Pullet disease, Bluecomb, Avian Monocytosis


A sudden onset condition of chickens early in lay with high morbidity and a mortality of 0-50%. It is associated with hot weather, water deprivation, toxin and possibly a virus infection. Affected birds have an increase in circulating monocytes in their blood. It was commonly reported prior to 1960 but is now rare.


  • Depression.
  • Loss of appetite.
  • Crop distension.
  • Dark comb and wattles.
  • Watery diarrhoea.
  • Dehydration.
  • Drop in egg production.

Post-mortem lesions

  • Dehydration.
  • Skin cyanosis of head.
  • Skeletal muscle necrosis.
  • Crop distended.
  • Catarrhal enteritis, mucoid casts in intestine.
  • Liver swollen with foci.
  • Kidneys swollen.
  • Pancreas chalky.


History, lesions, elimination of other causes. Differentiate from fowl cholera, vibriosis, capillariasis, coccidiosis, IBD and typhoid.


Adequate water supply, antibiotics, molasses, multivitamins in water.


Good management, hygiene, diet and water supply.