Leucocytozoon are parasitic protozoa which cause a malaria-like disease in poultry called leucocytozoonosis. It uses blackflies (
Simulium species), and sometimes biting midges, as the definitive host and birds as their intermediate host. There are more than 100 species of
Leucocytozoon described, however there are only a handful that are known to be of concern for poultry.
- L. simondi: Affects ducks and geese. S. anatinum and S. rugglesi, are the primary vectors.
- L. smithi: Affects turkeys, and is transmitted primarily by S. meridionale and S. slossonae.
- L. caulleryi: Frequently affects chickens in southern and eastern Asia, and the southeastern United States. According to one survey, 13.6% of domestic backyard chickens in South Carolina were infected.
Life Cycle: Leucocytozoon species undergo a complex malaria-like life cycle. Gametocytes in the blood of the host are acquired by a female black fly. The parasite then undergoes both asexual and sexual development within the fly, over a period of 3–4 days. During their next feeding, the fly transmits the parasites (as sporozoites), to another bird, which serves as a host for asexual development and gametocyte production.
