Species affected: Mostly Chickens, some species can also have disease including turkeys, quail and pheasants.
Age affected: All ages after 7 days of age.
Causes: Protozoan parasites of the genus Eimeria. Nine species occur in the chicken, of which E. tenella, E. maxima, E. necatrix, E. acervulina, E. dispersa are the most important.
Effects: Watery and/or bloody droppings, poor weight gain and feed conversion, anaemia, depression, drop in egg production in layers. Morbidity can be as high as 100%, mortality ranges from 0-50%.
Nine species of Eimeria occur in the chicken and 6 are important.(E. acervulina, E. maxima, E. brunetti. E. necatrix, E. mitis, E. tenella,). All avian Eimera with the exception of E. dispersia infect only one poultry species. E. dispersia may infect and cause disease in turkeys, quail and pheasants.
The Eimeria; oocyst contains 4 sporocysts. Each sporocyst contains 2 sporozoites. The organism undergoes two rounds of asexual reproduction (schizogony) and 1 round of sexual reproduction (gametogony).
All chicken coccidia are species-related (occur only in the chicken) and are tissue trophic (occur in particular areas of the intestine). Acute to chronic disease can occur after 7 days of age.
Direct transmission occurs by consumption of sporulated oocysts in the faecal material. Only birds reared on moist, contaminated used litter have access to sporulated oocysts. Soil may be contaminated. Oocysts need 48 hours to sporulate (sporogony). Oxygen and moisture are needed for sporulation.
The entire process takes 4-7 days depending on the species of Eimeria.
Coccidia which are deep tissue invaders such as E. maxima, E. necatrix and E. tenella cause severe necrosis, haemorrhage of the intestinal mucosa, and bloody diarrhoea and may result in death. Signs include watery and/or bloody droppings, mortality (0-50%), and morbidity (0-100%). Culls appear as pale birds with anaemia, depression, poor weight gain and feed conversion, and a drop in egg production.
Enteritis characteristic of Eimeria species is seen. The intestinal tract can be enlarged and have necrotic and/or haemorrhagic foci, undigested feed and gas. Localisation of lesions is Eimeria species- related.
Intestinal scrapings should be examined for oocysts. The site and degree of lesions and size and shape of oocysts and schizonts are all used to differentiate between Eimeria species. It appears similar to bacterial enteritis in chickens, especially necrotic enteritis.
Feeding anticoccidial feed additives for the entire broiler grow-out or at least 3 weeks for pullet reared on the ground. Vaccine containing live or attenuated oocysts can be given by coarse spray in the hatchery or drinking water in the field.
Coccidiosis, discovered in the late 1920’s, has a major economic impact on the poultry industry. Total estimated loss is massive, calculated at a gross €10 billion on an annual basis. Progress has been made in combating the disease but it is still a threat. Here you will find articles dedicated to this topic.
The use of antibiotics in broiler production has to decrease, as is prescribed by certain governments in Europe. Coccidiosis with enteric health repercussions have to be kept at bay to reach this goal. A field trial in Belgium with a live coccidiosis vaccine in rotation with anticoccidial feed additives gives promising results.