22 Questions
What is the characteristic feature of apicomplexa parasites?
They are obligate intracellular parasites
What is the role of the apical complex in Toxoplasma gondii?
It helps in penetration of host cells
Where does the parasite multiply sexually in the cat's body?
Inside the intestinal epithelial lining by Gametogony
What is the definitive host of Toxoplasma gondii?
Cat
What is the asexual form of Toxoplasma gondii?
Tachyzoite
Which stage of Toxoplasma gondii is infective during transplacental infection?
Tachyzoite
What is the shape of the tachyzoite?
Pyriform
What is the mode of infection by ingesting contaminated cat feces?
Ingestion of oocysts
Which of the following individuals are at high risk of life-threatening toxoplasmosis?
Immunologically impaired patients
In which cells of the human body does the parasite multiply asexually?
RES cells of the spleen, liver, and lymph nodes
What is the infective stage in organ transplantation?
Cyst
How many major genotypes of Toxoplasma gondii are known?
3
What is the fate of tachyzoites in the human body?
They form tissue cysts that persist for the person's life
What is the percentage of the population infected with Toxoplasma gondii?
1/3
What is the definitive host in the sexual cycle of Toxoplasma gondii?
Cat
What is the primary site of infection in Toxoplasma gondii infection?
Small intestine
What is the infective stage of Toxoplasma gondii that attacks epithelial cells?
Sporozoite
Which type of blood transfusion is safe from Toxoplasma gondii infection?
Pack red-cell transfusion
What is the type of infection that occurs when Toxoplasma gondii is transmitted from mother to fetus?
Congenital infection
What is the characteristic of Toxoplasma gondii infection in immunocompromised patients?
It can cause reactivated infection
What is the mode of transmission in research workers and butchers?
Contamination of mucous membrane and skin abrasion
What is the common symptom of acquired toxoplasmosis?
All of the above
Study Notes
Toxoplasma Gondii
- Intermediate hosts: humans and other mammals (e.g., sheep, cattle, pigs, birds, and mice)
- Infective stage: all forms of T. gondii are infective to humans
Life Cycle
- In cat:
- Intestinal stage: asexual multiplication by Schizogony, then sexual multiplication by Gametogony
- Extra-intestinal stage: asexual multiplication in other body organs
- In humans and other mammals:
- Asexual multiplication in RES cells of spleen, liver, lymph nodes, muscles, heart, bone marrow, brain, eye, and kidney
Mode of Infection
- Eating raw or undercooked beef, pork, or mutton containing T. gondii cysts
- Ingestion of oocysts in material contaminated with infected cat feces
- Transplacental transmission during active infection
- Blood, white cells, or platelet transfusion
- Organ transplantation
Phylum Apicomplexa (Sporozoa)
- General features:
- Obligate intracellular parasites
- Have an apical complex to attach to and penetrate host cells
- Complex life cycle with alternating sexual and asexual generations
- Members of this phylum include:
- Toxoplasma gondii
- Plasmodium spp.
- Babesia spp.
- Cryptosporidium parvum
- Isospora belli
Toxoplasmosis
- Geographical distribution: worldwide (except Antarctica)
- Toxoplasma gondii attacks humans and animals (cats)
- Three major genotypes (type I, type II, and type III) differ in pathogenicity and prevalence
- Infects a large number of the population (perhaps 1/3), but uncommonly causes clinically significant disease
- High-risk groups: immunologically impaired patients, fetuses, and newborns
Morphology of Toxoplasma Gondii
- Asexual forms:
- Tachyzoite (trophozoite): the actively multiplying, asexual form in humans
- Pyriform in shape with an apical complex at the pointed end
Life Cycle of Toxoplasma Gondii
- Development in cat intestines:
- Sporulated oocyst
- Sporozoites and bradyzoites attack epithelial cells
- Development in human intestine:
- Unsporulated oocyst passes in stool of the cat
- Sporulated oocyst infects humans
Pathogenesis and Clinical Picture of Toxoplasmosis
- Toxoplasmosis is considered an opportunistic infection
- Acquired infection: acquired toxoplasmosis
- Congenital infection: congenital toxoplasmosis
- Recrudescence in immunocompromised patients
Symptoms of Acquired Toxoplasmosis
- Depends on immune status and age of infected person, virulence of infecting strain
- Most cases are asymptomatic
- Mild form: lymphadenopathy, myalgia, low irregular fever, slight anemia with lymphocytosis, fatigue
Learn about the life cycle of Toxoplasma gondii, a parasitic protozoan, including its intermediate hosts, infective stages, and habitat in cats and other mammals.
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