Infectes a wide range of animals, birds but does not appear to cause disease in them
Toxoplasmosis (TOX-o-plaz-MO-sis )
A disease of the blood and lymphatic system.
Cats are a critical part of the life cycle.
It is usually acquired by eating undercooked meats but can also be acquired by contact with cat feces.
Primary problem is a congenital infection of fetus, resulting in either a stillbirth or a child with severe brain damage or vision problems.
The normal final host is cat and relatives in the family Felidae, only hosts in which the Oocyst – producing sexual stage of Toxoplasma can develop
By feeding on Mice brains Cats can get Infected
Events on Rat to Cat Transmission
Spread from Rats – Cats to Humans
Spread of Toxoplasmosis
Development in Cat
Organisms ( either sporozoites from Oocysts or Bradyzoites from tisse cysts ) invade the muscle cells of cats samll intestine where they from Schizonts or Gametocytes after sexual fusion of Gametes,oocysts develop exit from the host cells into the gut lumen of the cat and pass out via feces
Structure of Sporozoites
In each Oocysts two sporocysts form and in about 48 hours four sporozoites form within sporocyst.
The Oocyst with its each Sporozoites when ingested can either repeat its sexual cycle in a Cat
Events on Development in man
When man ingests Oocysts with eight Sporozoites excreted in Cats feces, can establish an infection and reproduces Asexually
In humans Oocysts open in duodenum and releases eight Sporozoites which pass through the gut wall
Circulate in body and invade various cells
Cycles of Development in Man
Invasion of Lymphnodes lead to chronic infections
Sporozoites invade various cells especially macrophages where they from Trophozoites further multiply break out and spread the infection to lymphnodes and other organs
The rapidly multiplying Crescentric cell (Tachyzoites ) initiate the acute stage of disease
Invade Organs Brain involvement carries higher Morbidity and Mortality
In futher development they penetrate new cells especially Eye and Brain.
Further development slows down in these organs called ad Bradyzoites to form a quiescent tissue cysts
The event lead to chronic stage of disease
Fate of Tissue Cysts Showing multiple tissue cysts
The tissue cysts are infective when ingested by cats or eaten by other animals, where tissue cysts are formed
In man it dead end of disease
Implications on Human Health
In Humans produces
1 Congenital Toxoplasmosis
2 Post natal Toxoplasmosis
Many Humans at risk with Toxoplasmosis
Congenital infection develop in fetus only when non immune mothers are infected during pregnancy
Post natal Toxoplasmosis is less severe.
Other Human Infections Early detection reduce Morbidity
Toxoplasmosis produces severe Human infections in patient with
The chronic infection is altered to Acute manifestations
Toxoplasmosis - Immunosupressed
Varying degrees of disease may occur in Immunosupressed indivudals results in
Other non specific manifestions
Toxoplasmosis - Retinitis
Morphology and Identification of Toxoplasmosis
The Trophozoites are boat shaped
Thin walled cell
Size is 4–7 x2-4 microns lie within tissue cells
But appear larger when outside the tissue cell
Stain lightly with Giemsa’s stain
True cysts contain many thousands of spore like Bradyzoites
Toxoplasma gondii may be cultured in the presence of living cells in the culture tissues or eggs
Organisms can be seen intracellularly or extracellularly
The Tacyzoites have predilection for parenchymal cells and Reticulo endothelial system and directly destroys the cells.
Humans are relatively resistant to infection
But low grade infection of lymph node persists
When tissue cysts ruptures – releases number of Bradyzoites
Local hypersensitivity reaction may cause inflammation.
Causes blocking of blood vessels
Causes death of cells near damaged area
Prenatal toxoplasmosis may manifest with blindness apart from congenital defects
Toxoplasmosis in Pregnancy
In 1 st Trimester
May lead to still birth
Major central nervous system anomalies
In 2 nd Trimester
Less severe complications
Birth Anomalies still common
Babies infected with congenital Toxoplasmosis manifest with
enlarged spleen and liver
poor motor coordination
unusually small head
Late Anomalies in Toxoplasmosis
Clinical manifestation in infected fetus may be delayed until long after birth
Even may present during early childhood.
Neurological problems of learning difficulties may be caused by long delayed effects of late prenatal infection.
Diagnosis of Toxoplasmosis
Blood ( Buffy coat of heparinised sample )
Striated muscle biopsy
Ventricular fluid in Neonates
Microscopic Examination of Tissues
Smears and sections stained with Giemsa’s stain
Periodic acid Schiff method preferred
The densely packed cysts seen in the brain or other parts of nervous system suggest chronic infection
Sabin Feldman dye
based on principle that Antibodies to Toxoplasma appear in 2-3 weeks that will render the membrane of the laboratory cultured living T.gondii impermeable to Alkaline methylene blue ,So the organism are unstained in the presence of serum with antibodies
Newer Methods in Diagnosis
Immuno florescent assay method.
ELISA for IgM and IgG detection
Frankel’s intracutaneous test useful for epidemiologcal purpose
Acquired immunity in women is particularly protective to the fetus.
In Immunosupressed and AIDS patients changes the host resitance and causes chronic infection becomes fulminating acute Toxoplasmosis
Combination of Pyramethamine and Sulphadiazine or Trisulfapyramidines
Other alternative Drugs
Trimethoprim – Sulphmethoxazole
In pregnancy – Spriamycin is recommended drug
Control of Toxoplasmosis
Avoidance of human contact with Cat feces is highly important measure.
Changing of Cat litter and safe disposal can prevent transmision
Pregnant women should avoid contact with kittens
Screening of pregnant women
Periodic screening of pregnant women with high risk for IgG and IgM antibodies to Toxoplasmosis is recommended
Care of the Meat
Avoid eating raw or undercooked meat.
Freezing < -20 0 c
Heating at 50 0 c for 4-6 minutes destroys the cysts and sterilizes the meat.
Created for Health Awareness on Toxoplasmosis Dr.T.V.Rao MD Email [email_address]