Alaskan
Herd Master
It is best to worm only when needed, since that way you are less likely to make the worms resistant to the drugs.
For parasites in general, I think it is best to know what is in your area, then learn their life cycles so you can manage them.
And if the vet has already been out....
Then if he needs to come out again... well... not sure.... I hate paying money for a vet to come out, so I have always done it as rarely as possible. You just have to decide if the visit is worth it to you. Completely personal choice. Because so often with livestock, by the time it looks serious it is often too late... so, lots of guessing is always involved.
For parasites in general, I think it is best to know what is in your area, then learn their life cycles so you can manage them.
And if the vet has already been out....
Then if he needs to come out again... well... not sure.... I hate paying money for a vet to come out, so I have always done it as rarely as possible. You just have to decide if the visit is worth it to you. Completely personal choice. Because so often with livestock, by the time it looks serious it is often too late... so, lots of guessing is always involved.