine possessing high antibody titres against IBR-virus, reacted upon the vaccination with inactivated Aujeszky's vaccine anamnestically, by early production of antibodies in high titres. Metaphylactic vaccination (2 ml of vaccine) of cattle in herds with an acute course days, however earlier during five days from the revaccination when it was carried out in seven days following the first vaccination.  相似文献   

18.
ELISA systems have been developed to quantitate the isotypic antibody response of sheep naturally infected with B. nodosus isolate 198 or injected with pili from isolate 198 in oil emulsion vaccines. The predominant humoral antibody detected following vaccination was IgG1, with substantially lower amounts of IgG2 and IgM. The antibody response was relatively specific for the pilus antigen from isolate 198. Although weak cross reactivities were detected with antiserums to some other isolates, ELISA IgG antibody titres in excess of 200 offer a tentative identification of the isolates of B. nodosus involved in natural outbreaks of footrot. A related ELISA was also developed to quantitate the amount of pili in cell suspensions and crude preparations of pili used in vaccines.  相似文献   

19.
Conventional equine influenza vaccination schedules consist of a primary course of two vaccinations given 4-6 weeks apart followed by a third vaccination (booster) given approximately 5 months later. In between the primary course and the third vaccination, horses are generally considered not to be adequately protected against influenza. This study aimed to investigate whether Thoroughbred foals would benefit from a vaccination schedule in which the third vaccination was given earlier than in conventional vaccination schedules. The vaccines used were an inactivated whole virus equine influenza vaccine and an inactivated whole virus combination vaccine containing equine influenza and equine herpesvirus antigens. Four groups of foals were vaccinated with the two vaccines according to a conventional and an accelerated vaccination schedule in which the third vaccination was given 14 weeks after the first administration. In both groups, the fourth vaccination was given at the normally recommended interval of 26 weeks after the third vaccination for the combination vaccine and 52 weeks after the third vaccination with the influenza only vaccine. The horses were 4-11 months of age and seronegative for influenza. Immunological responses after vaccination were monitored for several months using the single radial haemolysis test. The results indicated that 28 weeks after the first vaccination, antibody levels in horses vaccinated according to the accelerated schedule were not significantly higher than in horses vaccinated according to the conventional schedule. In addition, the total level of antibody production (area under the curve) was not significantly different at that point although antibody titres were slightly higher (but not significantly so) between 16-30 weeks in the accelerated schedule. Between the third and fourth doses, horses vaccinated according to the accelerated schedule had antibodies against influenza below the level required for clinical protection for 39 and 18 weeks for the influenza only and the combination vaccine, respectively, whereas those vaccinated according to the conventional schedule had antibody titres below the level for clinical protection for 9-15 weeks in the corresponding period for both vaccines. Horses vaccinated according to the accelerated schedule with the combination vaccine had lower antibody titres after the fourth vaccination than those vaccinated according to the conventional schedule after the third vaccination, although antibody titres prior to vaccination were similar. For the influenza only vaccine, titres after the accelerated fourth administration were not different to those after the conventional third vaccination. There was no benefit from early booster vaccinations with the vaccines used in this study, so for these vaccines the conventional schedule provided better protection than the selected accelerated alternative. This may contrast with some other vaccine formulations, although a direct comparison using similar protocols has not been made.  相似文献   

20.
An adjuvanted vaccine containing inactivated equine influenza, herpesvirus antigens, and tetanus toxoid was administered to young seronegative foals of 8 months of age by deep intramuscular injection in the neck (Group A). The first two vaccinations were given 4 weeks apart. The third was administered 6 months later. Another group of foals (Group B) was vaccinated according to the same scheme at the same time with monovalent equine herpes virus (EHV) vaccine (EHV1.4) vaccine. Antibody responses to the equine influenza (single radial haemolysis; SRH) and tetanus (ToBi ELISA) components of the vaccines were examined from first vaccination until 1 year after the third vaccination. The influenza components of the combination vaccine induced high antibody titres at two weeks after the second vaccination whereafter titres declined until the time of the third vaccination. After the third vaccination, the titres rose rapidly again to remain high for at least 1 year. Antibody titres against tetanus peaked only after the third vaccination but remained high enough to offer protective immunity for at least 1 year. Foals vaccinated with monovalent EHV1.4 remained seronegative for influenza and tetanus throughout the study. Four and a half months after the third vaccination of groups A and B, a third group of animals was vaccinated twice with monovalent EHV1.4 vaccine 4 weeks apart (Group C). Two weeks after the administration of the second dose in the later group, all groups (A, B, C and an unvaccinated control group D) were challenged with EHV-4. Vaccinated foals (Group A, B, C) showed a clear reduction of clinical symptoms and virus excretion after EHV-4 challenge compared with the unvaccinated control foals. No difference could be demonstrated among the vaccinated groups, suggesting that the combination vaccine protects as well as the monovalent vaccine. In EHV1.4-vaccinated foals both antigenic fractions induced clear protection up to 6 months after vaccination (9). It can therefore be anticipated that the efficacy of the combination vaccine against EHV-1 challenge is similar to the efficacy against EHV-1 induced by EHV1.4 vaccination.  相似文献   

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