This document summarizes information about Toxoplasma gondii, an opportunistic protozoan parasite that can cause toxoplasmosis. It discusses how T. gondii has a worldwide distribution and can infect nearly any warm-blooded animal. The parasite has two phases, intestinal and extraintestinal, and humans can become infected by ingesting undercooked meat or through contact with cat feces. While most infections are asymptomatic, toxoplasmosis can cause serious issues in immunocompromised individuals or congenitally. The document outlines the parasite's morphology, life cycle, diagnosis, treatment and prevention.

1. Opportunistic Pathogen
• Opportunistic parasitism can be defined as a
association between opportunistic parasites
and immunocompromised hosts; so that the
parasite causes opportunistic parasitic
infection
• Opportunistic infection
– An infection by a microorganism that
normally does not cause disease but
becomes pathogenic when the body's
immune system is impaired and unable to
fight off infection

2. Toxoplasma gondii
• Toxoplasma gondii (T. gondii), is a
protozoan parasite widely distributed
around the world.
• It has been estimated that up to third of the
world's population is infected by T. gondii.
• Toxoplasma gondii has very low host
specificity, and it will probably infect
almost any mammal.

3. • It has also been reported from birds also and
has been found in virtually every country of the
world .
• Like most of the Apicomplexa, Toxoplasma is an
obligate intracellular parasite.
• Its life cycle includes two phases called the
intestinal (Sexual) and (asexual) extraintestinal
phases
• The intestinal phase occurs in cats only (wild as
well as domesticated cats) and produces
"oocysts." The extraintestinal phase occurs in
all infected animals.

4. Geographic Distribution
• The protozoan parasite Toxoplasma gondii
infects more than a billion people
worldwide.
• Serologic prevalence data indicate that
toxoplasmosis is the one of the most
common of human infections throughout
the world.
• Infection is more common in warm
climates and at lower altitudes than in
cold climates and mountainous regions.

6. Morphology:
• T. gondii occurs in three forms;
Oocyst (Sexual phase)
• Double layered egg found in the feces of young
cats that survives for long periods
Tachyzoite (Asexual Phase)
• Rapidly multiplying tiny parasite found in
different cells of the body and the cells burst
releasing it into the bloodstream in crescent
form

7. Bradyzoite or tissue cyst (Asexual Phase)
• Dormant stage, found in cysts of the
muscle, nervous tissue and placenta.
• Slowly multiplying
• Resistant to gastric juices
• All three forms occur in the domestic cat
and other felines which is the definitive
host and which support both schizogony
and gametogony.

8. • The intracellular parasites (tachyzoite) are 3x6µ,
crescent shaped organisms that are enclosed in a
parasite membrane to form a cyst measuring 10-
100 µ in size.

9. Bradyzoite

11. Human Toxoplasmosis
• The primary means of acquiring the parasite is either
ingestion of inadequately cooked meat (e.g. beef,
pork, and lamb) containing tissue cysts or contact
with feral or domestic cats with oocysts.
• Congenital toxoplasmosis is a very serious disease,
and for this reason pregnant women should avoid
contact with litter boxes used by cats.
• Flies and roaches have been implicated as carriers of
the infective stages from cat feces to food. The
parasite can attack a wide variety of tissue cells, but
seems to favor muscle, lymph nodes and intestinal
epithelium

12. • Infection of intestinal epithelium cells
occurs only in felines and this
developmental pathway is termed the
enteric or enteroepithelial phase.
• during this stage sporozoite-containing
oocysts are formed that serve as the
primary source for human infection.
• In other hosts, including many species of
carnivores, insectivores and primates, only
the tissue or extraintestinal phase occurs

13. • The bradyzoites are released from the
oocyst in the lumen of the host’s small
intestine. In cats, some bradyzoites
penetrate intestinal epithelial cells to begin
the enteric phase, while others penetrate
the mucosa and develop in cells of
underlying tissues, including lymph nodes
and leukocytes
• In the enteric phase, the bradyzoites enter
the host cell, become trophozoites and
undergo merogony.

14. • Each trophozoite produces from 2-40
merozoites.
• Some of these invade host cells and develop
into micro-and macrogametocytes; undergo
gametogony to yield gametes.
• The microgametes then invade cells with
macrogametes to allow for fertilization and
gamete formation.
• The zygote develops in an oocyst that breaks
out of the cell into the lumen of the cat’s
intestine to be passed out with the feces.

15. • The oocyst undergoes sporogony, forming 2
sporocysts each containing 4 sporozoites.
• In extraintestinal development, the
sporozoites invade cells other than those of
the intestinal epithelium, reproduce, and
form merozoites – tachyzoites.
• In acute infections, an increase in the
number of tachyzoites causes the cell to
disintegrate, releasing the parasites to
invade new cells.

16. • As the disease becomes chronic,
parasites infecting the cells of the
brain, heart, and skeletal muscle
reproduce more slowly than during
the acute phase. At this time, they are
bradyzoites and they accumulate in
large numbers within a cell.

18. Epidemiology
• All mammals, including humans are capable of
transmitting toxoplasmosis transplacentally.
• Sporulated oocysts, tachyzoites and bradyzoites all
serve as infective agents.
• Sources of infection vary, ranging from direct
contamination to ingestion of inadequately cooked
food or raw milk.
• Immunological surveys reveal that humans
throughout the world carry antibodies to
Toxoplasma. Clinical toxoplasmosis is rare, and
infections are generally asymptomatic.

19. Diseases
• toxoplasmosis can cause serious pathology,
including hepatitis, pneumonia, blindness, and
severe neurological disorders. This is especially
true in individuals whose immune systems are
compromised (e.g., AIDS
patients). Toxoplasmosis can also be
transmitted transplacental resulting in a
spontaneous abortion, a still born, or a child
that is severely handicapped mentally and/or
physically.

20. Symptomology
•Symptomatic or clinical toxplamosis may be
classified as acute, subacute, chronic, or
congenital.
•Acute toxoplasmosis in humans is characterized
by parasitic invasion of the mesenteric lymph
nodes and liver parenchyma.
•The most common symptom is painful swollen
lymph glands, especially in the cervical region.

21. •It is accompanied by fever, headache,
anemia, muscle pain and sometimes lung
complications.
•Congenital toxoplasmosis results from fetal
transplacental infection. Such infection may
result in still birth.

22. • Toxoplasmosis is especially serious for people
who have weakened immune systems. For
these people, they are at risk of developing:
brain inflammation, causing headaches,
seizures, confusion and coma.
• a lung infection, causing cough, fever, and
shortness of breath
• an eye infection, causing blurry vision and eye
pain

23. Diagnosis
• Direct microscopy---Detection of tachyzoite in
blood and tissue cyst in tissue biopsy
• Staining method
• Giemsa
• Immunoperoxidase stain
• Silver Stain
Serology
Detection of toxoplasma antigens by ELISA
• IGM ELISA
• IGg ELISA

24. • Molecular Diagnosis
• Tissue Culture
• Imaging Method
• Antigen in amniotic fluid
• PCR
Treatment
Pyrimethamine (Daraprim) and sulfadiazine.
Pyrimethamine is also used to treat malaria.
Sulfadiazine is an antibiotic.

25. How Is Toxoplasmosis Prevented?
You can prevent toxoplasmosis by:
• washing all fresh produce before you eat it
• making sure all meat is properly cooked
• washing all utensils that are used to handle raw
meat
• washing your hands after cleaning or scooping
cat litter