1. COCCIDA – TOXOPLASMA- LECTURE NO 11
Dalia Kamal Eldien Mohammed

2. Introduction
Coccidia (Coccidiasina) are a subclass of microscopic, spore- forming, single-celled, obligate intracellular parasites belonging to the  Apicomplexa phylum and class  Sporozoa.
As obligate intracellular parasites, they must live and reproduce within an animal cell, Coccidian parasites infect the intestinal tracts of animals
The common of the coccidia that infect humans are:
Toxoplasma
Cryptosporidium
Isospora

3. Taxonomy Kingdom Animalia Subkingdom Protozoa Phylum Apicomplexa
Class Sporozoa
Order Coccidia
Genus Toxoplasma
Species gondii

4. Toxoplasma gondii
Toxoplasma gondii is an obligate, intracellular, parasitic protozoan that causes the disease toxoplasmosis.
Found worldwide,  In humans, it is one of the most common parasites, serological studies estimate that up to a third of the global population has been exposed to and may be chronically infected with T. gondii
The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid (cat) family
The definitive host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals (birds or mammals).

5. Toxoplasmosis, the disease of which T
Toxoplasmosis, the disease of which T. gondii is the causative agent, is usually minor and self-limiting but can have serious or even fatal effects on a fetus whose mother first contracts the disease during pregnancy or on an immunocompromised human.
Toxoplasma gondii is known to change the host's behavior. Studies show the capability for the parasite to make rats fearless near cats.

6. Morphology
3 forms :
Oocyst : oval in shape, contains 2 sporocystes each contains 4 sporozoites.
Tachyzoite: rapidly multiplying trophozoite, acute state, found intracellularly in phagocytic cells, cresentic in shape, one rounded end & other pointed end, one nucleus towards the rounded end.
Bradyzoite: slowly multiplying form, found intracellularly in tissues chronic stage-pseudocyst

7. Oocysts of Toxoplasma gondii

8. Tachyzoite

9. Tachyzoite

10. Bradyzoite

11. Bradyzoite

12. Transmission
Consumption of under-cooked infected meat( especially pork, lamb, or venison)-bradyzoite in pseudocyst
Contaminated food or water or hands-oocyst
Congenital ( By transmission from infected mother to fetus during pregnancy.)- tachyzoite
from a blood transfusion or organ transplant

13. Pathogenicity
Healthy people who become infected often do not have symptoms because their immune system keeps the parasite from causing sickness.
10–20 % of patients develop sore lymph nodes, muscle pains and other minor symptoms that last for several weeks and then go away (acute toxoplasmosis).
symptoms similar to those of the flu, including: Body aches, Swollen lymph nodes, Headache, Fever& Fatigue
The parasites remain in the body as tissue cysts (bradyzoites) and reactivate, if the person becomes immuno-suppressed by other diseases or by immunosuppressive drugs.

14. Pregnancy precautions
Usually if a woman has been infected before becoming pregnant, the unborn baby is safe because the mother has developed immunity.
If a woman is pregnant and becomes infected with toxoplasmosis during or right before pregnancy, she can transmit the disease to her unborn child (congenital transmission).
The earlier the transmission occurs the bigger effects.
A simple blood draw at the first prenatal doctor visit can determine whether or not a woman has had previous exposure and therefore whether or not she is at risk
Pregnant women should avoid handling raw meat, drinking raw milk (especially goat milk) and be advised to not eat raw or undercooked meat regardless of type

15. Symptoms might include:
Miscarriage or stillborn baby
Baby born with signs of toxoplasmosis (for example, abnormal enlargement or smallness of the head)
Baby with brain or eye damage.
An enlarged liver and spleen
Yellowing of the skin and whites of the eyes (jaundice)
Usually the babies have no symptoms initially, but can develop mental disability, vision loss (ocular toxoplasmosis) .

16. Life Cycle In Cat
A cat ingests either: a pseudocyst in an infected animals flesh or An oocyst from the environment
The tissue cyst or oocyst wall is dissolved during digestion, releasing bradyzoites or sporozoites, which enter the lamina propria of the small intestine and begin to multiply as tachyzoites.
The tachyzoites can disseminate to extra-intestinal tissues within a few hours of infection, via the lymph and blood.
The parasite multiply sexually & asexually within the intestinal epithelium to form the zygote which secrete a wall around its self forming un-sporulated oocyste
Oocyst sporulates 1 to 5 days after excretion.

17. Life Cycle In Intermediate host
Following ingestion of infective oocyst, the parasite becomes intracellular & multiply in the lymph glands , liver, muscle, CNS, placenta, etc
In the early acute stages of infection, the parasites tachyzoites invade phagocytic mononuclear cells.
In chronic stages the parasites bradyzoites multiply intracellularly in the tissues forming pseudocysts.  in the brain, the eyes, and striated muscle (including the heart)
Tissue cysts usually cause no host reaction and may remain for the life of the host.

20. Laboratory diagnosis
Toxoplasmosis can be diagnosed by direct observation of the parasites in tissues, including broncho alveolar lavage material and lymph node biopsies.
PCR techniques can be helpful, particularly for detecting congenital infections in uterus, By detecting the parasite's DNA in the amniotic fluid .
Immunohistochemical staining and electron microscopy are also used.

21. The diagnosis of toxoplasmosis is typically made by serologic testing:
A test that measures immunoglobulin G (IgG) is used to determine if a person has been infected.
If it is necessary to try to estimate the time of infection, which is of particular importance for pregnant women, a test which measures immunoglobulin M (IgM) is also used along with other tests such as an avidity test.
The IFA and ELISA tests are used most often in humans.