Pathogenesis
- 7 important Eimeria species
- 4 malabsorptive species
- 3 haemorrhagic species
- Eimeria tenella
- Eimeria necatrix
- Eimeria brunetti
- All highly pathogenic
- Form large sub-epithelial second generation schizonts at the base of intestinal crypts
- Deep eruptions form when cells rupture to release merozoites
- Destruction of crypt stem cells and marked haemorrhage
- Blood stained faeces
- High morbidity and high mortality
Diagnosis
- Post-mortem diagnosis of lesion severity
- Region of intestine affected
- Appearance of lesion
- Presence or absence of haemorrhage
- Size of schizonts and oocysts found in mucosal scrapings
- Eimeria acervulina
- Proximal gut
- Thickening of walls
- 'White ladder lesions' produced by dense foci of gamonts and oocysts
- Watery exudate
- Eimeria maxima
- Mid-gut
- Thickening of walls
- Pink exudate
- Eimeria tenella
- Swollen caeca
- Thickening of wall
- Dark colouring containing a core of necrotic tissue and blood
- Lesion scoring is the best method of diagnosing the severity of the lesions and therefore the causative Eimeria species
- Eimeria necatrix
- Mid-gut
- Ballooning of wall
- White spots and petechiae forming 'salt and pepper' lesions
- Haemorrhage into lumen
Immunity
- Different Eimeria species produce different levels of protective immunity
- E.maxima -> E.brunetti and E.acervulina -> E.tenella and E.necatrix
- There is no cross immunity between species
- There is very little passive immunity
- Evokes a cell-mediated response
- All ages of poultry are susceptible
Epidemiology
- Oocysts are ubiquitous and robust
- Able to survive several months to years
- It is impossible to keep buildings free from infection
- Chicks become infected by pecking the ground shortly after being placed in the poultry house
- Biotic potential is enormous
- Generation time is short
- Massive infections can build up rapidly
- Immunity develops relatively slowly
- With high stocking densities the situation is explosive
Control
- Chemical
- Intensive poultry production is largely dependent on the use of anticoccidial drugs
- For more information see here
- Vaccines
- Paracox
- Multivalent attenuated live vaccine for replacement layers and broilers
- Contains 7 live strains of Eimeria
- Lack the most pathogenic life cycle stage making the prepatent period shorter
- Known as precocious strains
- Chicks vaccinated on a single occasion when 1-9 days old through oocyst suspension in the feed or water
- Vaccinated birds have sub-optimal growth rates so is not used for broilers
- Paracox 5
- Contains 5 strains of the most pathogenic Eimeria
- Used for broilers
- Sprayed onto the first feed offered to new batches of chicks
- Paracox
- Integrated control
- Careful management is needed so in-feed prophylaxis and vaccination do not fail
- Remove litter and thoroughly clean houses in between crops
- Optimum turn-around time is 10 days
- Use the lowest stocking density which is compatible with economic production
- Water bowls, roofs and walls should be well maintained to prevent litter becoming damp
- Stress factors should be avoided and adequate nutrition provided
Literature Search
Use these links to find recent scientific publications via CAB Abstracts (log in required unless accessing from a subscribing organisation).
Coccidiosis in poultry: review on diagnosis, control, prevention and interaction with overall gut health. Gussem, M. de; World's Poultry Science Association (WPSA), Beekbergen, Netherlands, World Poultry Science Association, Proceedings of the 16th European Symposium on Poultry Nutrition, Strasbourg, France, 26-30 August, 2007, 2007, pp 253-261, 36 ref. - Full Text Article