2. Objectives
To be able to-
• Name the Tissue coccidia that cause human disease and
state the habitats of each
• State the source (s) of infection, entry to and exit of
agent from humans
• Describe the life cycle with stages and events
• Identify the stages that cause pathogenic effects
• Outline laboratory methods of identification of organism
• Identify points in the life cycle where preventive measures
are applicable
• Describe the pathogenicity
•List the clinical features
•Describe transmission, prevention and control of toxoplasmosis
3. COCCIDIA
Intracellular protozoans; alternation of asexual & asexual
Development in epithelial cells (usually gut) of
the definitive host
TISSUE COCCIDIA
INTESTINAL COCCIDIA-
Tissue coccidia
Toxoplasma gondii
Sarcocystis spp.
5. Toxoplasma gondii
• Coccidian parasite
• Cats ONLY known DEFINITIVE
HOST
• INTERMEDIATE HOSTS: widespread
in birds & mammals
6. TOXOPLASMOSIS
World wide distribution; most prevalent
parasitic infection of humans-
• on serological assays, rates vary in
communities 4-90%
Sri Lanka > 50% healthy adults have Ab.
Many animals (dogs, cats, rodents are
positive; cats 24% )
7. •obligate intracellular parasite of all nucleated cells
• Latent infection is common
• It is an important opportunistic parasite
• Causes fatal infections in the immuno-
compromised
eg.AIDS
8. Morphology – There are 3 forms:
1. Tachyzoites (endozoites) and pseudocysts–
Crescent shape, 4 – 8 µm with single nucleus
found in macrophages (pseudocyst) or any
nucleated cell . Multiply rapidly (tachyzoites) .
Pseudocysts can cross the placenta
Characteristic form is crescentic shaped trophozoite
9. 2. Bradyzoites ( cystozoites) and true cysts – can be
found in any part of the body Organs
commonly affected are brain, eye, heart.
Cyst wall is by the parasite and host.
Zoites in true cysts multiply slowly
(bradyzoites)
10. 3.Oocyst – formed in the small intestine of
the cat and passed in cat faeces. Each sporulated
oocyst contains 02 sporocysts and each sporocyst has
04 sporozoites
NOT FOUND IN HUMANS and other intermediate hosts
11. Definitive
host
Life cycle
Only known definitive hosts for Toxoplasma gondii
are members of family Felidae (domestic cats and
their relatives)
Unsporulated oocysts are
shed in the cat’s faeces
Oocysts take 2-5 days to sporulate in the
environment and become infective.
12. Toxoplasma in Definitive host
–Gut epithelial cells of cat
SCHIZOGONY
(asexual multiplication)
GAMETOGONY
male gametocytes
female gametocytes
Zygote
SPOROGONY oocyst
outside environment- (sporozoites)
13. Pathogenesis
• Tachyzoites actively invade the cells
• Multiply rapidly
• Form intracellulaer pseudocyst
• This leads to cellular disruption, released
tachyzoites infect adjacent cells
• As the host immunity develops,Tissue
true cyst form, containing bradyzoites
Periodic excystation can occur
15. fever, painless cervical lymphadenopathy
+ rash
Immunocompromised- organtransplant,AIDS
Severe disease- multiple tissue/organ
involvement
Symptomatic toxoplasmosis n normal
patients ( immuno-competant)
16. In Immunodeficient patients- mostly
due to reactivation
Common _ central nervous system
(CNS) disease – encephalitis
In patients with AIDS, toxoplasmic
encephalitis is the most common
cause of intracerebral mass lesions
but may have retinochoroiditis,
pneumonitis, or other systemic disease.
17. Ocular toxoplasmosis
Most common cause of infectious posterior Uveitis
Due to
• periodic reactivation of congenital toxoplasmosis or
• acquired acute infection
Clinical features
• Floaters
• Blurred vision
• Usually unilateral
• Active lesion is whitish with ill-
define margins ( cotton –wool
appearance) and pigmented when
quiescent
Involves macular in majority
18. CONGENITAL TOXOPLASMOSIS
occurs generally with acute (1ry) infection in
Mother –(endometrial reactivation reported))
Placental infection Zoites transmitted
to foetus
Risk of infection increases with duration
of pregnancy
but foetal damage severe during early
pregnancy- abortion, intra uterine death
19. diagnosis
The diagnosis of toxoplasmosis is
typically made by serologic testing.
Indirect
Detection of
IgM, IgA or low avidity IgG , rising IgG
titreindicate acute infection,
IgG – Past infection
21. •Use live tachyzoites
• live tachyzoites stain blue with
alkaline methylene blue dye
• If antibodies to T gondii are
present in the patient's serum, they
will damage the organisms
• damaged organisms will not take
up the dye and appear as pale
"ghosts" compared to undamaged
organisms.
• The test needs live tachyzoites and is difficult to perform, so
other serological tests are typically used. However, the test is
very sensitive and specific and remains the reference method.
Sabin-Felman dye test
23. Direct – Demonstration of Parasite
1. Observation of parasites in patient
specimens, such as bronchoalveolar lavage
material from immunocompromised patients,
or lymph node biopsy
2. Isolation of parasites from blood or other
body fluids, by intraperitoneal inoculation
into mice or tissue culture
mice should be tested for the presence of
Toxoplasma organisms in the peritoneal fluid
6 to 10 days post inoculation;
if no organisms are found – serology 4 -6
weeks post innoculation,
24. • especially in detecting congenital infections in
utero. Amniotic Fluid - parasite DNA by
PCR
Prenatal diagnosis:
•Fetal US - calcifications / hydrocephalus
•Isolation of parasite
placenta, amniotic fluid, foetal blood
Detection of parasite genetic material by PCR,
28. • Accidental ingestion of oocysts after cleaning a cat's litter box
when the cat has shed Toxoplasma in its faeces
• Accidental ingestion of oocysts after touching or ingesting
anything that has come into contact with a cat's faeces that
contain Toxoplasma
• Accidental ingestion of oocysts in contaminated soil (e.g. not
washing hands after gardening)
• Drinking water contaminated with the Toxoplasma oocysts
Animal-to-human (zoonotic) transmission
29. true cysts (bradyzoites)
• eating uncooked or undercooked meat of
infected animal
• Eating food that was contaminated
by knives, utensils, cutting boards,
or other foods that had contact with
raw, contaminated meat
•Organ transplant recipients
can become infected by
receiving an organ from a
Toxoplasma-positive donor.
Rarely
•Accidental ingestion of
undercooked, contaminated meat
after handling it and not washing
hands thoroughly (Toxoplasma
cannot be absorbed through intact
skin)
30. Mother-to-foetus (congenital) transmission
• A woman who is newly infected with
Toxoplasma during pregnancy can pass the
infection to her unborn child (congenital
infection).
Tachyzoites or pseudocysts
•Laboratory workers who handle
infected blood can also acquire
infection through accidental
inoculation. • Entering body through abrasions
(butchers, veterinarians),
• Blood transfusion
31. PREVENTION
Reduce Risk of Toxoplasmosis from Food
Avoid eating raw/undercooked meat
-15 C for 3 days
-65 C 4-5 minutes
-4 C persists for months
salt/nitrates kills cysts,
32. •Avoid eating raw/undercooked
meats
-
Wash foods such as green salads leaves
and fruits, especially if it is to be eaten
uncooked.
•Wash cutting boards, dishes, counters,
utensils, and hands with hot soapy
water after contact with raw meat,
poultry, seafood, or unwashed fruits or
vegetables.
To reduce risk
from food
33. Reduce Risk of Toxoplasmosis from the
Environment
• Wear gloves when gardening and during any contact
with soil or sand
•Keep outdoor sandboxes covered.
• Wash hands after contact with soil
34. •Feed cats only canned or dried
commercial food or well-cooked
food, not raw or undercooked
meats.
•
•Change the litter box daily .
•The Toxoplasma parasite does not
become infectious until 2 to 5 days
after it is shed in a cat's faeces
To reduce environmental
contamination
36. • Keep cats indoors.
• Do not adopt or handle stray
cats, especially kittens.
37. SARCOSPORIDIOSIS / SARCOCYSTOSIS
Two types - Intestinal sarcocystosis
Muscle sarcocystosis
Organism - Sarcocystis spp. many species present
coccidian parasite, tissue protozoan
Life cycle - requires two hosts ; a definitive host & an
intermediate host
man can be the definitive host for some species and an
intermediate host for some other species
In the definitive host - sporogony in intestinal mucosae
with the production of sporocysts (infective stage)
In the intermediate host-sarcocysts or Meischer’s
tubes in muscle (intermediate stage)
38. Muscle sarcocystosis
• Man act as the intermediate host
• Definitive host may be a carnivore; monkey, dog
• Sarcocysts are found in muscles andconnective
tissues of man
• Sarcocysts vary in size from few µm to 5 mm.
• These contain cystozoites. Similar to Toxoplasma
zoites but larger; banana shaped.
Cysts in the muscles can cause myositis
and muscle necrosis.
39. True/ false regarding toxoplasmosis
Cats act as definitive hosts
Oocysts could be found in human faeces
True cysts can be transmitted by blood transfusion
Tachyzoites can be transmitted by mosquito bite
Risk of congenital infection increase with duration of
pregnancy
If the mother get infected during the later part of pregnancy,
foetal damage is sever
Known to cause life- threatening infections in immuno-
compromized patients
40. Can cause sever disease in pregnancy
Serology is diagnosis of choice
Detection of IgM indicate a past infection
Prenatal diagnosis is usually rely on serology
Washing hands after going to toilet is good
method of preventing infection
Oocysts are infective as soon as it pass in the
faeces
