Leishmaniasis

Fatima Al-Awadh

INTRODUCTION

Learning Objectives

1. Define and classify parasites.

2. Explain the pathogenesis of parasite.

3. Define leishmaniasis.

4. Mention the types & causes, risk factors, signs & symptoms, diagnosis, complications, treatment & prevention.

5. Explain the life cycle of Leishmania.

What is a parasite ?

• A parasite is an organism that benefits from a close prolonged relationship with its host, which is harmed.

• The parasite grows, feeds, or uses shelter of the host organism (including the host itself) contributing negatively to the relationship.

• May be ectoparasites or endoparasites which can be intra- or extra- cellular

Classification Medically Important Parasites

Metazoa• Multicellular.• Helminthes &

Arthropods.

Protozoa• Unicellular.• Fagellates,

amoebozoa, sporozoa & ciliophora

Chromista• Unicellular.• Blastocystis

hominis.

Fungi• Unicellular.• Microsporidia.

Parasitic pathogenesis

• Given the wide diversity among human parasites, the pathogenesis is highly variable.

• Although the human parasites exhibit direct pathogenic mechanisms, in most instances the organisms themselves are not highly virulent!

Parasitic pathogenesis

Exposure and Entry

Adherence and Replication

Disruption, Evasion, and Inactivation of Host Defenses

1. E

xpos

ure

and

Ent

erin

g

Ingestion.

Direct penetration

Arthropod bite

Trans-placental penetration

Organism-directed penetration

Mediated by

Physical Chemical

Mechanical or biting mouthparts. interaction between parasite surface glycoproteins (adhesins) and specific glycoprotein or glycolipid receptors.

2.a. Adherence

2.b. Replication

• Parasites replicate intracellularly or extracellularly in human

• Helminthes generally do not replicate.• Temperature is important for the ability

to infect and cause disease.

Disruption, Evasion, and Inactivation of Host Defenses

• Like other organisms, parasites elicit humoral and cell-mediated immune responses.

• parasites are particularly adept at interfering with or avoiding these defense mechanisms.Antigen

ic variatio

n, Molecul

ar mimicry

& Maskin

g

Intra-cellular location

Immuno-

suppression

What is leishmaniasis ?

• Leishmaniasis is an infectious disease • caused by parasites belonging to genus

Leishmania • generally transmitted by the bite of

infected female Phlebotomus sand fly.

Leishmaniasis types & causes

Cutaneous leishmaniasis (CL)• Caused by L. major, L. tropica

& L. mexicana.• The most common form.• Days to few weeks.• on the extremities and face.

Leishmaniasis types & causes

Mucocutaneous leishmaniasis (ML)• Caused by L. braziliensis.• Not treated cutaneous lesion

on the face spreads to the nose or mouth.

• Months to years.• Lesions can be very

disfiguring

Leishmaniasis types & causes

Visceral leishmaniasis (VL)• Caused by L. donovani, L.

infantum & L. chagasi.• Most severe form of the

disease, fatal if untreated• Visceral disease from the

Middle East is usually milder.

Leishmania forms

Promastigote formWith flagella

Amastigote formWithout flagella

Life cycle of Leishmania

Types of leishmaniasis

“They have the same life cycle, but different tropisms generating different symptoms”

Risk factors

• The major risk factor is being exposed to infected sand flies.

• Infection is more common in adventure travelers, Corps workers, soldiers.

Risk factors

SIGNS AND SYMPTOMS

Cutaneous Mucocutaneous Visceral

one lesion or multiple lesions

initially a nodule at the bite of the sand fly

Sever weight loss

large scaly,ulcerated plaques, or shallow ulcerated nodules

nodules inside the nose, perforation of the nasal septum, and enlargement of the nose or lips

Pancytopenia

expanding and ulcerating over time

Change in voice Hepatosplenomegaly

dry or weeping Intermittent fever

painful if secondarily infected

Disfiguring scarring and tissue destruction

Hypergamma-globulinemia

Swollen lymph nodes near the sores.

Dark skin

Diagnosis

• A physical exam may show an enlarged spleen, liver, and lymph nodes. The patient may have been bitten by sandflies, or was in an area known for leishmaniasis.

Differential diagnosis

• Cutaneous leishmaniasis (CL) may look like other skin diseases, especially lepromatous leprosy, sarcoidosis, and skin cancer.

• Visceral leishmaniasis (VL) may resemble malaria or haematological malignancies.

• Mucocutaneous leishmaniasis (ML) may be similar to Tertiary syphilis.

Investigations

Cutaneous

Skin biopsy

CBC

Serologic testing

Visceral

Biopsy and culture of liver, spleen, bone marrow, or lymph

nodes

Leishmania-specific PCR test

Indirect immuno-fluorescent antibody test

Direct agglutination assay

Complication

• Fatal infections - due to immune system damage

• Bleeding (hemorrhage) VL• Facial disfigurement ML• ruptured spleen VL

Treatment

• meglumine antimonate.

• sodium stibogluconate.

Antimony-containing compounds :

• Pentamidine: CL

• amphotericin

Other drugs :

• Plastic surgery (ML).

• Splenectomy in drug-resistant (VL).

Surgery

PrognosisCutaneous Mucocutaneous Visceral

Localized cutaneous leishmaniasis lesions usually heal themselves completely.

relatively resistant to treatment.

Untreated visceral leishmaniasis has a 90% death rate, but only a 10% death rate with treatment.Diffuse cutaneous

leishmaniasis may smolder on for years without treatment

Prevention

Preventing sand fly bites is the most immediate form of protection. You can prevent a bite by:

• Putting fine mesh netting around the bed• Screening windows• Wearing insect repellent• Wearing protective clothing• Public health measures to reduce the sandfly

population and animal reservoirs. • There are no vaccines or drugs that prevent

leishmaniasis

Conclusion

References• Merck manual, Pg 1379-1381

Medical microbiology, Pg 797-801• http://www.youtube.com/watch?v=7poF

ARIxPoE• http://www.medicinenet.com/leishmania

sis/page6.htm#what_is_the_prognosis_of_leishmaniasis

• http://www.the-travel-doctor.com/leishmaniasis.htm