Haemoflagellates

Leishmania spp.

Trypanosoma spp.

Epimastigote

Haemoflagellates of medical importance

There are 4 parasitic stages (or forms):

• Amastigote & Trypomastigote occur in vertebrate hosts

• Promastigote & Epimastigote occur in invertebrate hosts

Amastigote Trypomastigote Promastigote

Leishmania spp. and Trypanosoma spp. have digenetic life cycles, involving vertebrate hosts (man and reservoir animals) and invertebrate hosts (arthropods: vectors).

Amastigotes (donovan bodies):• Non-motile intracellular stage.

• In vertebrates hosts.

Morphology)

Promasitogtes (flagellated form):• Motile (with anterior flagellum)

Morphology)

Trypomasitogtes (flagellated form):

• Motile (with anterior flagellum & undulating membrane).

Trypanosomes are flagellated protozoa,

trypomastigote in shape, with elongated body,

central nucleus, posterior kinetoplast ,

long undulating membrane and anterior free flagellum.

Trypanosomes

TrypanosomiasisParasitic diseases caused by Haemoflagellates

belonging to the genus Trypanosoma. There are 2 main forms:

[1] African Trypanosomiasis [Sleeping sickness]: A] West African Sleeping sickness

caused by Trypanosoma brucei gambiense

B] East African Sleeping sickness

caused by Trypanosoma brucei rhodesiense

[2] American trypanosomiasis [Chagas’ disease]: caused by Trypanosoma cruzi

Trypanosomiasis African Trypanosomiasis (Sleeping sickness): caused by species of T.

brucei complex and transmitted by Glossina spp. (tsetse fly):

T. b. gambiense West African Trypanosomiasis

T. b. rhodesiense East African Trypanosomiasis

American Trypanosomiasis (Chagas’ disease): caused by T. cruzi and transmitted by Triatoma spp. (winged bug). Occurs in Central & South America

Classification

1- Polymorphic trypanosomes

The parasite has different size & shape in blood

e.g. T. brucei complex:

a] T. brucei gambiense & b] T. brucei rhodesiense

2 -Monomorphic trypanosomes The parasite has the same size & shape in blood

e.g.T. cruzi

Polymorphic

trypanosomes

Monomorphic

trypanosomes

Trypanosomiasis

[1] African Trypanosomiasis [Sleeping sickness]:

Tributary of Lopori River near Bongan danga in

Gambiantrypanosomiasis-endemic area of

northwestern Democratic

Republic of the Congo. Note forested Tsetse

flies

[1] African Trypanosomiasis[Sleeping Sickness Disease]

Geographical distribution: corresponds to that of the vector which is approximately 20° N & 20° S of the equator

G. palpalis

In West & Central Africa

G. morsitans

In East Africa

Annual cases estimated in 50.000–70.000:

HabitatDuring the early stages of the disease; Trypanosomes are found extracellular in the peripheral blood

/ lymph / tissue spaces of various organs of R.E.S. [Liver, Lymph nodes, Bone marrow, Spleen].

In the terminal stages; in CNS

a- D.H. ( man) b- R.H. (animals) as,

antelopes, pigs, goats, dogs ;

in which the parasites exist as Trypomastigotes only in their blood stream.

5 mm

Tsetse Fly

• Glossina sp. (tsetse fly),

• the vector of African trypanosomiasis

• both males and females can serve as vectors

Vector: Glossina spp. [tse tse fly],

Transmission: Cyclopropagative transmission.

Infective stage: Metacyclic trypomastigotes.

Mode of transmission

Bite of the fly : infective stages are introduced with the Saliva of

infected vector; (Anterior station transmission,) &

may be transmitted by

- mechanical transmission (e.g. stomoxys)

- blood transfusion,

- organ transplantation

- congenital

T. brucei: only as trypomastigotes in vertebrate hosts, presenting with different size and shape in blood [Polymorphic].

Morphology

Morphology [Cont.]

a- Epimastigote in the midgut.

b- Metacyclic or short stumpy trypanosomes (infective stage) in salivary gland.

2 .in the vector

Life cycle of African trypanosomiasis

Life cycle of T. gambiense & T. rhodesiense During a bite, infected tsetse-flies ( & ♀

) inject ♂ metacyclic trypomastigotes into skin tissue of hosts.

These transform into bloodstream trypomastigotes and are carried to

various body fluids (blood, lymph, spinal, etc..) where they multiply by binary

fission (T. rhodesiense much more actively than T. gambiense).

Affected CNS sleeping sickness. New vectors ingest trypomastigotes

from infected hosts. These transform into dividing procyclic trypomastigotes that migrate to salivary gland, convert into

multiplying epimastigotes, then transform to infective metacyclic trypomastigotes.

2- Haemolymphatic stage [Blood & Lymph nodes]

Trypomastigotes invade blood & lymphatic system and multiply producing >>>Toxic manifestations & Lymphocytic hyperplasia.

Enlarged liver & spleen, lymphadenopathy especially in posterior triangle of neck >>>

“Winter bottom sign”

2- Haemolymphatic stage [Blood & Lymph nodes]

Trypomastigotes invade blood & lymphatic system and multiply producing >>>

Toxic manifestations: Patient gets irregular fever, headache, joint & muscle pain and rash.

Bone Marrow affection: Anaemia [Hypoplastic anaemia], Leucopenia & Thrombocytopenia.

3- Meningoencephalitis stage [CNS] (Sleeping sickness stage)

By end of 1st year; Trypomastigotes invade CNS >>

perivascular infiltration of cerebral vessel with chronic inflammatory cells

>> ischaemia & haemorrhage >> Meningoencephalitis & Meningomyelitis.

Patient suffers of: Severe headache, mental apathy, slow speech, tremors,

involuntary movements & convulsions.

Sleeping stage develops >> Coma & death [from the disease or from

intercurrent infections as pneumonia].

Coma before death

Section of cerebral cortex ofZambian patient with Rhodesiantrypanosomiasis, showing markedcongestion and scattered petechialhemorrhaging in white matter.

Gambian Sleeping sickness

[T. gambiense ]

Parasite: Less virulent

Disease Progresses slowly; Chronic

Parasite in blood: Scanty [Low parasitaemia.

Typical sleeping sickness symptoms.

Animal inoculation: Refractory

Rhodesian Sleeping Sickness

[T. rhodesiense ]

Extreme virulence

Progresses rapidly. Acute

Plenty [High parasitaemia].

Usually fatal before sleeping sickness symptoms appear.

Susceptible with posterior-nuclear shift.

Clinical features of Gambian and Rhodesian disease are similar, but they vary in severity and duration:

Diagnosis of African trypanosomiasis

I- Clinical diagnosis History Fever especially if associated with enlarged lymph nodesResidence or traveling to endemic area. Clinical picture.

II- Laboratory Diagnosis Direct. Indirect.

Direct Laboratory Diagnosis To demonstrate the parasite Early: in chancre aspirate, blood, lymph

node, bone marrow & Late: in CSF BY

a) Microscopic examination of fresh unstained or Giemsa

stained films: >>> polymorphic trypomastigote.

b) Culture (NNN or Weinmann’s media: >>>

epimastigote.

c) Animal inoculation

d) CSF examination: Trypomastigotes, and Morula cells;

vaculoted plasma cell. ==

. ==

Morula cell of Mott

Polymorphic Trypanosomes in blood film

Polymorphic Trypanosomes in blood film

Diagnosis

Aspiration of swollen gland Lumber puncture for CSF

==Laboratory diagnosis

Card Agglutination Trypanosomiasis Test [CATT]: It is a simple & rapid test for detection of circulating antigens in the blood of the patient. It is useful in surveys specially for T. b. gambiense.

Other methods: Molecular techniques (e.g. PCR).

==Indirect Laboratory diagnosis

Detecting anti-Trypanosoma Abs by serological methods (ELISA, IFA, IHA etc..), But can't distinguish between current and previous infections.

How can African trypanosomes evade the host immune system?

Parasite’s surface is coated with a layer of glycoprotein called Variable Surface Glycoprotein “VSG” - coat protein -.

Antigenic Variation

After infection, the host evokes an immune mechanism against Parasite’s surface coat protein [VSG].

The parasite changes this surface glycoprotein to protect the underlying surface membrane from the host’s defence mechanisms.

New populations of parasites with different coat proteins appear >>> can not be recognized >>> and can not be attacked by the immune factors specific to the previous generation .

TreatmentEarly

1- Suramin (Antrypol):

Late (Drugs that pass CNS barrier)1-Tryparsamide

2- Melarsoprol (Mel B)

Early & late stages 1- Eflornithine

Prevention & control

1- Protection by skin repellents.

2- Treatment of patients.

3- Control of Glossina (vector).

4- Chemoprophylaxis in endemic areas

[Pentamidine at 4-6 months intervals].

No vaccine