Coccidial monitoring of chickens and turkeys is done by routine intestinal lesion scoring, typically at 28 days of age.
The most widely used system for coccidial monitoring is the Johnson and Reid Scoring System. Using this system, lesion scores, noted from one to four (zero for a normal appearance of the intestine), are assigned for each of the five coccidial species likely to induce lesions in chickens. A similar system was developed for turkeys by ANSES, France.
Visible lesions in the gut mucosa typically appear in late schizogony or during gamogony, and their severity remains constant for a few days. The lesions are caused by the release of the merozoites and eventually the unsporulated oocysts. (A lesion score of three does not result from a lesion score of two the previous day, and will not evolve into a different severity the following day in the same bird). However, as the epithelium regenerates, the lesions slowly disappear making accurate scoring more difficult.
Lesion scores are useful for:
- Assessing the severity of coccidial development
- Identifying the coccidial species involved, and
- Establishing a link between the parasite manifestation observed on the farm and in production