1. eg. Moraxella transmission by Musca or Trypanosoma by tabanids
FLY VECTORS MECHANICAL TRANSMISSION OF PATHOGENS
eg. Moraxella transmission
by Musca
or Trypanosoma by tabanids
repeated egg batches
flies take many
meals for each egg
batch, thus rapid
transmission
on contaminated
mouthparts

2. repeated egg batches eg. encephalitis virus in mosquitoes
FLY VECTORS BIOLOGICAL TRANSMISSION OF PATHOGENS
repeated egg batches
one blood meal per egg batch, pathogen develops internally over ~10 days
eg. encephalitis virus
in mosquitoes

3. FLY VECTORS FLIES COMPARED TO TICKS AS VECTORS
single female fly
transmission by one female during feeds for repeated egg laying ~ 8 days
larva nymph adult
transmission from stage to stage, one feed per stage, interval 6-18 months
single tick

4. eg. bluetongue by Culicoides
FLY VECTORS VERTEBRATES AND VECTORS AS RESERVOIRS
eg. bluetongue by Culicoides
January January
seasonal peak of
vectors
reservoir host
new reservoir host
disease host
Nos

5. eg. bluetongue by Culicoides
FLY VECTORS AMPLIFICATION OF VIRUS TRANSMISSION
eg. bluetongue by Culicoides
vector needs to survive well and feed often
reservoir host
disease host
but insufficient
virus in vector
refractory host
disease host +
plenty virus in vector

6. increasingly milder winters >> longer midge survival during year
FLY VECTORS DISEASE SPREAD eg. AHS and Bluetongue
AFRICA
increasingly milder winters >> longer midge survival during year
EUROPE
Culicoides imicola in Africa is competent
vector of AHS and BT viruses. Spreads far on wind.
• Culicoides obsoletus in Europe could become
competent vector under warmer conditions.
• Can C.imicola become common in Europe?
• Baton effect, virus passes from African midges
>> cattle >> European midges
cattle are reservoirs for BTV
for ~200 days
sheep are not carriers
after infection .