14. Protozoans: Leishmaniasis

Question 1

what are the three main types of leishmaniasis

Answer 1

1. visceral leishmaniasis
2. cutaneous leishmaniasis
3. mucocutaneous leishmaniasis

Question 2

what is mucocutaneous leishmaniasis

Answer 2

disfiguring infection of the soft palate of the face

Question 3

how is leishmaniasis transmitted

Answer 3

bites of females sand flies

Question 4

name a species of sand fly that transmits leishmaniasis

Answer 4

phlebotomus

Question 5

briefly describe the life cycle of leishmaniasis

Answer 5

sandfly ejects the infected stage during blood meal

promastigotes are phagocytosed by macrophages

promastigotes transform into amastigotes before multiplying

sandfly takes next blood meal and consumes infected macrophages

Question 6

which type of leishmaniasis is fatal if left untreated

Answer 6

visceral (95% case fatality)

Question 7

what are some reservoirs for leishmaniasis

Answer 7

dogs & rodents

Question 8

what are some measures taken to control leishmaniasis reservoirs

Answer 8

ministry of health in Brazil order the culling of approx 1 million dogs per year

Question 9

what is the clinical diagnosis for VL

Answer 9

1 month - 10 years

Question 10

describe the onset of VL

Answer 10

fever, splenomegaly, anaemia

Question 11

VL can develop into post kala-azar dermal leishmaniasis, what is this?

Answer 11

skin rash with parasite rich nodules

Question 12

what is the gold standard diagnostic test for VL

Answer 12

culturing promastigotes from splenic or bone marrow samples

Question 13

describe the KAtex urine test

Answer 13

uses latex particles coated with antibodies against the leishmania antigen which is found in the urine
HIGH SPECIFICITY

Question 14

describe the direct agglutination test

Answer 14

detects antigens to the parasite In the blood or serum of the patient

Question 15

what is a negative result for the direct aggulitantion test (DAT)

Answer 15

dark blue = negative

Question 16

what is a positive result for the direct aggulitantion test (DAT)

Answer 16

pale blue = positive

Question 17

name a strength and limitation of DAT (direct agglutination test)

Answer 17

strength = easy to read, does not require specialist information

limitation: reproducibility problems (due to thermal instability of antigen)

Question 18

what does IFAT stand for

Answer 18

indirect fluorescent antibody test

Question 19

what does ELISA stand for

Answer 19

enzyme-linked immunosorbent assay

Question 20

how does ELISA work

Answer 20

well plates coated with antigen of interest, host serum containing antibodies are applied to the wells and BINDING is measured used an enzyme labelled secondary antibody

Question 21

what test can be used to diagnose L. Donovan and L. infantum

Answer 21

Immunochromatographic strip test

Question 22

how does immunochromatographic strip tests work, what’s the key issue with them?

Answer 22

ICT = rapid nitrocellulose test with specialised antigens that detect l. Donovan and l. infantum antibodies

issue: produces lots of false positives

Question 23

why is PCR based tests not appropriate for leishmaniasis

Answer 23

requires specialist equipment that is not field friendly

mainly used in specialist centres which many endemic countries lack

Question 24

what is the transmission cycle of VL in brazil

Answer 24

1. sandfly feeds infected dog
2. parasite cycles between sandfly’s and dogs - sylvatic cycle
3. sandfly takes blood meal on human
   = infection

Question 25

how can an electronic nose be used to detect the conductivity

Answer 25

analysis of infected and uninfected dog hair and blood

• nose was able to detect clear different between infected and uninfected dogs
• high se and sp > 94%

Question 26

what is the reason why infected dogs have different odours to uninfected dogs

Answer 26

to make the infected individual more attractive to sandflies

= more blood meals = more transmission

Question 27

What is a sylvatic cycle

Answer 27

Virus cycles between animal and sandfly, does not yet feed on a human