Incidence and Prevalence Rate for BVDPI in Feeder Operations
We compiled data from over 28,500 loads of cattle from 400  699 lbs to look at Incidence Rate. Incidence Rate is how often a
BVDPI animal occurs by load. Some instances, the Incidence Rate is over 40%; meaning 40% of the incoming loads will have a PI on them. Averages by weight class are as shown:

400  499 lbs  32.27%

500  599 lbs  26.69%

600  699 lbs  22.03%
Below that is Prevalence Rate. This shows the percentage of PI's in the total number of cattle in their specific weight class, not by load. Some instances, the Prevalence Rate can be over 0.50%, meaning there are 5 PI's per 1,000 head of cattle. Averages by weight class are as shown:

400  499 lbs  0.49% or 4.9 PI's per 1,000 head

500  599 lbs  0.40% or 4 PI's per 1,000 head

600  699 lbs  0.31% or 3.1 PI's per 1,000 head
This data is important as it shows that although the prevalence rate seems like a small number you don't need to worry about, it can cause detrimental effects to your operation. It will also show how many PI's you should be finding. If you find a significantly less amount of these numbers, we would recommend checking your testing protocols, specifically whether you are pooling samples or not.
The majority of cattle tested were sourced from sale barns in the southern, southeastern and eastern United States.