Cryptosporidiosis is a parasitic disease that affects quail, pheasants, peafowl, waterfowl, chickens, turkeys, finches and psittacines (such as parrots). Cryptosporidia are poorly host-specific and can affect other animal species including humans, other mammals, reptiles, amphibians and fish. However, species that infect birds are rarely infectious to humans. The disease is not egg transmitted.

Some infections are asymptomatic (infected hosts show no symptoms), however often the disease in birds is characterised by acute and/or chronic disease of the respiratory and digestive tracts. The disease is usually fatal in quail and more serious in turkeys than chickens. Symptoms of the respiratory forms of the disease include discharge from the nostrils and eyes, swollen sinuses, coughing, sneezing, breathing difficulties and rales (clicking, bubbling or rattling sounds in the lungs). The intestinal form is characterised by diarrhoea, weight loss and ruffled feathers.

What causes cryptosporidiosis?

Cryptosporidiosis is caused by protozoan parasites of the genus Cryptosporidium and are related to coccidia, but have much smaller oocysts (the spore-like infective stage of the lifecycle that is passed from the infected host to the new host). Cryptosporidium baileyi can cause respiratory disease in chickens and turkeys and can also cause infections of the hindgut and cloacal bursa in chickens, turkeys, and ducks. C. meleagridis also infects chicken and turkey species. The organism is transmitted by susceptible birds inhaling or ingesting oocysts passed in the droppings of infected birds. The oocysts are very resistant in the environment. Oocysts can also be carried between flocks by people on shoes and clothing and equipment.

Prevention and treatment of cryptosporidiosis

There are no satisfactory control measures except isolation and good sanitation. All known anticoccidial drugs are ineffective against Cryptosporidium spp and they are extremely resistant to chemical disinfection. Supportive therapy may reduce mortalities. Steam cleaning is effective in reducing infection as oocysts are inactivated above about 65°C. Treatment and prevention are both based on good hygiene, sanitation and biosecurity practices. All dead infected birds should be incinerated.