FLY VECTORS MECHANICAL TRANSMISSION OF PATHOGENS

flies take manymeals for each egg batch, thus rapid transmissionon contaminatedmouthparts

eg. Moraxella transmission by Musca or Trypanosoma by tabanids

repeated egg batches

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

FLY VECTORS FLIES COMPARED TO TICKS AS VECTORSsingle 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

FLY VECTORS VERTEBRATES AND VECTORS AS RESERVOIRS

January January

seasonal peak of vectors

reservoir host

new reservoir host

disease host

Nos

eg. bluetongue by Culicoides

FLY VECTORS AMPLIFICATION OF VIRUS TRANSMISSION

reservoir host disease host

but insufficient virus in vector

refractory host disease host + plenty virus in vector

vector needs to survive well and feed ofteneg. bluetongue by Culicoides

.

FLY VECTORS DISEASE SPREAD eg. AHS and Bluetongue

AFRICA

increasingly milder winters >> longer midge survival during yearEUROPE

Culicoides imicola in Africa is competentvector 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 BTVfor ~200 days

sheep are not carriersafter infection