Toxoplasma

Question 1

a protozoan parasite, phylum Apicomplexan and often referred to as a coccidian

Answer 1

Toxoplasma

Question 2

who does Toxoplasma infect?

Answer 2

infects most species of warm-blooded animals, including humans, but only multiply sexually in cats
- infect 1/3 of world popl’n = mostly asymptomatic

Question 3

Toxoplasma lives an obligate intracell lifestyle and has a unique ability to…

Answer 3

invade host cells and evade immune system

Question 4

two basic morphologies of toxoplasma

Answer 4

trophozoites and cysts
both extraintestinal and seen in several tissues

Question 5

toxoplasma trophozoites

Answer 5

two gens: tachyzoites (fast multiplying), bradyzoites (inert or slow multiplying = at this point, huddle together to form cysts)

shape: crescentic, single nucleus; asexual multiplication via endodyogeny (internal budding)

Question 6

T. gondii lytic cycle

Answer 6

process of invasion and destruction of host cell by indiv Toxoplasma trophozoites
- tachyzoite = initial invader = parasitophorous vacuole is thin membrane that protects it
- keep multiplying until host cell lysis
- parasite egress = frees out daughter trophozoites to start new cycle of destruction in neighbouring host cells

Question 7

toxoplasma cysts

Answer 7

• also extraintestinal AK tissue cyst)
• resting/chronic/diagnostic stage
• thick wall (protection from immune system, digestive enzymes, inflammatory rxn)
• result of asexual multiplication

Question 8

intestinal form of toxoplasma parasite

Answer 8

seen in cats only due to sexual repro (gamogony = jejunal epithelium of cats)

oocyst with two sporocysts containing 4 sporozoites; each protected with tough but flexible wall

Question 9

pathogenesis of toxoplasmosis

Answer 9

• intracellular parasite of both phagocytic & non-phagocytic cell, characteristically invading only nucleated cells !!!!
• cell invasion facilitated by the apical complex/drill- like conoid, micronemes, rhoptries, and dense granules
• survival assured by creation of protective parasitophorous vacuole (comes from repurposing host membrane) inside host cell

Question 10

conoid

Answer 10

• central part of apical complex
• hundreds of fibers in a spiral; like drill
• can retract, extend, rotate
• can secrete compounds that aid in attachment and penetration of host cell

Question 11

main secretory organelles that participate in cell entry for toxoplasma

Answer 11

micronemes, thoptries, and dense granules

Question 12

micronemes

Answer 12

• apical complex; toxoplasma
• release very early in
• host cell binding and gliding motility

Question 13

T or F. Apicala complexes are unique to Toxoplasma gondii

Answer 13

F! seen in apicomplexans

Question 14

rhoptries proteins

Answer 14

• Toxoplasma
• released early during invasion
• can be detected in lumen of newly generated paratoph vacuole

Question 15

dense granules

Answer 15

• Toxoplasma
• released after during/after formation of paratoph vacuoles
• often modify vacuoles environment
  = aiding intracell survival and replication of parasite

Question 16

organs affected by toxoplasma

Answer 16

retina (eyes)
brain
lymph nodes
liver

Question 17

T or F. Transmission across placenta in a pregnant woman to fetus can only occur if toxoplasma was ingested after conception

Answer 17

T!

Question 18

sites of invasion of Toxoplasma

Answer 18

• brain = behavioural changes
• eye (immunologically sequestered site, just like brain)
• lymph nodes
• cardiac or skeletal muscle

Question 19

Two phases of Toxoplasma during human stage

Answer 19

Early (acute) phase: - tachyzoites invading cells
- cell destruction/necrosis
- mononuclear cell inflammation
- blood vessel blockage

Late (chronic) phase:
- bradyzoites/tissue cysts
- latency/immunological evasion
- hypersensitivity

Reactivation of chronic infection after being latent

Question 20

clinical picture of toxoplasmosis

Answer 20

• acute:
  asymptomatic = 90%
  lymphadenopathy
  infectious mono-like
  hepatitis with jaundice
  splenomegaly
  rash
  RARE: involvement on CNs and eye
• chronic: ALWAYS asymptomatic (unless of course blind = residual effect)

Question 21

ocular toxoplasmosis

Answer 21

can be seen during ophthalmoscopic eye exam = dull area where hemorrhage occurred

Question 22

Neonatal Toxoplasmosis (2)

Answer 22

Transplacental transmission: acute toxoplasmosis in pregnancy

Congenital toxoplasmosis:
* abortion or stillbirth * CNS lesions = mental retardation
* eye involvement: blindness

Question 23

toxoplasmosis in pregnancy:risk of congenital infection

Answer 23

first trimester = 5%, 60% of offsprings show clinical signs

2nd trimester = 40%, and 25% of offsprings show clinical signs

third trimester = 70%, 10% of offsprings show clinical signs

Question 24

principal reservoir of toxoplasma

Answer 24

rodents

Question 25

how is toxoplasma transmitted?

Answer 25

ingestion
transfusion (not red cells) or transplantation
transplacentally

or.. reactivation of chronic infection

Question 26

epidemiology of toxoplasma

Answer 26

worldwide!
doesn’t kill ppl
humans, cats, lambs, swine, cattle, chickens

Question 27

lab diagnosis of toxoplasmosis

Answer 27

1. Direct demonstration:
   - Giemsa stain
   - PAS (Periodic Acid-Schiff)
   - Fluorescent antibody stains
   - NAAT testing Nucleic Acid Amplification Tests); PCR on tissue samples and body fluids(including amniotic fluid)
   - Animal inoculation/tissue cultures (now rarely used)
2. Serology :
   - Sabin Feldman dye test
   - Immunofluorescent assays (IFA)
   -Enzyme immunoassays (EIA) : IgG, IgM, other Ig classes