Trypanosomiasis Flashcards
What are the 2 subspecies of African Trypanosomiasis? What disease does this cause?
T. brucei rhodesiense
T. brucei gambiense
African sleeping sickness
What is the subspecies of American trypanosomiasis? What what disease does this cause?
T. cruzi and Chagas Disease
Describe the different Human Trypanosomiasis infections?
African Trypanosomiasis (African sleeping sickness)
- East African Trypanosomiasis is an acute infection caused by T. brucei rhodesiense
- West African Trypanosomiasis is a slow prgressing and chronic infection caused by T. brucei gambiense
American Trypanosomiasis (Chagas disease)
- caused by T. cruzi
What subspecies of Trypanosomiasis only affects animals? and what disease does this cause?
T. brucei brucei and Nagana
Nagana
Caused by T. brucei brucei and infects wild/ domestic animals (not humans)
Describe the physical properties of African trypanosomes.
- Protozoan hemoflagellates
- unicellular
- does not have an intracellular form
- T. brucei gambiense and T. brucei rhodesience are not morphologically distinguishable
What does African trypanosomasis replicate as in a host?
multiply as trypamastagotes that circulate mammilian blood stream and other extracellular spaces
What is the African trypanosome vector? How are they distinguishable?
Tse Tse fly (blood sucking fly)
They fold their wings completly so that 1 wing rests directly on top of the other and they have a long probosis which is attached by a distint bulb to the bottom of its head
Where does Human African trypanosomiasis occur?
Only in sub-Saharan Africa
How is African trypanosomiasis transmitted?
- mostly via vector (Tse tse fly)
- rarely via: transfusion, mother to child, mechanical transmission via other blood sucking insects, lab accidents, and sexual transmission
Describe the lifecycle of African Tryanosomiasis.
- Tsetse fly takes a blood meal and injects metacyclic trypomastigotes (infectious stage) into host
- Injected metacyclic trypamastagotes transform into bloodstream trypomastigotes which are carried to other sites
- Trypomastigotes multiply by binary fission and circulate (diagnosic phase)
- Tsetse fly takes a blood meal and injests the bloodstream trypomastigotes
- Bloodstream trypomastigotes transform into procyclic trypamastigotes in the tsetse fly midgut where they also mutiply by binary fission
6.Procyclic trypamastigotes leave the midgut and transorm into epimastigotes - epimastigotes multiply in the salivary glands and transform into metacyclic trypamastigotes and the cycle repeats with other blood meal
What is the incubation period for T. brucei rhodesiense?
3-21 days (usually 5-14)
What is the incubation period for T. brucei gambiense?
longer than the rhodensiense but not well defined
Describe the pathogenisis of T. brucei.
A bite from an infected tsetse fly causes a chancre where interstitial multiplication of trypanosomes occurs. Here there is an intense mononuclear cell rxn to the parasite causing the parasite to move to the lymph nodes causing an inflammatory response and they move through the bloodstream and lymphatic system (continuing to replicate). The parasite can alos egress from vessels into intersticial spaces and increase vessel impermeability.
The parasite can also reach the brain and menegies causing meningoencephalitis.
What are self-protecting machanisms of the parasite in the host?
- they change the surface coat of the outermembrane of the trypamastogotes to help them evade the host’s immune system
- Antigenic Variation: the trypomastigote surface is covered in a dense coast of vsg’s (variant surface proteins) which is changed about every 5-7 days and causes a wave of parasitemia every 1-2 weeks and allows the parasite to evade host immune responses
What are the 2 stages of African trypanosomiasis?
- hemolymphatic stage: from bite to brain, parasite is found in circulation but has not invaded the CNS
- Meningoencephalitis stage: infection of the CNS
What are the clinical manifestations of T. brucei gambiense?
- a cutaneous nodule (chancre) at the site of tsetse fly bite
- chronic illness occuring minths to years later and characterized by intermittent fever, posterier cervical lymphadenopathy (winterbottom sign; essencilly inflammed lymph nodes)
What are the clinical manifestations of T. brucei rhodesiense?
Generalized illness developed days to weeks after parasite inoculation. Acute illness characterized by high fever, thrombocytopenia, hepatitis, myocarditis, cutaneou chnacre, and anemia
What are the important differences between the rhodesiense and gambiense subspecies?
Rhodesiense:
- primary resovior’s are cattle, antelope, domestic pigs and dogs
- acute early CNS disease
- progresses rapidly
- a large sore at the site of tsetse fly bite
- severe symptomes at first: high fever, headache, muscle pain, enlarged lymph nodes
- death within months if not treated
Gambiense:
- Primary resovoir is humans
- Chronic late CNS disease
- progresses slowly
- mild symptoms at first: intermediate fever, headache, muscle and joint pain
- Death within years (6-7) if not treated
- Parasites in blood= low
How is African Trypanosomiasis diagnosed?
- microscopy of blood, lymph fluid, chancre biopsy/ aspirate, and CSF (must to do this): this is good for both subtypes
- Serology (not FDA approved)
Epimastigotes
- Nucleus and kinetoplast are close to each other
Trypomastigote
- Blood stream form
- Has a undulating membrane
- kinetoplast and kinetosome at the posterior end behind the nucleus
What are the labratory morphological features of T. cruzei and T. brucei?
T cruzei:
- trypomastigote form has a large posterior kinetoplast and undulating membrane with anteriorly directed flagellum
- exhibists a C-shaped form
- dividing form does not exist
T. brucei:
- flagellum that begins as an undulating membrane originating posterior to the kinetoplast
- have small kinetoplats
- dividing forms can be seen
Treatment for both subspecies of T. brucei for clinical stage 1 and 2?
Stage 1: Suramin and Pentamidine (only for gambiense)
Stage 2: Melarsoprol and Eflornithine (only for gambiense)
All thse drugs are very toxic and cause terrible side effects in paitents!!
