Control of Coccidiosis and Necrotic Enteritis - Greg Mathis

Agree with several of these comments so let me put some thoughts about my experience on coccidiosis. Necrotic enteritis would be for another occasion.
Let´s not forget that clean houses don´t allow the chicks to develop early immune response against coccidiosis, instead, this will delay the immune response which will typically play an important role of coccidiosis control when ionophores are used.
I recommend you to refer to the term "new house syndrome" a condition when coccidiosis outbreaks are more severe than outbreaks of old (and contaminated) houses. The downtime between flocks and disinfection is obviously important for any diseases but don´t play an important role in the coccidiosis incidence in a new flock (see M. K. Henken 1994). After all, the oocysts don´t live for a long time in the litter because they are killed by ammonia, bacteria etc (See Reyna et al. Avian Diseases Vol. 27, 1982).
Let´s also remind that different chemical anticoccidials and ionophores should not be put in the same basket. They will typically deliver quite different results, e.g: nicarbazin is not expected to generate widespread resistance (Biology of the Coccidia, by Peter Long /Larry McDougald page 396) but makes birds more sensitive to heat stress. Diclasuril and Robenidin have no problems with heath stress however as "vertical drugs" they generate resistant strains much quicker than nicarbazin or ionophores.
The ionophores are "horizontal anticoccidials" (Mike Eckman) and as such, are not as strong in preventing coccidiosis as the chemical / vertical drugs.
As a result of that, they don´t generate resistance easily. However, they usually allow some degree of lesions in the flocks. One detail that lacks proper investigation is how much stronger is each of the five ionophore drugs against each of the Eimeria species. Some ionophores can be quite strong against, say E. tenella, but weaker against E. acervulina or vice-versa. This means that most of the times when an ionophore is not delivering the expected level of protection, this is not related to resistance, instead, it is because that drug is not the best option for the challenge of that region/company/flock. There are lots of details to be discussed here but for the present time here is my opinion:

1-Disinfection against coccidiosis is not effective. In fact, when we kill bacteria and fungi, we are protecting the coccidia. In laboratory work, we protect coccidia strain with chlorine or potassium dichromate which are two very strong disinfectants.

2-Chemical drugs and ionophores should not be rotated under the same approach. Rotation is intended to avoid resistance but these two classes of drugs have different abilities to generate resistance.

3-Regardless of being monovalent or divalent drugs, each ionophore delivers different and specific degrees of protection against each coccidia species, therefore one important consideration to take into account for a good coccidiosis control is to check which species is more prevalent in a given region and which ionophore provides better efficacy against that species. Regards.
C. A. Lopes DVM

Cesar A. Lopes Well explained and outlined, thanks for sharing your insight and experience.

Never start any medicines at least in advance but start when morbity is 10 to 15 percent, it is better to give sulfa drugs on onset of coccidosis as amrolium is resistent to many strains. Fly control is necessary tool to avoid coccidiosis in cages. Ht of feeders may be so adjusted so the spilled litter does not make entry in feed any reduction in feed may be followed by increasing dose of coccidiostat. Ionophores and zinc bacitracin may not be given simultaneously.