susie, I think it's actually the esopagus (sp?), rather than the trachea.
"The young grubs burrowing through the skin cause rashes and sore spots that get infected easily. The grubs migrating in the animal's body injure the esophagus, the spinal cord, and other internal organs, and perhaps also produce substances that are harmful to the animal. The swelling and pain in the esophagus interfere with swallowing of food and chewing the cud and lead to loss in weight or gain and digestive disorders, including bloat. Sometimes the grubs injure the spinal cord and cause paralysis.
When grubs are accidentally crushed in the warbles, they may cause allergic reactions. Beef cattle infected with grubs do not finish well and sell for lower prices than grub-free ones. Grubs damage the flesh and the hide. Cattle grubs also cause the following packing-house losses:
Trim loss: The actual value of damaged tissue removed from the carcass plus a nominal labor charge.
Devaluation loss: The reduction in sales value of carcasses or prime cuts due to marred appearance.
Hide loss: The reduction in the value of hides because of warble holes.
All of these types of damages are directly caused by the presence of warbles in the back area."