The course of infection usually is rapid with visible symptoms seldom lasting more than 3 days, terminating in death or beginning recovery. Recovered birds may appear stunted, with the flock as a whole appearing to lack uniformity. In adult birds, clinical symptoms seldom are detectable. The most consistent pronounced gross lesion is spleen enlargement and congestion. Anemia and emaciation usually are evident in clinically ill birds.
Flesh often is flabby and yellowish.
Mild congestion of the upper intestinal tract is common. Prevention includes controlling black fly populations, and raising turkeys away from running streams. Segregate breeding and brooding operations since adults may be carriers. Brooding in screened houses will prevent infection in young birds. Drugs effective against malaria appear to have little if any value in treating Leucocytozoonosis.