Coccidia

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

Coccidia of Goats

Coccidia of Horses

Coccidia of Pigs

Isospora suis oocyst from pig faeces - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona

• Many species of Eimeria and Isospora

• Only Isospora suis is of clinical pathogenic importance

• Causes sporadic, serious and sometimes fatal disease in unweaned piglets
  • Causes profuse diarrhoea

• 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

Isospora canis - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona

• 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. canis – Rhipicephalus 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

Coccidia in Cat Faeces - Joel Mills

Isospora felis - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona

• 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