Climate is part of the reason why ticks are abundant, but there are other reasons.
The surge in deer — which feed ticks and spread them around — is a big factor. Deer are often considered the prime source of spreading Lyme disease–they act as hosts to adult ticks.
It is estimated, though, that nymphs are responsible for 90 percent of human disease transmission. They feed in the summer when people are most apt to be involved in outdoor activities.
Mice are very efficient transmitters of Lyme. Mice are responsible for infecting the majority of ticks–up to 95 percent– who carry Lyme in the Northeast. Mice are thriving in our degraded, fragmented landscapes because their predators need big forests to survive. Without as many foxes, hawks and owls to eat them, it results in forests loaded with mice infected with Lyme and covered with ticks. All these small areas of forest in the Northeast have turned into Lyme factories with infected ticks.
People think opossums might be rabid when they drool and hiss when threatened. In fact, opossums are resistant to rabies. Having once waddled around past dinosaurs, they are one of the oldest species of mammal. Among many opossum traits, they groom themselves like cats. If they find a tick, they lick it off and swallow it. In one season, an opossum can kill approximately 5,000 ticks. More than 90 percent of ticks they find end up getting groomed away and swallowed. http://www.caryinstitute.org/newsroom/opossums-killers-ticks
Japanese Barberry was brought to this country in 1875 because it is an attractive, hardy plant that requires little maintenance and is deer-resistant. The plant t was not considered a problem until the 1980s when it began to take the place of native plants. They are no considered invasive. Unfortunately, it is a perfect environment for ticks, especially immature ticks (nymphs) over a wide area. http://today.uconn.edu/2012/02/controlling-japanese-barberry-helps-stop-spread-of-tick-borne-diseases/