Serological surveillance of Leucocytozoon spp. in Taiwan.

Chicken Leucocytozoonosis is a protozoan disease that affects the blood and tissues of chickens. High summer temperatures create optimal conditions for reproducing biting midges, the primary vectors for transmitting Leucocytozoon to chickens. In Taiwan, a subtropical region, the disease remains prevalent throughout the year, except in winter, leading to significant economic losses due to increased mortality and reduced egg production. Despite its impact, diagnosing this disease remains challenging. While clinical symptoms may suggest infection, rapid serological diagnostic methods are essential for laboratory confirmation and effective disease management. This study used the recombinant R7 (rR7) antigen to measure enzyme-linked immunosorbent assay (ELISA) antibody titers. Blood samples from 260 chickens, including laying and breeding hens, were collected from Central and Southern Taiwan between August and October 2024. Both polymerase chain reaction (PCR) antigen and ELISA antibody tests were conducted from the blood. Clinically, the 23 tested chicken flocks exhibited common symptoms, including noticeable greenish diarrhea, reduced egg production, cracked- and soft-shelled eggs, and pale comb of anemia characterized by pale combs. The results revealed that the ELISA antibody test showed a 33.5 % positive infection rate, while the PCR test showed only 0.43 %. Thus, ELISA antibody testing proves to be a sufficient diagnostic method in the early infection stage. Because of the high infection rate of Leucocytozoon in Taiwan, this study highlights a renewed understanding of the prevalence of Lecocytozoonosis over the past three decades. It also emphasizes the urgency of introducing the vaccines in Taiwan.