BLOOD FLAGELLATES

DALIA KAMAL ELDIEN MOHAMMED

Introduction

The family Trypanosomatidae (include hemoflagellates), contain only two genera that parasitize humans.

Genus Trypanosoma contains members that may be found both in the circulating blood and intracellular

Genus Leishmania are always intracellular, mainly in the reticuloendothelial system.

vectors

In all probability, the hemoflagellates were originally parasites of insects, they are transmitted by insects, serves as intermediate host:-

American trypanosomiasis - transmitted by reduviid bugs; transmission occurs when infective feces of the bug contaminates the wound made by the insect's bite or an abrasion of the skin.

African trypanosomiasis - transmitted by Glossina spp. tsetse flies.

"Old World” leishmaniasis - transmitted by the bite of various species of sandflies of the genus Phlebotomus.

South American leishmaniasis - carried by Lutzomyia spp. sandflies.

TAXNOMAY

Kingdom: Protista Subkingdom: Protozoa Phylum: Euglenozoa Subphylum: Kinetoplasta (unique

mitochondrion with large disc of DNA called the Class Trypanosomatidea kinetoplast)

Order: Trypanosomatidea

Common species

Trypanosoma brucei brucei

Trypanosoma brucei rhodesiense

Trypanosoma brucei gambiense

Trypanosoma cruzi Trypanosoma

equiperidum Trypanosoma lewisi

Leishmania tropica Leishmania major Leishmania donovani Leishmania braziliensis Leishmania chagasi Leishmania mexicana

Morphological characteristic

Spindle-shaped body Central nucleus and Kinetoplast (mitochondrial

genome ) Motility by Flagellum or flagellum and undulating

membrane Most are heteroxenous, requiring development

within two hosts in life cycle

Morphology of Kinetoplast family

Genus Trypanosoma, cause 2 diseases in human

1- African trypanosomiasis (sleeping sickness) T. brucei rhodesiense, causing acute trypanosomiasis. T. brucei gambiense, causing chronic

trypanosomiasis.

2- American trypanosomiasis (Chagas’ disease) Trypanosoma cruzi Blood transfusions are a rare cause of parasitic

transmission

African trypanosomiasis

Life cycle

Infected tsetse fly bites a host to take a blood meal & inoculates metacyclic trypomastigotes with saliva into the bite wound.

The organisms rapidly transform into trypomastigotes and which multiply at the site of inoculation by binary fission, and later in the blood, lymphatic system, and tissue fluid.

They are carried to the heart and various organs of the body and in the later stages of infection

The tsetse fly takes blood meal from an infected host containing trypanosomes.

In the midgut of the fly, the parasites develop and multiply. After 2–3 weeks, the trypomastigotes migrate to the salivary glands of the tsetse fly where they become epimastigotes, multiply, and develop into infective metacyclic trypomastigotes.

tsetse fly

Epimastigote& trypomastigote

pathology

African trypanosomiasis is a wasting disease which is usually fatal unless treated.

For T. b. gambiense human is the main reservoir Rhodesiense trypanosomiasis is a zoonotic infection,

many game animals and cattle are infected. Early stage of infection, There is a high irregular

fever, sweating, and an increased pulse rate. There is a persistent headache, and usually pains in the neck and shoulders. The lymph glands become swollen.

Late stage of the disease The trypanosomes invade the central nervous system, giving symptoms of meningoencephalitis

Lymph node enlargement

laboratory diagnosis

Specimen:- Blood bone marrow aspirate from chancre(skin sore develops

at bite site ) lymph node aspirate late stage collect CSF.

chancre

Direct microscopical exam for trypomastigotes in the blood

1- Examination of a thick stained blood film.2-Microhaematocrit concentration technique3-Triple centrifugation tube technique to

concentrate trypanosomes when a microhaematocrit centrifuge is not available.

Thick blood film

Collect a drop of capillary blood on a slide and spread it to cover evenly an area 15–20 mm in diameter.

Allow the smear to dry completely in a safe place Stain the film using Field’s rapid technique for thick

blood films or Giemsa staining technique When dry, spread a drop of immersion oil on the film

and examine it microscopically by X100 Trypomastigote stage (the only stage found in

patients), posterior kinetoplast, a centrally located nucleus, an undulating membrane, and an anterior flagellum, length range is 14 to 33 µm.

Trypanosoma brucei sp. trypomastigotes

Microhaematocrit concentration Centrifuge the capillaries in a microhaematocrit

centrifuge for 3–5 minutes Examine immediately the plasma just above the

buffy coat layer for motile trypanosomes The preparation must be examined within a few

minutes of the blood being centrifuged For CSF Examine sediment, wet or fixed &

stained, examine the cells, it is increased with present of special cell name as Morula or Mott cells

Microhaematocrit

Morula

Indirect methods [Serologic tests]

Demonstrating Anti- trypanosoma antibodies in serum: e.g. IFAT, IHAT, ELISA.

Culture

CSF, blood, bone marrow aspirate, or tissue specimens can be performed in liquid media.

Other tests low hemoglobin with reticulocytosis high ESR moderate leucocytosis with monocytosis&

lymphocytosis

American trypanosomiasis

American trypanosomiasis

The vector is Reduviid bugs - blood sucking bugs, Reduviidae has 22 subfamilies, including the Triatominae

Infected insects take blood meals from humans and their domestic animals and deposit parasite‑laden feces.

morphology

Trypomastigotes found in lymphatics and bloodstream, have a prominent subterminal kinetoplast, an elongated nucleus and an undulating membrane, appear with a typical C or S-shaped form.

Amastigote phase, which grows in a variety of tissue cells especially muscle.

Epimastigotes are an extracellular and non infective form of the parasite found in the midgut of insect vectors, where they multiply by binary fission.

Metacyclic trypomastigotes, which are non dividing forms that have the capacity to infect mammalian cells.

Trypomastigotes& Amastigote

pathogen icity

Following penetration, the metacyclic trypomastigotes invade muscle and other tissue cells near the point of entry and multiply intracellularly as amastigotes.

Multiplication of T. cruzi at the site of infection, together with a host cellular immune response, can produce an inflamed swelling known as a chagoma which usually persists for several weeks.

If the site of infection is the eye, usually the conjunctiva becomes inflamed and oedema forms. This is known as Romana’s sign.

chagoma

Laboratory diagnosis

Microscopic examination

a) of fresh anticoagulated blood, or its buffy coat, for motile parasites

b) of thin and thick blood smears stained with Giemsa, for visualization of parasites.

Isolation

a) culture in specialized media

b) Xeno diagnosis, where uninfected reduviid bugs are fed on the patient's blood, and their gut contents examined for parasites 4 weeks later.

Serology

trypomastigote

Amastigotes in heart muscle