Examination of the Potential Transmission of Salmonella from House Flies to the Peripheral Lymph Nodes of Cattle via the Mucous Membranes

<p>Holstein steers (approx. BW 125 kg) will be utilized for the experiments. Previously, we demonstrated the transfer of a marked strain of Salmonella to spinach by blowflies using a similar experimental design as proposed in these objectives. Briefly, adult house flies will be chilled to immobilize, then the distal 2/3 of their wings cut off to prevent flight. De-winged flies will be placed individually into petri plates containing Salmonella and allowed to move freely to acquire the bacteria. Control flies will be exposed to sterile water. A sample of flies will be processed at this stage to determine the average uptake of bacteria, and thus the average exposure to the mucus membrane by an externally inoculated fly. The inoculated flies will be moved by soft forceps into a sterile container which will be affixed to Holstein steers, allowing the fly access to the mucous membranes. After, the flies will be cultured for Salmonella. Wipes will be made of the exposed area of the mucus membrane and processed for Salmonella to determine topical contamination. Cattle will be euthanized at varying time points and the PLN removed and examined for the challenge strain of Salmonella. Experimental procedures will be adjusted based on results from each experiment and successful experiments replicated as required.</p>