Attention! This is a potentially life-threatening condition for your bird and possibly your flock. Time is of the essence, contact your veterinarian immediately.Find me a Vet


Leucocytozoonosis is a vector-borne, parasitic disease of ducks, caused by infection with the blood parasite of the genus Leucocytozoon. Ducks and geese are primarily affected by L. simondi. These parasites are transmitted by black flies (Diptera: Simuliidae) and are known for infection and destruction of the duck's red blood cells, resulting in intravascular hemolytic anemia.

Black flies will carry the infective sporozoites in their salivary gland, which gets transferred into the duck upon the insect bite. One inside the duck's body, sporozoites travel to the liver, enter hepatocytes and replicate numerous times and migrate to different tissues and organs, such as the brain, spleen, heart, and lungs. The prepatent period for L. simondi infection is approximately two weeks. Young ducklings are more susceptible to infection and have more severe clinical signs then adult ducks. When adult ducks are affected, signs of disease usually occur gradually, and are much milder.


Rapid breathing
Loss of appetite
Increased thirst
Occasional sudden death


  • History
  • Clinical signs
  • Physical exam
  • PCR
  • Histopathology


MethodMethod Summary
Supportive care



Risk Factors

  • High populations of black flies on the premises