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LU-Tropical Diseases > Lecture 6 - Haemoflagellates > Flashcards

Lecture 6 - Haemoflagellates Flashcards

1
Q

Characteristics of haemoflagellates:

  • Group of … protists
  • All …-borne: transmitted by various … feeding insects
  • Have a … at some point in their life cycle
  • Blood or … living
  • … related - all members of Phylum Kinetoplasta -> possess a … (unique form of mtDNA)
  • Three groups of important human parasites: …, Trypanosoma … and Trypanosoma …
A
  • Group of parasitic eukaryotic protists
  • All vector-borne: transmitted by various blood feeding insects
  • Have a flagellum at some point in their life cycle
  • Blood or tissue living
  • Phylogenetically related - all members of Phylum Kinetoplasta -> possess a kinetoplast (unique form of mtDNA)
  • Three groups of important human parasites: Leishmania, Trypanosoma brucei and Trypanosoma cruzi
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2
Q

What is leishmaniasis?

  • One of the worlds most … diseases.
  • Caused by parasites of the genus … .
  • Spread by the bite of certain species of … .
  • Estimated … people at risk of the disease; In 2016, approximately 900,000–1.3 million cases and … deaths reported worldwide.
  • 3 Clinical Forms: Cutaneous, … and … .
A
  • One of the worlds most neglected tropical diseases.
  • Caused by parasites of the genus Leishmania.
  • Spread by the bite of certain species of sand-flies.
  • Estimated 350 million people at risk of the disease; In 2016, approximately 900,000–1.3 million cases and 30,000 to 50,000 deaths reported worldwide.
  • 3 Clinical Forms Cutaneous, Mucocutaneous and Visceral.
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3
Q

The life cycle of Leishmaniasis:

Describe the sandfly stages in three steps: ingestion, midgut and next feeding stage.

A
  1. Ingestion of parasitized cell through blood meal.
  2. The amastigotes transform into flagellated promastigote stage in midgut.
  3. The motile promastigotes move from the gut to proboscis and are injected in skin during feeding.
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4
Q

Describe the life cycle of Leishmaniasis:

In the intermediate/definitive host stage in 4 steps: starting with phagocytation and ending with sandfly blood meal.

A
  1. Promastigotes are phagocytized by macrophages.
  2. Promastigotes transform into amastigotes inside macrophages.
  3. Amastigotes multiply in cells of various tissues.
  4. Sandfly takes a blood meal and ingests macrophages infected with amastigotes.
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5
Q

What is Leishmania and HIV co-infection?

A

HIV co-infected individuals are more likely to develop active VL. Most cases are thought to be caused either by reactivation of latent infection or associated with IV drug use (IVDU).

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6
Q

Briefly describe Canine Visceral Leishmaniasis (CVL).

A

CVL is a zoonotic disease caused predominantly by Leishmania infantum parasites. In urbans areas, the domestic dog is the main reservoir host for the disease.

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7
Q

What is a natural reservoir host? And why is the dog the reservoir host in CVL?

A

A natural reservoir host can be defined as an animal or species which is infected by a parasite, and subsequently serves as a source of the infection for humans and/or another species.

Dogs live in close proximity to humans –> parasite easily transmitted from dog to human.

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8
Q

Name a few symptoms of CVL.

A

Very common for canines to become infected and be asymptomatic. Symptoms of CVL:

  • Alopecia
  • Skin lesions
  • Ulcerative or exfoliative dermatitis
  • Epistaxis (nose bleeds)
  • Kidney failure > increased urination and drinking
  • Progressive loss of weight with decreased appetite
  • Ocular signs
  • Swollen lymph nodes
  • Long nails
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9
Q

We control CVL by controlling animal reservoir hosts, because removal of infected dogs by culling, will reduce disease transmission.

What is necessary in order to do this?

A

Early diagnosis which is both accurate and efficient is necessary.

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10
Q

What is the biggest obstacle in evaluation of diagnostic tests for CVL?

A

There is no definitive diagnostic reference test or gold standard.

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11
Q

How do we get a laboratory diagnosis of CVL for cutaneaous leishmaniasis (1) and visceral leishmaniasis (4)?

A

Cutaneous leishmaniasis: tissue sample for smear and culture.

Visceral leishmaniasis:

  • Bone marrow biopsy or splenic aspirate for smear and culture
  • Serology (ELISA)
  • PCR/qPCR
  • Skin test
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12
Q

Enzyme-linked immunosorbent assay (…) is a … assay technique designed for detecting and … substances such as peptides, …, antibodies and … .

Via which ELISA type is CVL usually diagnosed?

A

Enzyme-linked immunosorbent assay (ELISA) is a plate-based assay technique designed for detecting and quantifying substances such as peptides, proteins, antibodies and hormones.

CVL is usually diagnosed by detecting IgG that binds specifically to Leishmania antigens –> indirect ELISA.

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13
Q

Why is ELISA a good option for screening of CVL?

A
  • ELISA allows screening of large numbers of samples
  • It has potential for absolute antibody quantification
  • Sensitivity (72-100%) and specificity (87-97%) is high.
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14
Q

Why is exclusively detecting for antibodies (ELISA) a cause for error?

A

It doesn’t indicate current infection state. Antibodies can be present in dogs that have been previously exposed to the infection.

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15
Q

Explain polymerase chain reaction (PCR) in one sentence.

Also name an advantage of PCR.

A

It allows scientists to amplify small specific segments of DNA.

PCR allows for amplification at an exponential rate.

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16
Q

Why is PCR-based method for CVL diagnosis appealing?

  • It’s …, … and specific.
  • It avoids culturing of … - by using either … specific primers, or general … primers.
  • High … compared to other methods
  • Allows detection of … and sometimes … dogs
  • Less … sampling and a better … predictive value
A
  • It’s rapid, sensitive and specific.
  • It avoids culturing of parasites - by using either leishmania species specific primers, or general leishmania genus primers.
  • High sensitivity compared to other methods
  • Allows detection of asymptomatic and sometimes seronegative dogs
  • Less invasive sampling and a better negative predictive value
17
Q

Current laboratory diagnostic techniques for CVL have considerably enhanced disease diagnosis, but why is it not optimal yet?

A
  • The diagnostic tests require a laboratory infrastructure and experienced staff
  • It is not a point of care – it cannot be implemented in the field
  • Lab based tests require samples to be taken to a clinic (often miles away from the rural community) –> delay in correct treatment
18
Q

Why is CVL field diagnosis necessary?

A

Being able to detect a disease in its early stages is crucial for disease control:

Early diagnosis –> early removal of infected dogs –> reduction of disease transmission.

19
Q

In field tests are rapid and simple. Allows diagnosis there and then –> catch disease early, better chance of treatment and transmission prevention.

Name a couple CVL field diagnosis tests.

A
  • Immunochromatographic (IC) rK39 test
  • Direct agglutination test (DAT)
  • Fast agglutination screening test (FAST)
  • Latex agglutination test (LAT)
  • DPP® CVL
20
Q

Briefly describe immunochromatographic (IC) rK39 test.

A

IC rK39 is a rapid dipstick test based on recombinant K39 protein derived from the kinesin protein of Leishmania major.

Diagnosis is made using serum - looking for antibodies that bind to rK39.

21
Q

Direct agglutination test (DAT) is a combination of particular … with its soluble antibody that forms an …, making the particles clump.

Name advantages of DAT.

A

Direct agglutination test (DAT) is a combination of particular insoluble antigen with its soluble antibody that forms an antigen-antibody complex, making the particles clump.

Advantages:

  • Use of whole stained promastigotes either as suspension or freeze-dried form
  • Freeze dried form is heat stable
  • Utilized for field purposes
22
Q

What are disadvantages of DAT?

A
  • Relative long incubation time of 18 hrs.
  • Need for serial dilutions of serum.
  • No prognostic value.
  • Does not indicate current infection status (patients remain positive for several years after cure).
23
Q

Fast agglutination-screening test (FAST) is a modification of DAT. It’s a rapid detection of anti-leishmania antibodies in serum and blood collected on filter paper.

Name three advantages of FAST.

A
  • Only need for one serial dilution.
  • Rapid: results available in less than 3 hours.
  • Suitable for screening of large populations.
  • High sensitivity.
24
Q

DPP CVL in field diagnostic test is recently developed. Describe the test in one sentence.

A

It’s an innovative colloidal gold-based immunochromatography assay that detects antibodies against rK26/rK39 antigens.

*Sensitivity and specificity vary.

25
Q

What is the difference between infected and non-infected individuals with CVL?

A

Parasites manipulate host by altering odour.

26
Q

Name characteristics of electronic nose (VOC analyser).

A
  • It mimics human olfactory system.
  • It’s intended to detect odours –> different diseases = distinct odour profiles.
  • It’s proven effective in detection of TB, UTI’s and cancers.

LU-Tropical Diseases (9 decks)

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