Theileria in cattle is common enough that the clinical cases are only the visible part of it. A countrywide molecular survey put 34.4 percent of 6,224 cattle and 11.5 percent of 1,467 sheep positive by PCR. Theileria orientalis reached all 17 surveyed provinces, and most carriers looked perfectly normal on the day of sampling. Why subclinical infection is the real problem Theileria is a genus, not a diagnosis. The parasites inside it differ in which ticks carry them, in which hosts they settle, and in how much damage they do once they are established. A herd that looks well will not reveal any of that. Herd decisions usually run on…