Did disease spread on cattle trails?

Absolutely. Cattle and horse born diseases spread all along the trail. Of course with any travel some human illnesses would travel too. Look at how smallpox spread to the Indians as explorers and traders moved west. Cattle would also carry seeds for noxious (unwanted/hard to kill) weeds and vermin. For many years cattle coming from Mexico had to be dipped in pesticides to kill the lice and tics before they could be brought to the US.