Detection of foot-and-mouth disease virus infection in vaccinated cattle

The aim of this study was to evaluate the value of commercially available kits for the detection of foot-and-mouth disease (FMD) virus infection in vaccinated cattle. The cattle were vaccinated with a commercial aqueous FMD vaccine type A24 and subsequently challenged 28 days post vaccination with homologous FMD virus. Seven of eight animals were protected from clinical disease and all became carriers. They were bled sequentially for up to 130 days post infection and samples of sera were tested with three ELISA kits: CHEKIT FMD-3ABC, Ceditest FMDV-NS and SVANOIR FMDV 3ABC-Ab ELISA. The Ceditest kit appears to be relatively higher sensitive than the others. When examined with this ELISA, all cattle developed of FMDV nonstructural proteins (NSPs) antibodies and remained positive throughout the period of the experiment. The response of antibodies against 3ABC antigen delayed in two cattle challenged with FMDV A24 virus. One of the cattle reacted negatively in Svanoir ELISA kit and sera from two animals were found negative in CHEKIT ELISA. It can be concluded that all tested kits can be a promising tool for FMD control and eradication campaigns in situation where emergency vaccination was applied.     

Serological evidence of FMD subclinical infection in sheep population during the 1999 epidemic in Morocco.

During 1999, 11 outbreaks of foot and mouth disease (FMD) were declared in the east and central part of Morocco. All the FMD clinical cases reported were cattle. In order to analyse the serological status of sheep from the FMD outbreak areas, 598 sheep sera were tested using a liquid-phase blocking ELISA (LPBE) to detect antibodies against FMDV structural proteins. The study confirmed the presence of FMDV specific antibodies in 77 clinically normal sheep, indicating that unrecognised FMDV-infected sheep could represent a potential risk of FMD dissemination in Morocco.Subsequently, sera from flocks of sheep that had been exposed to FMD outbreaks were assayed by an indirect ELISA using the recombinant FMDV non-structural protein 3ABC expressed in E. coli to evaluate the potential use of this serological test in future epidemiological studies and the development of FMD control strategies. The results indicated that the 3ABC-ELISA was able to detect antibodies indicative of infection with FMDV in asymptomatic sheep in field conditions.     

Development and evaluation of an indirect enzyme-linked immunosorbent assay for detection of foot-and-mouth disease virus nonstructural protein antibody using a chemically synthesized 2B peptide as antigen.

Forty peptides were synthesized corresponding to hydrophilic clusters of amino acids within the sequences of foot-and-mouth disease virus (FMDV) nonstructural proteins (NSP). Six peptides were studied in more detail and the most promising, a 2B peptide, was evaluated in enzyme-linked immunosorbent assay (ELISA) using sera from naive, vaccinated, and vaccinated-and-challenged cattle as well as bovine sera from field outbreaks. The performance of the new NSP peptide ELISA was compared to that of 4 commercial NSP ELISA kits. Antibody to 2B was detectable from the end of the first week to the second week after infection in most of the nonvaccinated animals and by the second to third week in vaccinated-and-challenged animals. The sensitivity of the 2B peptide ELISA was comparable to the 3ABC Ceditest (Ceditest FMDV-NS, Cedi Diagnostics B.V.; Chung et al., 2002). With some modification and further validation, this 2B test could be useful as a screening or conformational NSP test in postvaccination surveillance for FMD.     

Cedivac-FMD can be used according to a marker vaccine principle

In this study, we investigated whether Cedivac-FMD, an emergency vaccine against foot-and-mouth disease (FMD), is suitable for use conjointly with a screening program intended to confirm freedom from disease in vaccinated herds based on evidence of virus replication in vaccinates. Different sets of sera were tested using the Ceditest FMDV-NS ELISA for the detection of antibodies against non-structural proteins (NSPs) of FMD virus. During a vaccine safety study, serum samples were collected from 10 calves, 10 lambs and 10 piglets following administration of a double dose and a repeat dose of high payload trivalent Cedivac-FMD vaccine. All serum samples collected both 2 weeks following the administration of a double dose as well as those collected 2 weeks after the single dose booster (given 2 weeks after the double dose) were negative in the Ceditest FMDV-NS ELISA. In a series of vaccine potency experiments, serum samples were collected from 70 vaccinated cattle prior to and following exposure to infectious, homologous FMD virus. When testing cattle sera collected 4 weeks after vaccination with a regular dose of monovalent >6 PD(50) vaccines, 1 of 70 animals tested positive in the NSP antibody ELISA. After infection with FMD virus, antibodies to NSP were detected in 59 of 70 vaccinated cattle and 27 of 28 non-vaccinated control animals within 7 days. Cedivac-FMD vaccines do not induce NSP antibodies in cattle, pigs or sheep following administration of a double dose or a repeat dose. FMD-exposed animals can be detected in a vaccinated group within 7-14 days. Because Cedivac-FMD does not induce NSP antibodies, the principle of 'marker vaccine' applies.     

2016—2018年广西玉林市和百色市主要家畜疫病定点监测

为了解广西地区口蹄疫(FMD)、猪瘟(CSF)、猪繁殖与呼吸综合征(PRRS)、猪伪狂犬病(PR)、布鲁氏菌病和小反刍兽疫(PPR)等重大动物疫病的免疫动态、疫情流行风险,按照国家动物疫病定点监测实施方案相关要求,2016—2018年运用ELISA和实时荧光定量PCR方法,对玉林市和百色市20个定点监测场点的猪、牛、羊开展病原学监测和抗体监测。病原监测结果显示:2016—2018年,未在牛羊群中检出FMD、PPR病原;2016年和2017年CSF病原检出率均为0.38%;3年内均有PRRS病原检出,检出率介于1.89%~6.32%。抗体检测结果显示:2016—2018年,猪O型FMD、CSF、PRRS和PR-gB抗体阳性率均在70%以上,A型FMD抗体阳性率逐年上升,NSP抗体和PR-gE抗体阳性率呈波动状变化;牛O型FMD抗体阳性率分别为94.78%、18.26%、71.11%,亚洲I型分别为76.52%、25.22%、27.78%,NSP抗体阳性率在22.61%~41.74%之间波动;仅2016年检出1份牛布鲁氏菌抗体阳性;3年间,羊O型、亚洲I型FMD和PPR免疫抗体阳性率都很低,未达到70%,且呈下降趋势,NSP抗体阳性率在0.95%~7.62%之间波动,未检出羊布鲁氏菌抗体。结果表明,广西玉林市和百色市的猪群O型FMD、CSF、PRRS、PR免疫效果较好,但牛羊群FMD和PPR免疫效果较差,猪群中仍有CSF、PRRS、PR等疫病流行,牛羊群中存在FMD流行的风险,但牛羊布鲁氏菌病得到有效控制。结果提示,应继续加强上述疫病的免疫和监测,针对免疫效果较差、病原流行率偏高的疫病,要重点做好防控和净化。     

Presence of antibodies to non-structural proteins of foot-and-mouth disease virus in repeatedly vaccinated cattle

For the purpose of removing infected animals by detecting humoral immune responses to non-structural proteins of the foot-and-mouth disease (FMD) virus, antibodies induced by contaminated residual non-structural proteins contained in less pure FMD vaccine can be problematic for serological screening. The aim of the present study was to measure the possible presence of antibodies against these non-structural proteins in repeatedly vaccinated calves and beef cattle. Five imported FMD vaccines were examined using two commercial ELISA kits, UBI FMDV NS EIA and Ceditest FMDV-NS, for serological testing. After five doses of vaccination, the serum of one calf tested positive, and two vaccines induced a significant increase in anti-3ABC antibodies in calves. This finding demonstrated that a positive reaction to non-structural proteins due to impurities in the FMD vaccine was detectable using commercial tests. A low percentage of field sera sampled from beef cattle in Kinmen also tested positive, but the key factor resulting in the positive reactions could not be positively identified based on our data.     

O型口蹄疫抗体金标试纸盒检测免疫动物抗体效价与攻毒保护关系

本研究目的在于用O型口蹄疫金标试纸条研究免疫动物抗体效价与攻毒保护之间的对应关系以及免疫牛抗体消长规律.用金标试纸条检测了口蹄疫O型疫苗质量标准规定的牛、羊和猪免疫和攻毒血清抗体效价及不同免疫程序的牛血清效价.结果显示,当牛、猪和羊免疫血清稀释≥1∶8时,试纸条是阳性结果,表示有99％的被免疫动物属于抗体水平保护范围;被检测血清稀释≤1∶2时,是阴性结果,表示被免疫动物抗体水平属于不保护范围;血清稀释1∶2～1∶8时,是阳性结果,表示有50％的被免疫动物属于抗体水平保护范围.牛在首次免疫8周后加强免疫可以获得良好的保护率和保护时间.通过本试验确定了金标试纸条检测免疫动物抗体效价与攻毒保护之间的关系及牛加强免疫最佳的时间.     

Non-structural protein 3A for differentiation of foot-and-mouth disease infected and vaccinated animals in Haryana (India)

There are severe international trade restrictions on foot-and-mouth disease (FMD) affected areas. Because of endemic nature of FMD, India started FMD control programme (FMD-CP) using mass vaccination in selected states including Haryana (year 2003). Although no significant incidence of the disease was reported after launching FMD-CP in the state but in order to participate in international trade of animal and animal products, veterinary authorities have to prove that there is no FMD virus (FMDV) circulation in the animal population, for which it is necessary to differentiate the FMD infected and vaccinated animals. For this purpose, an in-house indirect ELISA utilizing baculovirus-expressed FMDV non-structural protein (NSP) 3A was used to find evidence for virus circulation (prevalence of anti-NSP 3A-specific antibodies) by examining serum samples that were collected either before start of FMD-CP or after completion of third phase (Pre-4th) of vaccination in Haryana (India). A significant reduction (P < 0.01) in prevalence of anti-NSP 3A-specific antibodies (possibly carriers) was observed 2 years after launching FMD-CP in Haryana. However, in cattle the percentage of animals with anti-NSP 3A-specific antibodies was found to be significantly higher (P < 0.01) than buffalo, both before (P < 0.01) and after (P < 0.01) launching FMD-CP in the state. The findings of this study suggest that use of FMDV vaccine in cattle and buffaloes in endemic areas reduces virus circulation (carriers) in the vaccinated herds and that the current 3ANSP-ELISA can be successfully used to monitor the FMDV circulation in endemic areas.     

Serosurveillance of foot-and-mouth disease in sheep and goat population of India

Serological investigation to detect foot-and-mouth disease (FMD) virus circulation in the domestic small ruminant population of India was conducted. A total of 4407 and 4035 serum samples from sheep and goats, respectively were collected at random covering majority of the states across the country during 2010–2012. These samples were analyzed for antibodies against the non-structural proteins (NSP) of FMD virus in an indirect 3AB NSP ELISA and against the structural proteins (SP) in a liquid phase blocking (LPB) ELISA. A total of 20.35% sheep and 13.60% goats were found to be positive for 3AB NSP antibodies providing a serological evidence of extensive viral activity. In LPB ELISA, only 4.54% sheep and 6.27% goats were found to have protective antibody (log₁₀ titre of ≥1.8) against all three serotype strains in the vaccine, which correlates with “no or sparse vaccination” scenario in these species in the country. Hence, to check silent amplification and dissemination of virus in a mixed farming set up, small ruminants may be brought under the ambit of routine vaccination and surveillance programmes.     

肉牛口蹄疫免疫抗体、3ABC抗体、RT-PCR核酸检测结果分析

[目的]为了掌握肉牛口蹄疫免疫抗体检测结果、口蹄疫非结构蛋白3ABC抗体检测结果、口蹄疫O-P液RT-PCR核酸检测结果三者的相关性,[方法]张掖市动物疫病预防控制中心对甘州区28头肉牛开展相关检测。[结果]检测结果表明:O型口蹄疫免疫抗体合格率28份,合格率100%,3ABC抗体阳性27份,阳性率96.4%;对3ABC抗体阳性的27头牛分2次进行实时荧光RT-PCR核酸检测,被检的27头牛均为阴性。