“Ticks on Nantucket” by Dan Driscoll for the Nantucket Board of Health
How to spot a tick
The adult female tick is red-brown with black legs, about 1/8 of an inch long; males are smaller and entirely brown/black. Both are teardrop shaped.
Ticks do not fly, jump or drop from trees. Instead, they climb to the tips of vegetation, typically along animal trials or paths, and wait for a host to brush against them.
What is a tick?
Ticks are not insects but, a class of what is known as Arthropods. This includes mites, spiders and scorpions. They are divided into two groups – hard bodied and soft bodied – both of which are capable of transmitting diseases in the United States.
Ticks are parasites that feed by latching on to an animal host, imbedding their mouthparts into the host’s skin and sucking its blood. This method of feeding makes ticks the perfect transmitter of disease. Ticks are responsible for at least ten different known diseases in humans in the U.S., including Lyme disease, Rocky Mountain spotted fever, babesiosis, and more recently, anaplasmosis and ehrlichiosis.
Life cycle of a deer tick
The deer (or black-legged) tick in the East and the related western black-legged tick are the only known transmitters of Lyme disease in the United States. Both are hard-bodied ticks with a two-year life cycle. Like all species of ticks, deer ticks and their relatives require a blood meal to progress to each successive stage in their life cycles.
The life cycle of the deer tick comprises three growth stages: the larva, nymph and adult. In both the northeastern and mid-western U.S., where Lyme disease has become prevalent, it takes about two years for the tick to hatch from the egg, go through all three stages, reproduce, and then die.
How ticks survive
Most ticks go through four life stages: egg, six-legged larva, eight-legged nymph, and adult. After hatching from the eggs, ticks must eat blood at every stage to survive. Ticks that require this many hosts can take up to 3 years to complete their full life cycle, and most will die because they don’t find a host for their next feeding.
How ticks find their hosts
Ticks find their hosts by detecting animals´ breath and body odors, or by sensing body heat, moisture, and vibrations. Some species can even recognize a shadow. In addition, ticks pick a place to wait by identifying well-used paths. Then they wait for a host, resting on the tips of grasses and shrubs. Ticks can’t fly or jump, but many tick species wait in a position known as “questing”.
While questing, ticks hold onto leaves and grass by their third and fourth pair of legs. They hold the first pair of legs outstretched, waiting to climb on to the host. When a host brushes the spot where a tick is waiting, it quickly climbs aboard. Some ticks will attach quickly and others will wander, looking for places like the ear, or other areas where the skin is thinner.
How ticks spread disease
Ticks transmit pathogens that cause disease through the process of feeding.
- Depending on the tick species and its stage of life, preparing to feed can take from 10 minutes to 2 hours. When the tick finds a feeding spot, it grasps the skin and cuts into the surface.
- The tick then inserts its feeding tube. Many species also secrete a cement-like substance that keeps them firmly attached during the meal. The feeding tube can have barbs which help keep the tick in place.
- Ticks also can secrete small amounts of saliva with anesthetic properties so that the animal or person can’t feel that the tick has attached itself. If the tick is in a sheltered spot, it can go unnoticed.
- A tick will suck the blood slowly for several days. If the host animal has a blood borne infection, the tick will ingest the pathogens with the blood.
- Small amounts of saliva from the tick may also enter the skin of the host animal during the feeding process. If the tick contains a pathogen, the organism may be transmitted to the host animal in this way.
- After feeding, most ticks will drop off and prepare for the next life stage. At its next feeding, it can then transmit an acquired disease to the new host.