Vector Incrimination

Question 1

What needs to be assessed to determine whether a disease is vector borne?

Answer 1

• Confirmation of pathogen in patient
• Who is infected
• When infected
• Disease correspond with reports/observations of increase in arthropod activity
• ?Perturbation of environment
• Evidence of bites

Question 2

What needs to be assessed when determining a vector?

Answer 2

• Vectors present
• Population studies
• Identify vectors (morphological and molecular)
• Vector proportions in population (and time of year)

Question 3

Collection methods for ectoparasites

Answer 3

• Anaesthesia
• Brushing
• Tick dragging

Question 4

Examples of ectoparasites

Answer 4

Ticks, fleas, mites, lice

Question 5

Trapping methods

Answer 5

• Light traps
• Resting boxes
• Tsetse traps

Question 6

What are the steps towards vector incrimination?

Answer 6

1) Demonstration of feeding or other infective contact with the host under natural conditions
e. g. Distinguish between zoophilic and anthropophilic -HLC vs Light traps or blood meal analysis
2) A convincing biological association in time and space of the suspected arthropod species and occurrence of clinical or subclinical infection of the host
3) Repeated demonstrations that the arthropod, under natural conditions, harbours the infectious agent in the infective stage
4) Transmission of the agent under controlled conditions

Question 7

Describe the steps to experimental transmission

Answer 7

1) naturally or experimentally infected animal fed on by arthropods
2) arthropods are then allowed to feed on uninfected animals after extrinsic incubation period
- problems of false positives and negatives with this approach

Question 8

What are the key factors affecting vector effectiveness or capacity?

Answer 8

1) pathogen receptivity in the vector
2) host specificity (contact with host)
3) longevity ( does the vector live long enough to allow the extrinsic incubation period)
4) frequency of biting
5) mobility
6) numbers
7) physiological and behavioural plasticity
8) susceptibility to control measures

Question 9

Give an example of vector incrimination

Answer 9

CL in peru
-7spp of sandfly
-5 anthropophilic
-3 confirmed vectors
They collected insects
then dissected and collected parasites from gut
then fed uninfected sand flies on infected hamsters
molecular characterisation