Toxoplasma gondii Flashcards
What are the 2 stages in the life cycle of T. gondii?
- intestinal epithelium
2. extrainstestinal
In which hosts do the 2 stages occur?
- intestinal epithelium - cats & other felines
2. extra intestinal - cats & other hosts
Which is the sexual stage?
intestinal epithelium
What stages of the parasite are infective to cats?
oocyst or pseudocyts
Trace the development of the parasite through the intesitnal epithelial stage.
- cat ingests oocyst or pseudocyst
- invades intestinal epithelial cell
- develops into troph
- schizogony
- merizotes lyze host cell & invade other peithelial cells -> several generations
- some trophs undergo gametogony: macro or microgamete
- fertilization -> oocyte
- immature oocyst escapes epithalial cell -> shed in feces
- sporogony -> mature oocyst
What happens during schizogony?
Production of 2-40 merozoites
Where does gametogony occur & what is produced?
production of micro or macrogamete
What stage is produced from fertilization?
oocyst
What occurs during sporogony
mature oocyst is produced
Describe a mature oocyst.
2 sporocysts
4 sporozoites
In what hosts does the extra intestinal stage occur?
cats & other hosts
What stages of the parasite are infective to the host?
oocyst or pseudocyst
Trace the development of the parasite in the host. (extraintestinal)
- host ingests oocyst or pseudocyst
- penetrates intestine & taken up macrophage
- spreads through body
- multiplies rapidly in macrophages & lymph tissue -> tachyzoites
- invade other cells
- immune response
- bradyzoite -> multiply rapidly
- psuedocyst
- predation
Do schizogony or gametogony occur in extraintestinal stage?
no
Describe a major difference between tachyzoites and bradyzoites. What is the cause of this difference?
bradyzoites - multiply slowly
tachyzoites - multiply rapidly
Allows bradyzoites to survive in the pseudocysts from months to years as long as the immune system is good
What is a pseudocyst?
intracellular
Large clumps of bradyzoites
mothers/yrs
as long as immunity intact
How is the parasite transmitted to the next host?
predation
What type of host is most likely a dead end in this life cycle?
-
Describe the acute and chronic stages of infection in humans. Is the parasite multiply quickly or slowly?
acute - painful & swollen lymph nodes, fever, headaches, muscle pain, lesions in brain, eye, heart, lungs, rarely causes death
chronic - asymptomatic, sometimes pseudocysts: in eye = blind spot, in brain = paralysis
quickly
Where in the body is the parasite found in the acute or chronic stages?
eyes and brain
What problems can be cause by pseudocysts?
blind spot in eye
paralysis if in brain
What happens in a n immunocompromised host?
parasite multiplies very rapidly
Give some examples of medical conditions in which infection with Toxoplasma could be a problem.
AIDS - opportunistic infection
chemotherapy patients
What is congenital toxoplasmosis?
mother contract toxo during 1st trimester
fetus has no immune response
10% die, 30% severe complications: hydrocephaly, impaired mental development
How does the fetus become infect w/ cognenital toxo and why is it so severely affected?
- Crosses over into the developing fetus
- Fetus has no immune response to contain the parasite host
- Hydroencephaly
How can infection with toxo be dignosed?
ELISA - antibody in blood
detection of toxo DNA in amniotic fluid
What is the mechanism of action in pyrimethamine?
blocks folic acid production
How can infections be controlled?
- cat: hunt -> infects w/ oocysts in litterbox/sandbox
- meat prep: beef tartar
- food storage: files &cockroaches can carry oocysts
- obstetrician recommendations: no cats, don’t change litter, no raw meat
