Bluetongue virus-induced interferon in cattle

Calves were inoculated IV with bluetongue virus (BTV), serotype 10. Titers of interferon (IFN) in serum and BTV in peripheral blood were determined. All inoculated calves produced circulating IFN that persisted for 2 to 4 days. Highest titers of BTV in peripheral blood were present after serum IFN was no longer detected. The persistence of BTV in peripheral blood, as compared with the transient IFN response, indicated that IFN was most important in the initial antiviral response of cattle to BTV infection. Bluetongue virus is probably not a suitable model inducer of circulating IFN in cattle because the profound neutropenia that accompanied BTV infection may predispose cattle to infections with other agents.     

Bluetongue virus as a cause of hydranencephaly in cattle.

Hydranencephaly was produced in a foetus and a calf by intra-uterine infection with an attenuated Type 10 bluetongue virus. Laparotomy was performed on the respective dams and the foetuses, respectively 126 days and 138 days old, were inoculated intramuscularly through the uterine wall with 1 ml of a virus suspension containing 5 x 103 tissue culture infective doese. The younger feotus was aborted on Day 262, while the other one was born alive on Day 273. Both foetuses showed marked hydranencephaly.     

Bluetongue infections in Louisiana cattle

Bluetongue virus (BTV) serotype 17 was isolated from cattle with clinical signs of bluetongue disease during 1978 and 1979 epizootics. Bovine sera from 6 herds located in an epizootic region were examined in 1979 for antibodies, using an immunodiffusion (ID) test. Of 300 sera, 164 (54.7%) were seropositive. Sera from statewide surveys of Louisiana cattle in July to August 1980 and December 1980 to January 1981 were tested for BTV antibodies, using the ID test. Fifty-eight of 70 herds (82.9%) and 164 of 597 (27.5%) individual cattle tested in July to August 1980 were seropositive. Fifty-four of 63 (85.7%) herds and 170 of 600 (28.3%) individual cattle tested in December 1980 to January 1981 were seropositive. Significant differences (P less than 0.01) were found in the seropositive rates between the various geographic regions of the state during each survey. Adult breeding-age cattle in 3 sentinel herds were tested for BTV antibodies beginning in 1976 and continuing through January 1981. During this interval, the seropositive rate in 2 of 3 herds was increased. Also, individual cattle in all 3 of these herds converted from seronegative to seropositive, indicating exposure during a particular interval for each herd. The age distribution of seropositive cattle in a dairy indicated that 2-year-old cattle had a seropositive rate comparable with that of older animals in the herd, suggesting that the 2-year-old animals had been exposed to a BTV before they entered the breeding herd.     

Bluetongue in cattle: a serologic survey of slaughter cattle in the United States

Serologic tests for bluetongue virus (BTV) were done on 19,758 blood serum samples systematically collected at brucellosis laboratories throughout the United States from Nov 28, 1977 to Feb 20, 1978. Prevalence of BTV antibody varied from 0 to 79% of the samples collected in various states, with a national prevalence of 18.2%. The prevalence was generally low in the northern states and high in the southwestern states. The highest prevalence rates were found in Puerto Rico and the Virgin Islands.     

The development of Akabane virus-induced congenital abnormalities in cattle

A prospective study of the incidence and severity of congenital deformities of calves, attributable to maternal infection by Akabane virus, was carried out on a population of 174 susceptible animals that were between one and nine months pregnant at the time of infection. The study was carried out in the Hunter Valley of New South Wales during 1983, after an epidemic of Akabane virus infection in late February to early March 1983. The incidence of virus-induced abnormalities in calves and fetuses was 17.8 per cent (31/174). The highest incidence of abnormalities occurred during the third and sixth months of gestation (27 to 29 per cent). The earliest abnormality was observed after infection at 76 days of gestation, and the last after infection at 249 days. The development of the pathological entities of hydranencephaly/porencephaly and arthrogryposis were found to be quite distinct. Cases of hydranencephaly and porencephaly developed after infection between 76 and 104 days of gestation whereas arthrogryposis developed after infection between 103 and 174 days of infection. It was concluded that the type of congenital deformity produced by maternal infection with Akabane virus was dependent on the stage of fetal development at the time of infection. The data suggest that the infection was transplacental and that fetuses of less than two months of age were protected from infection.     

Bluetongue sentinel surveillance program and cross-sectional serological survey in cattle in Belgium in 2010-2011

Bluetongue virus serotype 8 (BTV-8) emerged in Central Western Europe in 2006 causing a large scale epidemic in 2007 that involved several European Union (EU) countries including Belgium. As in several other EU member states, vaccination against BTV-8 with inactivated vaccines was initiated in Belgium in spring 2008 and appeared to be successful. Since 2009, no clinical cases of Bluetongue (BT) have been reported in Belgium and BTV-8 circulation seemed to have completely disappeared by spring 2010. Therefore, a series of repeated cross-sectional surveys, the BT sentinel surveillance program, based on virus detection in blood samples by means of real-time RT-PCR (RT-qPCR) were carried out in dairy cattle from the end of 2010 onwards with the aim to demonstrate the absence of BTV circulation in Belgium. This paper describes the results of the first two sampling rounds of this BT sentinel surveillance program carried out in October-November 2010 and January-February 2011. In addition, the level of BTV-specific maternal antibodies in young non-vaccinated animals was monitored and the level of herd immunity against BTV-8 after 3 consecutive years of compulsory BTV-8 vaccination was measured by ELISA. During the 1st sampling round of the BT sentinel surveillance program, 15 animals tested positive and 2 animals tested doubtful for BTV RNA by RT-qPCR. During the 2nd round, 17 animals tested positive and 5 animals tested doubtful. The positive/doubtful animals in both rounds were re-sampled 2-4 weeks after the original sampling and then all tested negative by RT-qPCR. These results demonstrate the absence of BTV circulation in Belgium in 2010 at a minimum expected prevalence of 2% and 95% confidence level. The study of the maternal antibodies in non-vaccinated animals showed that by the age of 7 months maternal antibodies against BTV had disappeared in most animals. The BTV seroprevalence at herd level after 3 years of compulsory BTV-8 vaccination was very high (97.4% [95% CI: 96.2-98.2]). The overall true within-herd BTV seroprevalence in 6-24 month old Belgian cattle in early 2011 was estimated at 73.4% (95% CI: 71.3-75.4).     

Bluetongue in cattle: effects of vector-transmitted bluetongue virus on calves previously infected in utero.

Three of 7 principal calves, after a challenge of immunity exposure by bites of bluetongue (BT) virus-infected Culicoides variipennis, became latently infected with BT virus. These calves were born to heifers infected with the homologous virus by bites of C variipennis at 60 or 120 days' gestation. Latent BT virus infection was detected by isolation of BT virus from washed erythrocyte samples obtained from the calves at 57, 100 to 102, 200 to 202, 300 to 302, and 400 to 402 days after challenge of immunity and from 1 of the calves over 5 years after challenge of immunity. The 3 latently infected calves were healthy; 2 were immunologically competent and 1 was immunologically incompetent to develop detectable BT virus antibodies in their blood. Bluetongue virus infection was detected (by viral isolation) in 2 other principal calves during the challenge of immunity, but they were not considered latently infected. The latter 2 calves were immunologically incompetent to develop detectable BT virus antibodies.     

Porencephaly and hydranencephaly in six dogs

A retrospective study was performed to identify dogs with cerebrospinal fluid-filled cavitatory lesions on MRI. Six dogs were included and the lesions were classified. In the three dogs in the present study with hydranencephaly, unilateral but complete loss of the temporal and parietal lobes was noted and had almost complete loss of the occipital and frontal lobes of a cerebral hemisphere. In the three dogs with porencephaly, there was unilateral incomplete loss of the parietal lobe and one dog had additional partial loss of the temporal and frontal lobes. Two of the dogs with porencephaly had seizures; the third showed no associated clinical signs. The dogs with hydranencephaly had mentation changes and circled compulsively. The two porencephalic dogs with seizures were treated with phenobarbitone. One of the dogs with hydranencephaly showed increased frequency and duration of circling; one dog's clinical signs did not progress and the third dog was euthanased due to increasing aggression. The dog with increased circling had ventriculoperitoneal shunt placement and the circling frequency reduced.     

Bluetongue vaccines in Europe

The article reviews the history, present status and the future of BT vaccines in Europe. So far, an attenuated (modified live viruses, MLV) and inactivated virus vaccines against BT were developed and used in the field. Moreover, the virus-like particles (VLPs) produced from recombinant baculovirus, and live recombinant vaccinia or canarypox virus-vectored vaccines were tested in the laboratory. The main aims of BT vaccination strategy are: to prevent clinical disease, to reduce the spread of the BTV in the environment and to protect movement of susceptible animals between affected and free zones. Actually, all of the most recent European BT vaccination campaigns have used exclusively inactivated vaccines. The use of inactivated vaccines avoid risk associated with the use of live-attenuated vaccines, such as reversion to virulence, reassortment of genes with field strain, teratogenicity and insufficient attenuation leading to clinical disease. The mass vaccinations of all susceptible animals are the most efficient veterinary method to fight against BT and successful control of disease. The vaccination of livestock has had a major role in reducing BTV circulation and even in eradicating the virus from most areas of Europe.