Coccidia

PARASITES PROTOZOA

Introduction

Poultry coccidiosis is caused by Eimeria species. The poultry industry has grown to its massive size through the development and administration of anticoccidial drugs. Most growing birds are fed compounded rations containing anticoccidial drugs which has radically reduced the deaths from coccidiosis bringing the mortality rate down to negligable levels. Careful management is needed to prevent decreased productivity from infection through decreased egg production, weight gain and feed conversion ratios.

Mammalian coccidiosis is usually associated with watery diarrhoea, dysentry and weight loss. It usually presents in young animals which are living in overcrowded and unhygienic conditions.

Pathogenicity of coccidiosis is related to the size of the endogenous stages, the location of the infection in the mucosa and the site of infection. For example, infection in the small intestine can lead to compensation whereas infection in the large intestine will affect water absorption. If mucosal stem cells are affected, it will cause villous atrophy and a slow recovery.

Coccidia of Cattle

• Many species affect cattle

• Cattle under a year old are usually infected sporadically

• 2-3 week prepatent period

• Eimeria bovis
  • Endogenous stages in central lacteal of villi and epithelial cells of caecum and colon
  • Causes diarrhoea and enteritis
  • Oocysts are 28x20μm
  • Moderately pathogenic

• Eimeria zuernii
  • Endogenous stages in connective tissue of lamina propria of the lower small intestine and in the epithelial cells of the caecum and colon
  • More pathogenic than Eimeria bovis
  • Causes blood stained dysentry, tenesmus and sloughed mucosa
  • Oocysts are spherical and measure 16μm

• Mainly occurs in calves in poor conditions and brought-in calves
  • Also occurs in suckler calves turned out in spring

• Eimeria alabamensis associated with diarrhoea in calves after spring turnout

• Passive immunity is sufficient during the neonatal period

• Can be concurrent with cryptosporidium, viral and bacterial agents

Diagnosis

• History, clinical signs, diarrhoea (often with blood) and a decrease in weight gain

• Post-mortem
  • Diffuse inflammation and thickening of caecal mucosa (and sometimes ileal and colonic mucosa)
  • Masses of gamonts and oocysts in scrapings

• High faecal oocyst count
  • However, healthy animals can pass millions of oocysts from mixed species infections which have no pathogenic significance
  • Animals may die before oocysts are shed

Control

• Improve husbandry
  • Improve sanitation
  • Increase bedding
  • Raise faecal and water troughs to avoid faecal contamination

• Preventative in-feed medication
  • E.g. Decoquinate

• Injectible antiprotozoals may limit oocyst production but animals should still be moved to a clean environment
  • E.g. Sulphamethoxypyridazine

Coccidia of Sheep

• 11 different Coccidia species although only two are of clinical significance
  • Giant schizonts visible as white spots

• Eimeria ovinoidalis
  • Highly pathogenic
  • Diarrhoea
  • Parasitises the caecum and colon

• Eimeria crandalis
  • Varying pathogenicity
  • Scours, grey, foul-smelling faeces
  • Parasitises the small intestine, caecum and colon

• 2 week prepatent period

• Disease frequently seen in lambs under 6 months old
  • More often in twins and triplets when single lambs

• Oocyts from ewes (immune carriers) accumulate in poorly managed litter or around feed and water troughs

• Lambs born early in the year amplify the parasite problem increasing the parasite risk to lambs born later in the year

• Affected lambs may die before oocysts are found in the faeces
  • Post-mortem diagnosis difficult

• Different species of Eimeria occurs in sheep and goats

• Infection may be coincident with Neospora or Cryptosporidium infections
  • Mixed infections complicate the diagnosis as oocyst differentiation is difficult

• Other non-pathogenic species can cause papillomatous mucosal growths

Control

• Improve husbandry
  • Avoid overcrowding
  • Decrease stress

• Improve hygiene by dagging ewes

• Avoid mixing lambs of different ages

• Preventative measures include creep feeding lambs with decoquinate or oral dosing with diclazuril when lambs are 4-6 weeks
  • A second dose can be given after 3 weeks

Coccidia of Goats

• 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 Eiemria

• 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

Coccidia in Cat Faeces - Joel Mills

• 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