Toxoplasmosis
•	A systemic coccidian protozoan disease. Common parasitic infection of humans and animals. Infection are frequently asymptomatic, or present as acute disease with lymphadenopathy or resemble infectious mononucliosis. 
•	 Agent:  Toxoplasma gondii an intracellular coccidian protozoan that complete its sexual life cycle phase in the cat.
Characteristics of organism:
•	Three infective stages:
•	Tachyzoites – rapid growth
•	Bradyzoites – tissue cyst form, slow growth
•	Sphorozoites – oocysts
•	Unsporulated
•	Sporulated
•	Capable of growth and replication in a variety of host cells

•	In macrophages – capable of evading immune mechanisms
•	Ability to survive (evading digestion by macrophage) may be due to prevention of lysomal fusion with phagocytic vacuole
•	Reproduction (sexual) occurs only in cats - multiplication by cell division; occurs in most host cell types
•	Epidemiology
•	Occurrence:  ubiquitous worldwide
•	Humans
•	Seroprevalence in humans estimated to be ~500,000,000
•	Congenital infection:  <0.1%
•	Animals
•	Widespread infection due to prolific oocyst shedding
•	At any given time, small numbers (~1%) of cats (primarily domestic) may be shedding oocysts
•	Reservoir:
•	The definitive hosts for T. gondii are cats and other felines which aquire the infection mainly from eating infected mammals esp. rodents or birds and propably from oocysts in soil contaminated with cat feces . Felines alone harbors parasites in int. tract where the sexual stage of the protozoan life cycle occurs resulting in excretion of oocyst in the feaces for 10-20 days and rarely longer .
•	The intermediate hosts: sheep,goats,rodents,swine cattle chickens and other birds all may carry the infective stage of T. gondii encysted  in the tissue ( muscle and brain)
Tissue cyst remain viable for long period perhaps lifelong.
Transmission (to humans):
•	Transplacental – tachyzooites
•	Orally – oocysts by hand to mouth, undercooked meat with tissue cysts; contaminated food or water. Consumption of raw gout milk
•	Inhalation –( sporilated oocysts ) rare associated with one outbreak
•	Infected tissue (blood, transplantation)from infected donor.
•	Life cycle:
•	Cats acquire infection by eating any of three infective stages in infected prey (rodents or birds)
•	Intraintestinal cycle – occurs only in cats
•	Multiply in wall of small intestine, produce oocysts
•	Oocysts shed in great numbers for 2-3 days
•	Oocysts sporulate within  5 days
•	Sporulated oocyts highly resistant
•	Healthy cats shed during acute stage, but not after (at least in sufficient numbers to be infective)
•	Congenital infections may occur in sheep and goats (and humans), but uncommon in cats
•	Life cycle:
•	Extraintestinal cycle – occurs in cats and intermediate hosts (including humans)
•	cyst from intraintestinal cycle penetrate deep into intestinal wall
•	multiply as tachyzoites, spread to other body sites
•	Immune system finally restrains infection, leading to dormant stage (cyst) in muscle or brain 
•	Clinical features
•	Cats
•	usually asymptomatic
•	Occasionally younger animals or immunocompromised animals show non-specific signs (fever, lethargy) followed by:
•	pneumonia (mainfested by respiratory distress with gradual increasing severity)
•	Hepatitis - jaundice, vomiting, diarrhea
•	CNS – seizures, hyperesthesia, ocular inflammation leading to blindness

•	Humans:
•	Normal hosts:
•	Incubation period:  10-23 days
•	~80% asymptomatic
•	Localized infection manifested as lymphadenopathy resolving spontaneously (wks to months)
•	Some may experience fever, myalgia, headache
•	Rash, hepatitis - rare

•	Humans:
•	Immunocompromised host (reactivation disease):
•	Encephalitis most common manifestation
•	Present with sever headache, altered mental status, seizure, neurological deficits, pneumonia, and myocarditis
•	Estimated up to 40,000 cases in AIDS patients in US in 1981
•	Most common cause of AIDS encephalitis in US
Humans:
•	Congenital infection:
•	Occurs when women becomes infected during pregnancy or with reactivation (if immunocompromised)
•	Most severe when occurs in first trimester
•	Varying signs
•	Ocular – impaired vision to blindness due to chorioretinitis, microophthalmia
•	CNS – hydrocephalus, seizures, microencephaly
•	Prevention and control
•	Thorough washing of hands after handling meat
•	Wear protective gloves when handling litter, gardening, childrens sand boxes
•	Testing pregnant women for antibodies (?)
Treatment:
•	Not routinely indicated for a healthy immunocompetent host except for confirmed initial infection durig pregnancy or presence of active chorioretinitis, myocarditis or other organ involvement.
•	Multi-drug therapy:  pyrimethamine plus trisulfapyrimidines (or sulfadiazine) and folinic acid ( for patients with sever symptomatic disease. For 4 weeks
•	Clindamycin + these agents to treat ocular toxo.
•	Systemic corticosteroids are indicated with irreversible loss of vision.
Infants whose mothers had primary infection or HIV positive during pregnancy should be treated with pyrimethamine- sulfadiazine- folinic acid during first year of life. 
•	Treatment in pregnancy is problematic. Spiramycin is used to prevent placental infection
•	Spiramycin – used in Europe; safe and effective in pregnancy