Deer are not the main carrier of lime disease. Ticks are the main carriers. This is because many reports have been done since the discovery of this problem, and in almost every cases, ticks seem to be the culprits. Since most people do not come into contact with deer, the bugs would be the carriers.
I dont think that deer would be the main carrier , however I do believe that ticks are the main carrier because its not like a deer can just get the disease without it being transfered to them, the reason they most likely get it just like humans is the tick biting them.
Ticks are the carriers of the bacteria that causes Lime (Lyme?) Disease in the human population. There are certain types of ticks called deer ticks that carry the bacteria and may feed on deer, but actual deer are not the main carriers of the disease. Also, deer do not give the disease to the ticks. They usually get it from infected rodents, such as mice.
Lyme disease is a tick-borne disease that is commonly spreading through deer ticks. Those ticks get their name because of how commonly they are found on deer, but that's where the commonality ends. Ultimately the bacteria that causes lyme disease comes from rodents, and accordingly the culprit is the tick - not the deer.
Lime disease are caused and transmitted by a variety of reasons. But various animals are responsible for carrying the disease. Deers as well as many different other mammals carry the disease, which is then carried over to humans when they are bit by something like a tick that had bitten an animal.
Lyme disease transmission to humans usually occurs during the late spring and early summer when young (nymph stage) ticks are active and feeding. Tick nymphs normally feed on small and medium sized animals, but will also feed on people. These ticks typically become infected with the Lyme disease agent by feeding as larvae on certain rodent species. (Tickbrochure.PDF). So a tick as well as a deer are not the main carriers, but in fact the rodent species are indeed the infected carrier.