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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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Geographical location of cattle herds in the outbreak area: (a) 8,313 case herds reported after clinical signs of Bluetongue virus serotype 8 (BTV-8) in 2007, (b) 74,169 non-reported herds (e.g., herds with an interpolated date of BTV-8 exposure); 2007; France.
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pone-0100137-g001: Geographical location of cattle herds in the outbreak area: (a) 8,313 case herds reported after clinical signs of Bluetongue virus serotype 8 (BTV-8) in 2007, (b) 74,169 non-reported herds (e.g., herds with an interpolated date of BTV-8 exposure); 2007; France.

Mentions: Cattle case herds reported after clinical signs in 2007 were located in the north-eastern part of France (Figure 1(a)). The overall 90-day-return-to-service rates were 56.9% for cows in case herds and 56.0% for cows in herds with uncertain BTV-8 status. The overall 90-day-return-to-service rate was 54.2% in the reference population and 54.3% for cows inseminated in 2005 in herds that were located in the 2007 outbreak area (Table 1).


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)

Geographical location of cattle herds in the outbreak area: (a) 8,313 case herds reported after clinical signs of Bluetongue virus serotype 8 (BTV-8) in 2007, (b) 74,169 non-reported herds (e.g., herds with an interpolated date of BTV-8 exposure); 2007; France.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0100137-g001: Geographical location of cattle herds in the outbreak area: (a) 8,313 case herds reported after clinical signs of Bluetongue virus serotype 8 (BTV-8) in 2007, (b) 74,169 non-reported herds (e.g., herds with an interpolated date of BTV-8 exposure); 2007; France.
Mentions: Cattle case herds reported after clinical signs in 2007 were located in the north-eastern part of France (Figure 1(a)). The overall 90-day-return-to-service rates were 56.9% for cows in case herds and 56.0% for cows in herds with uncertain BTV-8 status. The overall 90-day-return-to-service rate was 54.2% in the reference population and 54.3% for cows inseminated in 2005 in herds that were located in the 2007 outbreak area (Table 1).

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