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Created page with 'thumb|right|150px|''Toxoplasma gondii'' - Ke Hu and John Murray [[Image:Toxoplasma sporulated oocyst.jpg|thumb|right|150px|''Toxoplasma'' Sporulat…'
[[Image:Toxoplasma gondii.jpg|thumb|right|150px|''Toxoplasma gondii'' - Ke Hu and John Murray]]
[[Image:Toxoplasma sporulated oocyst.jpg|thumb|right|150px|''Toxoplasma'' Sporulated Oocyst - Wikimedia Commons]]
[[Image:Toxoplasma Tacchyzoites.jpg|thumb|right|150px|''Toxoplasma'' Tacchyzoites - Wikimedia Commons]]
[[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]]
*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
**Referred to as '''facultatively heteroxenous'''
**Intermediate host is not essential for completion of the life cycle
*Gametogony (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
*Cats
**Sporulation occurs in 2-3 days
**Cats either swallow infective (sporulated) oocysts where ''Toxoplasma gondii'' has a prepatent period of 3 weeks
**Or eat the tissues of an infected intermediate host where ''Toxoplasma gondii'' has a prepatent period of 3-10 days
**Self-limiting infection
**Oocysts are shed for 1-2 weeks
***Shedding can occur later if immunity wanes or cat is immuno-compromised
*Intermediate host
**3 sources of infection
***Oocysts from environment contaminated by cat faeces
***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
*Acute phase of infection
**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 '''endodyogeny''' (budding) producing 8-16 '''tachyzoites'''
***Tachyzoites are released when host cell bursts
***Haematogenous spread as more cells are infected
***Infection continues until the animal develops immunity (around 2 weeks) at which point the infection enters the chronic phase
*Chronic phase of infection
**Occurs once the host's immune response has become effective
***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
***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
*Meat animals
**Significant proportion of cattle, sheep, pigs and rabbits can tissue cysts
'''Pathogenesis'''
*Cattle and horses
**Sometimes infectious causing opthalmitis
*Dogs
**Complication of canine distemper
**Causes [[Respiratory Parasitic Infections - Pathology#Toxoplasmosis|pneumonia]] and encephalitis
*Toxoplasma can cause [[Pancreas Inflammatory - Pathology#Acute haemorrhagic pancreatitis|acute interstitial pancreatitis]] in systemic toxoplasmosis
*''Toxoplasma gondii'' causes [[Muscles Inflammatory - Pathology#Protozoa|myositis]]
<big>'''[[Toxoplasmosis - Cat|Cat Toxoplasmosis]]
*Sheep
**Mostly asymptomatic
**However, if a non-immune ewe is infected during pregnancy the consequences will be serious
***Infection during the first trimester leads to resorption
**Infection during the second trimester leads to foetal death and mummification
**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
**Diagnosis is confirmed by Giemsa and serology of the ewe's blood
Prevention:
*Clinical outbreaks of toxoplasmosis are '''sporadic'''
**Immunity is acquired before tupping
**Significant ill-effects are unlikely if immune ewes are infected during pregnancy
**Not shed from sheep to sheep so predicting outbreaks is difficult
*Sheep
**Toxovax vaccine
***Live, avirulent strain of ''Toxoplasma''
***Does not form bradyzoites or tissue cysts
***Killed by host immune system
***Single dose given 6 weeks before tupping
***Protects for 2 years
***Immunity boosted by natural challenge
**Medicated feed can be given daily during the main risk period
***14 weeks before lambing
**The best method of protection is to prevent cats from contaminating the pasture, lambing sheds and feed stores
*Humans
**Mostly asymptomatic
**Virulent strains cause flu-like symptoms, malaise and/or lymphadenopathy
**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
***E.g. Hydrocephalus, opthalmitis, mental retardation
*Human
**30% seropositive in UK, 70% seropositive in France
'''Prevention'''
**Avoid oocyst ingestion
***Wash potentially contaminated raw food thoroughly
***Wash hands after gardening or handling cats and especially before eating
***Clean out cat litter trays every day before oocysts sporulate
**Avoid ingestion of tissue cysts
***Do not eat undercooked meat
***Wash hands after handling raw meat
***Take care when lambing or dealing with sheep abortions and stillbirths
***Pregnant women should avoid lambing altogether
[[Category:Tissue_Cyst_Forming_Coccidia]]
[[Image:Toxoplasma sporulated oocyst.jpg|thumb|right|150px|''Toxoplasma'' Sporulated Oocyst - Wikimedia Commons]]
[[Image:Toxoplasma Tacchyzoites.jpg|thumb|right|150px|''Toxoplasma'' Tacchyzoites - Wikimedia Commons]]
[[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]]
*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
**Referred to as '''facultatively heteroxenous'''
**Intermediate host is not essential for completion of the life cycle
*Gametogony (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
*Cats
**Sporulation occurs in 2-3 days
**Cats either swallow infective (sporulated) oocysts where ''Toxoplasma gondii'' has a prepatent period of 3 weeks
**Or eat the tissues of an infected intermediate host where ''Toxoplasma gondii'' has a prepatent period of 3-10 days
**Self-limiting infection
**Oocysts are shed for 1-2 weeks
***Shedding can occur later if immunity wanes or cat is immuno-compromised
*Intermediate host
**3 sources of infection
***Oocysts from environment contaminated by cat faeces
***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
*Acute phase of infection
**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 '''endodyogeny''' (budding) producing 8-16 '''tachyzoites'''
***Tachyzoites are released when host cell bursts
***Haematogenous spread as more cells are infected
***Infection continues until the animal develops immunity (around 2 weeks) at which point the infection enters the chronic phase
*Chronic phase of infection
**Occurs once the host's immune response has become effective
***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
***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
*Meat animals
**Significant proportion of cattle, sheep, pigs and rabbits can tissue cysts
'''Pathogenesis'''
*Cattle and horses
**Sometimes infectious causing opthalmitis
*Dogs
**Complication of canine distemper
**Causes [[Respiratory Parasitic Infections - Pathology#Toxoplasmosis|pneumonia]] and encephalitis
*Toxoplasma can cause [[Pancreas Inflammatory - Pathology#Acute haemorrhagic pancreatitis|acute interstitial pancreatitis]] in systemic toxoplasmosis
*''Toxoplasma gondii'' causes [[Muscles Inflammatory - Pathology#Protozoa|myositis]]
<big>'''[[Toxoplasmosis - Cat|Cat Toxoplasmosis]]
*Sheep
**Mostly asymptomatic
**However, if a non-immune ewe is infected during pregnancy the consequences will be serious
***Infection during the first trimester leads to resorption
**Infection during the second trimester leads to foetal death and mummification
**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
**Diagnosis is confirmed by Giemsa and serology of the ewe's blood
Prevention:
*Clinical outbreaks of toxoplasmosis are '''sporadic'''
**Immunity is acquired before tupping
**Significant ill-effects are unlikely if immune ewes are infected during pregnancy
**Not shed from sheep to sheep so predicting outbreaks is difficult
*Sheep
**Toxovax vaccine
***Live, avirulent strain of ''Toxoplasma''
***Does not form bradyzoites or tissue cysts
***Killed by host immune system
***Single dose given 6 weeks before tupping
***Protects for 2 years
***Immunity boosted by natural challenge
**Medicated feed can be given daily during the main risk period
***14 weeks before lambing
**The best method of protection is to prevent cats from contaminating the pasture, lambing sheds and feed stores
*Humans
**Mostly asymptomatic
**Virulent strains cause flu-like symptoms, malaise and/or lymphadenopathy
**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
***E.g. Hydrocephalus, opthalmitis, mental retardation
*Human
**30% seropositive in UK, 70% seropositive in France
'''Prevention'''
**Avoid oocyst ingestion
***Wash potentially contaminated raw food thoroughly
***Wash hands after gardening or handling cats and especially before eating
***Clean out cat litter trays every day before oocysts sporulate
**Avoid ingestion of tissue cysts
***Do not eat undercooked meat
***Wash hands after handling raw meat
***Take care when lambing or dealing with sheep abortions and stillbirths
***Pregnant women should avoid lambing altogether
[[Category:Tissue_Cyst_Forming_Coccidia]]