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1.
OBJECTIVE: To evaluate humoral immune responses of emus vaccinated with commercially available equine polyvalent or experimental monovalent eastern equine encephalomyelitis (EEE) virus and western equine encephalomyelitis (WEE) virus vaccines and to determine whether vaccinated emus were protected against challenge with EEE virus. DESIGN: Cohort study. ANIMALS: 25 emus. PROCEDURE: Birds were randomly assigned to groups (n = 5/group) and vaccinated with 1 of 2 commercially available polyvalent equine vaccines, a monovalent EEE virus vaccine, or a monovalent WEE virus vaccine or were not vaccinated. Neutralizing antibody responses against EEE and WEE viruses were examined at regular intervals for up to 9 months. All emus vaccinated with the equine vaccines and 2 unvaccinated control birds were challenged with EEE virus. An additional unvaccinated bird was housed with the control birds to assess the possibility of contact transmission. RESULTS: All 4 vaccines induced detectable neutralizing antibody titers, and all birds vaccinated with the equine vaccines were fully protected against an otherwise lethal dose of EEE virus. Unvaccinated challenged birds developed viremia (> 10(9) plaque-forming units/ml of blood) and shed virus in feces, oral secretions, and regurgitated material. The unvaccinated pen-mate became infected in the absence of mosquito vectors, presumably as a result of direct virus transmission between birds. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that emus infected with EEE virus develop a high-titer viremia and suggest that they may serve as important virus reservoirs. Infected emus shed EEE virus in secretions and excretions, making them a direct hazard to pen-mates and attending humans. Commercially available polyvalent equine vaccines protect emus against EEE virus infection.  相似文献   

2.
As a result of the continuing threat of Venezuelan equine encephalomyelitis (VEE), a study was made to determine if revaccination against VEE (TC-83 vaccine) was feasible and if revaccination could be incorporated into other routine vaccination practices. Of the horses given annual vaccination with bivalent western equine encephalomyelitis (WEE) and eastern equine encephalomyelitis (EEE) vaccine, 57% retained detectable serum-neutralizing (SN) antiboyd titers for VEE 18 months after the initial VEE vaccination was given. Of horses with no record of WEE-EEE vacinnation, 100% retained detectable VEE SN antibody titers over the same period. The VEE geometric mean titer was 25 times greater for horses not previously vaccinated against WEE-EEE than for horses given annual WEE-EEE vaccination at the time of VEE vaccination. In horses vaccinated against VEE 18 months previously, the geometric mean titer increased from 4 to 70 at 48 days after the intitial WEE-EEE vaccination. This increase indicated that similar antigenic factors for VEE are possibly present in bivalent WEE-EEE vaccine. In horses previously vaccinated against WEE-EEE and VEE, the best SN antibody response to VEE revaccination occurred when VEE vaccine was given simultaneously with the bivalent WEE-EEE vaccine. Of 150 serum samples tested by both the SN and the hemagglutination-inhibiton tests, agreement between positive reactions at greater than or equal to 1:10 was 70% for VEE, 81% for EEE, and 87% for WEE.  相似文献   

3.
Sensitivity and specificity of an antigen-capture ELISA vs virus isolation in cell culture were evaluated for the detection of eastern equine encephalomyelitis (EEE) virus in the brain tissue of naturally infected equids. Brain specimens from 16 equids with neurologic disease were examined by ELISA and by inoculation onto baby hamster kidney cell cultures. Of 10 brain samples from which virus was isolated in the cell culture bioassay, all were correctly identified as containing EEE virus antigen by ELISA. None of the remaining 6 specimens, without detectable infectious EEE virus, contained detectable antigen. Sensitivity and specificity of the ELISA were 100% with no false-positive or false-negative results. The antigen-capture ELISA was a rapid, sensitive, specific, and simple alternative to a traditional bioassay for the detection of EEE virus.  相似文献   

4.
A prospective study was performed to determine the serologic response of previously vaccinated horses to revaccination against eastern and western equine encephalomyelitis (EEE and WEE). Horses responded variably to each antigen, and some horses had low or undetectable antibodies 6 months after vaccination. Some horses did not develop increasing titers to EEE or WEE despite recent vaccination. Geometric mean titers peaked 2 weeks after revaccination and were significantly increased from before revaccination. Except for one horse, EEE:WEE titer ratios ranged from 0.25 to 2.0. Regular vaccination against EEE and WEE did not interfere with testing for Saint Louis encephalitis.  相似文献   

5.
Venezuelan equine encephalomyelitis (VEE) TC-84 vaccinal virus, from 10-1. quantities of infected duck embryo fibroblast cell culture fluids, was isolated by combined continuous-flow centrifugation with isopycnic banding in sucrose. Most of the recovered infectivity and hemagglutinating activity were in a single band at a buoyant density (?) of 1.2. About 90% of the total input protein (450–520 mg) was removed with the effluent, whereas most of the remaining 10% also banded at a ? of 1.2. Infectivity was inactivated with formalin at a final concentration of 0.05% at 37°C for 24 hr. Formalin-inactivated virus retained its immunogenicity and induced VEE virus-specific antibody in horses and guinea pigs. The horses and those guinea pigs that received equivalent doses of vaccine survived after a challenge of their immunity with virulent VEE virus.  相似文献   

6.
The emergence of epidemic VEE viruses has been reported ever since the virus was first described; this phenomenon is likely to continue to occur because of the high mutation rate of these RNA viruses. A vaccine that was first developed by the US Military for human use has proved helpful in curtailing the spread of VEE virus during epizootics of the disease in equids but not during human epidemics. It has not, however, eliminated the source of these highly pathogenic and transmissible viruses. Occurrences of VEE in equids in Mexico in recent years suggest that the present vaccine is not effective in interrupting transmission of new epizootic viruses arising from what were previously known as avirulent enzootic cycles. Future vaccines against VEE should be based on immunogens derived from enzootic viruses to interrupt VEE virus transmission at the source itself rather than waiting for virulent phenotypes of VEE virus to emerge.  相似文献   

7.
Horses are commonly vaccinated to protect against pathogens which are responsible for diseases which are endemic within the general horse population, such as equine influenza virus (EIV) and equine herpesvirus-1 (EHV-1), and against a variety of diseases which are less common but which lead to greater morbidity and mortality, such as eastern equine encephalomyelitis virus (EEE) and tetanus. This study consisted of two trials which investigated the antigenicity of commercially available vaccines licensed in the USA to protect against EIV, EHV-1 respiratory disease, EHV-1 abortion, EEE and tetanus in horses. Trial I was conducted to compare serological responses to vaccines produced by three manufacturers against EIV, EHV-1 (respiratory disease), EEE, and tetanus given as multivalent preparations or as multiple vaccine courses. Trial II compared vaccines from two manufacturers licensed to protect against EHV-1 abortion, and measured EHV-1-specific interferon-gamma (IFN-gamma) mRNA production in addition to serological evidence of antigenicity. In Trial I significant differences were found between the antigenicity of different commercial vaccines that should be considered in product selection. It was difficult to identify vaccines that generate significant immune responses to respiratory viruses. The most dramatic differences in vaccine performance occurred in the case of the tetanus antigen. In Trial II both vaccines generated significant antibody responses and showed evidence of EHV-1-specific IFN-gamma mRNA responses. Overall there were wide variations in vaccine response, and the vaccines with the best responses were not produced by a single manufacturer. Differences in vaccine performance may have resulted from differences in antigen load and adjuvant formulation.  相似文献   

8.
The dominant immunoglobulin against eastern equine encephalomyelitis (EEE) virus and its duration and the longevity of the EEE virus haemagglutination inhibition (HI) antibodies were determined in sentinel and 125 immunised and hyperimmunised domestic chickens by enzyme-linked immunosorbent assay and the HI test respectively. The chickens ranged in age from 10 weeks to 18 months, were of varied pedigrees and from different countries. Results show that the HI antibody (IgG) is short-lived. It peaks and disappears within 30 days. The secondary response is dominated by the IgM immunoglobulin which is relatively long-lasting. These results are contrary to classical expectations and were observed in all the chickens studied. If these observations are found to be characteristic of birds generally, the present standard method of EEE virus seroepidemiological surveillance must be modified to be effective.  相似文献   

9.
The pathogenesis of Venezuelan equine encephalitis (VEE) virus infection was compared in intraperitoneally inoculated mice (n = 24, 6 to 8 weeks old) and hamsters (n = 9, 90-110 g) using histopathology and immunohistochemical localization of VEE virus antigen. Infected mice developed paralysis, and the majority died by 9 days after inoculation. In contrast, hamsters did not survive beyond 3 days after inoculation, and they did not develop any neurologic signs. VEE virus antigen, demonstrated by immunoperoxidase staining, and pathologic changes were present in extraneural organs of both mice and hamsters. There was more severe involvement in hamsters, particularly in Peyer's patches of the distal small intestine. There was a severe encephalomyelitis in mice, but pathologic changes were not well established in the brains of hamsters before death. VEE virus antigen was widespread in the central nervous system of both mice and hamsters. VEE virus was found to be highly neurotropic in hamsters and had a similar distribution in the brain as in mice, but hamsters died from their extraneural disease before major central nervous system disease developed.  相似文献   

10.
Of 39 captive whooping cranes (Grus americana), 7 died during a 7-week period (Sept 17 through Nov 4, 1984) at the Patuxent Wildlife Research Center, Laurel, Md. Before their deaths, 4 cranes did not develop clinical signs, whereas the other 3 cranes were lethargic and ataxic, with high aspartate transaminase, gamma-glutamyl transferase, and lactic acid dehydrogenase activities, and high uric acid concentrations. Necropsies indicated that the birds had ascites, intestinal mucosal discoloration, fat depletion, hepatomegaly, splenomegaly, and visceral gout. Microscopically, extensive necrosis and inflammation were seen in many visceral organs; the CNS was not affected. Eastern equine encephalitis (EEE) virus was isolated from specimens of the livers, kidneys, lungs, brains, and intestines of 4 of the 7 birds that died, and EEE virus-neutralizing antibody was detected in 14 (44%) of the 32 surviving birds. Other infectious or toxic agents were not found. Morbidity or mortality was not detected in 240 sandhill cranes (Grus canadensis) interspersed among the whooping cranes; however, 13 of the 32 sandhill cranes evaluated had EEE virus-neutralizing antibody. Of the 41 wild birds evaluated in the area, 3 (4%) had EEE virus-neutralizing antibody. Immature Culiseta melanura (the most probable mosquito vector) were found in scattered foci 5 km from the research center.  相似文献   

11.
Recent studies using molecular genetic approaches have made important contributions to our understanding of the epidemiology of veterinary arboviral encephalitides. Viruses utilizing avian enzootic hosts, such as Western equine encephalitis virus (WEEV) and North American Eastern equine encephalitis virus (EEEV), evolve as relatively few, highly conserved genotypes that extend over wide geographic regions; viruses utilizing mammalian hosts with more limited dispersal evolve within multiple genotypes, each geographically restricted. Similar findings have been reported for Australian alphaviruses. This difference may be related to vertebrate host relationships and the relative mobility of mammals and avians. Whereas EEEV and Venezualan equine encephalitis virus (VEEV) utilize small mammalian hosts in the tropics, most WEEV genotypes probably utilize avian hosts in both North and South America. The ability of mobile, infected avian hosts to disperse alphaviruses may result in continual mixing of virus populations, and thus limit diversification. This high degree of genetic conservation is also exhibited by EEE and Highlands J viruses in North America, where passerine birds serve as amplifying hosts in enzootic transmission foci. Most equine arboviral pathogens, including EEEV, WEEV and Japanese encephalitis virus (JEV), occur in a naturally virulent enzootic state and require only appropriate ecological conditions to cause epizootics and epidemics. However, VEE epizootics apparently require genetic changes to convert avirulent enzootic strains into distinct epizootic serotypes. All of these arboviruses have the potential to cause severe disease of veterinary and human health importance, and further molecular epidemiological studies will undoubtedly improve our ability to understand and control future emergence.  相似文献   

12.
Eastern equine encephalomyelitis (EEE) was diagnosed in 19 horses and a flock of emus in the province of Quebec in fall 2008. The EEE virus caused unusual gross lesions in the central nervous system of one horse. This disease is not usually present in Quebec and the relation between the outbreak and favorable environmental conditions that summer are discussed.  相似文献   

13.
The complement fixation-inhibition (CFI) test was described for the detection of antibodies to arboviruses in bird sera. The CFI antibody present in bird sera inhibited the standard complement-fixation reaction of a reference complement-fixing antigen-antibody pair. Using reference antigens (St. Louis encephalitis, eastern equine encephalomyelitis, western equine encephalomyelitis, and yellow fever) prepared from infected mouse brains and reference antisera prepared in rabbits or horses, reproducible CFI antibody titers were obtained in artificially immunized chickens. Time-course studies on the CFI immune response in birds inoculated with live St. Louis encephalitis virus indicated that the CFI antibody was distinct from the antibody detected by the hemagglutination-inhibition test.  相似文献   

14.
Western equine encephalitis (WEE) antibodies were found in blood samples from garter snakes and leopard frogs collected in Saskatchewan but WEE virus was not recovered from any of the specimens. Evidence of natural WEE infection in snakes was found in 8 different localities while in frogs in two only. Experimentally, garter snakes were readily infected and developed a high, relatively sustained viremia without signs of disease. After experimental exposure, viremia persisted regularly for 10 to 12 days, while the longest observed duration of viremia was 30 days. Anamnestic responses were elicited in snakes as a result of second inoculations of virus after the antibody levels from first exposures had fallen. Newborn snakes were observed to be more sensitive to infection than adults. The possibility of virus and antibody transmission from infected pregnant garter snakes to their offspring was investigated. Snakes and frogs were both susceptible to infection by the oral route. Two bull snakes collected at Steveville, Alberta, were found to have antibody for St. Louis Encephalitis virus.  相似文献   

15.
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16.
Paired sera from 28 nonvaccinated horses with serologically confirmed western equine encephalitis (WEE) virus infections were evaluated for immunoglobulin (Ig)M and IgG directed against WEE virus, by use of enzyme immunoassay. Twenty-one of the horses developed greater than or equal to 4-fold increases or decreases in serum IgM titers in paired serum samples, confirming the diagnosis of WEE in these horses. Of the remaining 7 horses, 1 had stable IgM titers, 1 had a 2-fold increase in IgM titer between paired sera, 2 had 2-fold decreases in IgM titer, and for 3 horses adequate volumes were not available for both sera of the pair. Twenty-nine of 56 blood samples collected from these 28 horses had been collected within the first 3 days after clinical disease was recognized; all 28 horses and 48 of 53 available serum samples had IgM antibody to WEE virus. Immunoglobulin M also was detected in sera of 27 of 45 other nonvaccinated horses that had illnesses clinically compatible with WEE. Sera with IgM did not have cross-reacting IgM against eastern equine encephalitis virus. Therefore, the sensitivity, specificity, and lack of persistence of IgM was useful in the rapid diagnosis of WEE virus infections in horses.  相似文献   

17.
Sera from horses and human beings with clinically diagnosed western equine encephalitis (WEE) virus infections were tested for hemagglutination-inhibition (HI), complement-fixation (CF), and neutralizing (N) antibody to WEE virus. These tests confirmed infection in 43.8% (HI), 56.3% (CF), and 80.4% (N) of horses and 54.5% (HI), 59.1% (CF), and 77.3% (N) of human beings. Use of the N test as an adjunct to the HI and CF tests increased the likelihood of serologic confirmation to 91.7%. In both horses and human beings, N antibody increased steeply at the end of the 1st week after onset. The results suggested that the presence of a high HI, CF, and/or N antibody titer in a single serum obtained from horses during the acute phase of illness caused by WEE virus can be used as presumptive evidence for infection with this virus.  相似文献   

18.
African horse sickness (AHS) is an arboviral disease of equids transmitted by Culicoides biting midges. The virus is endemic in parts of sub‐Saharan Africa and official AHS disease‐free status can be obtained from the World Organization for Animal Health on fulfilment of a number of criteria. AHS is associated with case fatality rates of up to 95%, making an outbreak among naïve horses both a welfare and economic disaster. The worldwide distributions of similar vector‐borne diseases (particularly bluetongue disease of ruminants) are changing rapidly, probably due to a combination of globalisation and climate change. There is extensive evidence that the requisite conditions for an AHS epizootic currently exist in disease‐free countries. In particular, although the stringent regulations enforced upon competition horses make them extremely unlikely to redistribute the virus, there are great concerns over the effects of illegal equid movement. An outbreak of AHS in a disease free region would have catastrophic effects on equine welfare and industry, particularly for international events such as the Olympic Games. While many regions have contingency plans in place to manage an outbreak of AHS, further research is urgently required if the equine industry is to avoid or effectively contain an AHS epizootic in disease‐free regions. This review describes the key aspects of AHS as a global issue and discusses the evidence supporting concerns that an epizootic may occur in AHS free countries, the planned government responses, and the roles and responsibilities of equine veterinarians.  相似文献   

19.
为建立一种快速、有效的检测马流感病毒(Equine influenza virus,EIV)的方法,以EIV中国分离株A/马/新疆/07(H3N8)制备的多克隆抗体为捕获抗体,原核表达的核蛋白(NP)制备的单克隆抗体为检测抗体,在国内首次建立了检测EIV的双抗体夹心ELISA方法.用该检测方法分别检测EIV、马动脉炎病毒、马疱疹病毒1型、马疱疹病毒4型和马乙型脑炎病毒阳性样品.结果表明,该ELISA方法具有良好的特异性;与常规检测EIV的血凝试验相比,其敏感性是后者的2.5～10倍;同时与H7N7亚型EIV有交叉反应.攻毒试验结果表明该方法可有效检测鼻腔分泌物中的EIV.该方法的建立为EIV的检测及早期防控提供了有效工具.  相似文献   

20.
Fewer than 25% of 12-hour-old chicks died after subcutaneous inoculation of 5 strains or intracranial inoculation of 3 strains of Venezuelan equine encephalomyelitis virus. Mortality of embryonating chicken eggs inoculated by the allantoic route decreased from approximately 75% to 35% between 9 and 18 days of incubation, although all 18-day-old embryos died after intraembryonic inoculation. Thus, neither newly hatched chicks nor chicken embryos (unless inoculated intraembryonically) would be of value in safety testing inactivated Venezuelan equine encephalomyelitis viral vaccines.  相似文献   

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