MMI 426 - Lec 2 African Trypanosomiasis

features of African trypanosome

• posteriorly located kinetoplast

• centrally located nucleus

• dividing body

• undulating membrane + a flagellum running along undulating membrane

trypanosome classification

order = kinetoplastida family = trypanosomatidae genus = trypanosoma

what are the two African trypanosomiasis subspecies

1. T. brucei rhodesiense

2. T. brucei gambiense

species causing East African Trypanosomiasis

T. brucei rhodesiense -- assoc w/ acute

species causing West African Trypanosomiasis

T. brucei gambiense -- assoc w/ chronic

T. brucei brucei

infects wild and domestic animals (not human) and causes a disease called nagana

another name for African trypanosomiasis

African sleeping sickness

species causing American trypanosomiasis

T. cruzi

Another name for American trypanosomiasis

Chagas disease

morphological description of African trypanosomes

• protozoan hemoflagellates

• no intracellular form and multiply as trypomasteogotes that circulate in blood + extracellular space

are the 2 subspecies of African trypanosomes morphologically distinguishable

no

vector for African trypanosomes

tsetse fly from Glossina genus (found only in sub-Saharan Africa)

rare modes of transmission of T. brucei

• transfusion

• mom to baby

• mechanical transmission that isn't blood sucking fly

• lab oopsies

• sexual contact

glossina morphology

• fold wings so one will sit on top of the other over their abdomen

• long proboscis that extend directly fwd and is attached by bulb to the bottom of head

glossina features

obligate parasites

incubation period of T. brucei rhodesiense

3-21 days (usually 5-14)

incubation period of T. brucei gambiense

not well defined

longer than 3-21 days tho

stages of T. brucei pathogenesis

1. hemolymphatic stage

2. CNS stage

hemolymphatic stage of T. brucei pathogenesis

• bite -> chancre -> brain

• parasite found in circulation but not yet in CNS

CNS stage of T. brucei pathogenesis

also known as meningoencephalitis stage

unqiue feature of African trypanosomes (self protecting mechanism against host)

can change their surface antigen to evade host immune response

clinical manifestations of T. brucei gambiense

• cutaneous nodule or chancre
• chronic
• Winterbottom's sign

Winterbottom's sign

posterior cervical lymphadenopathy that shows up below the neck during 1st stage of disease

clinical manifestations of T. brucei rhodesiense

- generalized illness, shows up more acute after parasite inoculation

- symptoms of high fever, thrombocytopenia, hepatitis, myocarditis, cutaneous chancre, anemia

diagnosis of T. b. rhodensiense

microscopy using blood (see high parasitemia), lymph node fluid, chancre biopsy + aspirate, and CSF

diagnosis of T. b. gambiense

microscopy using lymph node aspirate (usually posterior cervical node), blood, chancre aspirate, CSF

can you use serology to diagnose T. b spp

can do CATT, ELISA, and IFA but not FDA approved

when are trypomastigotes highest in blood

during febrile periods

infective stage of African trypanosome

metacyclic trypomastigotes

morphological features of African trypanosome

looks more slender, smaller nuclei, more delicate and thinner

how are infected patients with African trypanosomiasis isolated

follow standard iso precautions because infection is spread by flies

prevention of African trypanosomiasis

• elimination of vector using SIT
• drug treatment
• use insect repellant

do African trypanosomes have intracellular forms and multiply as trypomastigotes that circulate the mammalian blood stream and extracellular space

true