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Using animal performance data to evidence the under-reporting of case herds during an epizootic: application to an outbreak of bluetongue in cattle.

Nusinovici S, Monestiez P, Seegers H, Beaudeau F, Fourichon C - PLoS ONE (2014)

Bottom Line: This system did not allow a precise estimation of the extent of the epizootic.This interpolation was based on the spatiotemporal dynamic of confirmed case herds reported in 2007.Overall, results indicate that performance data can be used to evidence the under-reporting during an epizootic.

View Article: PubMed Central - PubMed

Affiliation: INRA, UMR1300 Biology, Epidemiology and Risk Analysis in animal health, Nantes, France; LUNAM Université, Oniris, Ecole nationale vétérinaire, agroalimentaire et de l'alimentation Nantes-Atlantique, Nantes, France.

ABSTRACT
Following the emergence of the Bluetongue virus serotype 8 (BTV-8) in France in 2006, a surveillance system (both passive and active) was implemented to detect and follow precociously the progression of the epizootic wave. This system did not allow a precise estimation of the extent of the epizootic. Infection by BTV-8 is associated with a decrease of fertility. The objective of this study was to evaluate whether a decrease in fertility can be used to evidence the under-reporting of cases during an epizootic and to quantify to what extent non-reported cases contribute to the total burden of the epizootic. The cow fertility in herds in the outbreak area (reported or not) was monitored around the date of clinical signs. A geostatistical interpolation method was used to estimate a date of clinical signs for non-reported herds. This interpolation was based on the spatiotemporal dynamic of confirmed case herds reported in 2007. Decreases in fertility were evidenced for both types of herds around the date of clinical signs. In non-reported herds, the decrease fertility was large (60% of the effect in reported herds), suggesting that some of these herds have been infected by the virus during 2007. Production losses in non-reported infected herds could thus contribute to an important part of the total burden of the epizootic. Overall, results indicate that performance data can be used to evidence the under-reporting during an epizootic. This approach could be generalized to pathogens that affect cattle's performance, including zoonotic agents such as Coxiella burnetii or Rift Valley fever virus.

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Hazard Ratio (HR) of 90-d-return-to-service before and after (a) the date of Bluetongue virus serotype 8 (BTV-8) clinical detection for case herds reported during the 2007 epizootic, (b) the interpolated date of BTV-8 clinical detection for non-reported herds located in the 2007 outbreak area, (c) the transposed date in a previous year free of BTV (2005) for herds in 2005 located in the 2007 outbreak area, France.
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pone-0100137-g004: Hazard Ratio (HR) of 90-d-return-to-service before and after (a) the date of Bluetongue virus serotype 8 (BTV-8) clinical detection for case herds reported during the 2007 epizootic, (b) the interpolated date of BTV-8 clinical detection for non-reported herds located in the 2007 outbreak area, (c) the transposed date in a previous year free of BTV (2005) for herds in 2005 located in the 2007 outbreak area, France.

Mentions: As expected, exposure to BTV-8 at the time were clinical signs were observed was associated with an increase of 90-d-return-to-service rate for cows in case herds (Figure 4-a). The period of fertility decrease corresponded to AIs performed between 6 weeks before to 10 weeks after the date of clinical detection (HR between 1.05 and 1.18). More interestingly, for cows in herds with uncertain BTV-8 status, an increase of the 90-day-return-to-service rate was also found (Figure 4-b). The period of decreased fertility corresponded to AIs performed between 6 weeks before and 8 weeks after the interpolated date (HR between 1.04 and 1.08). Finally, for cows inseminated in 2005 in herds that were located in the 2007 outbreak area, only a very slight increase of 90-day-return-to-service rate was observed for AIs performed 2 weeks before the date in a previous year free of BTV-8 (HR = 1.04) (Figure 4-c). These fertility decreases corresponded to an increase of 5.2 and 3.0 percentage points of 90-day-return-to-service for cows in case herds and cows in herds with uncertain BTV-8 status, respectively.


Using animal performance data to evidence the under-reporting of case herds during an epizootic: application to an outbreak of bluetongue in cattle.

Nusinovici S, Monestiez P, Seegers H, Beaudeau F, Fourichon C - PLoS ONE (2014)

Hazard Ratio (HR) of 90-d-return-to-service before and after (a) the date of Bluetongue virus serotype 8 (BTV-8) clinical detection for case herds reported during the 2007 epizootic, (b) the interpolated date of BTV-8 clinical detection for non-reported herds located in the 2007 outbreak area, (c) the transposed date in a previous year free of BTV (2005) for herds in 2005 located in the 2007 outbreak area, France.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061093&req=5

pone-0100137-g004: Hazard Ratio (HR) of 90-d-return-to-service before and after (a) the date of Bluetongue virus serotype 8 (BTV-8) clinical detection for case herds reported during the 2007 epizootic, (b) the interpolated date of BTV-8 clinical detection for non-reported herds located in the 2007 outbreak area, (c) the transposed date in a previous year free of BTV (2005) for herds in 2005 located in the 2007 outbreak area, France.
Mentions: As expected, exposure to BTV-8 at the time were clinical signs were observed was associated with an increase of 90-d-return-to-service rate for cows in case herds (Figure 4-a). The period of fertility decrease corresponded to AIs performed between 6 weeks before to 10 weeks after the date of clinical detection (HR between 1.05 and 1.18). More interestingly, for cows in herds with uncertain BTV-8 status, an increase of the 90-day-return-to-service rate was also found (Figure 4-b). The period of decreased fertility corresponded to AIs performed between 6 weeks before and 8 weeks after the interpolated date (HR between 1.04 and 1.08). Finally, for cows inseminated in 2005 in herds that were located in the 2007 outbreak area, only a very slight increase of 90-day-return-to-service rate was observed for AIs performed 2 weeks before the date in a previous year free of BTV-8 (HR = 1.04) (Figure 4-c). These fertility decreases corresponded to an increase of 5.2 and 3.0 percentage points of 90-day-return-to-service for cows in case herds and cows in herds with uncertain BTV-8 status, respectively.

Bottom Line: This system did not allow a precise estimation of the extent of the epizootic.This interpolation was based on the spatiotemporal dynamic of confirmed case herds reported in 2007.Overall, results indicate that performance data can be used to evidence the under-reporting during an epizootic.

View Article: PubMed Central - PubMed

Affiliation: INRA, UMR1300 Biology, Epidemiology and Risk Analysis in animal health, Nantes, France; LUNAM Université, Oniris, Ecole nationale vétérinaire, agroalimentaire et de l'alimentation Nantes-Atlantique, Nantes, France.

ABSTRACT
Following the emergence of the Bluetongue virus serotype 8 (BTV-8) in France in 2006, a surveillance system (both passive and active) was implemented to detect and follow precociously the progression of the epizootic wave. This system did not allow a precise estimation of the extent of the epizootic. Infection by BTV-8 is associated with a decrease of fertility. The objective of this study was to evaluate whether a decrease in fertility can be used to evidence the under-reporting of cases during an epizootic and to quantify to what extent non-reported cases contribute to the total burden of the epizootic. The cow fertility in herds in the outbreak area (reported or not) was monitored around the date of clinical signs. A geostatistical interpolation method was used to estimate a date of clinical signs for non-reported herds. This interpolation was based on the spatiotemporal dynamic of confirmed case herds reported in 2007. Decreases in fertility were evidenced for both types of herds around the date of clinical signs. In non-reported herds, the decrease fertility was large (60% of the effect in reported herds), suggesting that some of these herds have been infected by the virus during 2007. Production losses in non-reported infected herds could thus contribute to an important part of the total burden of the epizootic. Overall, results indicate that performance data can be used to evidence the under-reporting during an epizootic. This approach could be generalized to pathogens that affect cattle's performance, including zoonotic agents such as Coxiella burnetii or Rift Valley fever virus.

Show MeSH
Related in: MedlinePlus