Lecture 14 - Leishmaniasis

Question 1

Types of leishmaniasis

Answer 1

Visceral Leishmaniasis (VL)
- most severe
Cutaneous Leishmaniasis
Mucocutaneous Leishmaniasis

Can be co-infection with HIV - more serious complications

Question 2

Transmission of leishmaniasis

Answer 2

Transmitted via bite of infected female sand flies

Caused by multiple species of Leishmania

Question 3

Life Cycle and diagnostic stages of leishmaniasis

Answer 3

Amastigote
host: human
main diagnostic form in humans

Promastigote
Vector: Sand fly

Question 4

leishmaniasis incubation and disease progression

Answer 4

Incubation: Ranges from 1–2 months to >10 years

Disease progression phases:

Asymptomatic

Subclinical

Acute (severe)

Chronic (persistent)

Question 5

Typical Clinical Features of leishmaniasis

Answer 5

Low-grade fever

Progressive splenomegaly (enlarged spleen)

Hepatomegaly (enlarged liver)

Anaemia

Wasting

Pigmentation changes

Swollen lymph nodes

Question 6

Diagnosis of Visceral Leishmaniasis: Indirect: Clinical indications

Answer 6

Doctors may suspect VL in patients with:

Anaemia: Low red blood cell count

Leucopenia: Low white blood cell count

Thrombocytopenia: Low platelet count

Question 7

Diagnosis of Visceral Leishmaniasis: Indirect: Antibody Detection Tests (indirect)

Answer 7

These tests detect human immune responses (antibodies) to Leishmania, not the parasite itself.

DAT (Direct Agglutination Test)

IFAT (Indirect Fluorescent Antibody Test)

ELISA (Enzyme-Linked Immunosorbent Assay)

Question 8

Diagnosis of Visceral Leishmaniasis: Indirect: Antibody Detection Tests:
DAT (Direct Agglutination Test)

Answer 8

Relies on agglutination between L. donovani promastigotes and patient antibodies.

Easy to read (dark blue spot = negative, pale blue solution = positive)

High sensitivity (96.5–100%) and specificity (91–95%)

Ideal for field use, but antigen stability issues and batch variability can affect results

Question 9

Diagnosis of Visceral Leishmaniasis: Indirect: Antibody Detection Tests: IFAT (Indirect Fluorescent Antibody Test)

Answer 9

Uses fluorescent-labelled secondary antibodies to detect binding between host antibodies and fixed promastigotes.

Very sensitive (96%) and specific (98%), but needs fluorescence microscope – not field-suitable

Question 10

Diagnosis of Visceral Leishmaniasis: Indirect: Antibody Detection Tests: ELISA (Enzyme-Linked Immunosorbent Assay)

Answer 10

96-well plates coated with antigen detect antibodies using enzyme-labelled anti-Ig.

High throughput, good for large-scale surveys

Needs lab facilities – not usable in the field

Question 11

Diagnosis of Visceral Leishmaniasis: Direct: Parasitological Tests

Answer 11

Splenic Aspirate
Microscopy
Promastigote Culture

Question 12

Diagnosis of Visceral Leishmaniasis: Direct: Parasitological Tests: Splenic Aspirate

Answer 12

Method: A long needle is inserted through the abdomen into the spleen to extract a small sample

Spleen contains high concentrations of Leishmania amastigotes

Highest sensitivity among parasitological methods

Invasive, painful, risk of bleeding, needs skilled personnel

Used in hospital settings only

Question 13

Diagnosis of Visceral Leishmaniasis: Direct: Parasitological Tests: Microscopy

Answer 13

Mainly used for cutaneous leishmaniasis (CL).

Tissue (e.g. from cutaneous lesions) stained with Giemsa to detect amastigotes

Confirmatory if amastigotes found, but:

Low sensitivity in early/low-level infections

Requires skilled microscopist

Question 14

Diagnosis of Visceral Leishmaniasis: Direct: Parasitological Tests: Promastigote Culture

Answer 14

Used to improve sensitivity when microscopy fails to detect parasites directly.Method:

Biopsy specimens (e.g. from spleen, bone marrow, or skin) are placed in special culture media under aseptic (sterile) conditions.

If Leishmania is present, it will grow in the form of motile promastigotes (the insect-stage form).

Time consuming, required trained technical staff and lab environment

Question 15

Diagnosis of Visceral Leishmaniasis: Direct: Antigen Detection (Direct)

Answer 15

KAtex Urine Test
Detects Leishmania antigens in urine

Latex agglutination format; non-invasive

Variable sensitivity (47–95%), high specificity (82–100%)

Question 16

Diagnosis of Visceral Leishmaniasis: Direct: Molecular Biology Methods

Answer 16

PCR: high sensitivity/specificity; can identify species (important for treatment choice)

NASBA: detects RNA – can be used to quantify parasite load