If the birds have been exposed for some time and are not symptomatic, then I do not treat. For me, birds that are symptomatic with round worms are culled and if worthy treated but removed from flock permanently. With my strategy, the assumption is made all birds are ultimately exposed to parasites such as round worms and coccidia and chronically so. With coccidia, if the initial exposure is gradual the birds develop an immune response that suppresses the coccidia population in their guts enough that impacts on the birds quality of life is minimal. If initial exposure is too rapid, then immunity can not develope quickly enough and you can have mortalites. It is under the overly rapid exposure scenario that I step in with the medication and I make certain it is fresh / properly stored before use. It is generally not practical to prevent exposure to cocci but with proper management you can make the initial introduction gradual. That should be your concern next go around. Treatment of balance of your existing flock is your option. Since they are not showing signs, risk from the treatment should be minimal.
