Toxoplasmosis Flashcards
What group of organisms does Toxoplasma belong to?
Toxoplasma is an Apicomplexa in the protozoa parasite group.
What is the full name of the parasite commonly referred to as Toxoplasma?
Toxoplasma gondii.
What type of parasite is Toxoplasma gondii?
Intracellular parasite.
What types of cells can Toxoplasma gondii potentially infect?
All nucleated cells.
What percentage of the human population is chronically infected with Toxoplasma gondii?
1/3 of the human population.
What are the main stages of the Toxoplasma gondii parasite?
- Tachyzoite
- Bradyzoite
- Sporozoite
What characterizes the tachyzoite stage of Toxoplasma gondii?
Extracellular, parasitophorus vacuole (intracellular), acute phase, systemic infection.
What is the bradyzoite stage associated with in Toxoplasma gondii?
Tissue cyst, chronic phase, brain and skeletal muscle.
What does the sporozoite stage of Toxoplasma gondii indicate?
Within oocyst, resistance in the environment.
What stages of Toxoplasma gondii occur in the intestinal tract?
Merozoites and gametocytes.
In which host do the intestinal stages of Toxoplasma gondii only occur?
Intermediate host (cat).
Describe the life cycle of T.gondii?
- Definitive Host feline:
This is the sexual stage of the parasite
Oocyst formation: infected cats shed oocystsin their faeces. These oocysts can survive in the environemnet for months or even years - Transmission to intermediate Hosts (Humans, rodents other animals)
Ingestion of oocysts: intermediate hosts including humans can become by ingesting oocysts from contaminated water soil etc. or by direct contact with poo.
Ingestion of tissue cysts: intermediate hosts can aquire the parasite through consuming tissue cyst present in the meat of infected animals (raw uncooked pork etc.) - Asexual Reproduction in intermediate Hosts:
After ingestion the cysts release T.gondii parasites into the hosts intestines
Tachyzoites: Intestines, T.gondii rapidly transform into tachyzoites, MOTILE FORM which spread across the body and infect various tissuese, Formation of tissue systs:; as the immune system responds tachyzoites eventually form tissue cysts containing Bradyzoites (slow dividing,cyst forming stage) - Reinfection and sexual reproduction in the definitive Host:
If intermediate host is eaten by definitive host the tissue cyst in the intermediate host’s tissue release bradyzoites in the cats intestines.
Sexual repro: these bradyzoites undergo sexual reproduction in the cats intestines, where they form new oocyts. These oocysts are then shed in the cats faeces completing the life cycle
Summary:
Oocysts shed in the feces of definitive hosts (cats).
Ingestion of oocysts by intermediate hosts (humans, rodents, etc.).
Tachyzoites spread and multiply inside the intermediate host.
Bradyzoites form cysts in tissues of intermediate hosts (e.g., brain, muscles).
Definitive host eats infected intermediate host, and the cycle begins again.
What is the difference between Horizontal and vertical transmission of toxoplasmosis?
Horizontal: between individuals, ingestion of oocysts ot tissue cysts.(raw meat, direct contact with poo unwashed veg, unfiltered water wtc.)
Vertical: between mother and offspring: dissemination of tachyzoites in foetus
What happens to immunocompetent individuals when they are infected?
Asymptomatic
10-20% develop flu like symptoms or cervial lymphadenopathy
What happens to pregnant individuals when they are infected?
Can cause abortion
Congenital Toxoplasmosis: no signs, ocular Toxoplasma infection
What happens to Immunocompromised individuals when they are infected?
Encephalitis(inflammation of the active tissues of the brain)
Retinochoroiditis
Lung inflammation
How the time of infection in pregnancy affects the outcomes of the ovine toxoplasmosis?
firs trimester: days 1 to 40, Abortion
Second trimester: Days 40 -110, Abortion/stillbirth, congenitally infected lambs(neurological signs)
Third trimester: Days 110- 147, Neonatal mortality, congenitally infected lambs(no signs)
All have economic impacts
Why pregnancy is so susceptible and dangerous for toxoplasmosis?
Pregnancy: reduced Th1 IFNy increased IL4 and IL10—>POLIFERATION OF TACHYZOITES
Placenta and Foetus invasion—>necrosis and inflammation—> lesions (nervous system, heart)
What are the control measurs used in farm animals against toxoplasmosis?
Farm management: avoiding the presence of definitive host cats
accurate dignostics, maintain immune animals, appropriate disposal of contaminated material
Therapeutic treatment: Decoquinate (deccox can be used during pregnancy)
Vaccinaction Toxovax: Only comercial vaccine—>live attenuated tachyzoites (cannot dev into bradyzoites)
Long term protection.
Why is Toxvax not the best?
It gives good protection however:
Safety is low, production and stability is low
You cant differentiate infected animals from differentiated ones
