Oregon Hard Tick ID
Biology of Hard Ticks
Tick are arthropod ectoparasites can live upwards of 2-3 years, and live on an obligate diet of blood from mammals, birds, reptiles, and amphibians. Ticks are generally separated into 2 distinct groups: Soft Ticks (argasidae) and Hard Ticks (ixodidae) and there are approximately 878 species worldwide. Some ticks will progress to successive life stages on a single host, while others will find new hosts as they grow larger with each molt.
One-host Ticks – these ticks will remain on the same host through all 3 life stages from larva to nymph. When they reach adulthood, the females will drop off the host after feeding to lay their batch of eggs.
Two-host Ticks – these ticks will feed on two hosts during their lives, staying on a single host for the larval and nymph stages. As an adult, it drops off the 1st host to attach to a 2nd host for its final bloodmeal and will drop off the 2nd host to lay eggs.
Three-host Ticks – these ticks will attach to a new host with every life stage: a larval host, a nymph host, and an adult host. After the 3rd host and a bloodmeal, it drops off to lay eggs.
In all 3 of these life cycles, the fed adult female will die after laying her eggs and the cycle begins anew.
Eggs – each female tick can lay ~ 3000 eggs and hatch in the late summer. To be reproductively ready, a tick must go through a year of development, laying eggs the 2nd spring after being hatched. Each female tick will only produce a single batch of eggs before dying along with the male after reproduction is complete.
Larvae – Before the larvae’s first molt, it will have only 6 legs, rather than 8 and be the size of a period (.). Freshly hatched larvae are disease free but can easily become pathogenic carriers by feeding off small rodents and rabbits. Eggs are usually positioned near small animal trails to give easy access for the larvae to find potential hosts. Once larvae have finished feeding on a host, they will detach and continue to develop into nymphs throughout the fall and winter, sheltering beneath leaf litter or nesting on a host for warmth.
Nymph – After overwintering on the ground, larvae are now nymphs and will have 8 legs and are as small as a poppy seed. To grow further and molt into an adult, it must find a new host. This is usually when ticks may choose a larger host like deer, raccoons, and humans. Throughout May, June, and July, nymphs are still very tiny and possibly infected. Nymphs that became infected with disease-causing bacteria during their larva stage can transmit these pathogens to hosts such as humans or pets at this point (Lyme).
Alternatively, uninfected nymphs can become infected with bacterial diseases from new hosts such as deer, which can then be transmitted even in the adult stage. Since they are hard to see due to their size, nymphs are responsible for nearly all human Lyme disease cases.
Adult – After feeding, nymphs transition into adults by their second fall or winter. With the end of their lifecycle nearing, adults will drop off hosts to reproduce and lay eggs. Peak activity for adults is between October and November. Adults contribute few cases of Lyme due to their large noticeable size and are removed before the Lyme spirochete can be transmitted (more than 36 hours).
Seasonal Activity of the Deer Tick (Ixodes pacificus/ I. scapularis)
Year 1 – Spring – Adult females on their 2nd year will lay thousands of eggs, then die shortly after. The male will also die after mating 1-2 times. By late Summer, eggs are hatched and larvae are looking for a 1st small host (Birds, mice, rabbits). By Fall, larvae have dropped off the 1st host and developed into nymphs. Nymphs will become dormant, overwintering under leaf litter all through Winter.
Year 2 – Spring – Nymphs will emerge from dormancy and begin looking for a 2nd host (rodents, deer, dogs, humans) well into early summer. Throughout Summer, the nymph will continue to develop and by early Fall, the nymph is now a reproductive adult. Between fall and early Winter, adults will find a final host (deer) before going dormant until spring or until temperatures improve. Adults that fail to find a suitable host will shelter in leaf litter, becoming inactive when temperatures dip below 45° F. In late Winter to early Spring (March – April), the 2nd peak of adult activity begins as those ticks who failed to find winter hosts will find a bloodmeal host to prepare for mating. The female will engorge herself for one week, while males will feed intermittently, then mate on or off the host deer, with the male dying after mating. The female then drops off the host (if attached), becomes gravid (egg-laden), laying her eggs under the leaf litter in the early Spring, then dies as her two year lifecycle is complete.
Q: Why are Deer ticks so active in the fall? The main host animal is the deer, which are most active in the fall months. This gives the tick much more host encounters, since they use ‘questing’ tactics along common game trails.
Q: How do ticks attach to hosts? Ticks use something called ‘questing”, in which they crawl and perch onto the tips of long grasses or stems. Their 6 back legs are used for grip, while the front legs are extended out to easily latch onto a passing host. As larvae, they attach when a bird or mouse come close to them on the ground after hatching from their egg
Q: Why are ticks so hard to remove from skin?
Ticks have a mouthpart that is barbed (Hypostome) like backwards-facing teeth to help keep them inserted. On either side of the hypostome is a pair of chelicerae that act as retractable rods with hooks on the ends. These chelicerae actually open up the skin for the hypostome to embed itself, while using the hooks to go deeper to secure itself for multiple days. Ticks use a kind of cement in their saliva injected via the hypostome as well as an analgesic (numbing compound) to help it go unnoticed.
Diseases transmitted by ticks in the U.S.
Ticks can transmit many different types of pathogens including: viruses, rickettsiae,
spirochetes and bacteria, fungi, protozoa, and filarial nematodes – surpassing even mosquitoes in this regard. Some of the human diseases of current concern are Lyme, ehrlichiosis, babesiosis, rocky mountain spotted fever, tularemia, and tick-borne relapsing fever.