Buffalo in the northern Natal game parks show no serological evidence of infection with foot-and-mouth disease virus

A total of 594 sera collected from buffalo (Syncerus caffer) in the Hluhluwe/Umfolozi Game Reserve complex, Ndumu Game Reserve and the eastern shores of Lake St Lucia were examined for antibody to SAT 1, 2 and 3 types of foot-and-mouth disease (FMD) virus in neutralization tests. No neutralization of SAT 2 or 3 viruses was exhibited by any of the sera tested at final dilutions greater than 10. A small proportion (2,9%) of sera neutralized SAT 1 virus at dilutions up to 10, but these were considered to be due to non-specific reactions. This, together with the absence of clinical FMD in both cattle and game in this region over at least a 45-year period and the failure to isolate FMD virus from pharyngeal scrapings of buffalo sampled in the area, leads to the conclusion that FMD does not occur in these buffalo populations.     

Cross reaction between bovine enterovirus and South African Territories I5 foot-and-mouth disease virus.

A bovine enterovirus (E76T) isolated from a 2-year-old bull produced serologic cross reactions to South African Territories (SAT) I5 foot-and-mouth disease virus when inoculated into guinea pigs and cattle. Cross-reacting serum titers to SAT I5 virus of 1:320 by the plaque-reduction neutralization test and 1:20 by the radial immunodiffusion test occurred in 2 steers after they were inoculated with the E76T virus. In 1 steer, maximal cross-reacting titers appeared related to a 2nd exposure to the viruses or to a hyperimmune state. Ultracentrifugation and 2-mercaptoethanol studies indicated that the cross reactions were due to immunoglobulin M antibody. Sera from guinea pigs immunized with the E76T or the SAT I5 virus cross reacted with the heterologous virus by postinoculation day 7. Cross-reacting titers had decreased markedly by postinoculation day 35, whereas the homologous virus titer remained constant. Cross reactivity of the E76T virus was primarily with the SAT I5 virus, and to a lesser degree with SAT II3. Cross reactions did not occur with representatives of the 5 other antigenic types of foot-and-mouth disease virus.     

Occurrence of cross reactions to foot-and-mouth disease virus in normal swine sera.

Sera from 101 swine never exposed to foot-and-mouth disease virus were tested by the plaque-reduction neutralization (PRN) and radial immunodiffusion techniques for cross-reactions to 5 types of foot-and-mouth disease viruses. Depending on the group of sera and the virus used, the percentage of sera cross-reacting at low levels varied from 0 to 50% with the PRN technique and 0 to 20% with the radial immunodiffusion technique. 5erum-neutralization tests in mice support the finding of neutralizing antibody by the PRN technique. Ultracentrifugation and 2-mercaptoethanol studies indicate that the cross-reactions are the result of immunoglobulin M or similar macroglobulins.     

Comparison of sensitivity and specificity in three commercial foot-and-mouth disease virus non-structural protein ELISA kits with swine sera in Taiwan

Three commercialized ELISA kits for the detection of antibodies to the non-structural proteins (NSPs) of FMD virus were compared, using sera from uninfected, vaccinated, challenged and naturally infected pigs. The kinetics of the antibody response to NSPs was compared on sequential serum samples in swine from challenge studies and outbreaks. The results showed that ELISA A (UBI) and ELISA B (CEDI) had better sensitivity than that of the 3ABC recombinant protein-based ELISA C (Chekit). The peak for detection of antibodies to NSPs in ELISA C was significantly delayed in sera from natural infection and challenged swine as compared to the ELISA A and B. The sensitivity of the three ELISAs gradually declined during the 6-month post-infection as antibodies to NSP decline. ELISA kits A and B detected NSP antibody in 50% of challenged pigs by the 9-10th-day and 7-8th-day post-challenge, respectively. ELISA B and C had better specificity than ELISA A on sequential serum samples obtained from swine immunized with a type O FMD vaccine commercially available in Taiwan. Antibody to NSPs before vaccination was not detected in swine not exposed to FMD virus, however, antibody to NSPs was found in sera of some pigs after vaccination. All assays had significantly lower specificity when testing sera from repeatedly vaccinated sows and finishers in 1997 that were tested after the 1997 FMD outbreak. However, when testing sera from repeatedly vaccinated sows or finishers in 2003-2004, the specificity for ELISAs A, B and C were significantly better than those in 1997. This effect was less marked for ELISA A. The ELISA B was the best test in terms of the highest sensitivity and specificity and the lowest reactivity with residual NSP in vaccinates.     

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.     

比较3种间接ELISA试验检测口蹄疫感染抗体的研究

将3种检测口蹄疫非结构蛋白抗体的间接ELISA试验进行了比较。这3种间接ELISA试验检测田间血清样品的最低符合率为96％，最高符合率达98％：有2种间接ELISA试验可以检测到感染口蹄疫第10天后血清中的口蹄疫感染抗体．有1种间接ELISA试验可以检测到感染口蹄疫第14天后血清中的口蹄疫感染抗体；这3种间接ELISA试验检测12份已知口蹄疫阳性血清的试验结果吻合。研究表明．这3种间接ELISA试验方法对于检测口蹄疫感染抗体具有较好的特异性．其中猪口蹄疫3A蛋白间接ELISA诊断试剂盒在灵敏性、特异性和符合率方面更优于另外2种试剂盒。     

Serological Evidence of Pandemic H1N1 Influenza Virus Infections in Greek Swine

The introduction of the 2009 pandemic H1N1 (pH1N1) influenza virus in pigs changed the epidemiology of influenza A viruses (IAVs) in swine in Europe and the rest of the world. Previously, three IAV subtypes were found in the European pig population: an avian‐like H1N1 and two reassortant H1N2 and H3N2 viruses with human‐origin haemagglutinin (HA) and neuraminidase proteins and internal genes of avian decent. These viruses pose antigenically distinct HAs, which allow the retrospective diagnosis of infection in serological investigations. However, cross‐reactions between the HA of pH1N1 and the HAs of the other circulating H1 IAVs complicate serological diagnosis. The prevalence of IAVs in Greek swine has been poorly investigated. In this study, we examined and compared haemagglutination inhibition (HI) antibody titres against previously established IAVs and pH1N1 in 908 swine sera from 88 herds, collected before and after the 2009 pandemic. While we confirmed the historic presence of the three IAVs established in European swine, we also found that 4% of the pig sera examined after 2009 had HI antibodies only against the pH1N1 virus. Our results indicate that pH1N1 is circulating in Greek pigs and stress out the importance of a vigorous virological surveillance programme.     

Prevalence of seroreagents to FMDV in the cattle population in Poland: results of 9-year monitoring studies

The aim of this study was to evaluate the occurrence of antibodies to foot-and-mouth disease virus (FMDV) in sera of cattle in Poland. The examinations were performed using the virus neutralization (VN) test and ELISA methods: liquid-phase blocking ELISA (LPBE) and 3ABC-ELISA. During 1993-2001, about 681,000 samples of sera collected from animals held on the territory of Poland were tested. Of about 600,000 sera taken from animals exported to the European Union, 963 samples (0.16%) were found to be positive to FMDV types A, O and/or C. During 1996-2001 out of 85,000 sera tested as part of the national serological surveillance program for FMD, the FMDV antibodies were recorded in 51 (0.06%) samples. Persistence of FMD antibodies was observed in sera of cattle from the region around Zduńska Wola, which had been vaccinated annually during 1985-1985 with trivalent FMD vaccine. The results of the serological studies of 550 animals from this region indicates the presence of FMDV antibodies in sera of 240 (44%) cattle. A half-life of maternal antibodies in sera of calves born to seropositive dams was estimated; the highest level of FMDV antibodies was detected in sera taken from new-born calves aged 5-10 days. The level of FMDV antibodies in beestings of dams was highest during the first 10 hours after parturition; after 24 hours a significant decrease (3-5 times) was found and in two weeks post parturition FMDV antibodies were undetectable in the milk. It was established that all LPBE/VN positive sera of cattle exported from Poland, from the vaccination zone around Zduńska Wola as well as those tested as part of the national serological surveillance program for FMD, were taken exclusively from vaccinated animals or calves born to vaccinated dams.     

Elimination of mycoplasmal plate agglutination cross-reactions in sera from chickens inoculated with infectious bursal disease viruses

Sera from chickens inoculated with various challenge infectious bursal disease viruses or infectious bursal disease vaccines were found to cross-react in the Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) serum plate agglutination (SPA) tests. Two-fold dilutions of these cross-reacting sera with phosphate-buffered saline before retesting eliminated all non-specific agglutination in the MG and MS SPA tests. Cross-reactions were observed in the SPA test using sera from chickens inoculated with either MG or MS. Dilutions of these sera 1:2 had little effect on the number of these cross-reactions. At 1:4 serum dilutions, however, the number of cross-reactions between MG and MS was reduced. At 1:8 dilution of test sera, cross-reactions between MG and MS were further reduced. Some reduction in specific MG and MS SPA reactions, however, also occurred at the 1:8 dilution of sera with some of the plate antigen.     

羊口蹄疫免疫程序初探

采用间接血凝试验对在不同时间、使用不同剂量疫苗加强免疫的羊进行血清抗体测定 ,以建立和探讨羊口蹄疫 (FMD)的免疫方法和程序。试验将羊随机分成A ,B ,C ,D 4组。A组在首免后第 1 5天加强免疫 ,B ,C ,D组在首免后第 2 5天加强免疫 ,4个组的免疫剂量分别为 2 0 ,1 5 ,2 0和 2 5mL/只。在首免的第 0 ,1 1 ,2 1 ,31 ,41 ,55 ,70 ,90和 1 2 0天采血 ,检测血清中的抗体水平。B ,C ,D 3组的抗体效价显著地高于A组 (P <0 0 5) ,且持续时间较长。在B ,C ,D 3组之间 ,C组抗体效价显著地高于B组和D组 (P <0 0 5)。结果表明羊口蹄疫的最佳免疫程序为 :首免后 2 5d加强免疫 ,剂量为 2 0mL/只。     

Seroepidemiological evidence of avian H4, H5, and H9 influenza A virus transmission to pigs in southeastern China

Pig serum samples collected in southeastern China were examined for antibodies to influenza A viruses. Since the hemagglutination inhibition (HI) test does not accurately detect antibodies to the hemagglutinins (HAs) of "avian" influenza viruses, we utilized the neutralization (NT) test to detect subtype-specific antibodies to the HA of avian viruses in pig sera. Neutralizing antibodies to H1, H3, H4, and H5 influenza viruses were detected in the serum samples collected in 1977-1982 and 1998, suggesting that pigs in China have been sporadically infected with avian H4 and H5 viruses in addition to swine and human H1 and H3 viruses. Antibodies to H9 virus, on the other hand, were found only in the sera collected in 1998, not in those collected in 1977-1982, correlating with the recent spread in poultry and subsequent isolation of H9N2 viruses from pigs and humans in 1998. The present results indicate that avian influenza viruses have been transmitted to pig populations in southeastern China.     

Rapid and specific serodiagnosis of western equine encephalitis virus infection in horses

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.     

Comparison of competitive ELISA, indirect ELISA and standard AGID tests for detecting blue-tongue virus antibodies in cattle and sheep

The performances of a competitive enzyme-linked immunosorbent assay (ELISA) using a group specific monoclonal antibody against bluetongue virus, an indirect ELISA and the standard agar gel immunodiffusion (AGID) test were compared in the detection of serum antibody against bluetongue virus. Test sera consisted of 1300 bovine, 530 ovine and 160 carpine samples from bluetongue-free areas of Canada, 605 bovine and ovine field samples from the USA and Barbados and 464 samples from 79 cattle and sheep experimentally infected with 19 South African and five USA serotypes of bluetongue virus. The diagnostic specificity of the competitive ELISA, as determined for the bluetongue virus-free cattle sera was superior (99.92 per cent) to that of the indirect ELISA (99.85 per cent) and the AGID (99.0 per cent). The specificities of the competitive ELISA for sheep (99.63 per cent) and goats (100.0 per cent) sera were also higher than those of the AGID test. The performance of the ELISA tests was similar whether a gamma-ray-irradiated (2.0 Mrad) or a non-irradiated bluetongue virus antigen preparation was used. The competitive ELISA results for bovine field sera from endemic areas demonstrated a relatively low level of agreement (92.04 per cent) with AGID test results, with 9.7 per cent false negatives. The possible presence in these sera of antibody to cross-reacting antigens or to other orbiviruses, eg, epizootic haemorrhagic disease virus, which react in the AGID but not in the competitive ELISA may account for this lack of agreement.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of foot and mouth vaccination for yak (<Emphasis Type="Italic">Bos grunniens</Emphasis>) in Pakistan

In northern Pakistan, many farming communities rely on domestic yak (Bos grunniens) as a principle source of income. A 2006 participatory disease surveillance report from this region indicated that foot-and-mouth disease (FMD) is the most prevalent annual disease of yak. Our objectives of this study were to determine exposure levels of yak to FMD virus; implement a vaccination program based on current, regional FMD virus serotypes and subtypes; and quantify immune responses following vaccination. Blood samples were used to determine pre-vaccination exposure of animals to FMD virus by antibody presence to non-structural proteins of FMD virus using a 3-ABC trapping indirect ELISA. Vaccine used consisted of FMD serotypes ‘O’ (PanAsia-2), ‘A’ (Iran-05), and ‘Asia-1’ (Shamir), but changed later during the study to match newly circulating viruses in the country (‘O’-PanAsia-2; ‘A’-Turk-06 and Asia-1-Sindh-08). Three hundred sixty-three blood samples were tested from selected villages to determine pre-vaccination FMD virus exposure in yak with an average of 37.7%. Immune responses from initial vaccination and booster dose 30 days later showed clear protective levels (as mean percent inhibition) of antibodies against structural proteins of serotypes ‘O,’ ‘A,’ and ‘Asia-1.’ These responses remained above threshold positive level even at day 210 following initial vaccination. Results of sero-surveillance and anecdotal information of repeated FMD outbreaks demonstrate the persistence of FMD virus of yak in northern Pakistan. Laboratory results and field observations clearly indicated that yak can be protected against FMD with a good quality vaccine with FMD serotype(s) matching current, regionally circulating FMD virus.     

Cross-reactions of normal bovine serums to foot-and-mouth disease virus in plaque-reduction neutralization and radial immunodiffusion.

Serums from 150 cattle with no known exposure to foot-and-mouth disease (FMD) virus were tested by both the plaque-reduction neutralization (PRN) technique and the radial immunodiffusion (RID) technique to evaluate the significance and the extent of cross-reactions in these tests. Serums from 30 cattle from each of 5 locations were tested against representative viruses of each of the 7 types of FMD virus. High levels of cross-reactions with both the RID and PRN techniques were found in serums of specific groups. Higher levels of cross-reactions were noted for Asia, SAT I, SAT II, and SAT III than for A, O, or C viruses with the PRN technique, and higher levels for SAT II and SAT III with the RID technique. The reactions for most serums appeared to be quite specific; a given serum was often reactive with only 1 or 2 viruses.     

Noncytopathogenic Bovine Viral Diarrhea Viruses Detected and Titrated by Immunofluorescence

Noncytopathogenic (NCP) bovine viral diarrhea (BVD) disease agents can be detected and titrated in tissue culture systems by a method employing immunofluorescence. Cytopathogenic (CP) and NCP viruses cross react with fluorescein-conjugated serum globulins produced against either CP and NCP viruses, but the fluorescence is more intense in the homologous system. Serum neutralization titers of sera against both CP and NCP groups were compared for both groups of viruses, and results of cross reactions were in agreement with results from immunofluorescence tests. Results of these two tests were discussed as to possible antigenic groupings of CP and NCP viruses. Use of immunofluorescence as a diagnostic test for BVD and as an alternate method of titrating NCP viruses in tissue culture systems is proposed.     

Evaluation of an enzyme-labeled antiglobulin test for anti-Brucella immunoglobulin G among 3 cattle populations

Antibody to smooth Brucella abortus lipopolysaccharide antigen on the surface of polystyrene tubes was detected with peroxidase-labeled antibody against bovine immunoglobulin G. The enzyme-labeled antiglobulin test (ELAT) activity of samples was expressed in arbitrary units/0.01 ml by reference to a standard curve based on tests of dilutions of a positive serum pool. Reactions greater than 3.0 U/0.01 ml were classified positive because specificity at this level was 99.8% (417/418 samples correctly classified negative) with agglutination test-negative sera from 33 Brucella-free herds. Results of the ELAT were compared with results of agglutination tests and the complement-fixation test (CFT), using 430 sera from cattle in 7 infected herds. Activity of greater than 5.0 ELAT U/0.01 ml was detected in all 54 sera classified as positive (titer greater than 1:10) by the CFT, including 5 sera classified as negative by the tube agglutination test. Sera from 8 nonvaccinated cows in the infected herds reacted only by the ELAT, whereas reactions were obtained with 25 and 5 sera by only agglutination tests and the CFT, respectively. The ELAT and CFT results were in agreement for 25 of 26 sera from agglutination test-reactor cattle in herds of unknown status. Comparisons of milk ring and whey agglutination tests with the whey ELAT on 146 quarter samples from cows in an infected herd revealed no ELAT activity greater than or equal to 1.0 U/0.01 ml in the 73 samples considered negative by the 2 other tests. Samples (n = 47) that contained greater than or equal to 1.0 ELAT U/0.01 ml included all (n = 40) samples with milk ring or whey agglutination titers greater than or equal to 1:16 and greater than or equal to 32, respectively, and 7 samples that gave weaker reactions to the latter tests.     

Relationship between the anti-FMD virus antibody reaction as measured by different assays, and protection in vivo against challenge infection.

The antibody response of cattle after vaccination against foot-and-mouth disease (FMD) virus was monitored using the serum neutralization test (SNT), the sandwich ELISA, liquid-phase ELISA, sandwich competition ELISA, liquid-phase competition ELISA, and the liquid-phase sandwich competition (blocking) ELISA. The competition ELISAs (in particular the "blocking" ELISA) were the most effective at detecting reactivity in these cattle sera. However, 95% of negative sera also competed in the most sensitive ELISA (the "blocking" ELISA) to titres of 1:32 (4% of the sera competed to a titre of 1:128). Comparisons between the different ELISAs, and between these ELISAs and the SNT, demonstrated that the tests were not measuring exactly the same reaction of antibody with FMD virus. With respect to the capacity of animals to resist FMD virus challenge, neither the SNT nor the competition ELISAs were consistently able to identify such animals. The anti-FMD virus antibody titres obtained could be classified into three zones; the "white zone" wherein antibody titres were high and donor animals likely to be protected; the "black zone" wherein antibody titres were low and donor animals likely to be susceptible to infection; the "grey zone" wherein the antibody titres were intermediary and no interpretation could be made with respect to protection. Assays such as ELISA and SNT cannot and do not measure immunological protection; they are a measure of antibody responses and nothing more, and should be interpreted in terms of the "three zone" phenomenon.