Toxoplasma gondii

Question 1

Structure

Answer 1

intracellular coccidian protozoa that infects cats -> 3 dominant genotypes

Question 2

Definitive hosts

Answer 2

felids, but infects nearly all mammal and bird species

Question 3

Origin

Answer 3

South American felids-> migratory birds-> worldwide distribution

Question 4

Is it zoonotic

Answer 4

yes

Question 5

Life Cycle parts

Answer 5

Oocyst, Tachyzoite, Bradyzoite

Question 6

Oocyst

Answer 6

a cyst that contains a zygote of the parasite-> process of producing spores is called sporulation

Question 7

Tachyzoite

Answer 7

rapidly growing life stage-> endozoites or trophozoites-> attack the neural and muscle tissues and form other tissues known as the cyst bradyzoites

Question 8

Bradyzoite

Answer 8

formed in tissue cysts found in muscle cells and within cells of the nervous system-> cystozoites

Question 9

Transmission Cycle

Answer 9

1a. Toxoplasma eggs are passed in cat stool usually for only 1-2 weeks
○ After 1-5 days in environment, eggs become able to cause infection
● 1b. Cats become reinfected by consuming food or other materials contaminated with eggs
● 2. Other animals (especially rodents) may consume eggs in contaminated soil, water, plant
material, or cat litter
● 3. Eggs are consumed → release forms of parasite that can move (tachyzoites).
● 4. Tachyzoites spread throughout animal’s body and form cysts in nerve and muscle tissue
● 5. Cats become infected after eating animals that contain cysts
● 6a. People become infected by eating undercooked meat containing cysts
● 6b. Or by food, water, or other materials contaminated with cat stool or when clean litter
boxes and don’t wash their hands
● 7. Rarely, people are infected from blood transfusion or organ transplant that contains
● 8. Rarely, infection is spread from mother to fetus → miscarriage
● 9. In people, parasites form cysts in tissues, usually in muscle and heart, brain, and eyes →
cysts may remain for rest of the person’s life without causing symptoms → may become
active and cause symptoms if person’s immune system is weakened by a disorder,
pregnancy, or medication

Question 10

Pathogenesis

Answer 10

ingested by intermediate host-> oocysts transform to tachyzoites-> multiply in pseudocytes by binary fission-> destroy infected cells in acute infection-> localize in neural and muscle tissue-> spread by macrophages-> mesentric lymph nodes-> distant organs by lymphatic system

Question 11

Pathogenesis in cats

Answer 11

more infected by bradyzoites than oocysts->penetrate through intestinal epithelia-> multiplies and forms schizonts-> oocysts discharged into intestinal lumen

Question 12

Clinical signs in cats

Answer 12

immunosuppression induces cyst rupture, tachyzoite replication and tissue damage-> oocysts-induced most severe in intermediates

Question 13

Clinical Signs

Answer 13

fetal death, fever, dyspnea, jaundice, ascites, Uveitis, CNS deficits, splenomegaly, lymphadenomegaly

Question 14

Pathologic Lesions

Answer 14

-congested, mottled, hemorrhagic lungs->immune cell infiltrates
-hepatic necrosis
-necrotizing myocarditis and splenitis
-encephalitis

Question 15

Diagnostics

Answer 15

ELISA->positive IgM titres develop in 80% of animals 1-4 weeks post-infection-> negative by 16 weeks-> positive IgG titres develop 3-4 weeks post-infection->2-4 weeks after initial detection
Indirect fluorescent antibody test, Modified agglutination test, Immunosorbent agglutination assay

Question 16

Management

Answer 16

-secure zoos to prevent free-roaming cats entrance-> zoo animals very susceptible to disease
-limit contact with wild and feral cat populations
-reduce intermediate host populations
-thoroughly clean hands and avoid contamination products