Parameters | Scenario 1 High impact | Scenario 2 Low impact | References | Reasoning |
---|---|---|---|---|
Number of calves stillborn or malformed due to SBV out of 100 calves born | 1-10 most likely = 2 | 0-1 most likely = 1 | [15] and expert opinion | Martinelle et al. 2012 [15]: median SBV morbidity rate in calves was 2% ; the minimum reported by Martinelle et al.[15] was taken as the lower range value and the median value plus one standard deviation as the upper range value. |
Number of cows with dystocia out of 100 cows giving birth to a stillborn or malformed calf due to SBV | 30 | Baseline dystocia rates in UK are 6.9% in heifers and 2% in cows with abnormal presentations being the cause in 19.8% on average. With an increased proportion of malformations, dystocia rate was assumed to be higher. | ||
Number of cows that need caesarean out of 100 cows with dystocia due to SBV | 5-7 most likely = 6 | The proportion of caesareans conducted in the case of dystocia was reported to be between 5 and 7%. | ||
Number of cows with clinical episodes due to SBV out of 100 cows in a herd | 3-31 most likely = 7.5 | 0 | [15] and expert opinion | Martinelle et al. 2012 [15]: Median SBV morbidity rate in cattle was 7.5%. The minimum reported by Martinelle et al.[15] was taken as the lower range value and the median value plus one standard deviation as the upper range value. |
Number of cows that require treatment out of 100 cows with clinical episodes due to SBV | 10 | Expert opinion | This figure reflects the regular need for treatment of beef sucklers in the UK presented with unspecific diarrhoea, fever, general depression and/or inappetence. | |
Number of cows with SBV abortions out of 100 cows in a herd | 0-2 most likely = 2 | 0-1 most likely = 1 | Expert opinion | The proportion of abortions due to SBV is uncertain (lack of studies). Experts agreed on these approximated figures based on abortion rates seen in other diseases. |
Probability of an aborted foetuses, stillborn, malformed and calves culled to be tested for SBV | 0.05 | Expert opinion | Investigation of abortions is recommended if incidence >3% in a herd per year or if several abortions occur in quick succession (http://www.defra.gov.uk/ahvla-en/files/pub-cattle-abortion.pdf). Due to the absence of "abortion storms" due to SBV and farmers suspecting the disease, it is assumed that only a small proportion submit aborted foetuses, stillborn or malformed calves to be tested for SBV. | |
Number of cows that die due to calving difficulties out of 100 cows with dystocia | 10 | Day and Meijering report mortality rate due to dystocia as 3.5% on average, and 16.7% for a clinical case observation. Given that SBV causes malformations, the mortality rate is assumed to be on higher than the reported average. | ||
Number of aborted cows that will need to be replaced out of 100 cows with abortions | 10 | Expert opinion | It was assumed that only in a small proportion of cows the reproductive system will be affected such that the cow is not able to breed anymore and will therefore be replaced. |