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Estimation of French cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015
BACKGROUND: From 2006 to 2010, France experienced two bluetongue epidemics caused by serotype 1 (BTV-1) and 8 (BTV-8) which were controlled by mass vaccination campaigns. After five years without any detected cases, a sick ram was confirmed in August 2015 to be infected by a BTV-8 strain almost iden...
Autores principales: | , , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
BioMed Central
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5834897/ https://www.ncbi.nlm.nih.gov/pubmed/29499711 http://dx.doi.org/10.1186/s12917-018-1388-1 |
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author | Bournez, L. Cavalerie, L. Sailleau, C. Bréard, E. Zanella, G. Servan de Almeida, R. Pedarrieu, A. Garin, E. Tourette, I. Dion, F. Hendrikx, P. Calavas, D. |
author_facet | Bournez, L. Cavalerie, L. Sailleau, C. Bréard, E. Zanella, G. Servan de Almeida, R. Pedarrieu, A. Garin, E. Tourette, I. Dion, F. Hendrikx, P. Calavas, D. |
author_sort | Bournez, L. |
collection | PubMed |
description | BACKGROUND: From 2006 to 2010, France experienced two bluetongue epidemics caused by serotype 1 (BTV-1) and 8 (BTV-8) which were controlled by mass vaccination campaigns. After five years without any detected cases, a sick ram was confirmed in August 2015 to be infected by a BTV-8 strain almost identical to that circulating during the previous outbreak. By then, part of the French cattle population was expected to be still protected, since bluetongue antibodies are known to last for many years after natural infection or vaccination. The objective of this study was to estimate the proportion of cattle in France still immune to BTV-8 at the time of its re-emergence in 2015. RESULTS: We used BTV group-specific cELISA results from 8525 cattle born before the vaccination ban in 2013 and 15,799 cattle born after the ban. Samples were collected from January to April 2016 to estimate seroprevalence per birth cohort. The overall seroprevalence in cattle at national and local levels was extrapolated from seroprevalence results per birth cohort and their respective proportion at each level. To indirectly assess pre-immune status of birth cohorts, we computed prevalence per birth cohort on infected farms in autumn 2015 using 1377 RT-PCR results. These revealed limited BTV circulation in 2015. Seroprevalence per birth cohort was likely to be connected to past exposure to natural infection and/or vaccination with higher seroprevalence levels in older animals. A seroprevalence of 95% was observed for animals born before 2008, of which > 90% were exposed to two compulsory vaccination campaigns in 2008-2010. None of the animals born before 2008 were found to be infected, unlike 19% of the young cattle which had never been vaccinated. This suggests that most ELISA-positive animals were pre-immune to BTV-8. We estimated that 18% (from 12% to 32% per département) of the French cattle population was probably pre-immune in 2015. CONCLUSIONS: These results strongly suggest a persistence of antibodies for at least 5-6 years after natural infection or vaccination. The herd immunity of the French cattle population probably limited BTV circulation up to 2015, by which time more than 80% of cattle were naive. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12917-018-1388-1) contains supplementary material, which is available to authorized users. |
format | Online Article Text |
id | pubmed-5834897 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-58348972018-03-05 Estimation of French cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015 Bournez, L. Cavalerie, L. Sailleau, C. Bréard, E. Zanella, G. Servan de Almeida, R. Pedarrieu, A. Garin, E. Tourette, I. Dion, F. Hendrikx, P. Calavas, D. BMC Vet Res Research Article BACKGROUND: From 2006 to 2010, France experienced two bluetongue epidemics caused by serotype 1 (BTV-1) and 8 (BTV-8) which were controlled by mass vaccination campaigns. After five years without any detected cases, a sick ram was confirmed in August 2015 to be infected by a BTV-8 strain almost identical to that circulating during the previous outbreak. By then, part of the French cattle population was expected to be still protected, since bluetongue antibodies are known to last for many years after natural infection or vaccination. The objective of this study was to estimate the proportion of cattle in France still immune to BTV-8 at the time of its re-emergence in 2015. RESULTS: We used BTV group-specific cELISA results from 8525 cattle born before the vaccination ban in 2013 and 15,799 cattle born after the ban. Samples were collected from January to April 2016 to estimate seroprevalence per birth cohort. The overall seroprevalence in cattle at national and local levels was extrapolated from seroprevalence results per birth cohort and their respective proportion at each level. To indirectly assess pre-immune status of birth cohorts, we computed prevalence per birth cohort on infected farms in autumn 2015 using 1377 RT-PCR results. These revealed limited BTV circulation in 2015. Seroprevalence per birth cohort was likely to be connected to past exposure to natural infection and/or vaccination with higher seroprevalence levels in older animals. A seroprevalence of 95% was observed for animals born before 2008, of which > 90% were exposed to two compulsory vaccination campaigns in 2008-2010. None of the animals born before 2008 were found to be infected, unlike 19% of the young cattle which had never been vaccinated. This suggests that most ELISA-positive animals were pre-immune to BTV-8. We estimated that 18% (from 12% to 32% per département) of the French cattle population was probably pre-immune in 2015. CONCLUSIONS: These results strongly suggest a persistence of antibodies for at least 5-6 years after natural infection or vaccination. The herd immunity of the French cattle population probably limited BTV circulation up to 2015, by which time more than 80% of cattle were naive. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12917-018-1388-1) contains supplementary material, which is available to authorized users. BioMed Central 2018-03-02 /pmc/articles/PMC5834897/ /pubmed/29499711 http://dx.doi.org/10.1186/s12917-018-1388-1 Text en © The Author(s). 2018 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. |
spellingShingle | Research Article Bournez, L. Cavalerie, L. Sailleau, C. Bréard, E. Zanella, G. Servan de Almeida, R. Pedarrieu, A. Garin, E. Tourette, I. Dion, F. Hendrikx, P. Calavas, D. Estimation of French cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015 |
title | Estimation of French cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015 |
title_full | Estimation of French cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015 |
title_fullStr | Estimation of French cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015 |
title_full_unstemmed | Estimation of French cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015 |
title_short | Estimation of French cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015 |
title_sort | estimation of french cattle herd immunity against bluetongue serotype 8 at the time of its re-emergence in 2015 |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5834897/ https://www.ncbi.nlm.nih.gov/pubmed/29499711 http://dx.doi.org/10.1186/s12917-018-1388-1 |
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