1. Toxoplasma gondii is a protozoan parasite that is the most prevalent in the global human population. 2. It has a complex life cycle involving felines as the definitive host and warm-blooded animals as intermediate hosts. Transmission occurs via ingestion of oocysts from cat feces or consumption of undercooked meat containing tissue cysts. 3. In humans, T. gondii exists in tachyzoite and tissue cyst forms and usually causes a mild, self-limiting illness but can cause severe disease in immunocompromised or congenitally infected individuals.

1. Prepared by:
NOE P. MENDEZ
CENTRAL MINDANAO UNIVERSITY (CMU)
npolomendez@gmail.com

2. REFERENCES/LITERATURE CITED
 BARRAGAN, A and L.D. SIBLEY. 2003. Migration of Toxoplasma gondii across
biological barriers. Trends Microbiology. 11:426-30.
 COHEN, B.A. 1999. Neurologic manifestations of toxoplasmosis in AIDS. Semin
Neurol. 19:201-11.
 FROMONT, E.G., M. LELU, M.L. DARDE, C. RICHOMME, D. AUBERT, E.
AFONSO, A. MERCIER, C. GOTTELAND and I. VILLENA. 2012. The Life Cycle
of Toxoplasma gondii in the Natural Environment.
 NICOLLE C. and L. MANCEAUX. 1909. Sur um protozoaire nouveau du gondii.
Paris. 147:763-6.
 PEYRON, F., A.B. ATEBA, M. WALLON, et al. 2003. Congenital toxoplasmosis in
twins: a report of fourteen consecutive cases and a comparison with published data.
Pediatrics Infection Diseases J. 22:695-01.
 SILVEIRA, C., R. JR. BELFORT, C. MUCCIOLI and M.T. ABREU, et al. 2001. A
follow-up study of Toxoplasma gondii infection in southern Brazil. Am J Ophth.
131:351-4.
 TENTER, A.M., A.R. HECKEROTH and L.M. WEISS. 2000. Toxoplasma gondii:
from animals to humans. Int. j. parasitology. 30: 1217-1258.
 VOLLAIRE, M.R. et al. 2005. Seroprevalence of Toxoplasma gondii antibodies in
clinically ill cats in the United States. Am. J. Vet. Res. 66, 874–877.

3.  Protozoan parasite
Toxoplasma
toxon (bow)
plasmid (form)
 The most prevalent parasites in the global
human population
 The most successful parasites
THE ORGANISM
Tenter (2000); Fromont (2012)
Scanning (a) and transmission (b)
electron micrographs of the
microgamete of Toxoplasma gondii.
Abbreviations: F, flagella; Mi,
mitochondrion; N, electron-dense
nucleus. Scale bars = 200 nm.

4.  Human–to–human transmission, other than
transplacental transmission, does not
occur.
 Usually acquired by ingestion and
transplacental transmission from an
infected mother to the fetus can occur.
 After infection of the intestinal epithelium,
the organisms spread to other organs,
especially the brain, lungs, liver and eyes.
THE ORGANISM
Scanning (a) and transmission (b)
electron micrographs of the
microgamete of Toxoplasma gondii.
Abbreviations: F, flagella; Mi,
mitochondrion; N, electron-dense
nucleus. Scale bars = 200 nm.

5. TAXONOMIC CLASSIFICATION
D: Eukarya
K: Protista (Alveolata)
P: Apicomplexa
C: Coccidia
O: Eucoccidiorida
F: Sarcocystidae
G: Toxoplasma
S: gondii
© NCBI Taxonomy Database as cited by Dr. Sabri

7.  Widely-distributed zoonosis caused by T.
gondii protozoa.
TOXOPLASMOSIS
Nicolle and Manceaux (1909)
 The definitive host is the domestic cat and
other felines.
 Humans and other mammals are
intermediate hosts.

8. Toxoplasma gondii exists in four forms
All parasite stages are infectious.
1. TACHYZOITES
2. TISSUE CYSTS
3. BRADYZOIT
4. OOCYSTS
Oocysts

9.  Cysts in cat feces (oocysts) are 10-13 µ in
diameter
 The intracellular parasites (tachyzoite) are
3x6µ and crescent shaped organisms that
are enclosed in a parasite membrane to
form a cyst measuring 10-100 µ in size.
MORPHOLOGY

10.  Form of Toxoplasma gondii : tachyzoites.
MORPHOLOGY

11.  Intracellular tachyzoites of Toxoplasma
gondii.
MORPHOLOGY

12.  A zoitocyst of Toxoplasma gondii filled
with bradyzoites; this zoitocyst is in
cardiac muscle.
MORPHOLOGY

13.  A sporulated oocyst of Toxoplasma
gondii. The oocyst contains two
sporocysts, each of which contain four
sporozoites.
MORPHOLOGY
 Thus, they resemble the oocysts of
Isospora sp.
 Only cats will produce and pass
Toxoplasma oocysts; approximate
diameter = 10 µm.

14. MORPHOLOGY

16. Tissue phase (intermediate hosts).
Intermediate host gets
infected by ingesting
sporulated oocysts.
Oocytes do not become infectious until
they sporulate, sporulation occurs
1- 5 days after that the oocyte is excreted
in the feces.
Intermediate host
Human, cattle,
birds, rodents,
pigs, and sheep.

17. Common symptoms of T. gondii
infection in cats includes:
Fever;
Ocular inflammation;
Anorexia;
Lethargy;
Abdominal discomfort; and
Neurologic abnormalities (Vollaire).
SYMPTOMS

18.  Both humoral and cell mediated
immune responses are stimulated in
normal individuals.
IMMUNOLOGY

19. Confirmation by isolation of
organism from tonsil or lymph gland
biopsy.
DIAGNOSIS

20.  Acute infections benefit from
pyrimethamine or sulphadiazine.
TREATMENT
 Spiramycin is a successful alternative.
 Pregnant women are advised to avoid cat
litter, handle uncooked meat carefully and
undercooked meat.
 Pregnant women are advised to avoid cat
litter, handle uncooked meat carefully and
undercooked meat.

21. NOE P. MENDEZ
Central Mindanao University
npolomendez@gmail.com