Alighting Dipterous Insects on Cattle are Associated to Contaminative Transmission of Foot-and-Mouth Disease During Epidemics in Ngaoundere- Cameroon

This study was designed to identify the landing preference sites of common hematophagous symbovine Dipterans and relate it to the FMD shedding sites. Three sets of zebu Goudali (from the DFG-COBE project herd) of different colors (black, brown and white) of same ages were restrained to sticks. Observations were made in October/November 2016 (seven days consecutively) and January 2017 (7days consecutively). Data from literature on FMDV infectious doses (TCID50/ml) shedding areas in clinical cases was used to map such sites on cattle and associate it to the landing predilection sites of hematophagous dipterous insects. The total number of observed biting insects on cattle was 26779 and the following fly-groups were identified in order of magnitude: Stomoxys (17453), culicids (8925), Simulium (293), Chrysops (74) and Tabanus (34). Chrysops preferred biting front legs. Culicids preferred biting around legs and neck. Tabanus preferred biting around head and legs. Stomoxys preferred biting around neck and legs. The neck and legs were body parts with the highest insect-vector frequency. The alighting predilection of each insect-group differed statistically (P<0.05). From the association test, an important number of each insect group was associated to at least one of the FMD contamination spots on cattle, but Stomoxys and culicids had a higher propensity of being contaminated as compared to others based on their high landing numbers on the exposed animals.