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Flashcards in Microbiology-Trypanosomes Deck (22)

Why are trypanosomes also called kinetoplastidae?

They have an organelle called the kinetoplast which has its own DNA and is in close association with the basal body of the flagella.


Causative agent of west African trypanosomiasis? How does it present? What is the vector?

T.b. gambiense. This is the more subacute form of HAT and can cause changes in cognition, behavior and psychosis. It is transmitted by the glossina palpalis tsetse fly near water.


Causative agent of east African trypanosomiasis? How does it present? What is the vector?

T.b. rhodesiense. This is the more acute and severe form that results in death within a year. It is transmitted by the glossina mortisans tsetse fly in savannah areas and feeds on wild game.


What is the life cycle of trypanosoma brucei gambiense and trypanosoma rhodesiense?

Tsetse fly takes blood meal & injects metacyclic trypomastigote -> Trypomastigotes multiply by binary fission in blood, lymph, CSF -> Tsetse fly takes blood meal and bloodstream trypomastigotes are ingested -> Bloodstream trypomastigotes transform into pro cyclic trypomastigotes in tsetse fly gut and multiply -> Procyclic masticates transform to epimastigotes -> epimastigotes multiply in salivary gland and become metacyclic trypomastigotes.


Identifying the tsetse fly

Male & female mate 1x. Cleaver cell in wing.


Presence of tsetse fly means absence of what?

Cattle. They carry nagana which causes lots of livestock death.


Stages of Human African Trypanosomiasis (HAT) infection?

1) Hemo-lymphatic stage: chancre at inoculation site, fever, headaches, muscle pain and Winterbottom’s sign (enlarged posterior cervical lymph nodes) 2) Meningo-encephalitic stage: elevated ICP, Mott cells (plasma cells containing lots of IgM), elevated protein in the CSF and polysomnography (discombobulation of REM cycles throughout day)


Why is there not a vaccine for HAT?

Antigenic variation of the variant surface glycoprotein (VSG) is continually rearranged by the var gene.


Diagnosing HAT?

Giemsa-stained blood smears. LP must be done for stage 2. Card agglutination trypanosomiasis test for T. b. gambiense (CATT test).


Tx for HAT

Stage I) Pentamidine and suramin. Stage II) Melarsoprol (both gambiense and rhodesiense) or eflornithine (gambiense)


Side effects of melarsoprol

Local site and vein sclerosis, it is basically arsenic. It also causes encephalopathy and peripheral neuropathy.


Vector controls for HAT

The tsetse fly (glossina) like the color blue, so make the traps blue. 


Life cycle of American trypanosomiasis

Triatomine bug takes blood meal -> Metacyclic trypomastigote passed in feces and enters bite wound -> Transform into amastigotes and multiply by binary fission -> Infect other cells -> Intracellular amastigotes transform to trypomastigotes and lyse cells to enter blood stream -> Triatomine bug takes blood meal -> Epimastigotes in midgut -> Multiply and become metacyclic trypomastigotes in hindgut


Important reservoirs of T. cruzi? Important vectors?

Reservoirs: Possums, armadillos and tree sloths. Vectors: reduviidae: triatoma (infestans is most notorious), rhodnius and panstrongylus. 


How does the kinetoplast differ in Chagas from HAT?

It is much larger in T. cruzi.


Where do the triatomes like to live?

In cracks of poorly constructed housing


2 pathogens involved in Chagas disease?

T. cruzi I: less pathogenic, more commonly seen in animal reservoirs. T. cruzi II: more commonly seen in human reservoirs


Non-vector transmission of Chagas disease

Blood transfusions, organ transplants, vertical transmission (pregnancy)


Common presentations of Chagas disease

Romania’s sign: unilateral painless periorbital edema. Chagoma: indurated lesion at site of parasite entry.


Progression of disease with Chagas

60% remain indeterminate (asymptomatic). The parasites nest in the heart, cause bundle branch block, apical aneurism and chronic cardiomyopathy. It also causes mega-esophagus and mega-colon.


Diagnosing Chagas disease

Serology, PCR, peripheral blood smear and xenodiagnosis (lab raised bugs are sacrifices and you look for parasites in them)


Treating Chagas? What is the cure rate?

Benznidazole and nifurtimox. If disease has been presented longer cure rates go lower, but if tx happens < 1 year after infection, resolution is 100%.