Difference between revisions of "Tissue cyst-forming coccidia"

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#REDIRECT[[:Category:Tissue Cyst Forming Coccidia]]
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|backcolour =
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|linkpage =Parasites
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|linktext =PARASITES
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|pagetype=Bugs
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|sublink1=Protozoa
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|subtext1=PROTOZOA
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<br>
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==Toxoplasma==
 +
 
 +
*1 major pathogenic species called ''Toxoplasma gondii''
 +
 
 +
*Causes disease in a wide range of animal species including humans
 +
 
 +
*Important cause of abortion in sheep
 +
 
 +
*Zoonotic
 +
**Can cause abortion
 +
**Can cause congenitally aquired defects
 +
 
 +
*Forms a sporulated oocyst which is only 10μm
 +
**Contains 2 sporocysts with 4 sporozoites
 +
 
 +
*Transmission through ingesting the intermediate host or via the faecal-oral route
 +
 
 +
'''Life Cycle'''
 +
*Complex
 +
 
 +
*Usually indirect
 +
 
 +
*Gametogeny (sexual stage) is host specific for felids
 +
 
 +
*Any warm blooded animal can act as a facultative intermediate host
 +
**Asexual reproduction occurs in the intermediate host forming tissue cysts
 +
**Intermediate host swallows sporulated oocysts or tissue cysts
 +
**Can be transferred between intermediate hosts by carnivorism
 +
 
 +
Toxoplasma can cause [[Pancreas Inflammatory - Pathology#Acute haemorrhagic pancreatitis|acute interstitial pancreatitis]] in systemic toxoplasmosis
 +
*''T. gondii'' in [[Respiratory Parasitic Infections - Pathology#Toxoplasmosis|pneumonia]]
 +
*''Toxoplasma gondii'', ''Sarcocystis'' and ''Neospora caninum'' in [[Muscles Inflammatory - Pathology#Protozoa|myositis]]
 +
 
 +
==Sarcocystis==
 +
*Most infections are asymptomatic
 +
 
 +
*Heavy infections are causes of chronic wasting in large animals, hide sondemnation and downgrading of carcasses
 +
 
 +
*''Sarcocystis'' should be differentiated from other tissue-cyst forming coccidia
 +
 
 +
*There are many species of ''Sarcocystis''
 +
 
 +
*Sporulated oocyst has 2 sporocysts containing 4 sporozoites
 +
**Naked oocyst usually seen in faeces as the oocyst wall is very delicate
 +
 
 +
*Indirect life cycle
 +
 
 +
*Life cycle alternates between the final and the obligatory intermediate host
 +
 
 +
*Only one final and one intermediate host
 +
 
 +
==Neospora==
 +
*2 main species
 +
**''Neospora caninum'' in the dog
 +
**''Neospora hughesi'' in the horse
 +
 
 +
*Sporulated oocysts measuring just 10μm
 +
 
 +
*Oocyst contains 2 sporocysts with 4 sporozoites
 +
 
 +
*Route of transmission not fully understood
 +
 
 +
*Often misdiagnosed as ''Toxoplasma gondii''
 +
**''Sarcocystis'' cysts have thicker walls
 +
 
 +
*Infection diagnosed by IFAT, ELISA or PCR
 +
**Identification of lesions and organisms in tissue using immunohistochemical staining
 +
**Eliminate other causes of abortion first
 +
 
 +
'''Life cycle'''
 +
*Life cycle similar to ''Toxoplasma gondii''
 +
 
 +
*Limited range of warm-blooded intermediate hosts
 +
**Asexual reproduction occurs in intermediate host forming tissue cysts
 +
 
 +
*Host range of sexual stage is unknown for ''N.caninum''
 +
**Intermediate host for ''N.hughesi'' is the horse, but the definitive host is unknown
 +
 
 +
*Final host
 +
**Dogs pass oocysts
 +
**Role not fully understood in pathogenesis
 +
**5 day prepatent period
 +
**Other wild canids may also act as final definitive hosts
 +
 
 +
*Intermediate host
 +
**Mostly cattle
 +
**Natural infection has been documented in other herbivores
 +
 
 +
*Transmission
 +
**Transplacental infection occurs in all intermediate hosts and in the canine final host
 +
***Transplacental can occur in '''successive pregnancies'''
 +
**In cattle, vertical transmission occurs
 +
***Post-natal infection occurs but is less common
 +
 
 +
'''Pathogenesis'''
 +
*Dogs
 +
**Occurs mainly in puppies
 +
**Causes ascending paralysis, especially of hind limbs, with muscle wasting
 +
**Causes sudden collapse due to myocarditis
 +
**More than puppy in a litter may be affected, although this may not occur simultaneously
 +
**Successive litters affected
 +
 
 +
*Cattle
 +
**Commenest cause of infectious abortion in dairy cattle
 +
**Congenitally infected calves can have encephalomyelitis and paresis
 +
**Abortion usually occurs between 5-7 months of gestation but can occur as early as 3 months
 +
**No other clinical signs in the cow
 +
**Repeat abortions possible in same cow (persistently infected)
 +
 
 +
*Horses
 +
**Myeloencephalitis
 +
**Transplacental infection occurs
 +
**Disease only diagnosed in USA
 +
 
 +
'''Prevention and Control'''
 +
*Do not allow dogs access to calving cows, placental membranes and aborted or dead calves
 +
 
 +
*Do not allow dogs to defecate in cattle feeding areas
 +
 
 +
*Identify and cull seropositive cattle, or do not breed from them or their progeny
 +
 
 +
*Select seronegative cattle for breeding
 +
 
 +
*Vaccinate
 +
**Only in the USA
 +
**Neoguard or Intervet
 +
**Killed protozoal vaccine for healthy, preganant cows
 +
**Dosed in first 3 weeks of pregnancy and then every 3-4 weeks during gestation
 +
**Revaccination with 2 doses during each subsequent pregnancy

Revision as of 09:24, 17 November 2008


 This article is still under construction.


Infectious agents and parasitesWikiBugs Banner.png
PARASITES
PROTOZOA



Toxoplasma

  • 1 major pathogenic species called Toxoplasma gondii
  • Causes disease in a wide range of animal species including humans
  • Important cause of abortion in sheep
  • Zoonotic
    • Can cause abortion
    • Can cause congenitally aquired defects
  • Forms a sporulated oocyst which is only 10μm
    • Contains 2 sporocysts with 4 sporozoites
  • Transmission through ingesting the intermediate host or via the faecal-oral route

Life Cycle

  • Complex
  • Usually indirect
  • Gametogeny (sexual stage) is host specific for felids
  • Any warm blooded animal can act as a facultative intermediate host
    • Asexual reproduction occurs in the intermediate host forming tissue cysts
    • Intermediate host swallows sporulated oocysts or tissue cysts
    • Can be transferred between intermediate hosts by carnivorism

Toxoplasma can cause acute interstitial pancreatitis in systemic toxoplasmosis

  • T. gondii in pneumonia
  • Toxoplasma gondii, Sarcocystis and Neospora caninum in myositis

Sarcocystis

  • Most infections are asymptomatic
  • Heavy infections are causes of chronic wasting in large animals, hide sondemnation and downgrading of carcasses
  • Sarcocystis should be differentiated from other tissue-cyst forming coccidia
  • There are many species of Sarcocystis
  • Sporulated oocyst has 2 sporocysts containing 4 sporozoites
    • Naked oocyst usually seen in faeces as the oocyst wall is very delicate
  • Indirect life cycle
  • Life cycle alternates between the final and the obligatory intermediate host
  • Only one final and one intermediate host

Neospora

  • 2 main species
    • Neospora caninum in the dog
    • Neospora hughesi in the horse
  • Sporulated oocysts measuring just 10μm
  • Oocyst contains 2 sporocysts with 4 sporozoites
  • Route of transmission not fully understood
  • Often misdiagnosed as Toxoplasma gondii
    • Sarcocystis cysts have thicker walls
  • Infection diagnosed by IFAT, ELISA or PCR
    • Identification of lesions and organisms in tissue using immunohistochemical staining
    • Eliminate other causes of abortion first

Life cycle

  • Life cycle similar to Toxoplasma gondii
  • Limited range of warm-blooded intermediate hosts
    • Asexual reproduction occurs in intermediate host forming tissue cysts
  • Host range of sexual stage is unknown for N.caninum
    • Intermediate host for N.hughesi is the horse, but the definitive host is unknown
  • Final host
    • Dogs pass oocysts
    • Role not fully understood in pathogenesis
    • 5 day prepatent period
    • Other wild canids may also act as final definitive hosts
  • Intermediate host
    • Mostly cattle
    • Natural infection has been documented in other herbivores
  • Transmission
    • Transplacental infection occurs in all intermediate hosts and in the canine final host
      • Transplacental can occur in successive pregnancies
    • In cattle, vertical transmission occurs
      • Post-natal infection occurs but is less common

Pathogenesis

  • Dogs
    • Occurs mainly in puppies
    • Causes ascending paralysis, especially of hind limbs, with muscle wasting
    • Causes sudden collapse due to myocarditis
    • More than puppy in a litter may be affected, although this may not occur simultaneously
    • Successive litters affected
  • Cattle
    • Commenest cause of infectious abortion in dairy cattle
    • Congenitally infected calves can have encephalomyelitis and paresis
    • Abortion usually occurs between 5-7 months of gestation but can occur as early as 3 months
    • No other clinical signs in the cow
    • Repeat abortions possible in same cow (persistently infected)
  • Horses
    • Myeloencephalitis
    • Transplacental infection occurs
    • Disease only diagnosed in USA

Prevention and Control

  • Do not allow dogs access to calving cows, placental membranes and aborted or dead calves
  • Do not allow dogs to defecate in cattle feeding areas
  • Identify and cull seropositive cattle, or do not breed from them or their progeny
  • Select seronegative cattle for breeding
  • Vaccinate
    • Only in the USA
    • Neoguard or Intervet
    • Killed protozoal vaccine for healthy, preganant cows
    • Dosed in first 3 weeks of pregnancy and then every 3-4 weeks during gestation
    • Revaccination with 2 doses during each subsequent pregnancy
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