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

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
  • Cause diarrhoea and a decreased growth rate

• 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

• Occasionally causes diarrhoea

• 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
  • 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

• 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

• 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