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*Transmission
 
*Transmission
 
**Transplacental infection occurs in all intermediate hosts and in the canine final host
 
**Transplacental infection occurs in all intermediate hosts and in the canine final host
***Transplacental can occur in '''successive pregnancies'''
+
***Transplacental transmission can occur in '''successive pregnancies'''
 
**In cattle, vertical transmission occurs
 
**In cattle, vertical transmission occurs
 
***Post-natal infection occurs but is less common
 
***Post-natal infection occurs but is less common
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**Causes ascending paralysis, especially of hind limbs, with muscle wasting
 
**Causes ascending paralysis, especially of hind limbs, with muscle wasting
 
**Causes sudden collapse due to myocarditis
 
**Causes sudden collapse due to myocarditis
**More than puppy in a litter may be affected, although this may not occur simultaneously
+
**More than 1 puppy in a litter may be affected, although this may not occur simultaneously
 
**Successive litters affected
 
**Successive litters affected
    
*Cattle
 
*Cattle
**Commenest cause of infectious abortion in dairy cattle
+
**Commonest cause of infectious abortion in dairy cattle
 
**Congenitally infected calves can have encephalomyelitis and paresis
 
**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
 
**Abortion usually occurs between 5-7 months of gestation but can occur as early as 3 months
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**Only in the USA
 
**Only in the USA
 
**Neoguard or Intervet
 
**Neoguard or Intervet
**Killed protozoal vaccine for healthy, preganant cows
+
**Killed protozoal vaccine for healthy, pregnant cows
 
**Dosed in first 3 weeks of pregnancy and then every 3-4 weeks during gestation
 
**Dosed in first 3 weeks of pregnancy and then every 3-4 weeks during gestation
 
**Revaccination with 2 doses during each subsequent pregnancy
 
**Revaccination with 2 doses during each subsequent pregnancy
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*Most infections are asymptomatic
 
*Most infections are asymptomatic
   −
*Heavy infections are causes of chronic wasting in large animals, hide sondemnation and downgrading of carcasses
+
*Heavy infections are causes of chronic wasting in large animals, hide condemnation and downgrading of carcasses
    
*''Sarcocystis'' should be differentiated from other tissue-cyst forming coccidia
 
*''Sarcocystis'' should be differentiated from other tissue-cyst forming coccidia
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'''Life Cycle'''
 
'''Life Cycle'''
*Individual life cycles incompletely misunderstood
+
*The individual life cycle of some species is incompletely understood
    
*Indirect life cycle
 
*Indirect life cycle
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*Sporulated oocyst has 2 sporocysts containing 4 sporozoites
 
*Sporulated oocyst has 2 sporocysts containing 4 sporozoites
**Naked oocyst usually seen in faeces as the oocyst wall is very delicate
+
**Naked sporocyst usually seen in faeces as the oocyst wall is very delicate
 
**Oocyst measures 15μm in length
 
**Oocyst measures 15μm in length
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*''Sarcocystis'' in [[Muscles Inflammatory - Pathology#Protozoa|myositis]]
 
*''Sarcocystis'' in [[Muscles Inflammatory - Pathology#Protozoa|myositis]]
   −
*Experimental infections cause severe, acute pyrrhexic disease when the organism multiplies in the vascular endothelium
+
*Experimental infections cause severe, acute pyrexic disease when the organism multiplies in the vascular endothelium
    
*Can cause chronic wasting disease in cattle and horses
 
*Can cause chronic wasting disease in cattle and horses
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[[Image:Toxoplasma Life Cycle.jpg|thumb|right|150px|''Toxoplasma'' Life Cycle Diagram - Dennis Jacobs & Mark Fox RVC]]
 
[[Image:Toxoplasma Life Cycle.jpg|thumb|right|150px|''Toxoplasma'' Life Cycle Diagram - Dennis Jacobs & Mark Fox RVC]]
 
[[Image:Toxoplasma gondii 2.jpg|thumb|right|150px|''Toxoplasma gondii'' - Courtesy of the Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine]]
 
[[Image:Toxoplasma gondii 2.jpg|thumb|right|150px|''Toxoplasma gondii'' - Courtesy of the Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine]]
*1 major pathogenic species called ''Toxoplasma gondii''
+
*Major pathogenic species called ''Toxoplasma gondii''
    
*Causes disease in a wide range of animal species including humans
 
*Causes disease in a wide range of animal species including humans
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*Usually indirect
 
*Usually indirect
**Reffered to as '''facultatively heterxenous'''
+
**Referred to as '''facultatively heteroxenous'''
 
**Intermediate host is not essential for completion of the life cycle
 
**Intermediate host is not essential for completion of the life cycle
   −
*Gametogeny (sexual stage) is host specific for felids
+
*Gametogony (sexual stage) is host specific for felids
    
*Any warm blooded animal can act as a facultative intermediate host
 
*Any warm blooded animal can act as a facultative intermediate host
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*Cats
 
*Cats
 
**Sporulation occurs in 2-3 days
 
**Sporulation occurs in 2-3 days
**Cats either swallow infective (sporulated) oocysts where ''Toxoplasma gondii'' as a prepatent period of 3 weeks
+
**Cats either swallow infective (sporulated) oocysts where ''Toxoplasma gondii'' has a prepatent period of 3 weeks
**Or eat the tissues of an infective intermediate host where ''Toxoplasma gondii'' as a prepatent period of 3-10 days
+
**Or eat the tissues of an infected intermediate host where ''Toxoplasma gondii'' has a prepatent period of 3-10 days
 
**Self-limiting infection
 
**Self-limiting infection
**Oocysts shed for 1-2 weeks
+
**Oocysts are shed for 1-2 weeks
***Shedding can occur later if immunity wanes or cat is immunocompromised
+
***Shedding can occur later if immunity wanes or cat is immuno-compromised
    
*Intermediate host
 
*Intermediate host
 
**3 sources of infection
 
**3 sources of infection
 
***Oocysts from environment contaminated by cat faeces
 
***Oocysts from environment contaminated by cat faeces
***Eating cysts in tissues or other infected hosts through carnivorism or undercooked meat
+
***Eating cysts in tissues of other infected hosts through carnivorism or undercooked meat
 
***Transplacental transmission in some host species during the acute phase of infection
 
***Transplacental transmission in some host species during the acute phase of infection
    
*Acute phase of infection
 
*Acute phase of infection
 
**After infection of the intermediate host the organism undergoes a phase of rapid division and dissemination throughout the body
 
**After infection of the intermediate host the organism undergoes a phase of rapid division and dissemination throughout the body
***Parasite enters cell and asexual reproduction occurs by '''endogeny''' (budding) producing 8-16 '''tachyzoites'''
+
***Parasite enters cell and asexual reproduction occurs by '''endodyogeny''' (budding) producing 8-16 '''tachyzoites'''
 
***Tachyzoites are released when host cell bursts
 
***Tachyzoites are released when host cell bursts
 
***Haematogenous spread as more cells are infected
 
***Haematogenous spread as more cells are infected
***Infection continues until the animal develops an immunity in 2 weeks when the infection enters the chronic phase
+
***Infection continues until the animal develops immunity (around 2 weeks) at which point the infection enters the chronic phase
    
*Chronic phase of infection
 
*Chronic phase of infection
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***Groups of slow growing intracellular '''bradyzoites''' become walled off forming infective '''cysts'''
 
***Groups of slow growing intracellular '''bradyzoites''' become walled off forming infective '''cysts'''
 
***Bradyzoites inside cysts are protected from the host immune response whereas extracellular tachyzoites are killed
 
***Bradyzoites inside cysts are protected from the host immune response whereas extracellular tachyzoites are killed
***Cysts remain viable for months to years and are particulary numerous in muscle and nervous tissue
+
***Cysts remain viable for months to years and are particularly numerous in muscle and nervous tissue
 
***If immunity is suppressed the infection can revert to the acute form
 
***If immunity is suppressed the infection can revert to the acute form
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*Sheep
 
*Sheep
 
**Mostly asymptomatic
 
**Mostly asymptomatic
**If a non-immune ewe is infected during pregnancy the consequences will be serious
+
**However, if a non-immune ewe is infected during pregnancy the consequences will be serious
***Infection during the first trimester leads to resorbtion
+
***Infection during the first trimester leads to resorption
**Infection during the second trimester leads to fetal death and mummification
+
**Infection during the second trimester leads to foetal death and mummification
 
**Infection during the last trimester leads to a weak or stillborn lamb
 
**Infection during the last trimester leads to a weak or stillborn lamb
 
**Aborted ewes show focal necrotic placentitis with white lesions in the cotyledons and foetal tissue
 
**Aborted ewes show focal necrotic placentitis with white lesions in the cotyledons and foetal tissue
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*Clinical outbreaks of toxoplasmosis are '''sporadic'''
 
*Clinical outbreaks of toxoplasmosis are '''sporadic'''
**Immunity is aquired before tupping
+
**Immunity is acquired before tupping
 
**Significant ill-effects are unlikely if immune ewes are infected during pregnancy
 
**Significant ill-effects are unlikely if immune ewes are infected during pregnancy
 
**Not shed from sheep to sheep so predicting outbreaks is difficult
 
**Not shed from sheep to sheep so predicting outbreaks is difficult
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**Mostly asymptomatic
 
**Mostly asymptomatic
 
**Virulent strains cause flu-like symptoms, malaise and/or lymphadenopathy
 
**Virulent strains cause flu-like symptoms, malaise and/or lymphadenopathy
**In immunodeficient patients, disease can be caused by even avirulent strains
+
**In immunodeficient patients, disease can even be caused by avirulent strains
 
**If a non-immune women is infected during pregnancy, abortion or the birth of a congenitally infected child can result
 
**If a non-immune women is infected during pregnancy, abortion or the birth of a congenitally infected child can result
 
***E.g. Hydrocephalus, opthalmitis, mental retardation
 
***E.g. Hydrocephalus, opthalmitis, mental retardation
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**Sabin-Feldman Dye test (old method)
 
**Sabin-Feldman Dye test (old method)
 
**ELISA
 
**ELISA
**Mouse innoculation for confirmation
+
**Mouse inoculation for confirmation
    
*Cat
 
*Cat
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'''Prevention'''
 
'''Prevention'''
 
*Cat
 
*Cat
**Impossible if cat is allowed outdoors (will hunt!)
+
**Impossible if cat is allowed outdoors due to hunting
 
**If kept indoors, only canned food should be fed and vermin controlled
 
**If kept indoors, only canned food should be fed and vermin controlled
 
**ELISA to check if seropositive
 
**ELISA to check if seropositive
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**Avoid ingestion of tissue cysts
 
**Avoid ingestion of tissue cysts
 
***Do not eat undercooked meat
 
***Do not eat undercooked meat
***Wash hands after eating raw meat
+
***Wash hands after handling raw meat
 
***Take care when lambing or dealing with sheep abortions and stillbirths
 
***Take care when lambing or dealing with sheep abortions and stillbirths
***Pregnant women should avoid lambing altogether when pregnant
+
***Pregnant women should avoid lambing altogether
    
*Sheep
 
*Sheep
292

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