Identification of seven serotypes of bluetongue virus from the People's Republic of China

Seven serotypes (1, 2, 3, 4, 12, 15 and 16) of bluetongue virus were isolated from the blood of sheep and cattle in the People's Republic of China between 1986 and 1996. Six of these viruses were isolated in Yunnan province. The sheep from which serotypes 1 and 16 were isolated showed obvious signs of bluetongue disease, whereas the cattle from which serotypes 2, 3, 4, 12 and 15 were isolated were clinically normal. Phylogenetic analyses of these viruses indicate that they are more closely related to one another, and to an Australian strain of serotype 1, than they are to prototype strains of bluetongue virus serotypes 2, 10, 11, 13 and 17 from the USA.     

Anti-idiotype technique: an alternative approach for immunodiagnosis of bluetongue

In development of a bluetongue alternative immunodiagnostic rest, the polyclonal anti-idiotypic antibodies were generated by the sequential immunization of rabbits with three monoclonal antibodies to VP7 of bluetongue virus. The anti-idiotypic antibodies recognize the idiotypes that are located within or near the antigen-combining sites and are associated with both heavy and light chains of the antibodies to VP7 of bluetongue virus. The anti-idiotypic antibodies mimic the VP7 antigen by recognizing the anti-VP7 antibodies from cattle and sheep that were infected with various serotypes of bluetongue viruses. The results indicate that the rabbit anti-idiotypic antibodies may be used as surrogate antigen in serological assays to detect the antibodies from different species of animals infected with various serotypes of bluetongue viruses.     

Antigenic relationship of Ibaraki,bluetongue, and epizootic Hemorrhagic disease viruses

Ibaraki virus, which causes a bluetongue-like disease of cattle in Japan, was compared antigenically with the four serotypes of bluetongue virus (BTV) found in the U.S. and with the two serotypes of epizootic hemorrhagic disease virus (EHDV). No antigenic relationship was found between Ibaraki virus and BTV serotypes 10, 11, 13, and 17 in tests for group or serotype-specific antigens. However, Ibaraki virus and EHDV were related antigenically. The agar gel precipitin and indirect fluorescent antibody tests for group antigens showed two-way cross relationships between Ibaraki virus and EHDV serotypes 1 and 2. The more restrictive serotype-specific neutralization test revealed that antigenic relatedness was stronger between Ibaraki virus and the serotype 2 (Alberta strain) of EHDV than between Ibaraki virus and the serotype 1 (New Jersey strain) of EHDV.     

Serologic responses of calves to sequential infections with epizootic hemorrhagic disease virus serotypes

Six calves were inoculated with 1 of 2 North American serotypes of epizootic hemorrhagic disease virus (EHDV) and then inoculated with the second serotype 16 weeks later. One calf did not develop an immune response to EHDV after primary inoculation and was removed from the study. Viremia after primary inoculation was transient. Although each infected calf developed a high serum neutralizing antibody titer to EHDV, at no time after inoculation with one or both viruses was antibody detected that neutralized any US serotypes of bluetongue virus. After exposure to both serotypes of EHDV, 4 of 5 calves developed antibodies that cross-reacted with group-specific bluetongue virus antigens.     

Recombinant cDNA probe from bluetongue virus genome segment 10 for identification of bluetongue virus

Genome segment 10 of bluetongue virus (BTV) serotype 11 UC8 strain was cloned and subsequently hybridized to viral double-stranded RNA extracted from 90 field isolates of BTV serotypes 10, 11, 13, and 17; the prototype strains of BTV 2, 10, 11, 13, and 17; the prototype strain epizootic hemorrhagic disease virus (EHDV) serotype 1; and 4 field isolates of EHDV serotype 2. The 90 field isolates were obtained from different counties in California, Louisiana, and Idaho during the years 1979, 1980, and 1981. The cloned genetic probe hybridized with all the BTV samples tested, showing different degrees of cross-hybridization at the stringency conditions used in this study. This indicated that BTV genome segment 10 has conserved nucleotide sequences among the BTV serotypes 2, 10, 11, 13, and 17. No cross-hybridization signals were detected between the cloned genome segment 10 of BTV 11 UC8 strain and the prototype strain of EHDV serotype 1 and the field isolates of serotype 2. This probe recognized a wide variety of BTV isolates.     

Antibodies to bluetongue viruses in animals imported into United States zoological gardens.

Three hundred forty-five serum samples from 30 zoological animal species which had been imported into the United States were examined retrospectively for the presence of antibody to bluetongue viruses. Ninety eight (28.4%) were positive for antibody to bluetongue group antigen by the bluetongue agar gel immunodiffusion test. Bluetongue antibodies, most of which were against serotypes exotic to the United States, were detected in 13 animal species from Africa not previously reported to be infected by bluetongue virus. The lack of virus neutralizing antibody to any of the 20 known bluetongue virus types in four of the 28 positive serums studied may indicate the existence of new bluetongue virus serotypes, cross reactions with other orbiviruses or a more rapid decline of neutralizing than precipitating antibody. The possibility of recrudescence of bluetongue virus infection from some inapparently infected zoological animals and existence of a known bluetongue vector (Culicoides variipennis) in the United States would suggest that further assessment of bluetongue in zoological animals be made.     

Interferon induction in bovine and feline monolayer cultures by four bluetongue virus serotypes.

The interferon inducing ability of bluetongue viruses was studied in bovine and feline monolayer cultures inoculated with each of four bluetongue virus serotypes. Interferon was assayed by a plaque reduction method in monolayer cultures with vesicular stomatitis virus as challenge virus. Interferon was produced by bovine turbinate, Georgia bovine kidney, and Crandell feline kidney monolayer cultures in response to bluetongue virus serotypes 10, 11, 13 and 17. The antiviral substances produced by the bluetongue virus infected cultures had properties of interferon.     

The use of a membrane feeding technique to determine the infection rate of Culicoides imicola (Diptera, Ceratopogonidae) for 2 bluetongue virus serotypes in South Africa.

Culicoides spp. in the Lowveld of the northern Transvaal, Republic of South Africa, were fed bluetongue virus serotypes 3 and 6 and African horsesickness virus serotype 1 through latex and chicken skin membranes. After an incubation period of 10 days at 25-27 degrees C, the infection rate of C. imicola for bluetongue virus serotypes 3 and 6 was established at 31% and 24% respectively. No African horsesickness virus could be recovered. The membrane feeding technique and handling procedures proved to be suitable for field studies.     

用RT—PCR技术检测蓝舌病病毒的研究

蓝舌病病毒非结构蛋白NS_1基因在各型中具有高同源性,可作为群特异性检测的依据。采用NS_1基因中210bp的区段作为PCR扩增模板,经逆转录酶合成第一股cDNA后,再进行PCR扩增。结果对BTV可扩增出特异片段,而鹿流行性出血病病毒和茨城病病毒则不出现扩增。     

Bluetongue virus serotypes 1 and 3 infection in Poll Dorset sheep

Objective To study the clinical signs following bluetongue virus serotypes 1 and 3 infection in Poll Dorset sheep.
Design A clinical and pathological study.
Procedure Twenty Poll Dorset sheep were inoculated with bluetongue virus serotypes 1 or 3, each inoculum having a different passage history. The sheep were examined daily and their clinical appearance and rectal temperatures recorded. Heparinised and non-heparinised blood samples were taken at intervals for virological and serological study. Gross pathological findings were recorded for several sheep at necropsy and tissue samples were collected from three sheep for virological studies.
Results All inoculated sheep developed clinical disease. The clinical signs and gross pathological changes varied considerably but were consistent with damage to the vascular endothelial system. There was a decline in the titres of infectious bluetongue virus and of antigen in tissues collected between 7 and 12 days after infection.
Conclusions The severity of disease was related to the speed of onset and duration of pyrexia and not the development or titre of viraemia. Generally, those animals with sensitive mouths, depression, coronitis, recumbency and reluctance to move were the most debilitated. Whole blood was the most reliable source of infectious virus from acutely and chronically infected and convalescent animals. However, tissue samples particularly spleen, collected from dead or killed animals suffering from either peracute or acute forms of disease were most appropriate for the rapid confirmation of a clinical diagnosis.     

Virological, clinical and serological responses of sheep infected with tissue culture adapted bluetongue virus serotypes 10, 11, 13 and 17

Sheep were experimentally infected with cloned strains of tissue culture adapted bluetongue virus (BTV) serotypes 10, 11, 13 and 17. All the infected animals developed viremia by Day 2 or 3 post-inoculation (P.I.) and reached maximum viremia on Day 7 P.I. The viremia lasted for 2 to 3 weeks. Animals infected with the different serotypes showed mild clinical bluetongue (BT) responses, characterized by pyrexia and leukopenia, which coincided with the peak of viremia. Antibodies appeared by Day 10 P.I. and reached maximum by Day 28 P.I. There was a temporal relationship between the increase in neutralizing antibody titer, the drop in titer and clearance of virus from the peripheral circulation. Recovery from primary infection protected the animals against secondary challenge with homologous virus.     

蓝舌病毒群特异性RT—PCR检测技术及其应用

目的:建立一种适于蓝舌病毒(BTV)群特异性基因检测的RT-PCR方法。方法:根据本实验室设计的一对BTVNS1基因通用型检测引物建立BTV群特异性RT-PCR检测技术;对不同血清型BTV及鹿流行性出血热病毒(EHDV)进行检测,验证其特异性;同时,利用该方法检测血清模拟样品及抗病毒血清样品。结果:所设计的检测方法特异性好,与EHDV无交叉反应,可检测至少17个血清型BTV,并能有效检出不同病毒浓度的模拟样品及不同型的血清样品。结论:建立的RT-PCR方法可用于BTV群的特异性通用检测。     

Clinical and serological outcome following the simultaneous inoculation of three bluetongue virus types into sheep

The simultaneous inoculation of sheep with three different bluetongue virus types resulted in the replication of only two of the virus types and the formation of neutralising antibodies to only those two types and a failure in the production of heterotypic antibodies. This suggests that the present system of control, using multivalent vaccines in areas in which a number of bluetongue serotypes exist, should be reappraised.     

Serological differentiation of five bluetongue virus serotypes in indirect ELISA.

The serological reactivity in indirect ELISA of five different bluetongue virus (BTV) serotypes (4, 10, 15, 16 & 20) was compared using polyclonal antisera raised against virus particles and an outer structural protein, VP2. Rabbit and sheep antisera against BTV-10 produced higher ELISA values with their homologous antigens than with heterologous serotypes. A hyperimmune rabbit serum specific for virus particles was able to distinguish heterologous serotypes from each other, but a sheep serum from an infected animal was not. An antiserum directed against VP2, the protein responsible for serotype specificity in neutralization tests, was not serotype-specific in ELISA and cross-reacted with other serotypes. The discriminatory ability of a BTV-4 antiserum was improved by cross-absorption with heterologous antigens. This greatly reduced the ELISA signals with heterologous serotypes and produced an antiserum that was effectively serotype-specific.     

Peptide mapping of the group-specific antigens from the Australian bluetongue virus (BTV-20) and serotypes from southern Africa and North America

The Australian bluetongue virus (BTV-20) was compared with six serotypes isolated in southern Africa and North America by peptide mapping of the virus proteins with group antigen properties. The p7 group antigens from each of the seven serotypes analysed did not have identical primary structures and a comparison of shared and unique tryptic peptides has been used as a means of estimating virus relationships. Whereas serological studies have suggested that BTV-20 is closely related to BTV serotypes 4 and 17, comparative peptide mapping of p7 indicates a different set of relationships with viruses from both southern Africa and North America. In contrast with cross-immune precipitation results, peptide mapping of p3 suggest that this protein is not a group specific antigen.     

Isolation of an exotic serotype of bluetongue virus from imported cattle in quarantine.

In 1980, 60 zebu cattle from Brazil were admitted into quarantine in Florida for 150 days. During the 30 days between their last test in Brazil and their first test in Florida, four animals developed antibody to bluetongue virus detectable by agar gel immunodiffusion test. Within 62 days after arrival in Florida, three more seroconverted and one more was positive by the 86th day. Virus neutralizing titers of serums from the first four cattle were highest against bluetongue virus serotype 4 and 20; both of these serotypes are exotic to the United States. A bluetongue virus serotype 4 was isolated from one of these animals. The eight positive reactors were slaughtered; the other 52 cattle, which did not develop detectable antibody titers to bluetongue virus, were released into the United States.     

Recovery of dual serotypes of bluetongue virus from infected sheep and cattle

Dual serotypes of bluetongue virus (BTV) were recovered from field-collected samples of sheep and cattle blood. Two sheep, each infected with both BTV serotypes 10 and 17, were found in a flock with bluetongue disease associated with these two serotypes. One sheep infected with BTV serotypes 11 and 17 was found in a second flock; it was the only viremic sheep detected and was clinically ill. Dual serotype infections of one beef and two dairy cattle were found in three geographically separate herds; mixtures recovered were of BTV serotypes 10 and 17 and serotypes 11 and 17. Clinical signs of illness were absent in the cattle in two herds, but severe conjuctivitis was seen in several cows in a third herd, including the cow with a dual serotype infection (BTV 11 and 17). Two of the cattle with dual infections had no serological evidence of BTV as determined by the agar gel precipitin test; serum was not available from the other cow with a dual serotype infection. The significance of dual infections and immune tolerance are discussed.     

Spatial analysis of seroconversion of sentinel cattle to bluetongue viruses in Queensland

Objective To assess quantitatively the spatial distribution of seroconversion of Queensland cattle to bluetongue viruses.
Design A sentinel herd study. Sample population Sixty-nine sentinel herds at 30 locations.
Procedure Spatial clustering of seroconversion to blue-tongue viruses was investigated during the period from 1990 to 1994.
Results Seroconversion to only two bluetongue virus serotypes, 1 and 21, was observed. The 14 herds, in which seroconversion to bluetongue virus serotype 1 was detected, were located only along the eastern coastal and subcoastal region of Queensland, and were significantly (P < 0.05) clustered. Locations at which seroconversion to serotype 21 was detected, were not significantly clustered. The results generally agree with field observations, except for the failure to detect seroconversion to bluetongue viruses in north-western Queensland.
Conclusion Bluetongue infection of cattle in north-western Queensland may be temporally sporadic. The dominance of serotype 1 in the Queensland cattle population may be the result of differential transmission by potential vector species. Long-term surveillance programs are important for defining disease status of animal populations.     

Serological survey of ruminants in some Caribbean and South American countries for type-specific antibody to bluetongue and epizootic haemorrhagic disease viruses

The results of a serological survey of ruminant livestock in some countries of the Caribbean and South America for type-specific antibody to bluetongue virus are reported. Using the microneutralisation test with the international serotypes 1 to 22 of bluetongue virus, antibodies to several types were detected. Analysis of the data indicated that in 1981-82 bluetongue virus types 6, 14 and 17, or viruses closely related to them, were infecting ruminants in this region of the world. Antibody to the related virus of epizootic haemorrhagic disease (serotype 1) was also detected in cattle. The difficulty in interpreting the epidemiological significance of data generated by a serological survey of this kind is discussed.     

Evidence of genome segment 5 reassortment in bluetongue virus field isolates.

A recombinant cDNA probe from genome segment 5 obtained from a virulent US bluetongue virus strain (BTV-11 strain UC8) was hybridized to US and Israeli BTV prototypes and field isolates. The cloned genetic probe hybridized with US BTV prototype 10, but not with US prototypes 2, 11, 13, and 17; with the avirulent BTV-11 strain UC2; and with the Israeli prototype 10. When the probe was hybridized to field isolates from the US serotypes, it hybridized to 12 of 14 BTV-10 isolates and 4 of 17 BTV-11 samples, but not to the BTV-13 and BTV-17 samples tested. Hybridization was not observed with the Israeli field isolates studied. Results indicate that a reassortant event occurred between a strain of US BTV-10 and US BTV-11 that originated the BTV-11 strain UC8.