38-39 - Toxoplasma gondii

How is Toxoplasma gondii transmitted?

• Ingestion of sporulated oocysts

• Ingestion of tissue cysts

• Both modes for IH and DH

What is the morphology of Toxoplasma gondii oocytes

2 sporocysts with 4 sporozoites

What is the only definitive host that allows for sexual replication of Toxoplasma gondii?

Cats (domestic and wild)

Life Cycle of Toxoplasma gondii

• Sexual reproduction in SI of cats

• Asexual replication in CNS and edible tissues in domestic livestock, birds, grazing wildlife, dogs, people

What species are possible IH for transmitting Toxoplasma gondii to cats?

All endothermic vertebrates (including people)

Clinical symptoms of Toxoplasma gondii

• Clinical Dz → typically in IH

  • Dogs → neuro dz, lymphadenopathy, respiratory, myositis

  • Sheep/Goats → abortion storms

• Cats → asymptomatic/non-specific

  • Intestinal Phase: diarrhea, soft stool

  • Tissue Phase: (asexual reproduction) repiratory dz + lymphadenopathy → can also migrate to brain, liver, lungs and many other organs

if a pregnant women’s toxoplasmosis test is IgM titer negative, but IgG titer is positive, who is at risk?

Both mother and baby are safe

• Will cause birth defects if mom is infected for the first time in her life (IgM positive)

• IgG → old infection → immune-compenent mom

• If she was IgM + → confirmatory test must be done to confirm

Pathogenesis of Toxoplasma gondii

• IC replication of tachyzoites in lungs → respiratory dz

• Tachyzoites in lymph nodes and macrophages → lymphadenopathy

Toxoplasma gondii → ~12um

Toxoplasma gondii → tachyzoites in upper left corner

• Banana-shape

Toxoplasma gondii → bradyzoites in brain of infected mouse

What is the 2nd leading cause of death from foodborne illness in the US?

Toxoplasma gondii

Why is Toxoplasma gondii a serious health issue in pregnant women?

• Congenital birth defects (blindness, hearing loss, learning disabilities) → won’t typically show until 10-20 years old

• Abortion

• Immunocompromised (HIV etc.) moms → death

How is Toxoplasma gondii diagnosed?

• Fecal exam

• ELISA

• MAT

• IFA

• PCR

• Tissue/Serum/Fluid Samples

What type of behavioral changes are found with Toxoplasmosis?

• Suble bx changes

• Women → more intelligent, outgoing, conscientious and kind

• Men → oppposite behavioral trends

• More prone to feelings of guilt

• Schizophrenia

Does eating meat increase the risk of toxoplasmosis?

Potentially, pork more likely than beef/chicken

How is Toxoplasmosis prevented?

• NOT based on cat exposure! → doesn’t increase infection

• Prevent exposure → most important! (especially in pregnant women and immunocompromised)

• Test cat → seronegative cat is more problematic

• Non-pregnant member should clean litterbox to get rid of oocytes

• Pregnant women eat well-done meat, avoid gardening

• Clean all meat/veggies

How specific and sensitive is PCR of toxoplasmosis?

90% specificity, 60% sensitivity

How is Toxoplasmosis treated?

• No FDA approved therapies!

• Trimethoprim-sulfa and pyrimethamine → against tachyzoites

• Clindamycin → tx of choice

• Atovaquone

• Ponazuril/Diclazuril → activity against apicoplast and tachyzoites