2. CHARACTERISTICS
• T.GONDII IS A COSMOPOLITAN
PARASITE INFECTING A WIDE RANGE
OF ANIMALS INCLUDING BIRDS AND
MAN.
• OOCYST CONTAINS EIGHT
SPOROZOITES ENCLOSED WITHIN
TWO SPOROCYSTS.
3. • THEY ARE CRECENT
SHAPED (6 X 3 ΜM)
AND UNDERGO
MULTIPLICATION
INSIDE THE
PHAGOCYTIC CELLS,
BUT CAN INFECT ALL
NUCLEATED CELLS.
• ON THE OTHER HAND,
THE BRADYZOITES ARE
ENCLOSED WITHIN A
CYST AND ARE FOUND
IN TISSUES INCLUDING
THE BRAIN.
4. • ONE CYST MAY CONTAIN THOUSANDS OF
BRADYZOITE.
• TACHYZOITES AND BRADYZOITES ARE
INFECTIVE TO BOTH DEFINITIVE AND
INTERMEDIATE HOSTS.
• APPROXIMATELY ONE THIRD OF THE
POPULATION IN THE WORLD HAS BEEN
INFECTED BY T.GONDII (HOWEVER, MOST
OF THE INFECTIONS REMAIN
ASYMPTOMATIC).
5. MODE OF TRANSMISSION
• IN THE INTERMEDIATE HOST, IT IS FOUND IN TWO FORMS:
TACHYZOITE (THE RAPIDLY PROLIFERATING FORM) AND
BRADYZOITE (THE SLOWLY PROLIFERATING FORM).
• THE SPORULATED OOCYST (10-13 X 9-11 ΜM) PASSED IN
THE FECES OF DEFINITIVE HOST ARE INFECTIVE TO ALL
INTERMEDIATE HOSTS.
• THE TACHYZOITES CAN ALSO CROSS THE PLACENTAL
BARRIER DURING PREGNANCY AND INFECT THE FETUS.
• UPON INGESTION BY DEFINITIVE HOST, THE PARASITES
ENTER INTO THE ENTEROCYTES AND UNDERGO MEROGONY,
GAMETOGONY AND FINALLY PRODUCE OOCYSTS THAT ARE
PASSED IN THE FAECES.
6. LIFE CYCLE
• UPON INGESTION BY INTERMEDIATE HOSTS, THE
SPOROZOITES RELEASED FROM OOCYST ENTER INTO
ALL TYPES OF NUCLEATED CELLS PARTICULARLY IN
PHAGOCYTIC CELLS AND INITIATE MULTIPLICATION.
• INFECTION IN MAN IS ACQUIRED EITHER THROUGH
INGESTION OF OOCYST AND BRADYZOITES OR
THROUGH BLOOD TRANSFUSION, ABRADED SKIN OR
WOUND CONTAMINATION, AND TRANSPLACENTAL
ROUTE.
7. DISEASES AND SYMPTOMS
• TOXOPLASMOSIS IN MAN MAY MANIFEST AS
MILD-FLUE TO AS SEVERE AS FATAL
TOXOPLASMIC ENCEPHALITIS INCLUDING
ABORTION AND VARIOUS OTHER REPRODUCTIVE
DISORDERS.
• SEVERE DISEASE OCCURS PRIMARILY IN
IMMUNOCOMPROMISED SUBJECTS.
• THUS, TOXOPLASMA INFECTIONS HAVE EMERGED
AS ONE OF THE MAJOR CAUSE OF DEATH AMONG
AIDS PATIENTS.
8. DIAGNOSIS
Diagnosis is made mainly by serological tests.
However, culture, animal inoculation, and PCR
techniques are also available but are either time
consuming or expensive.
9. 78. T. GONDII TACHYZOITES AND T. GONDII INFECTED MACROPHAGE.
79. T. GONDII TACHYZOITES (GIEMSA STAIN).
