Leishmaniasis

Question 1

Classification of lesihmania

Answer 1

Genesis of protozoan parasites, come under kinetoplastids order
all members of order have kinetoplast
- dense granule of DNA, formed from mini and maxi circles

Question 2

What are the three kinetoplastid diseases?

Answer 2

• Leishmania - sand fly vector
• Chagas disease - triatomine bug vector
• African sleeping sickness - tsetse fly vector

Question 3

How is leishmania transmitted?

Answer 3

Female sand flies, two genera that transmit in different geographical locations
- phlembotomus spp. - transmits in old world, africa, eastern europe, middle east, central asia
- lutzomyia spp - new world

transmission when taking blood meal, can transmit bartonella and other viruses too

Question 4

Life cycle of female sand fly

Answer 4

Transmission occurs during vector feeding

Promastigotes are phagocytosed by macrophage

Promastigote differentiates into amastigote inside macrophage

Reproduces asexually in vacuole

Amastigotes multiply in parasitophorous vacuole

Sand fly becomes infected when taking a blood meal from infected human (or other mammal) - takes up amastigote

In the midgut of the sand fly amastigotes transform into flagellated promastigotes and divide and migrate into salivary glands of the fly

Can take from 1-2 weeks, fly can once again infect hosts

Question 5

Disease manigestations are caused by different leishmania species

Answer 5

Visceral leishmaniasis (VL)
- Leishmania donovani
- Leishmania infantum

Post-kala-azar dermal leishmaniasis (PKDL)
- Leishmania donovani

Cutaneous leishmaniasis (CL)
- Localised or simple – L.major, tropica, mexicana, braziliensis
- Mucosal leisons (ML) - L.aethiopica
- Diffuse (DCL) - L.mexicana, L.aethiopica
- Recidivans (LR) - L.tropica

Mucocutaneous leishmaniasis (MCL) - L.Viannia sub-genus

Question 6

Describe VL

Answer 6

Most severe and systemic disease manifestation
- Fatal if untreated, 30,000 deaths per year
- Disease onset from 2 weeks to 6 months following an infectious bite
- Also known as kala-azar – black fever
- Identified in 1903 by Leishman and donovan

Signs and symptoms
- Fever
- Weight loss
- Anaemia
- Hepatosplenomegaly

VL primarily caused by two leishmania species
- Leishmania donovani – OW
- And leishmania infantum – OW and NW - domestic dogs

Question 7

Describe post-kala azar dermal leishmaniasis (PKDL)

Answer 7

• Complication of following infection by L.donovani or L.infantum
• Important reservoir of infection

Can present in either macular or papular form
Can affect person’s quality of life.

Lesions are infections to the sand fly, where if blood meal is taken from around the edges of the lesions, the sandfly will take that up and pass it onto other hosts.

Disease is similar to leprosy, distinguished from leprosy as patient retains sensation to lesions.

Question 8

Describe cutaneous leishmaniasis

Answer 8

Majority of leishmania cases
Also known as oriental sore
0.7-1 million new cases a year

Non-fatal
- Cosmetic morbidity
- Socially stigmatising
- Psychological effects

• L.tropica, major, aethiopica OW
• mexican and amazonensis NW
• surface lesions on oral/nasal/genital mucosa, not to be confused with MCL

Lesion form at bite site unlike VL where parasites migrate from bite site
localised or diffuse, begin with single nodule, spread to cover large parts of skin

Question 9

Describe mucocutaneous leishmaniasis (MCL)

Answer 9

Invasive sequelae of CL – 1-10% cases

Caused primarily by species of leishmania Vianna sub-genus
- L.V. brazilienesis
- L.V. panamensis
- L.V peruviana
- L.L aethiopica

Life threatening
Permanent disfigurement

Question 10

Describe leishmaniasis recidivans

Answer 10

Rare complication of CL
L.tropica, major and braziliensis
Reappearance of lesion sometimes years later

Question 11

Indoor residual spraying IRS

Answer 11

• Primary vector control
• Coat inner walls of house with insecticide
• Done twice a year
• Commonly used for control programmes for other vector borne diseases
• There is DDT resistance so different class used

Most african leishmania vectors endophagic, feed outside, IRS not effective

Question 12

Bed nets

Answer 12

More common for malaria but sandflies are smaller than mosquitoes so need nets with smaller mesh size

Nets coated with insecticide and a different class of insecticide to that used for IRS, used together to reduce emergence of resistance

Question 13

What is the gold standard for diagnosis of VL?

Answer 13

Leishmania has non specific signs and symptoms
Gold standard is observation of parasites by microscopy
- Either splenic or bone marrow aspirate from patient, stained and identified under microscope
- Or lesion biopsy for CL

aspiration of lesion (CL)
or bone marrow (VL)

Question 14

What are the disadvantages of using the gold standard?

Answer 14

• Poor sensitivity
• Require skilled microscopist to do diagnosis and trained healthcare professional to take clinical sample and facilities
• not suitable for remote field use

Question 15

Diagnostics - splenic aspirate

Answer 15

Stain with giemsa stain
can’t speciate between leishmania with this approach

Question 16

Serological assays for leishmania and their advantages/disadvantages

Answer 16

Either detects anti-leishmania antibodies or antigen from a clinical sample

Advantage compared to microscopy is you don’t need splenic or bone marrow aspirate or skilled microscopist to identify parasite

Cheap and easy to use

Not used for CL, often used to support VL diagnosis

Can be less sensitive and specific compared to gold standard

Varies in different regions, parasites and populations

Less sensitive in patients with HIV, especially if HIV predates leishmania

Question 17

KAtex and Kalazar test

Answer 17

KAtex - antigen detection
- Leishmania antigen detected in urine using antibody coated latex beads

Kalazar - antibody detection
- detection of antibodies against recombinant product of 39 aa antigen encoded by kinesin-like gene of leishmania donovani complex
- low sensitivity in east africa where lower levels of anti-kinesin antibodies are seen

Question 18

Leishmania skin test

Answer 18

Uses preserved promastigotes as antigen

Gives a delayed type hypersensitivity (DTH) reaction after 48-72 hours positive after cured VL

Useful in epidemiological surveys, used to determine cutaneous leishmaniasis exposure.

Also known as Montenegro test
e.g someone has suspicious skin lesions, can do this test to rule out CL

Disadvantage of this is that you need to culture parasites for the test and require facilities and personnel to do this.

And comes up positive for past infection.

Question 19

Nucleic acid tests for leishmania

Answer 19

PCR amplification of either kinetoplast DNA or 16s rRNA

Identification to species level, identifying leishmania DNA

Use of primers specific for 16s rRNA or kinetoplast DNA

Highly sensitive
Expensive, need equipment
Used in eastern Europe and parts of middle east – L.infatum
Travel clinics
Not yet widely in field
Point of care device – next gen diagnostics

Question 20

Treatment of CL, 1st and 2nd line drugs

Answer 20

1st line – pentavalent antimonials

2nd line - systemic
- Amphotericin B
- Pentamidine
- Miltefosine

Local
- Paromycin
- Thermotherapy

Question 21

Challenges of treating CL

Answer 21

CL estimated one million cases worldwide, major outbreaks in Syria, afghanistan, ethiopia

Self-curing 3-18 months in 95% cases but disfiguring

Cochrane analyses in 2007 and 08 showed deficiency in treatments and in clinical studies

Not on the agenda of funders – a real NTD

TT4CL-SGUL coordinated H2020 funded project to develop new drug, D121, for CL

Question 22

Vaccine for leishmaniasis

Answer 22

No fully licensed vaccine

Several in clinical and pre-clinical development

Reservoirs –canine vaccine used in south america on dog

Leishmanisation - vaccination done in middle eastern countries. Take parasites scraped from cutaneous lesion, inoculate them somewhere isn’t visible on patient, e.g back of leg, effectively lets you control where lesion and scar would form. Avoid face at all costs.