Vector incrimination

Question 1

What are the four principles for incrimination?

Answer 1

1. Bites humans
2. Able to incubate an transmit parasite
3. Distribution of vector spatially and temporally correlates with human infection
4. Natural infection of the species is indistinguishable from parasites isolated from humans.

Question 2

How can we elucidate if a species bites humans?

Answer 2

• human landing catches
• Baited traps
• Human biting catches (GOLD STANDARD)
• Blood meal analysis of resting collections (indirect evidence)

Question 3

How does a shannon trap work?

Answer 3

BLocks the odours that the vectors find attractive

Question 4

What is a mbitu bednet trap?

Answer 4

Human sleeping under a net and causes vectors to get trapped in various areas of the net.

Question 5

Which spcies may a human baited trap not work well for and why?

Answer 5

May not be the best for An arbiensis as the efficiency is only 25%- mitigate by using traps depending on which vector species you are looking for

Question 6

Which trap is the best proxy for a human landing catch? What is its efficiency?

Answer 6

CDC light trap- is about 70% efficient depending on the species.
However it doesn’t fully represent which species land and bite on humans.

Question 7

What factors affect the results of a precipitin test?

Answer 7

The amount of blood present and what state it is in- e.g. not as good for partially or wholly digested blood.
Affects the specificity and sensitivity of the test.

Question 8

Describe the steps you can take to determine the vectorial competence

Answer 8

1. Feed on an infected animal or via a membrane
2. Expose to suspected vector
3. Use a naive animal to allow transmission to a susceptible host
4. See if parasites are in saliva, faeces or regurgitated.

Question 9

Where is the location of viannia leishmania in the vector

Answer 9

Travel to the hindgut before travelling forwards to the midgut

Question 10

How long after an infected blood meal does it take for leishmania parasites to be in a mature and transmissible state?

Answer 10

5 days. This is the best time for parasites to be defaecated out so parasite population starts to regrow after this initial loss.

Question 11

How would we go about testing the spatiotemporal distribution of the parasite. What are the levels of proof we could get?

Answer 11

• Passive data of spatial data and disease incidence.
• Active spatial surveys of infection and vector abundance
• Seasonal patterns of passively detected disease.
• Comparing EIR where there is more than one vector species in an area
• Quantitative methods using regression analysis and odds ratios for better evidence.

Question 12

How would we test if vector parasites are indistinguishable from human infections?

Answer 12

Vector dissection, culture and ID of parasites (e.g. using PCR). Rely on qPCR for some stored specimens as they cannot be cultured. 
Could  use:
-IFAT
-ELISA
-PCR/ DNA probe

Question 13

How could we demonstrate that a species bites humans?

Answer 13

Use a proxy of flies caught in human living quarters as may be unethical to look at human blood feeding insects, especially for diseases where there is no effective prophylaxis e.g. leoshmania.

Question 14

How can mice be used as a proxy for human immune respnses?

Answer 14

Recolonise mice with human bone marrow so they can produce human erythrocytes.