Leishmania And Trypanosoma

Blood and Tissue Flagellates – Chapter 5

Phylum Euglenozoa Class Kinetoplasta Order Trypanosomatida

The Order Trypanosomatida contains members which are _________________________ - live in blood or fixed tissues of vertebrates at some time in their life cycle.

Life cycles involve ___________________________- represent the original hosts of these parasites.

All forms utilize ___________________________- absorb nutrients from their hosts through the cell membrane (no phagocytosis or cytostomal ingestion)

Morphological Characteristics

All species possess a_____________________________, _______________________________, & _____________________________

__________________________– structure that gives rise to the flagellum

__________________________- dense area of mitochondrial DNA that gives rise to a mitochondrion - located just posterior to kinetosome

Kinetosome and kinetoplast are very close together – the kinetosome is too small to be resolved – only the kinetoplast is seen

Four Morphological Forms

1. _______________________________ (Leishman-Donovan [L-D] body) - intracellular form

- ovoid; 3 - 4 µm in size

- _____________________________

______________________________

Flagellum

Kinetosome

Kinetoplast

Nucleus

Four Morphological Forms

2. ______________________________ - elongate form

- 15 - 30 µm long

- ____________________________

- ____________________________

_____________________________

Flagellum

Kinetosome

Kinetoplast

Nucleus

anterior

posterior

Four Morphological Forms

3. ______________________________

- elongate form

- ______________________________

______________________________

- _______________________________

______________________________

Undulating membrane

posterior

Flagellated forms are adapted for movement through fluids of their hosts.

anterior

Four Morphological Forms

4. ______________________________

- elongate form

- _______________________________

______________________________

- _______________________________

______________________________

- _______________________________

______________________________

- 10 to 30 µm in length

Undulating membrane

posterior

Flagellated forms are adapted for movement through fluids of their hosts.

anterior

Leishmania and Trypanosoma

Of the seven genera in the Family Trypanosomatidae, only 2 genera, Leishmania and Trypanosoma, are important parasites of humans.

Not all parasites in the family possess all 4 morphological forms:

Leishmania spp. - possesses only amastigote & promastigote forms

Trypanosoma brucei - has only epimastigote & trypomastigote

Trypanosoma cruzi - has all four forms

Leishmania

Of the 12 species of Leishmania, 5 major recognized species infect humans:

Leishmania tropica

Leishmania major

Leishmania braziliensis - 3 subspecies

Leishmania mexicana - 3 subspecies

Leishmania donovani - 2 subspecies

Leishmania

Similarities:

1.

2.

Species are differentiated by:

1.

2.

3.

4.

5.

1. Sandfly bites infected vertebrate (human or reservoir host) and _______________

_________________________________________________________in the blood meal.

2. In sandfly midgut, amastigotes transform into ______________________________ that multiply by binary fission.

3. Promastigotes move to esophagus and pharynx of sandfly and are inoculated into vertebrate when sandfly takes another blood meal.

Life Cycle of Leishmania spp.

Amastigotes in lesions in skin & cartilage of the ear causing CHICLERO ULCER

4. In human, promastigotes transform into ___________________________________ that are then ___________________________________

5. Instead of being killed by the macrophage, the _____________________________ ________________________________________ and multiply by binary fission.

6. Amastigotes rupture out of macrophage, destroying it, and are phagocytized by new macrophages. Cycle is repeated for many generations.

Life Cycle of Leishmania spp.

Amastigotes in lesions in skin & cartilage of the ear causing CHICLERO ULCER

Leishmania tropica and Leishmania major

These two species have similar life cycles and clinical symptoms.

Both produce a cutaneous ulcer - disease is called _________________________ or CUTANEOUS LEISHMANIASIS (many other local names as well)

DISTRIBUTION:

L. tropica - densely populated areas of Middle East & India

 L. major - sparsely populated regions in Africa, Middle East & SW Asia

Leishmania tropica and Leishmania major

Both are vectored by Phlebotomus sandflies.

Reservoir hosts include ____________________________.

Disease is enzootic in these hosts and is capable of being transmitted from these reservoir hosts via sandflies to humans; thus, these parasites are ZOONOSIS.

Leishmania tropica and Leishmania major pathology

1. L. tropica and L. major are parasites in the _____________ of humans

• Promastigotes are inoculated into the skin during a sandfly bite and transform into amastigotes which are engulfed by skin macrophages.

• These skin cells are eventually destroyed by the multiplying amastigotes which then invade new macrophages, repeating to produce a __________________

_____________________________________

• other regions involved?

Leishmania tropica & Leishmania major pathology

L. tropica lesion is dry and persists for months.

In both species, the lesion eventually dries up to produce a depressed, depigmented scar.

Immunity?

L. major lesion bleeds quickly and is of short duration.

Leishmania tropica pathology

2. Recent finding of a mild "viscerotropic" form of L. tropica during Desert Storm in 1991 in Middle East

- pathology? ______________________________________

_________________________________________________

- it is a mild disease but little else is known of its pathology

- difficult to diagnose because there are no skin leasions

- only 12 cases reported in U.S. personnel 

Leishmania tropica and Leishmania major

DIAGNOSIS - _____________________________________ in skin scrapings from edge of the lesion.

• Skin smear is stained with Wright or Giemsa blood stain.

TREATMENT - Antimony compound called Pentostam(sodium stibogluconate) is given intravenously.

• Done only when lesion is on exposed body region where it may cause disfigurement.

• Treatment not necessary due to complete natural immunity after one exposure.

Leishmania tropica and Leishmania major

Major concern now is that many US soldiers are being exposed to these parasites in Iraq and Afghanistan. Over ____________cases have been reported from 2003-present.

A soldier with hundreds of sandfly bites received in one night.

Officer holding Iraqi child with Leishmania tropica on face

Soldier in Afghanistan with Leishmania tropica on hand

Leishmania mexicana

Causative agent of ___________________________________

Originally thought to be a subspecies of L. braziliensis, it has recently been recognized as a separate species.

DISTRIBUTION –

VECTOR - Lutzomyia sandflies

Leishmania mexicana

RESERVOIR HOSTS - ______________________________

- Is a _______________________________, as these rodents are common source of infection to persons clearing forests or harvesting

- Chicle in forests is harvested for use in gum by chicleros who are bitten by sandfly vectors

Leishmania mexicana

PATHOLOGY:

1.

2. If sandfly bites the ________________, amastigotes cause _________________________________________________________________________________. Ear lesions may last for many years.

Leishmania mexicana

DIAGNOSIS AND TREATMENT: Identify ______________________ in smears from ____________________________.

_____________________________are used to treat skin sores

Leishmania braziliensis

Causative agent of espundia, uta, or ___________________________ _________________________________.

DISTRIBUTION - central Mexico through Central and South America to northern Argentina

VECTOR - sandflies in the genus Lutzomyia

RESERVOIR HOSTS - ______________________________________

Leishmania braziliensis pathology

1. Promastigotes inoculated into ________________transform into amastigotes and enter ___________________________causing a small, ulcerating lesion, at sandfly bit site similar to oriental sore.

Leishmania braziliensis pathology

2. Amastigotes metastasize and spread from the skin lesion to the____________________________________________

- secondary lesion involves the

_________________________________________________

  - amastigotes are thought to be carried in bloodstream but little known how metastasis occurs

  - mucous membranes and cartilaginous tissues of the lips, nose, palate, and pharynx are destroyed; larynx may also be involved, destroying voice

  - condition is chronic, lasting for many years

  - death often results from ______________________________ and ______________________________________

Leishmania braziliensis pathology

DIAGNOSIS AND TREATMENT - identify ___________________________ in smears from lesion. 1.Antimony compounds are used to treat skin sores, but are not as effective against mucocutaneous lesions.

2. New oral drug Miltefosine (Impavido®) - Recent studies from Boliva show a high cure rate for mucocutaneous leishmaniasis .

Vaccine? ______________________________________________

Leishmania donovani

Causative agent of _____________________________________, or visceral leishmaniasis

Identified by William Leishman in 1900 from a soldier who died of fever in Dum-Dum, India. Charles Donovan identified the parasites in the spleen of an infected person in 1903. Parasite is named in honor of these two men.

William Boog LEISHMAN (1865-1926)Charles DONOVAN (1863-1915)

Leishmania donovani

DISTRIBUTION - Mediterranean coast, Middle East, India & Pakistan into China. Also found in parts of Central and South America.

- Of major concern during Desert Storm in Middle East in 1990-91 but few cases have been reported in US soldiers

- Concern now? ________________________________________

Leishmania donovani

VECTOR - many species of Phlebotomus

RESERVOIR HOSTS - ______________________are most common reservoir hosts; thus, it is a __________________ There are often campaigns to eliminate ____________________ in endemic areas.

Leishmania donovani

PATHOLOGY:

1.

2. Promastigotes inoculated into human skin transform into _________________ that are phagocytized by _____________________________

• Amastigotes multiply in macrophage, eventually rupturing the cell

• Free amastigotes then invade the circulatory system.

3. Invasion of ____________________________________________

• Free amastigotes in bloodstream are phagocytized by cells of the reticulo-endothelial system (RE system). These cells are then destroyed by the multiplying amastigotes.

• RE system is a system of phagocytic cells in the __________________________________________________________ which cleanses foreign materials from the bloodstream and provides natural immunity to many diseases.

• Destruction of cells of the RE system by the amastigotes results in_________________________________to many diseases and death by secondary infections.

RE cell

Rbc

liver cell

RE cell

Leishmania donovani

Symptoms - _____________________________________ (if bone marrow invaded), and ____________________________________

- death occurs in 6 to 12 mo. after infection in untreated cases (75-95% mortality rate)

Leishmania donovani

4. A secondary condition called _________________________________

_________________________________ commonly occurs in India. Involves formation of reddish skin nodules on the face.

Cause?

Leishmania donovani

DIAGNOSIS – identify _____________________________ in smear from ______________________

________________________________ . Such a diagnosis is risky.

TREATMENT - injection of________________________________ Drugs are highly toxic; thus, many quit taking the drug or reduce its dosage (develop dermal leishmanoid).

Trials underway on new drugs:

1. Antifungal drug amphotericin B

2. Antibiotic paromomycin

3. Anticancer drug meltifosine

Prevention for all species of Leishmania

1.

2.

3.

4.  

Trypanosoma spp.

Members of the genus Trypanosoma are parasitic in all classes of vertebrates. Most species are transmitted to the vertebrate via a vector - usually a bloodsucking insect. 

Trypanosoma spp.

Trypanosomes are divided into 2 sections based on where they develop in their vectors: SECTION ______________________________ - parasites develop in the anterior part of the vector's digestive tract (= anterior station development) –parasites are transmitted to vertebrate through vector bite.  SECTION _______________________________ - parasites develop in the hindgut of vector (= posterior station development) - parasites are transmitted to vertebrate via vector fecal contamination.  Parasites of medical and veterinary importance occur in both sections.

SECTION SALIVARIA - Trypanosoma brucei

Consists of 3 subspecies - Trypanosoma brucei brucei

Trypanosoma brucei gambiense

Trypanosoma brucei rhodesiense

These subspecies are morphologically identical and have similar life cycles.

Differences?

They were originally considered as 3 separate species:

  Trypanosoma brucei brucei represents the ancestral form. T. b. gambiense and T. b. rhodesiense have evolved from it.

SECTION SALIVARIA - Trypanosoma brucei

Identified by ___________________________________.

He also identified the _____________________________________

SECTION SALIVARIA - Trypanosoma brucei

All utilize the _________________________________as the vector.

ID by _________________________________ in wing.

Trypanosoma brucei life cycle

Only 2 stages in life cycle -________________________________________________ 1. Uninfected tsetse fly (Glossina) bites an infected vertebrate host and ingests ________________________ circulating in the bloodstream. 2. Trypomastigotes multiply by longitudinal binary fission in __________________________________________________ 

Trypanosoma brucei life cycle3. Trypomastigotes migrate to the salivary glands and transform into ______________________________ and multiply for several generation. 4. Epimastigotes transform back into ______________________ (short stumpy forms) in the salivary glands. These form the ___________________________.

5. Tsetse fly bites a human or ruminant host and inoculates _______________________________ into bloodstream.

6. Trypomastigotes live and multiply in the ______________________. In some cases, trypomastigotes migrate to the __________________________________________________________________

Trypanosoma brucei brucei

Causative agent of a disease called _______________________________ in Africa

Trypomastigotes are parasitic in the bloodstream of __________________ ___________________________________________________________

• parasites cause little pathology in these hosts indicating a long term host-parasite association

Trypomastigotes also infect ___________ ______________________(sheep, goats, cattle, horses, pigs, and dogs may also be infected but cattle most important)

Trypanosoma brucei brucei

Pathology is severe:

___________________________ occur in bloodstream and cerebrospinal fluid

cattle become emaciated and uncoordinated

cattle die in a few weeks to months

Trypanosoma brucei brucei

Although the parasite _________________________________________________, it makes 4.5 million square miles of central Africa an area where it is impractical to have domestic animals

• this region is called the tsetse fly belt

• nagana is associated with _____________________ _____________________, as source of nutrition (milk, beef) and beasts of burden cannot survive

Trypanosoma brucei brucei

Diagnosis – ID _________________________ in cow blood smear

Treatment – drugs are available but these are expensive

Most common one used is Berenil

Trypanosoma brucei gambiense

Infects humans only causing ____________________________________ ____________________________________________________________

VECTOR - Glossina palpalis

RESERVOIR HOSTS?

DISTRIBUTION -

Trypanosoma brucei gambiense

PATHOLOGY - produces a chronic disease with four progressive stages

1. ______________________ - skin sore develops at bite site where trypomastigotes are inoculated into bloodstream

Trypanosoma brucei gambiense

2. Trypomastigotes multiply in the ______________________; seen in blood 1-2 weeks after infection

• Symptoms?

• ID?

Trypanosoma brucei gambiense

3. Trypomastigotes invade the __________________________________ - cause swelling.

• Symptoms are Winterbottom's sign –

4. Trypomastigotes invade ________________ and initiate the chronic sleeping sickness stage.

• Symptoms -

Trypanosoma brucei gambiense

Cause of pathogenesis:

• damage to capillaries of brain – called _______________________________________

• ______________________________due to overproduction of immunoglobulins by host in response to the trypomastigotes

• normal physiological processes are disrupted, and death may result from ______________________________________

________________________________

DIAGNOSIS - identify _____________________

___________________________- must be done early in the infection; prognosis is poor once CNS is involved.

Trypanosoma brucei gambiense

TREATMENT - a number of drugs are useful – most common used are ____________________________________________________________ but they have severe side effects

Trypanosoma brucei rhodesiense

Causes_______________________________________________________

___________________________________________________________

HOSTS - _______________________________________

- antelope are important reservoir hosts

- disease is a ____________________________

VECTOR - Glossina morsitans

DISTRIBUTION -

Trypanosoma brucei rhodesiense

PATHOLOGY - disease in humans is acute - two stages:

1. ___________________________- small skin sore similar to that of gambian infection

2. Trypomastigotes quickly multiply in ___________________________

• Toxemia due to parasites in bloodstream causes rapid weight loss

• Death due to

DIAGNOSIS AND TREATMENT –

– Identify ________________________________________

• Melarsoprol or Suramin useful

• early diagnosis is critical if treatment is to be successful.

Prevention of Trypanosoma brucei1. _________________________________________________________

- use of DDT and other insecticides

- use of male sterile techniques (discussed in movie)

- clearing of bushes in grasslands - adult flies release their larvae from these bushes & larvae develop in shady soil beneath the bushes

2. ________________________________________________________

- not too popular among conservationists

- not effective in T. b. gambiense infections 

3. ____________________________________________________ (important in T. b. gambiense infections)

SECTION STERCORARIA – Trypanosoma cruzi

Causative agent of _____________________________________

____________________________________________________

Disease is named after ____________________________, a Brazilian who discovered T. cruzi in cone-nosed bugs in 1910.

It was not until the early 1930's that the parasite was shown to cause a human disease.

Trypanosoma cruzi distribution

  Distribution –

- infects over 15 million people (35 million are exposed) 

- disease is highly prevalent in Brazil; 30% of deaths are attributable to Chagas' disease

- in U.S.?

Trypanosoma cruzi

VECTOR - ____________________________ order Hemiptera – family Reduviidae (Text, chapter 37)

- genera Triatoma, Panstrongylus, and Rhodnius

- common names: cone-nosed bug, assassin bug, kissing bug, vinchuca

- adobe huts –

- control

Trypanosoma cruzi

 RESERVOIR HOSTS - __________________________ are important reservoir hosts in Central and South America - disease is a _______________________

 - In the U.S. _____________________________ _________________________________________are infected in the southern states - recent identifications in mammals as far north as Indiana and Maryland are of concern that disease is moving northward

Trypanosoma cruzi life cycle

. All 4 morphological forms exist:

1. Reduviid bug feeds on infected human (or reservoir host) and ingests _______________________ in blood meal.

2. In the midgut of the bug, trypomastigotes transform into _____________________________ that multiply by longitudinal binary fission.

Epimastigotes are the predominant stage in bugs.

Trypanosoma cruzi life cycle

3. Epimastigotes migrate into the bug's hindgut and transform into ______________________________

4. Trypomastigotes are passed in the _____________________________ (posterior station) and are infective to humans.

How do they enter?

Trypanosoma cruzi life cycle

5. Trypomastigotes in human leave the bloodstream and transform into ______________________________

6. Amastigotes multiply and eventually attack other cells -

preference for what cells?

_______________________________

_______________________________

Trypanosoma cruzi life cycle

7. Some amastigotes ruptured from cells transform into ___________________________and ___________________________ in the tissue fluid

8. These then become ___________________________as they enter the peripheral bloodstream where they are available to the biting bug

Morphology of Trypanosoma cruzi in humans

Trypomastigote:

• Shape?

• important structure?  

Morphology of Trypanosoma cruzi in humans

____________________

– occurs in pockets in cardiac ganglion cells or autonomic ganglion cells

Morphology of Trypanosoma cruzi in bugs

__________________________ are the predominant stage in the reduviid bug.

Characteristics of epimastigote?

____________________________

____________________________

Pathology of Trypanosoma cruzi

1. Inoculation of trypomastigotes into human:

(1) ______________________________ - inflammation of lymph nodes in region

of bite

(2) ______________________________

- swelling (edema) of eye if bug feces are rubbed into eye

2. Acute phase - occurs in children (age 5 or less)

- amastigotes quickly invade many body cells including the ____________________________ where they cause destruction of _____________________________ (abnormal EKG's are common)

  - death?

Pathology of Trypanosoma cruzi

3. Chronic phase - occurs in adults

- _______________________ cause gradual destruction of body cells

- 2 commonly affected areas:

 (1) ________________________

___________________________

• apex of heart usually becomes very thin

• impulses into ventricles are affected - _______________ _______________________

• death?

Pathology of Trypanosoma cruzi

(2)_________________________________

___________________________________

• muscle tone and peristalsis is destroyed

• organs increase their diameters greatly causing _______________________________

_______________________________

• victim may not be able to swallow and dies from starvation

• feces not formed effectively and victim

• death?

Trypanosoma cruzi

DIAGNOSIS – identify _____________________________________________

• ?, S, or C shape and large kinetoplast are diagnostic

____________________________________is used to diagnose cases in which there are too few trypomastigotes in bloodstream. Procedure involves feeding an uninfected lab-reared reduviid bug on a patient; bug is examined for epimastigotes in a 10-30 days.

RECENT CONCERN - __________________________________________

Trypanosoma cruzi

TREATMENT - there is no effective treatment

Why?

Can anything be done?

• Chronic infection may last for years before reaching a fatal climax - Old age security is a minor problem in areas where Chagas' disease is highly endemic.

Section Stercoraria - Trypanosoma rangeli

Common parasite in the bloodstream of _____________________________________

Where? _____________________________________________

Stage in humans? ____________________________________

Pathology? __________________________________________

Although trypomastigotes are morphologically distinct (small kinetoplast) from those of T. cruzi, parasite may cause a diagnostic problem in the untrained technician.

Vector? ______________________

• importance?

Section Stercoraria - Trypanosoma lewisi

Cosmopolitan parasite of __________________________ (no other host can be infected)

Stage? __________________________________

Pathology?__________________________________________

Vector?

Importance?

How are Leishmania and Trypanosoma able to evade the human immune response?

Amastigotes of Leishmania spp. and Trypanosoma cruzi:

• amastigotes live ___________________________________

• Leishmania inside _________________________

• T. cruzi inside _________________________________

• the immune system cannot find parasites in these cells 

• amastigotes are “in danger” when free, but invade cells to “hide”

How are Leishmania and Trypanosoma able to evade the human immune response?

Trypomastigotes of Trypanosoma brucei:

• trypomastigotes are able to live in the human bloodstream where they are in constant contact with immune cells.

• they are successful here due to __________________________________ - the production of __________________________________over time.

 - trypomastigote possesses chemicals on its surface coat which are recognized by our immune system as __________________________.

- a primary immune response is initiated and __________________________are produced in 7-10 days to destroy these antigens.

How are Leishmania and Trypanosoma able to evade the human immune response?

Trypomastigotes of Trypanosoma brucei cont:

• By the time these antibodies are produced, the trypomastigote changes its __________________________________

• So?

This cycle is repeated over and over (one trypanosome has changed its surface antigens 101 times in lab.)

Result?