Transcript MEDICAL PARASITOLOGY & ENTOMOLOGY

MEDICAL PARASITOLOGY
&
ENTOMOLOGY
LECTURER:
SR. NORAZSIDA RAMLI
BLOOD & TISSUE
FLAGELLATES/
HAEMOFLAGELLATES
Morphologic forms
There are 4 morphologic forms seen in
hemoflagellates:
1) Amastigote
2) Promastigote
3) Epimastigote
4) Trypomastigote
-they can exist in two or more of the 4
morphologic forms  depending on the
species.
Kingdom: Protisata
Phylum: Sarcomastigophora
Class: Zoomastrgophora
Order: Kimetplastida
Family: Trypanosomatidae
Genus: Trypanosoma
Species: brucei, cruzi, rangeli
Trypanosoma sp.
T. brucei gambiense
- cause: West African sleeping sickness
T. brucei rhodesiense
- cause: East African sleeping sickness
T. cruzi
- cause: American trypanosomiasis or
‘Chagas’ disease.
T. rangeli
- Cause: T. rangeli infection.
T. b. gambiense
Cause West African sleeping sickness.
“tsetse fly belt” is a large area of Africa that
has reported cases of African sleeping
sickness.
Vector/ intermediate host: Glossina
(tsetse) fly.
T. burgei gambiense
Tsetse fly
West African sleeping sickness
Also known as Gambian trypanosomiasis.
Can be found in the wet lowlands and
rainforest of west and central Africa where
the tsetse breed in the moist areas around
riverbanks.
Chronic course- ends with central nervous
involvement and death after several years
of durations.
Geographical
distribution
The savanna vectors
G.morsitans and G.
palidipes are
responsible for the
transmission of T.
rhodesiense in East
Africa, while the
principal vectors of
west African sleeping
sickness are G.
palpalis, G. fuscipes
and G. tachinoides.
Life cycle of T.brucei
Transmission
-
-
Occurs through:
the bite of an infected tsetse fly,
blood transfusion,
Organ transplant, and
congenital transmission (from pregnant
mother to fetus).
Pathogenesis
Infection is characterized by 3 progressive
stages:
1) An asymtomatic incubation period
-right after infection
-a few days to several weeks.
-non African shorter than African natives.
-parasite multiply locally.
-local inflammation leads to the development
of a painful ulcerative lesion called:
trypanosomal chancre at the bite site.
2) Hematogenous spread of the parasites
and the involvement of the lymphatic
system.
- Trypomastigotes may be seen in the blood
film examination.
- Symptoms: febrile (fever) followed by
afebrile periods, headache, malaise,
weakness, anorexia, and night sweats.
- Glandular enlargement and
lymphadenopathy (enlargement of the
lymph nodes).
- Enlargement of the postcervical chain of
lymph nodes, which is known as
‘Winterbottom’s sign’.
Symptoms of glandular stage:
-erythematous (red) rash
-pruritus (severe itching)
-localized joint edema (swelling)
-delayed sensation of pain (Kerandel’s sign).
3)Meningoencephalitic stage
-CNS involvement
-6 months to a year after the onset of 1st
symptoms.
-the patient’s health deteriorates with increased
fatigue
-mental dullness
-apathy
-diminished motor control
-somnolence (excessive sleepiness)
-emaciation
-trypomastigotes may be seen in the patient’s
spinal fluid
-sleepiness progresses to coma and eventual
death
Diagnosis
Microscopic examination
Concentration technique – centrifugation
Serologic technique – Card Agglutination
Trypanosomiasis Test (CATT)
Treatment
Pentamidine isothionate
-used to cure Gambian trypanosomiasis in
the hemolymphatic stage of infection.
-administered by intramuscular injection.
-effective only in the early stage of disease
bcoz of its inability to cross the ‘bloodbrain barrier’.
-
Suramin
Effective only in the early stage of disease
b4 CNS involvement
Administered intravenously
Has more toxic side effects than
pentamidine.
May be prescribed during pregnancy.
-
Melarsoprol
A triavalent arsenic compound.
Much more toxic than pentamidine or
suramin.
Effective for later stages
Administered intravenously
Can effectively penetrate the blood brain
barrier
Prevention
Control, management & avoidance of the insect
vector
Clearing of vegetation where tsetse flies breed
Wide use of insecticides
Travelers to endemic areas encouraged to wear
long sleeved protective clothing
Wear thick Khaki or olive drab clothing coz
tsetse flies are attracted to bright and dark
colors.
Use bed net
Insect repellent
T. burgei rhodesiensi
T. brucei rhodesiense
Course of East African sleeping sickness
1st isolated from a patient in Rhodesia
Clinical presentation- more fulminant
course and severe symptoms
The incidence is far less than Gambian
disease but if left untreated – death will
ensure within several weeks to months
rather than years.
Life cycle
Similar to T.b. gambiense
Transmission
Transmitted by the bite of an infected
tsetse fly:
-G. pallidipes
-G. morsitans
-G. swynnertoni
Pathogenesis
Produce a more acute form
Stages of disease and symptomology
similar with Gambian infection.
Disease progress rapidly
Much shorter clinical course
Incubation period: shortened by the abrupt
onset of febrile episodes
Laboratory diagnosis
Similar to T.b.gambiense
Treatment
Similar to T.b.gambiense
No vaccine available
T. cruzi
Cause of American trypanosomiasis/
chagas disease.
Chagas disease: named for the Brazilian
medical student, Carlos Chagas – who
has discovered the parasite in 1909.
Has an intracellular amastigote stage that
develops in cardiac, brain and visceral
tissues.
Also has trypomastigotes in the peripheral
circulation.
T. cruzi
Geographical distribution
Life cycle of T. cruzi
Trypanosoma cruzi vector
Triatomine bug,,
defecating on the
wound after taking
a blood meal
Reduviid bug - triatoma species
Ideal habitat for reduviid bugs
Transmission
Transmitted by : reduviid bug
-also known as kissing bug or triatomid bug.
-vector: genus Panstrongylus or Triatoma
Transmitted via:
-the bite of infected vector
-blood transfusion
-transplacental route
-accidental ingestion of an infected insect
Treatment
Nifurtimox
Allupurinol
Benznidazole
Diuretic treatment
Surgical intervention