They have four stages of life: egg, larva, nymph, and adult. Ticks tend to feed and mate mostly on deer and a female tick can lay up to a few thousand eggs per season, dying afterward. After hatching they search for their first meal, often from an animal such as a mouse, chipmunk, bird or deer. Following this they are able to transmit disease to other animals and/or humans. In each stage, they suck blood from a host, then drop off, enter a dormant period and molt to the next stage. They don’t begin life carrying Borrelia burgdorferi, that occurs when they feed of an infected host, most often a small rodent such as a mouse. Other strains such as Borrelia myamotoi and infections like Powassan virus can be transmitted from adult female ticks to their eggs.
The majority of cases of disease are caused by nymph-stage ticks. They are as small as a poppy seed and with a painless bite often go unnoticed. Adult ticks are also capable of transmitting infections, but are more noticeable and easier to remove.
The length of time a tick needs to be attached in order to transmit Lyme is most commonly placed between 24 to 48 hours. However, this is a hotly debated issue as there is no scientific evidence currently available that conclusively proves such a statement. Many individuals also don’t know how long a tick was on them or ever saw one at all. Contrary to statements proclaiming very clear attachment times before pathogens can be passed from a tick to a human, there are documented cases of Lyme disease transmission with only 6 hours of attachment time. Tick-borne coinfections can be transmitted quicker.
Not all ticks are pathogen carriers either. Rates of infection in the tick population are not always consistent and can change depending on the local climate and season. During years of larger than average acorn crops, tick populations tend to rise. This is directly affected by an increase in rodent populations, acorns being their main food source.
While particular species of ticks are still largely considered to be regionally located, climate change and migratory birds are leading to species and strains of the diseases they carry to be discovered in areas where they traditionally wouldn’t be. This also goes for the types of infections particular ticks can transmit to humans.
The majority of medical literature states that the only tick species to carry Lyme disease is the Deer Tick (Ixodes scapularis), but this has not been proven. It is best to stay away from all ticks and not assume that one species is safer than another.