Coccidia are protozoal parasites which transmit through infected droppings. Infected birds are listless, with diarrhoea, sometimes bloody droppings, pale combs and poor appetites. There is often a drop in, or complete cessation of, egg laying. Coccidiostats can be given to help prevent development of the coccidia, but there is a large degree of resistance. Good management and hygiene are particularly important.
Histomonas (blackhead) is a protozoal parasite transmitted by infected water or feed, or indirectly by eggs of the caecal worms. Affected birds are depressed, with ruffled feathers, yellowish diarrhoea and darkening of the head parts. Treatment is medical, with strict worm control also being important.