Coccidiosis - Poultry

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Coccidia - Poultry

Pathogenesis

  • 4 malabsorptive species
    • Eimeria acervulina which is moderately pathogenic
    • Eimeria maxima which is moderately pathogenic
    • Eimeria mitis which has low pathogenicity
    • Eimeria praecox which has low pathogenicity
  • 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
  • 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

Test yourself with the Coccidia Flashcards

Coccidia Flashcards