Bluetongue and related viruses in New South Wales: isolations from, and serological tests on samples from sentinel cattle

Sentinel cattle at a number of localities in northern and central coastal New South Wales were sampled over the summer and autumn seasons of the years 1979, 1980 and 1981. A total of 118 orbiviruses were isolated; 99 were of the Palyam group, 15 were of the epizootic haemorrhagic disease (EHD) of deer group, and 4 of the bluetongue group. The Palyam group viruses were identified by serotype as 68 Bunyip Creek, 23 CSIRO Village, 7 D'Aguilar and one was not typed. The EHD viruses were identified as 13 type 5 and 2 type 6. All 4 bluetongue viruses were type 21. There was also convincing serological evidence that bluetongue type 1 infection occurred in 1980. Antibody to the bluetongue group, as demonstrated in a gel diffusion precipitin test, was often transient. It appeared to be mostly cross-reactive with, and induced by, other orbivirus infections, particularly those of the EHD group. Viruses of the Palyam group also seemed to be implicated in some circumstances. Where infections by viruses of the bluetongue group were demonstrated, the precipitating antibody responses to a bluetongue group antigen were not noticeably stronger than many which followed EHD virus infection. The results generally confirm previous conclusions, deduced from serological surveys, regarding the frequency of orbivirus infections, the presence of bluetongue viruses, and the transient nature of many bluetongue group antibody reactions.     

The occurrence of antibody to bluetongue virus in New South Wales. I. Statewide surveys of cattle and sheep

Two State-wide surveys were carried out in 1978 to detect bluetongue (BLU) virus antibody in cattle and sheep sera in New South Wales (NSW). The first survey showed that BLU group antibody in cattle 18-24 months old was confined to the coastal regions (east of the Great Dividing Range) and the Hunter Valley. However, in the second survey, of cattle more than 5 years old, reactors were much more widely distributed over the north-eastern third of the State and into the western division with prevalences up to 85% in some areas. In contrast, very few reactors were detected in sheep in either survey (less than 1% of the sheep sera tested). In a retrospective study of stored cattle sera, BLU group reactors were detected in the north-east of the State in each year examined since 1968, the earliest year in which samples were available from that region. Areas to the south and west were free of antibody from 1966 until the summer of 1973, but subsequently reactors were common. Examination of selected area for type-specific antibody indicated that infection of cattle with two of the three Australian BLU serotypes which were known at the time, BLU-1 and BLU-21, had occurred in NSW. No antibody to BLU-20, the original Australian isolate, was detected. A close association was observed between strong group antibody reactions and type-specific neutralizing activity against BLU-1 and BLU-21. Both were largely confined to that area of the State in which a high (75% or more) prevalence of group antibody was recognised in the older animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bluetongue virus: Detection of antiviral immunoglobulin G by means of enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay was developed to detect antiviral IgG in the sere of sheep exposed to bluetongue virus. It was found that the enzyme-linked immunosorbent assay is a rapid and sensitive method for the detection of anti-bluetongue virus antibody. Bluetongue virus antigen prepared from extracts of virus infected BHK and Vero cells were equally effective. Antigen prepared from uninfected cells when used as coating antigen did not bind IgG from either exposed or unexposed animals. Sera raised against each of the four individual BTV serotypes, 10, 11, 13, and 17, found in the United States reacted equally with all four bluetongue virus serotype antigen preparations. Thus, any of the four serotypes can be used as the bluetongue virus antigen for the detection of anti-bluetongue virus antibody in the bluetongue virus-enzymelinked immunosorbent assay system. Antiviral IgG was readily detectable 6 days postinoculation. The anti-bluetongue virus antibody concentration continued to increase through the 35-day postinoculation test period. At 35 days postexposure, antibody titers of 1:1,600 to >1:3,200 were found. The rapid and sensitive nature of the bluetongue virus enzyme-linked immunosorbent assay indicates that this system should significantly extend serological studies on bluetongue virus.     

Precipitating antibodies to epizootic hemorrhagic disease and bluetongue viruses in white-tailed deer in the southeastern United States.

From 1981 to 1989, sera were collected from 3,077 white-tailed deer (Odocoileus virginianus) in Georgia and from 1,749 deer from 12 additional states in the southeastern United States. In Georgia, prevalence of precipitating antibodies to epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV), as determined by agar gel immunodiffusion tests, was dependent on physiographic region, age, and year. Overall prevalence of antibodies to EHDV and/or BTV was 11, 33, 48, and 14% for the Mountain, Piedmont, Coastal Plain, and Barrier Island regions, respectively. Results suggested varying patterns of EHDV and BTV activity throughout the state. Serologic results from other southeastern states were consistent with the Georgia sample; prevalence estimates (EHDV and/or BTV) for corresponding physiographic regions deviated by less than 10%. Over this larger geographical area, antibody prevalence in deer appeared to increase with decreasing latitude.     

Serologic survey for selected microbial pathogens in bison from Kansas.

A serologic survey was conducted on an American bison (Bison bison) herd in Kansas for antibodies against Brucella spp., Leptospira interrogans serovar canicola, pomona, grippotyphosa, icterohaemorrhagiae, and hardjo, Anaplasma spp., bluetongue virus, infectious bovine rhinotracheitis virus and bovine viral diarrhea virus. There was an increase in prevalence of bluetongue antibodies from 38% in 1987 to 100% in 1989 in animals greater than or equal to 24-mo-old. Prevalences of antibodies against the other livestock pathogens were either negative or at levels associated with previous vaccination.     

Embryo transfer as a means of controlling viral infections. VI. Bluetongue virus-free calves from infectious semen

Four Holstein heifers were superovulated and inseminated with infectious semen from a bull experimentally infected with type 17 bluetongue virus (BTV). A total of 20 embryos were collected at donor slaughter and transferred to 16 recipients. Ten recipients became pregnant of which one subsequently aborted, one gave birth to twins which died at birth, one was killed at term because of dystocia, and 7 gave birth to live calves one of which died perinatally. All animals were tested for BTV antibodies at the time of slaughter which was at least 30 days post partum for surviving heifers and calves. Two of the four donor heifers were retrospectively determined to have been infected by the semen (viremia demonstrated) and their embryos accounted for 9 of the 10 pregnancies including the six surviving calves. None of the recipients or calves developed BTV antibody by the termination of the experiment. This study suggests that BTV-free calves can be readily obtained from the use of BTV-positive semen.     

Prevalence of <Emphasis Type="Italic">Coxiella burnetii</Emphasis> antibodies in Danish dairy herds

During recent years in Denmark higher rates of antibodies to Coxiella burnetii have been detected in animals and humans than previously reported. A study based on bulk tank milk samples from 100 randomly selected dairy herds was performed to estimate the prevalence and geographical distribution of antibody positive dairy herds. Using the CHEKIT Q-Fever Antibody ELISA Test Kit (IDEXX), the study demonstrated a prevalence of 59% antibody positive herds, 11% antibody intermediate herds and 30% antibody negative herds based on the instructions provided by the manufacturer. The geographical distribution does not indicate a relationship between the regional density of dairy farms and the prevalence of antibody positive dairy farms. The result supports the hypothesis of an increase in the prevalence of positive dairy herds compared to previous years.     

Expression of largest RNA segment and synthesis of VP1 protein of bluetongue virus in insect cells by recombinant baculovirus: association of VP1 protein with RNA polymerase activity.

The bluetongue virus core particles have been shown to contain an RNA-directed RNA polymerase (1). To identify the protein responsible for the virion RNA polymerase activity, the complete 3.9 Kb DNA clone representing the largest RNA segment 1 (L1) of bluetongue virus (BTV-10) was placed under control of the polyhedrin promoter of Autographa californica nuclear polyhedrosis virus (AcNPV). The derived recombinant virus was used to infect Spodoptera frugiperda cells. As demonstrated by stained polyacrylamide gel electrophoresis and by the use of bluetongue virus antibody, infected insect cells synthesized the largest protein of BTV-10 (VP1, 150 k Da). Antibody raised in rabbit to recombinant VP1 protein recognized bluetongue virus VP1 protein. The recombinant virus infected cell lysate had significantly inducible levels of RNA polymerase enzymatic activity as determined by a poly (U)-oligo (A) polymerase assay. The availability of enzymatically active bluetongue virus RNA polymerase provides a system in which we can precisely delineate the role this protein plays in the regulation of bluetongue replication.     

Embryo transfer as a means of controlling viral infections. III non transmission of bluetongue virus from viremic cattle

Ten holstein heifers were made viremic by inoculation with type 17 or type 18 bluetongue virus (BTV), superovulated, bred artificially with semen from a BTV seronegative bull and slaughtered for the collection of 8-day embryos. A total of 28 embryos were transferred into 28 BTV seronegative recipients.Fourteen transfers resulted in pregnancies. None of the recipients developed BTV antibody during pregnancy or within 30 days of parturition. No antibody or virus was detected in the 14 calves at parturition (of which 4 were lost due to dystocia), in one recumbent calf at the time of euthanasia at 5 days of age or in the remaining 9 healthy calves at 30 days of age. This study suggests that BTV-free calves can be obtained from infected dams by embryo transfer.     

A cross sectional survey for B virus antibody in a colony of group housed rhesus macaques

A systematic sampling technique was used in combination with a highly sensitive and specific ELISA to provide unbiased age-specific prevalence estimates of B virus antibody in rhesus monkeys housed in three different outdoor breeding corrals. Among 146 sampled monkeys, 97% of animals 2.5 years and older were seropositive, while only 22% of younger animals were seropositive. Neither gender nor social dominance ranking were predictive of B virus antibody status. The strong age association was not inconsistent with hypothesized venereal transmission of B virus. Improvements in the epidemiologic understanding of B virus are necessary to assist efforts to eradicate this agent from breeding colonies of rhesus monkeys.     

Comparison of the Prevalence and Incidence of Infection with Bovine Virus Diarrhoea Virus (BVDV) in Denmark and Michigan and Association with Possible Risk Factors

Based on 2 previous surveys on the occurrence of infection with bovine virus diarrhoea virus (BVDV) in Danish and Michigan dairy herds, the prevalence and incidence of the infection were compared. The presence of certain possible risk factors for the occurrence of infection in the 2 areas were summarized and it was investigated if any of these risk factors had significant effect on the presence of animals persistently infected (PI) with BVDV in the dairy herds. Information on the cattle population density in the 2 areas was obtained from statistical yearbooks. Further information for the individual farms on age distribution, housing of animals, herd size, pasturing and purchasing policy was gathered. The prevalence of PI animals was more than 10 times higher in Denmark as compared to Michigan. In herds without PI animals, the annual incidence of seroconversion as calculated from the age specific prevalence of antibody carriers varied in most age groups between 20–25% in Denmark and between 5–10% in Michigan. All investigated risk factors except for herd size were in favour of a lower prevalence of infection in Michigan. The use of having animals on pasture and at the same time having purchased more than 40 animals within recent 31/2–4 years were significantly associated with presence of PI animals in the dairy herds (p = 0.01) when tested by the Mantel-Haenszel χ2. Using mul-tivariable logistic regression, the occurrence of PI animals was found to be significantly related to the study area (Michigan and Denmark) as well as to herd size and purchase intensity.     

Corynebacterium Pseudotuberculosis Infection in Goats II.

The precalen-ce of caseous lymphadenitis was surveyed in 36 goat herds in Northern Norway. In each herd, information concerning the occurrence of the disease was obtained from the farmer. Adult animals (1 year of age or older) in 35 herds were examined for superficial swellings, and serum samples were collected from most animals in the herds. The sera were examined for antibodies to Corynebacterium pseudotuber-culosis using the bacterial agglutination test (BAT) and the hemolysis inhibition test (HIT). Gaseous lymphadenitis was diagnosed with certainty in 19 herds. Information from the farmers indicated that the disease indeed oc-curred in these herds, and that the majority had been infected with the disease for many years. The herds had apparently become infected through contact with animals from infected herds. Clinical examina-tions were carried out in 18 of these herds and superficial swellings were found in 26 % of the examined animals. The prevalence of ani-mals with lesions varied from 11 to 40 % among the herds. Of the animals in these herds, 81 % were positive in BAT and 84 % in HIT. The prevalence of positive animals varied from 26 to 99 % in BAT and 28 to 99 % in HIT. The prevalence of seropositive animals was lowest in a herd in which animals were kept separately in stalls. Caseous lymphadenitis could not be diagnosed in 16 herds. In-formation from the farmers indicated that the disease indeed seemed to be absent in 14 of these herds. These 14 herds had no history of contact with animals from herds considered to be infected. However, in the remaining 2 herds, the farmers were somewhat uncertain about the occurrence of the disease. One of these 2 herds had a history of contact with infected herds through participation in a goat “breeding circle”. Only a few of the animals were, however, seropositive and all these had low antibody titres. In 1 newly established herd, a single animal showed a high posi-tive titre in BAT only. All the other animals were negative in both tests. This particular herd consisted of animals obtained both from herds with caseous lymphadenitis and from herds in which the disease was not considered to occur.     

A sero-epidemiological study of Leptospira interrogans serovar Balcanica in four brush-tailed possum populations in Victoria, Australia.

The microscopic agglutination (MA) test was utilised to study the prevalence of antibodies to Leptospira interrogans serovar hardjo in 4 populations of brush-tailed possums (Trichosurus vulpecula). The overall antibody prevalence varied from 14% to 66%; however, the age distribution of MA test titres was remarkably similar in all 4 populations. Antibody prevalence was similar in both males and females and demonstrable antibodies were limited to sexually mature animals. The greater prevalence of high titres (greater than or equal to 1:128) in the 18- to 24-month age group suggested that primary infections were acquired at this age. The findings suggested that infection was maintained in possum populations by direct transmission, probably associated with breeding. Focal interstitial nephritis was observed in kidneys of possums greater than 18 months of age and was associated with MA titres to hardjo (P less than 0.001). Serovar balcanica was isolated from possum kidneys from 2 of these populations, suggesting that balcanica infections were responsible for most of the hardjo titres. However, agglutinin-absorption tests indicated that some possums may be infected with a leptospire more closely related to hardjo than to balcanica.     

Determining prevalence of bluetongue and epizootic hemorrhagic disease viruses in mule deer in Arizona (USA) using whole blood dried on paper strips compared to serum analyses

We investigated the feasibility of using whole blood dried on paper strips as a means to collect antibody prevalence data for the epizootic hemorrhagic disease viruses (EHDV) and bluetongue viruses (BTV) from hunter-harvested male mule deer (Odocoileus hemionus) in October 2002 from Arizona, USA. We compared antibody prevalence estimates in mule deer from paired paper strip and serum samples. Prevalence data obtained from elution of dried blood on paper strips proved to be consistent with results from serum in 94% of the samples tested. The paper strip method allows easy collection of blood from dead animals, with a smaller amount of blood being needed for analyses. Also, samples do not need to be refrigerated before analyses. We also used serum samples to determine hemorrhagic disease (HD) serotype exposure status of mule deer harvested from 4 distinct areas in Arizona. Antibodies to BTV and EHDV were identified in 3 of the 4 areas, with positive results to EHDV-1, EHDV-2, BTV-10, and BTV-11 being most common. Many animals did not have antibodies against the BTV serotypes. Exposure varied geographically and potentially with elevation. Hemorrhagic disease viruses commonly infect Arizona mule deer, except on the Kaibab Plateau in northern Arizona.     

Seroepizootiological survey on bluetongue virus infection in cattle in Japan

Bovine sera collected in various parts of Japan were subjected to seroepizootiological tests with bluetongue virus type 1 (BTV1), type 12 (BTV12), and type 20 (BTV20). All these viruses have been widely disseminated among cattle in the southern part of Japan in 1974. Relatively high incidences of neutralizing (NT) antibody against the three viruses were shown among cattle in the Kyushu district, including Okinawa Prefecture, or the southern part of Japan, but extremely low or incidences in Hokkaido, or the northern part of Japan. The incidence of reactors was higher in old animals. Cattle in Okinawa Prefecture showed a high rate of seroconversion for all the viruses during the summer of 1979. None of the animals seroconverted, however, manifested any sign of disease. Seroepizootiological investigation made it clear that BTV1, BTV12 and BTV20 had existed in Japan and that the epizootic of bluetongue virus infection started during a period from summer through early autumn.     

Serosurvey for selected infectious disease agents in free-ranging black and white rhinoceros in Africa

Two hundred and eighty one serum samples collected from free-ranging black (Diceros bicornis) and white (Ceratotherium simum) rhinoceros, in the Republic of South Africa (RSA), Namibia, and Kenya from 1987-97, were examined for antibody to 16 different infectious agents. Positive antibody titers were detected against Akabane (59.8%), bluetongue (55%), African horse sickness (27.9%), epizootic haemorrhagic disease of deer (19.4%), parainfluenza type 3 (25.3%), bovine herpes virus 1 (3.1%), equine herpes virus 1 (8.8%) and bovine viral diarrhea (1.2%) viruses, and four serovars of Leptospira interrogans, (ranging 1.2 to 8.8%). No antibody was detected against Rift Valley fever virus, encephalomyocarditis virus, Brucella abortus, and Trypanosoma equiperdum. Interspecies differences were detected for African horse sickness, epizootic haemorrhagic disease of deer and parainfluenza type 3 viruses. There appeared to be some geographic variation in the prevalence of antibody for African horse sickness, bluetongue, epizootic haemorrhagic disease of deer, parainfluenza type 3, equine herpes virus 1 and Leptospira interrogans serovar bratislava.     

Characterization of protection afforded by a bivalent virus-like particle vaccine against bluetongue virus serotypes 1 and 4 in sheep

Background

Bluetongue virus (BTV) is an economically important, arthropod borne, emerging pathogen in Europe, causing disease mainly in sheep and cattle. Routine vaccination for bluetongue would require the ability to distinguish between vaccinated and infected individuals (DIVA). Current vaccines are effective but are not DIVA. Virus-like particles (VLPs) are highly immunogenic structural mimics of virus particles, that only contain a subset of the proteins present in a natural infection. VLPs therefore offer the potential for the development of DIVA compatible bluetongue vaccines.

Methodology/Principal Findings

Merino sheep were vaccinated with either monovalent BTV-1 VLPs or a bivalent mixture of BTV-1 VLPs and BTV-4 VLPs, and challenged with virulent BTV-1 or BTV-4. Animals were monitored for clinical signs, antibody responses, and viral RNA. 19/20 animals vaccinated with BTV-1 VLPs either alone or in combination with BTV-4 VLPs developed neutralizing antibodies to BTV-1, and group specific antibodies to BTV VP7. The one animal that showed no detectable neutralizing antibodies, or group specific antibodies, had detectable viral RNA following challenge but did not display any clinical signs on challenge with virulent BTV-1. In contrast, all control animals'' demonstrated classical clinical signs for bluetongue on challenge with the same virus. Six animals were vaccinated with bivalent vaccine and challenged with virulent BTV-4, two of these animals had detectable viral levels of viral RNA, and one of these showed clinical signs consistent with BTV infection and died.

Conclusions

There is good evidence that BTV-1 VLPs delivered as monovalent or bivalent immunogen protect from bluetongue disease on challenge with virulent BTV-1. However, it is possible that there is some interference in protective response for BTV-4 in the bivalent BTV-1 and BTV-4 VLP vaccine. This raises the question of whether all combinations of bivalent BTV vaccines are possible, or if immunodominance of particular serotypes could interfere with vaccine efficacy.     

Haemagglutination-inhibiting antibodies to B.K. virus in Hungary.

Antibody inhibiting the haemagglutination by B.K. virus was found in 64% of the serum samples collected from 949 subjects in Hungary. The frequency of seropositivity was the lowest (17%) among infants 1 and 2 years of age and the highest (93%) in the age group 16 to 20 years. The subsequent age groups showed a slow continuous decline. The age-distribution curve drawn on the basis of the geometric means of titres has two peaks, one between 3 and 5 years of age and another between 21 and 30 years of age, reaching 6.74 and 7.05, respectively, as expressed in terms of log2 units. The prevalence of haemagglutination-inhibiting antibody to B.K. virus in Hungary and its distribution by age are similar to those reported from other European countries.     

Shifting seroepidemiology of hepatitis A in Japan, 1973-2003

BACKGROUND: Hepatitis A infection is caused by hepatitis A virus (HAV) contracted through fecal-oral transmission. Life-long immunity is conferred after infection. Improved sanitary conditions have generally resulted in a significant decline in the incidence of hepatitis A. However, a low incidence of infection results in increased HAV susceptibility. The present study investigates the prevalence of anti-HAV antibody and clarifies the current HAV status and HAV susceptibility in Japan at 2003. METHODS: A total of 2,430 serum specimens collected during 2003 from Japanese individuals ranging in age from 0-92 years, were tested for anti-HAV antibody using an inhibition enzyme linked immunosorbent assay. All specimens were obtained from the WHO and the National Serum Reference Bank/National Institute of Infectious Diseases, Tokyo, Japan. RESULTS: The overall seroprevalence was 12.2%. Anti-HAV antibodies were rarely detected in individuals between 0-44 years of age. Starting from the age of 45-49 years, seropositivity gradually increased through age 65 years and above. Seroprevalence was not affected by gender, and geographic distribution did not affect age-specific seroprevalence until the age of 60 years. CONCLUSIONS: HAV susceptibility in Japan is increasing annually. Particularly, the prevalence of anti-HAV antibody in individuals older than 50 years in 2003 was 50.3%, which is significantly lower than that of corresponding studies in 1994 (74.3%), 1984 (96.9%) and 1973 (96.9%). The growing susceptible population of advanced age results in more frequent HAV infection among them. The surveillance of anti-HAV antibody prevalence is useful for implementing preventive measures and for controlling the spread of HAV.     

Prevalence of antibody to hepatitis A virus in a Canadian Inuit community.

To determine the prevalence of hepatitis A in a Canadian Inuit population, serum from 85% of the 850 inhabitants of Baker Lake, Northwest Territories, was tested by radioimmunoassay for antibody to the hepatitis A virus (anti-HAV). The overall prevalence of anti-HAV in the community was 71%. Exposure to the virus occurred early in life, such that by the age of 6 years 53% of the children had anti-HAV in their serum. The rate approached 100% by the age of 50 years. These findings document the ubiquitous nature of the hepatitis A virus in this northern Inuit settlement and suggest that immunoprophylaxis be considered for individuals taking short-term employment in such places.