Leishmaniasis / Toxoplasmosis / Trypanosomiasis Flashcards
What is the definitive host of Toxoplasma gondii?
Cats
How long is someone infected with Toxoplasma gondii?
Lifelong
Who will present with Toxoplasma gondii infection?
Most people are asymptomatic
Disease manifests in immunocompromised or neonates infected in utero
What are the 3 stages of the life cycle of Toxoplasma gondii?
Oocysts - excreted in feces of cats (definitive host)
Tissue cysts - intracellularly in muscle of intermediate hosts
Tachyzoites - replicate within cells
What are modes of transmission of toxoplasmosis?
Oocysts - soil, cat litter
Tissue cysts - undercooked meat (espec pork and lamb)
Tachyzoites - transplacentally, transplant, transfusion
In what environment is toxoplasmosis common?
Places where meat is undercooked (steak tartar, pork)
How does toxoplasmosis present in healthy host?
Acute infection - tachyzoites
- Usually asymptomatic, occasionally lymphadenopathy
Chronic infection - tissue cysts
- Asymptomatic, lifelong
How does toxoplasmosis present in immunocompromised host?
Usually reactivated infection Cerebral infection (lesions) more common than cardiac or pulmonary
How does toxoplasmosis present in pregnancy?
Maternal infection early in pregnancy can cause miscarriage, abortion, severe neurological or ocular disease, generalized illness
Most congenitally infected infants are asymptomatic at birth but high risk for sequelae later in life
What is the presentation of ocular toxoplasmosis?
Common sequela of congenital toxoplasmosis
Focal necrotizing retinitis
Granulomatous inflammation of choroid
Blurred vision, pain
Focal scars with permanent loss of vision
How is toxoplasmosis diagnosed?
Serology
Appearance of lesions on MRI or CT
Atypical: brain biopsy
What is the treatment of choice for toxoplasmosis?
Pyrimethamine + sulfadiazine
How can toxoplasmosis be managed in pregnancy?
Spiramycin
How can toxoplasmosis be prevented?
Get rid of cat or change litter better
For HIV-infected <200 CD4 - TMP-SMX preventive therapy
What is the agent of Chagas disease?
Trypanosoma cruzi
What is the vector of Chagas disease?
Riduviid bugs
How is Chagas disease transmitted?
Vector borne - riduviid bug takes blood meal and defecates, rub feces into bite wound
Transplacental, transfusion, transplantation
Oral (unusual)
What is the life cycle of Trypanosoma cruzi?
Riduviid bug takes blood meal and defecates
Rub bite and innoculate parasite into wound
Goes through circulation to muscle, tryptomastigotes invade cells
Differentiates into amastigote and replicates
Amastigotes become trypomastigotes and rupture cell, enter blood stream
What is the clinical presentation of acute T. cruzi infection (acute Chagas disease)?
Usually asymptomatic
Mononucleosis-like febrile illness
Rarely - acute myocarditis (see amastigotes in cardiac myocytes), meningoencephalitis
What is the clinical presentation of chronic T. cruzi infection (chronic Chagas disease)?
Usually asymptomatic
Cardiomyopathy (destruction of cardiomyocytes and replaced with fibrotic tissue) - can get arrhythmias and complete heart block
GI disease - megaesophagus, megacolon
How is Chagas disease diagnosed?
Direct visualization of parasites in blood
Serology (IgG for chronic/past infection, IgM suggests acute)
What is the treatment for Chagas disease?
Nifurtimox
Benznidazole
What is the vector for Leishmania?
Sand fly
What is the life cycle of Leishmania?
Sand fly takes blood meal, innoculates parasite into skin
Promastigote stage ingested by macrophage
Multiplies and transforms into amastigotes inside macrophages
Sand fly takes another blood meal and ingests macrophages containing amastigotes
What immune response is required to control Leishmaniasis?
Cellular
What immune response dominates in visceral leishmaniasis?
Only humoral, no cellular (cannot control parasite well with just antibodies)
What immune response dominates in treated visceral, cutaneous, or mucosal leishmaniasis?
Cellular
What is the clinical presentation of visceral leishmaniasis (kala-azar)?
Hepatosplenomegaly (parasites in macrophages, macrophages building up)
Spiking fevers
What is the clinical presentation of mucosal leishmaniasis?
Almost all Leishmaniasis braziliensis
Lesions on nose
Immunological hyperreactivity but failure to clear parasites
What is the clinical presentation of disseminated leishmaniasis?
Lack of immunological reactivity
Get lesions filled with parasites
What is the clinical presentation of cutaneous leishmaniasis?
Small lesions on skin
See cells filled with amastigotes on histology
How is the diagnosis for visceral Leishmaniasis made?
Smears, cultures, PCR
Serological tests
Leshmanin skin test negative
How is the diagnosis for cutaneous Leishmaniasis made?
Smears, cultures, PCR
Sological tests
Leishmanin skin test positive
What is the treatment for Leishmaniasis?
Pentavalent antimony - Sodium stibogluconate (but very toxic)
Liposomal ampho B (treatment of choice in US)
Miltefosine (recently approved)
