Difference between revisions of "Coccidia"

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[[Coccidiosis - Poultry]]
 
[[Coccidiosis - Poultry]]
'''Pathogenesis'''
 
*7 important ''Eimeria'' species
 
  
*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 [[Caecum - Anatomy & Physiology|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 [[Anti-Protozoal Drugs|here]]
 
 
*[[Vaccines - WikiBlood|Vaccines]]
 
**Paracox
 
***Multivalent attenuated [[Vaccines - WikiBlood#What antigen(s) do we use in the vaccine?|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 [[Vaccines - WikiBlood|vaccinated]] on a single occasion when 1-9 days old through oocyst suspension in the feed or water
 
***[[Vaccines - WikiBlood|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 [[Vaccines - WikiBlood|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
 
  
 
==Other Avian Coccidia==
 
==Other Avian Coccidia==

Revision as of 21:44, 8 April 2010

Coccidiosis

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.


Coccidia - Poultry

Coccidiosis - Poultry


Other Avian Coccidia

Coccidia of Turkeys

  • 5 Eimeria species
    • 2 important pathogenically
  • Eimeria in caeca causes petechial haemorrhages and caseous caecal cores
  • Eimeria in the anterior and mid-intestine causes necrotic enteritis and petechial haemorrhages
  • Causes watery diarrhoea in young poults and some mortality

Coccidia of Geese

  • 3 Eimeria species
  • 2 intestinal species causing macroscopic lesions in kidney tubules
    • Oocysts carried in urine and pass out with faeces
  • Renal species cause severe disease in goslings
    • Depression, emaciation, diarrhoea and sometimes death

Coccidia of Ducks

Crested duck - nabrown RVC
  • Several Eimeria species
  • Another coccidia species which produces 8 sporozoites but these are not enclosed in a sporocyst
  • Causes severe enteritis and mortality in ducklings

Coccidia of Game Birds

  • 3 main species

Coccidia of Cattle

Eimeria sp. of ruminants - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona
Coccidia oocyst from ruminant faeces - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona
  • 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 dysentery, tenesmus and sloughed mucosa
    • Oocysts are spherical and measure 16μm
  • Mainly occurs in calves in poor conditions and bought-in calves
    • Also occurs in suckler calves turned out in spring
  • Eimeria alabamensis associated with diarrhoea in calves after spring turnout
  • 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 food and water troughs to avoid faecal contamination
  • Preventative in-feed medication
    • E.g. Decoquinate
  • Injectable antiprotozoals may limit oocyst production but animals should still be moved to a clean environment
    • E.g. Sulphamethoxypyridazine

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

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