Coccidiosis is a very common protozoal disease of poultry caused by different species of coccidia (Eimeria
), which are single celled parasites that live in and damage different parts of the gut wall of their host resulting in nutrient malabsorption, dehydration and blood loss, and make the bird susceptible to secondary infections. Outbreaks in flocks often occur when birds are stressed, overcrowded, and living in poor sanitary conditions. Even seemingly healthy flocks may be infected with coccidia, without showing any signs of disease. Adult chickens exposed to small amounts of coccidia gradually or who have recovered from a previous infection, may develop immunity in their environment. However, if their immune system is lowered due to infection with another disease, stress, or exposed to new species of coccidia, they may develop coccidiosis.
There are seven different species of Eimeria
(coccidia) that affect chickens which include E. acervulina, E. brunetti, E. maxima, E. mitis, E. necatric, E. praecox
and E. tenella
. The majority of coccidia cause intestinal coccidiosis, and one species causes caecal coccidiosis. More than 1 species of coccidia can infect the same chicken at the same time. The severity of the disease in affected chickens varies from mild to severe, depending on the levels of coccidia present, site of infection, and the age and health status of the bird.
Eimeria Life Cycle
are maintained in flocks through a complex life cycle. Chickens become infected initially by consuming sporulated oocysts present in contaminated environments. Once infected with the parasite, these chickens will shed the oocysts produced by the organism, thus contaminating the environment. The cycle continues.Eimeria
have a short life cycle, varying between 4 to 6 days depending on the species.
Oocysts can survive for up to 18 months in the environment under optimal soil moisture and temperature conditions.
Coccidiosis has traditionally and is still currently primarily treated or controlled through anticoccidial drugs. However, due to their frequent and irrational use, it as caused the development of anticoccidial drug resistance to different Eimeria
species. Exploration of alternative treatment methods is currently underway by many researchers worldwide. Some potential alternative methods identified include:
- Botanicals: Contain several useful compounds such as tannins, flavonids, natural polyphenols, and essential oils which have shown great promise.
- Vaccinations: Vaccines are available in certain geographic areas, and are available in both live and attenuated forms.