Coccidia

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Introduction

Coccidia - Joel Mills
  • The oocyst is the resistant stage in the environment
  • The infective sporozoite is released from the oocyst
  • Inside the host, the sporozoites invade the intestinal epithelial tissue
    • Sporozoites feed and grow
  • As the sporozoite grows the nucleus divides forming a schizont
  • The schizont contains numerous elongated merozoites
  • The formation of merozoites is the first asexual reproductive stage called schizogony
  • The schizont ruptures releasing the merozoites which also invade the epithelial cells
  • Another generation of schizonts form which is the beginning of the sexual phase of reproduction called gametogony
  • The merozoites form male microgamonts or female macrogamonts
    • Collectively known as gamonts or gametocytes
  • The microgamonts released from the microgametocyte penetrate and fertilise the macrogamont (which is contained within the macrogametocyte)
  • Gametogony forms the zygote
    • Surrounded by a cyst wall
    • Forms the oocyst
  • The oocyst is passed in the faeces and is unsporulated
  • The oocyst becomes sporulated in the second asexual reproductive phase called sporogony
  • Once the oocyst is sporulated it is infective

Eimeria spp.

Isospora spp.

Coccidiosis

Coccidia of Poultry

Coccidiosis - Poultry

Coccidia of Turkeys

Coccidia of Geese

Coccidia of Ducks

Coccidia of Game Birds

Coccidia of Cattle

Coccidia of Sheep

Isospora felis sporulated - Courtesy of the Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine
Isospora felis unsporulated - Courtesy of the Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine


Coccidia of Goats

Goats - nabrown RVC
Eimeria leukarti - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona
Isospora suis oocyst from pig faeces - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona
Isospora canis - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona
Coccidia in Cat Faeces - Joel Mills
Isospora felis - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona
  • Many Eimeria species
  • 2 Eimeria are pathogenic
  • Different species of Eimeria occurs in sheep and goats

Coccidia of Horses

  • Only one atypical Eimeria
  • Forms large subepithelial gametocytes in villi
  • Large, dark coloured oocysts
    • Approximately 12μm
  • Besnoitia bennetti in larynx of horses

Coccidia of Pigs

  • Many species of Eimeria and Isospora
  • Only Isospora suis is of clinical pathogenic importance
  • Causes sporadic, serious and sometimes fatal disease in unweaned piglets
  • Very short 1 week prepatent period
  • Diarrhoea starts before oocysts are shed in faeces
    • Ante-mortem diagnosis is difficult
  • Death usually occurs after parasites have left the host
    • Post-mortem diagnosis difficult
    • Isospora infections are self-limiting

Coccidia of Dogs

  • 2 common and 2 less common Isospora species
  • Occasionally can cause disease
  • Little pathogenicity
  • Even if faecal oocyst count is high, other causes of diarrhoea should be looked for
  • Hepatozoon americanum and subclinical H. canis in periosteal bone formation
    • Both are Tick borne diseases
      • H. canisRhipicephalus sanguineus
      • Ticks become infected by ingesting a blood meal containing macrophages and neutrophils infected with the parasite gamonts -> sexual replication in the gut of the tick -> oocysts containing infective sporozoites -> dogs ingest the tick  schizogony occurs in numerous tissues

Coccidia of Cats

  • 2 common Isospora species with little clinical significance
  • Oocysts in faeces have to be distinguised from those of Toxoplasma (smaller) and Sarcocytis (sporulated or naked sporocyts in faeces)

Coccidia of Rabbits

  • 3 pathogenic Eimeria species
    • 2 in the caecum
    • 1 in the bile duct
  • Eimeria steidae
    • Parasitises the bile duct epithelium
    • Travels via the bile duct to the liver where it forms large white nodules
    • Oocysts travel in the bile and are passed out in the faeces
    • Causes ascites, diarrhoea, weight loss and polyuria
  • Serious disease of both pet and farmed rabbits
  • Treatment is by administration of drugs in drinking water
    • E.g. Toltrazuril
  • Hygiene is the best method of prevention to prevent sporocysts from sporulating
  • Medicated feed can be used in commercial units
    • E.g. Rabenidine

Coccidia Flashcards