Leucocytozoon spp

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.



  • Order: Haemosporida
  • Family: Leucocytozoidae
  • Genus: Leucocytozoon


  • wild birds
  • chickens
  • ducks
  • geese
  • turkeys

Associated Diseases