Difference between revisions of "Tissue cyst-forming coccidia"

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#REDIRECT[[:Category:Tissue Cyst Forming Coccidia]]
 
 
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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'''
 

Latest revision as of 23:31, 9 April 2010