EIMERIA

 

 

 

 

 

Coccidiosis

Coccidiosis, caused by species of intracellular protozoan parasites belonging to the genus Eimeria (phylum Apicomplexa), remains one of the economically most important diseases in modern poultry production.

The disease is caused by the replication within the intestine of the asexual and/or sexual stages of seven species of Eimeria (usually several species occur concurrently) and although clinical disease in intensively reared poultry is now relatively uncommon, sub clinical infections are the norm.

The total cost of coccidial infections in the UK (circa 780 million broilers) has been estimated to be at least £42m per annum, of which 74% is due to sub-clinical effects on weight gain and feed conversion and 24% is the cost of prophylaxis and therapy of commercial birds (Williams, 1999; A compartmentalized model for the estimation of the cost of coccidiosis to the world’s poultry production industry. International Journal for Parasitology, 1209-1229)

Infections with Eimeria spp. in intensively reared poultry have always been controlled primarily by prophylactic in-feed medication (especially for broiler production), but vaccination with live, virulent or attenuated parasites has a role to play.

A list of some of the features of Eimeria parasites:

  • First of all, Eimeria are coccidial parasites.

  • Coccidia are protozoa and are obligatory intracellular for most of their life cycle.

  • Coccidia are generally regarded as belonging specifically to the taxonomic family Eimeriidae (Levine, 1982) placed within the phylum Apicomplexa.

  • Members of the phylum apicomplexa are characterised by an "apical complex" of organelles that is involved in the entry of the host cell.

  • The phylum Apicomplexa comprises many protozoa of medical and/or veterinary importance and includes the causative agents of malaria (Plasmodium spp.), the zoonotic organisms Cryptosporidium spp. and Toxoplasma and the many Eimeria spp. that are responsible for the disease of coccidiosis in livestock.

  • Coccidiosis is essentially a disease of livestock that are reared intensively.

  • Domestic poultry are major hosts for Eimeria spp. as up to 25,000 birds may be reared together on the floor at any one time.

  • The parasites undergo a faecal:oral type of life cycle.

  • The rearing of so many birds together in conditions where they are in contact with faeces provides ideal opportunities for the spread of infection.

  • Infection with Eimeria spp. leads to protection against subsequent challenges with the same species.

  • Different host are infected by different species of Eimeria.

  • The domestic chicken is host to seven species.

  • All species of Eimeria infect only one type of host - i.e. they show species specificity.

  • Coccidiosis must be prevented (or controlled) in poultry flocks.

  • Drugs have been used since the 1950's.

  • Vaccines are now becoming more important.

You are visitor number Hit Counter to this site