Within 36 to 48 hours, merozoites are released into the bloodstream and transported to macrophages in the brain, liver, spleen, kidney, and lung. Subsequently, the parasites commence asexual reproduction, generating copies of themselves. The new generations of merozoites infect red blood cells, where they grow, reproduce, and eventually cause the cells to burst open.
This sudden release of parasites and the loss of red cells trigger the acute phase of infection. In susceptible birds, this phase is primarily characterized by anemia, accompanied by symptoms of weakness, depression, and loss of appetite. Some birds may even become comatose and die.