Bluetongue (BT) is an insect-transmitted, economically important disease of domestic and wild rum... more Bluetongue (BT) is an insect-transmitted, economically important disease of domestic and wild ruminants. Although only five of the 26 reported bluetongue virus (BTV) serotypes are considered endemic to the USA, 10 exotic serotypes have been isolated primarily in the southeastern region of the country since 1999. For an exotic BTV serotype to become endemic there must be susceptible animal species and competent vectors. In the USA, sheep and white-tailed deer (WTD) are the primary sentinel livestock and wildlife species, respectively. In 2006, BTV-8 was introduced into Northern Europe and subsequently overwintered, causing unprecedented livestock disease and mortality during the 2006– 2007 vector seasons. To assess the risk of the European strain of BTV-8 to North American WTD, and understand the role they could play after a similar introduction, eight bluetongue-seronegative WTD were inoculated with BTV-8. Body temperatures and clinical signs were recorded daily. Blood samples were ...
Revue d’élevage et de médecine vétérinaire des pays tropicaux, 2009
Since August 2006, the Netherlands has been facing outbreaks of bluetongue (BT) caused by serotyp... more Since August 2006, the Netherlands has been facing outbreaks of bluetongue (BT) caused by serotype 8 (BTV-8). In this first BT-season about 470 affected holdings were reported in the southern part of the country. It was believed that restrictions to animal movements slowed down the northwards spread of BTV. After a relatively mild winter, BT simultaneously resurfaced in July 2007 at many locations indicating that BTV-8 had survived well. Thousands of affected holdings across the country were reported during that year. After another mild winter, a vaccination campaign for serotype 8 was launched in May 2008, with massive vaccination of sheep, goats and cattle. In 2008, less than 150 outbreaks were reported. The reported BTV-8 cases were in the north-eastern part of the country where the level of natural immunity and the willingness to vaccinate were relatively low. This third year with outbreaks was followed by a cold winter. In 2009, no BTV-positive animals were reported from mid-...
Background The main objective of this study was to determine the prevalence of nine vector-borne ... more Background The main objective of this study was to determine the prevalence of nine vector-borne pathogens or pathogen genera in roe deer (Capreolus capreolus) in the Netherlands, and to identify which host variables predict vector-borne pathogen presence in roe deer. The host variables examined were the four host factors ‘age category’, ‘sex’, ‘nutritional condition’ and ‘health status’, as well as ‘roe deer density’. Methods From December 2009 to September 2010, blood samples of 461 roe deer were collected and analysed by polymerase chain reaction (PCR) for the presence of genetic material from Anaplasma phagocytophilum, Bartonella spp., Babesia spp., Borrelia burgdorferi sensu lato (s.l.), Borrelia miyamotoi, Neoehrlichia mikurensis, Rickettsia spp., and epizootic haemorrhagic disease virus (EHDV), and by commercial enzyme-linked immunosorbent assay (ELISA) for antibodies against bluetongue virus (BTV). The possible associations of host factors and density with pathogen prevalenc...
<b>Copyright information:</b>Taken from "A cross-sectional study to determine th... more <b>Copyright information:</b>Taken from "A cross-sectional study to determine the seroprevalence of bluetongue virus serotype 8 in sheep and goats in 2006 and 2007 in the Netherlands"http://www.biomedcentral.com/1746-6148/4/33BMC Veterinary Research 2008;4():33-33.Published online 27 Aug 2008PMCID:PMC2531099.
Bluetongue (BT) is a disease of ruminants caused by bluetongue virus (BTV) transmitted by biting ... more Bluetongue (BT) is a disease of ruminants caused by bluetongue virus (BTV) transmitted by biting midges of the Culicoides genus. Outbreaks have been controlled successfully by vaccination, however, currently available BT vaccines have several shortcomings. Recently, we have developed BT Disabled Infectious Single Animal (DISA) vaccines based on live-attenuated BTV without expression of dispensable non-structural NS3/NS3a protein. DISA vaccines are non-pathogenic replicating vaccines, do not cause viremia, enable DIVA and are highly protective. NS3/NS3a protein is involved in virus release, cytopathogenic effect and suppression of Interferon-I induction, suggesting that the vaccination route can be of importance. A standardized dose of DISA vaccine for serotype 8 has successfully been tested by subcutaneous vaccination. We show that 10 and 100times dilutions of this previously tested dose did not reduce the VP7 humoral response. Further, the vaccination route of DISA vaccine strongly...
ABSTRACTBluetongue virus (BTV) is endemic in many parts of the world, often causing severe hemorr... more ABSTRACTBluetongue virus (BTV) is endemic in many parts of the world, often causing severe hemorrhagic disease in livestock. To date, at least 27 different serotypes have been recognized. Vaccination against all serotypes is necessary to protect susceptible animals and to prevent onward spread of the virus by insect vectors. In our previous studies, we generated replication-deficient (disabled infectious single-cycle [DISC]) virus strains for a number of serotypes and reported preliminary data on their protective efficacy in animals. In this report, to advance the DISC vaccines to the marketplace, we investigated different parameters of these DISC vaccines. First, we demonstrated the genetic stabilities of these vaccine strains and also the complementing cell line. Subsequently, the optimal storage conditions of vaccines, including additives, temperature, and desiccation, were determined and their protective efficacies in animals confirmed. Furthermore, to test if mixtures of differ...
Monoclonal antibodies (MAbs) directed against envelope glycoprotein E1 (gp51-54) of hog cholera v... more Monoclonal antibodies (MAbs) directed against envelope glycoprotein E1 (gp51-54) of hog cholera virus (HCV) strain Brescia have been shown to recognize four different antigenic domains A, B, C and D. Epitopes of within domain A have mainly been found conserved among HCV strains, whereas epitopes within domains B, C and D are not conserved. We used transiently expressed hybrid E1 genes of HCV strains Brescia and &amp;amp;amp;amp;amp;amp;quot;C&amp;amp;amp;amp;amp;amp;quot; to map the non-conserved epitopes on E1. Epitopes in domains B and C are located within the ultimate N-terminal 104 amino acids. The non-conserved subdomain A3 is most probably located between domains B/C and a hydrophobic region, which is highly conserved between HCV strains Brescia and &amp;amp;amp;amp;amp;amp;quot;C&amp;amp;amp;amp;amp;amp;quot;. The conserved subdomains A1 and A2 are probably located in the vicinity and C-terminally of this conserved, hydrophobic region, which is near the centre of the E1 amino acid sequence.
To study the efficacy and safety of bovine virus diarrhea virus (BVDV) vaccines there is need for... more To study the efficacy and safety of bovine virus diarrhea virus (BVDV) vaccines there is need for a valid challenge model. We investigated whether sheep can be used in such a challenge model. We intranasally inoculated six groups (A-F) of seronegative sheep at day 49 of gestation with either of five antigenically different BVDV strains and one border disease virus strain. A seventh group (G) was housed for 10 days with a persistently infected calf and an eighth group (H) served as control. From each group half of the sheep were killed at 2 weeks, and half at 4 weeks after infection. For virus isolation five organs were collected from the sheep and seven from the fetuses. All sheep of groups A and H remained seronegative in the ELISA and in the serum neutralization test. At 2 and 4 weeks after infection virus was isolated from almost all fetal organs in six groups. In group A and in the control group no virus was isolated from the fetal organs. The virus distribution patterns in fetuses from sheep housed with the persistently infected calf or intranasally inoculated with the same strain were similar. We concluded that (i) antigenically different BVDV strains can induce congenital infection in sheep and that (ii) the consequences of a contact infection were similar to those after intranasal infection. In a second experiment we infected two groups of seronegative sheep with one of the strains used in the first experiment, before mating. A control group was left uninfected. The sheep were served and all sheep were challenged with antigenically homologous or heterologous BVDV at day 49 of pregnancy. Three weeks after challenge, sheep were killed and the procedure as in the first experiment was followed. None of the fetuses sheep were virus positive whereas all fetuses of the control sheep were virus positive. Hence, the immune response after BVDV infection protects fetuses against homologous and heterologous infection during pregnancy. Sheep may therefore be used in vaccination-challenge experiments to evaluate BVDV vaccine efficacy in preventing congenital infection.
Cattle persistently infected (PI) with noncytopathic (ncp) bovine virus diarrhea virus (BVDV) are... more Cattle persistently infected (PI) with noncytopathic (ncp) bovine virus diarrhea virus (BVDV) are at risk for developing fatal mucosal disease (MD), which is considered to occur after superinfection with antigenically homologous cytopathic (cp) BVDV. In this study, we intranasally inoculated four PI-animals, that were PI with 2 ncp BVDV strains with 10(5) TCID50 antigenically closely related cp BVDV. Two PI-animals were inoculated with 10(5) TCID50 ncp BVDV and one PI-animal, with virus free cell culture medium. Two out of four PI-animals that were inoculated with cp BVDV, developed MD and were euthanized at day 17 and at day 24 after infection. Postmortem, both animals showed typical lesions of MD and cp BVDV was isolated. The other two PI-animals that were inoculated with cp BVDV did not develop MD and were euthanized at day 51. They showed ulcerations in the gastrointestinal tract, cp BVDV was isolated and neutralizing antibodies were detected. From the three PI-animals, that were inoculated with ncp BVDV or cell culture medium, cp BVDV was also isolated. Cross neutralization tests were performed and no antigenic differences could be detected between the cp strains isolated from the PI-animals. Lymphocyte subsets of these PI-animals were determined by flow cytometric analysis. Before superinfection, the percentages of gamma delta subsets were much higher in the PI-animals that did not develop MD than in nonviremic control animals and in the PI-animals that died of MD. From this study we conclude that the presence of antigenically closely related cp BVDV in PI-animals does not necessarily lead to the development of MD and that besides the antigenic relatedness between the persisting ncp BVDV and cp BVDV other factors, for instance the number of circulating gamma delta cells, might determine whether or not PI-animals develop MD.
In 2007, BTV-8 re-emerged for the second year in the Netherlands and caused morbidity and increas... more In 2007, BTV-8 re-emerged for the second year in the Netherlands and caused morbidity and increased mortality in cattle herds. In addition, cattle farmers reported reduced fertility in their cows. For this study, fifteen herds that were not vaccinated were selected. These were matched to 10 vaccinated herds by geographic region. At the start of the study, in July 2008, all cattle in the non-vaccinated herds &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1 year old were sampled. All seronegative cows entered the study program and blood samples from these cows were tested for antibodies against BTV-8 in an ELISA. Cows were sampled at intervals of three weeks and sampling was stopped once a cow tested seropositive. Sampling ceased in all remaining cows in December 2008. Newborn calves originating from infected dams or from vaccinated dams were tested by PCR for BTV-8. Fertility data were obtained from the Royal Dutch Cattle Syndicate (CRV). Multi-level generalized latent and linear models were used for analyses. In 2008, 185 (17.2%) out of 1,074 initially seronegative non-vaccinated cattle seroconverted and were assumed to be infected with BTV-8. Infected cows were 5 (95% CI: 1.9-14.3) times more likely to return for insemination within 56 days after first insemination. In addition, these cows needed 1.7 (95% CI: 1.4-2.0) times more inseminations for an assumed pregnancy, and needed 2.5 (95% CI: 2.4-2.6) times more days between first and last insemination compared to the period prior to seroconversion and compared to cows not infected by BTV-8 in 2008. No association between BTV-8 infection and the chance to abort between 100 and 260 days after last insemination was found. In total, 48 calves originating from infected cows were tested by PCR for the presence of BTV-8. Ten (20.8%) out of these 48 calves were born PCR-positive. None of 256 calves from vaccinated dams tested PCR-positive. Further, cows infected during the second half of gestation had a 15.5 times (95% CI: 1.3-190.4) higher chance of a PCR-positive newborn calf compared to cows infected in the first half of gestation. This study showed that BTV-8 has a negative effect on fertility of dairy cattle.
Bluetongue is a major infectious disease of ruminants caused by bluetongue virus (BTV), an arbovi... more Bluetongue is a major infectious disease of ruminants caused by bluetongue virus (BTV), an arbovirus transmitted by Culicoides. Here, we assessed virus and host factors influencing the clinical outcome of BTV infection using a single experimental framework. We investigated how mammalian host species, breed, age, BTV serotypes, and strains within a serotype affect the clinical course of bluetongue. Results obtained indicate that in small ruminants, there is a marked difference in the susceptibility to clinical disease induced by BTV at the host species level but less so at the breed level. No major differences in virulence were found between divergent serotypes (BTV-8 and BTV-2). However, we observed striking differences in virulence between closely related strains of the same serotype collected toward the beginning and the end of the European BTV-8 outbreak. As observed previously, differences in disease severity were also observed when animals were infected with either blood from a...
Since 1998, Bluetongue virus (BTV)-serotypes 1, 2, 4, 9, and 16 have invaded European countries a... more Since 1998, Bluetongue virus (BTV)-serotypes 1, 2, 4, 9, and 16 have invaded European countries around the Mediterranean Basin. In 2006, a huge BT outbreak started after incursion of BTV serotype 8 (BTV8) in North-Western Europe. IN 2008, BTV6 and BTV11 were reported in the Netherlands and Germany, and in Belgium, respectively. In addition, Toggenburg orbivirus (TOV) was detected in 2008 in Swiss goats, which was recognized as a new serotype of BTV (BTV25). The (re-)emergency of BTV serotypes needs a rapid response to supply effective vaccines. Reverse genetics has been developed for BTV1 and more recently also for BTV6. This latter strain, BTV6/net08, is closely related to live-attenuated vaccine for serotype 6 as determined by full genome sequencing. Here, we used this strain as backbone and exchanged segment 2 and 6, respectively Seg-2 (VP2) and Seg-6 (VP5), for those of BTV serotype 1 and 8 using reverse genetics. These so-called ‘serotyped ’ vaccine viruses, as mono-serotype an...
Bluetongue (BT) is an insect-transmitted, economically important disease of domestic and wild rum... more Bluetongue (BT) is an insect-transmitted, economically important disease of domestic and wild ruminants. Although only five of the 26 reported bluetongue virus (BTV) serotypes are considered endemic to the USA, 10 exotic serotypes have been isolated primarily in the southeastern region of the country since 1999. For an exotic BTV serotype to become endemic there must be susceptible animal species and competent vectors. In the USA, sheep and white-tailed deer (WTD) are the primary sentinel livestock and wildlife species, respectively. In 2006, BTV-8 was introduced into Northern Europe and subsequently overwintered, causing unprecedented livestock disease and mortality during the 2006– 2007 vector seasons. To assess the risk of the European strain of BTV-8 to North American WTD, and understand the role they could play after a similar introduction, eight bluetongue-seronegative WTD were inoculated with BTV-8. Body temperatures and clinical signs were recorded daily. Blood samples were ...
Revue d’élevage et de médecine vétérinaire des pays tropicaux, 2009
Since August 2006, the Netherlands has been facing outbreaks of bluetongue (BT) caused by serotyp... more Since August 2006, the Netherlands has been facing outbreaks of bluetongue (BT) caused by serotype 8 (BTV-8). In this first BT-season about 470 affected holdings were reported in the southern part of the country. It was believed that restrictions to animal movements slowed down the northwards spread of BTV. After a relatively mild winter, BT simultaneously resurfaced in July 2007 at many locations indicating that BTV-8 had survived well. Thousands of affected holdings across the country were reported during that year. After another mild winter, a vaccination campaign for serotype 8 was launched in May 2008, with massive vaccination of sheep, goats and cattle. In 2008, less than 150 outbreaks were reported. The reported BTV-8 cases were in the north-eastern part of the country where the level of natural immunity and the willingness to vaccinate were relatively low. This third year with outbreaks was followed by a cold winter. In 2009, no BTV-positive animals were reported from mid-...
Background The main objective of this study was to determine the prevalence of nine vector-borne ... more Background The main objective of this study was to determine the prevalence of nine vector-borne pathogens or pathogen genera in roe deer (Capreolus capreolus) in the Netherlands, and to identify which host variables predict vector-borne pathogen presence in roe deer. The host variables examined were the four host factors ‘age category’, ‘sex’, ‘nutritional condition’ and ‘health status’, as well as ‘roe deer density’. Methods From December 2009 to September 2010, blood samples of 461 roe deer were collected and analysed by polymerase chain reaction (PCR) for the presence of genetic material from Anaplasma phagocytophilum, Bartonella spp., Babesia spp., Borrelia burgdorferi sensu lato (s.l.), Borrelia miyamotoi, Neoehrlichia mikurensis, Rickettsia spp., and epizootic haemorrhagic disease virus (EHDV), and by commercial enzyme-linked immunosorbent assay (ELISA) for antibodies against bluetongue virus (BTV). The possible associations of host factors and density with pathogen prevalenc...
<b>Copyright information:</b>Taken from "A cross-sectional study to determine th... more <b>Copyright information:</b>Taken from "A cross-sectional study to determine the seroprevalence of bluetongue virus serotype 8 in sheep and goats in 2006 and 2007 in the Netherlands"http://www.biomedcentral.com/1746-6148/4/33BMC Veterinary Research 2008;4():33-33.Published online 27 Aug 2008PMCID:PMC2531099.
Bluetongue (BT) is a disease of ruminants caused by bluetongue virus (BTV) transmitted by biting ... more Bluetongue (BT) is a disease of ruminants caused by bluetongue virus (BTV) transmitted by biting midges of the Culicoides genus. Outbreaks have been controlled successfully by vaccination, however, currently available BT vaccines have several shortcomings. Recently, we have developed BT Disabled Infectious Single Animal (DISA) vaccines based on live-attenuated BTV without expression of dispensable non-structural NS3/NS3a protein. DISA vaccines are non-pathogenic replicating vaccines, do not cause viremia, enable DIVA and are highly protective. NS3/NS3a protein is involved in virus release, cytopathogenic effect and suppression of Interferon-I induction, suggesting that the vaccination route can be of importance. A standardized dose of DISA vaccine for serotype 8 has successfully been tested by subcutaneous vaccination. We show that 10 and 100times dilutions of this previously tested dose did not reduce the VP7 humoral response. Further, the vaccination route of DISA vaccine strongly...
ABSTRACTBluetongue virus (BTV) is endemic in many parts of the world, often causing severe hemorr... more ABSTRACTBluetongue virus (BTV) is endemic in many parts of the world, often causing severe hemorrhagic disease in livestock. To date, at least 27 different serotypes have been recognized. Vaccination against all serotypes is necessary to protect susceptible animals and to prevent onward spread of the virus by insect vectors. In our previous studies, we generated replication-deficient (disabled infectious single-cycle [DISC]) virus strains for a number of serotypes and reported preliminary data on their protective efficacy in animals. In this report, to advance the DISC vaccines to the marketplace, we investigated different parameters of these DISC vaccines. First, we demonstrated the genetic stabilities of these vaccine strains and also the complementing cell line. Subsequently, the optimal storage conditions of vaccines, including additives, temperature, and desiccation, were determined and their protective efficacies in animals confirmed. Furthermore, to test if mixtures of differ...
Monoclonal antibodies (MAbs) directed against envelope glycoprotein E1 (gp51-54) of hog cholera v... more Monoclonal antibodies (MAbs) directed against envelope glycoprotein E1 (gp51-54) of hog cholera virus (HCV) strain Brescia have been shown to recognize four different antigenic domains A, B, C and D. Epitopes of within domain A have mainly been found conserved among HCV strains, whereas epitopes within domains B, C and D are not conserved. We used transiently expressed hybrid E1 genes of HCV strains Brescia and &amp;amp;amp;amp;amp;amp;quot;C&amp;amp;amp;amp;amp;amp;quot; to map the non-conserved epitopes on E1. Epitopes in domains B and C are located within the ultimate N-terminal 104 amino acids. The non-conserved subdomain A3 is most probably located between domains B/C and a hydrophobic region, which is highly conserved between HCV strains Brescia and &amp;amp;amp;amp;amp;amp;quot;C&amp;amp;amp;amp;amp;amp;quot;. The conserved subdomains A1 and A2 are probably located in the vicinity and C-terminally of this conserved, hydrophobic region, which is near the centre of the E1 amino acid sequence.
To study the efficacy and safety of bovine virus diarrhea virus (BVDV) vaccines there is need for... more To study the efficacy and safety of bovine virus diarrhea virus (BVDV) vaccines there is need for a valid challenge model. We investigated whether sheep can be used in such a challenge model. We intranasally inoculated six groups (A-F) of seronegative sheep at day 49 of gestation with either of five antigenically different BVDV strains and one border disease virus strain. A seventh group (G) was housed for 10 days with a persistently infected calf and an eighth group (H) served as control. From each group half of the sheep were killed at 2 weeks, and half at 4 weeks after infection. For virus isolation five organs were collected from the sheep and seven from the fetuses. All sheep of groups A and H remained seronegative in the ELISA and in the serum neutralization test. At 2 and 4 weeks after infection virus was isolated from almost all fetal organs in six groups. In group A and in the control group no virus was isolated from the fetal organs. The virus distribution patterns in fetuses from sheep housed with the persistently infected calf or intranasally inoculated with the same strain were similar. We concluded that (i) antigenically different BVDV strains can induce congenital infection in sheep and that (ii) the consequences of a contact infection were similar to those after intranasal infection. In a second experiment we infected two groups of seronegative sheep with one of the strains used in the first experiment, before mating. A control group was left uninfected. The sheep were served and all sheep were challenged with antigenically homologous or heterologous BVDV at day 49 of pregnancy. Three weeks after challenge, sheep were killed and the procedure as in the first experiment was followed. None of the fetuses sheep were virus positive whereas all fetuses of the control sheep were virus positive. Hence, the immune response after BVDV infection protects fetuses against homologous and heterologous infection during pregnancy. Sheep may therefore be used in vaccination-challenge experiments to evaluate BVDV vaccine efficacy in preventing congenital infection.
Cattle persistently infected (PI) with noncytopathic (ncp) bovine virus diarrhea virus (BVDV) are... more Cattle persistently infected (PI) with noncytopathic (ncp) bovine virus diarrhea virus (BVDV) are at risk for developing fatal mucosal disease (MD), which is considered to occur after superinfection with antigenically homologous cytopathic (cp) BVDV. In this study, we intranasally inoculated four PI-animals, that were PI with 2 ncp BVDV strains with 10(5) TCID50 antigenically closely related cp BVDV. Two PI-animals were inoculated with 10(5) TCID50 ncp BVDV and one PI-animal, with virus free cell culture medium. Two out of four PI-animals that were inoculated with cp BVDV, developed MD and were euthanized at day 17 and at day 24 after infection. Postmortem, both animals showed typical lesions of MD and cp BVDV was isolated. The other two PI-animals that were inoculated with cp BVDV did not develop MD and were euthanized at day 51. They showed ulcerations in the gastrointestinal tract, cp BVDV was isolated and neutralizing antibodies were detected. From the three PI-animals, that were inoculated with ncp BVDV or cell culture medium, cp BVDV was also isolated. Cross neutralization tests were performed and no antigenic differences could be detected between the cp strains isolated from the PI-animals. Lymphocyte subsets of these PI-animals were determined by flow cytometric analysis. Before superinfection, the percentages of gamma delta subsets were much higher in the PI-animals that did not develop MD than in nonviremic control animals and in the PI-animals that died of MD. From this study we conclude that the presence of antigenically closely related cp BVDV in PI-animals does not necessarily lead to the development of MD and that besides the antigenic relatedness between the persisting ncp BVDV and cp BVDV other factors, for instance the number of circulating gamma delta cells, might determine whether or not PI-animals develop MD.
In 2007, BTV-8 re-emerged for the second year in the Netherlands and caused morbidity and increas... more In 2007, BTV-8 re-emerged for the second year in the Netherlands and caused morbidity and increased mortality in cattle herds. In addition, cattle farmers reported reduced fertility in their cows. For this study, fifteen herds that were not vaccinated were selected. These were matched to 10 vaccinated herds by geographic region. At the start of the study, in July 2008, all cattle in the non-vaccinated herds &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1 year old were sampled. All seronegative cows entered the study program and blood samples from these cows were tested for antibodies against BTV-8 in an ELISA. Cows were sampled at intervals of three weeks and sampling was stopped once a cow tested seropositive. Sampling ceased in all remaining cows in December 2008. Newborn calves originating from infected dams or from vaccinated dams were tested by PCR for BTV-8. Fertility data were obtained from the Royal Dutch Cattle Syndicate (CRV). Multi-level generalized latent and linear models were used for analyses. In 2008, 185 (17.2%) out of 1,074 initially seronegative non-vaccinated cattle seroconverted and were assumed to be infected with BTV-8. Infected cows were 5 (95% CI: 1.9-14.3) times more likely to return for insemination within 56 days after first insemination. In addition, these cows needed 1.7 (95% CI: 1.4-2.0) times more inseminations for an assumed pregnancy, and needed 2.5 (95% CI: 2.4-2.6) times more days between first and last insemination compared to the period prior to seroconversion and compared to cows not infected by BTV-8 in 2008. No association between BTV-8 infection and the chance to abort between 100 and 260 days after last insemination was found. In total, 48 calves originating from infected cows were tested by PCR for the presence of BTV-8. Ten (20.8%) out of these 48 calves were born PCR-positive. None of 256 calves from vaccinated dams tested PCR-positive. Further, cows infected during the second half of gestation had a 15.5 times (95% CI: 1.3-190.4) higher chance of a PCR-positive newborn calf compared to cows infected in the first half of gestation. This study showed that BTV-8 has a negative effect on fertility of dairy cattle.
Bluetongue is a major infectious disease of ruminants caused by bluetongue virus (BTV), an arbovi... more Bluetongue is a major infectious disease of ruminants caused by bluetongue virus (BTV), an arbovirus transmitted by Culicoides. Here, we assessed virus and host factors influencing the clinical outcome of BTV infection using a single experimental framework. We investigated how mammalian host species, breed, age, BTV serotypes, and strains within a serotype affect the clinical course of bluetongue. Results obtained indicate that in small ruminants, there is a marked difference in the susceptibility to clinical disease induced by BTV at the host species level but less so at the breed level. No major differences in virulence were found between divergent serotypes (BTV-8 and BTV-2). However, we observed striking differences in virulence between closely related strains of the same serotype collected toward the beginning and the end of the European BTV-8 outbreak. As observed previously, differences in disease severity were also observed when animals were infected with either blood from a...
Since 1998, Bluetongue virus (BTV)-serotypes 1, 2, 4, 9, and 16 have invaded European countries a... more Since 1998, Bluetongue virus (BTV)-serotypes 1, 2, 4, 9, and 16 have invaded European countries around the Mediterranean Basin. In 2006, a huge BT outbreak started after incursion of BTV serotype 8 (BTV8) in North-Western Europe. IN 2008, BTV6 and BTV11 were reported in the Netherlands and Germany, and in Belgium, respectively. In addition, Toggenburg orbivirus (TOV) was detected in 2008 in Swiss goats, which was recognized as a new serotype of BTV (BTV25). The (re-)emergency of BTV serotypes needs a rapid response to supply effective vaccines. Reverse genetics has been developed for BTV1 and more recently also for BTV6. This latter strain, BTV6/net08, is closely related to live-attenuated vaccine for serotype 6 as determined by full genome sequencing. Here, we used this strain as backbone and exchanged segment 2 and 6, respectively Seg-2 (VP2) and Seg-6 (VP5), for those of BTV serotype 1 and 8 using reverse genetics. These so-called ‘serotyped ’ vaccine viruses, as mono-serotype an...
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