Rocky Mountain Wood Tick

Dermacentor andersoni

Description

Appropriately named, the Rocky Mountain wood tick is found predominantly in states with the Rocky Mountains, and is typically found in shrubs, lightly wooded areas, and grassland. It is a known vector of Rocky Mountain spotted fever and tularemia. Adult ticks feed primarily on large mammals, while larvae and nymphs feed on small rodents. Adult stage ticks are the ones primarily associated with pathogen transmission to humans. Wood ticks typically take two to three years to complete their life cycle.

 

Nymph
Adult Male Adult Female Engorged Female


Biology

In the Mountain region of the U.S., adult male and female wood ticks can be active from January through November, but are most common in the late spring/early summer and their activity diminishes during the hot and dry mid-summer period. Further west in the northern inter-mountain region, large numbers of adult wood ticks can occur in April and May. Adult wood ticks survive for up to 600 days without feeding. Adult ticks prefer to feed on medium to large mammals and can be found questing about knee-high on the tips of vegetation. Males only blood feed for short periods of time to initiate spermatogenesis, after which they seek to attach to and mate with female ticks. Female wood ticks feed for 4-17 days before dropping off their host and laying up to 6,000 eggs.

 


Disease Transmission

All life stages of the tick can transmit Colorado tick fever to humans, and Rocky Mountain spotted fever (Rickettsia rickettsii) to humans, cats, and dogs.Rocky Mountain wood tick saliva contains a neurotoxin that can occasionally cause tick paralysis in humans and pets. A bite from an adult female can induce an ascending paralysis that should stop after just a few minutes after the tick being removed, however may persist for up to a day or more. Both nymphs and adults of this tick can transmit tularemia to a variety of hosts, including humans, cats, and dogs.

Rocky Mountain wood tick saliva contains a neurotoxin that can occasionally cause tick paralysis in humans and pets; usually a bite from an adult female induces an ascending paralysis that dissipates within 24-72 hrs after tick removal. Both nymphs and adults of this tick can transmit the agent of tularemia (Francisella tularensis) to a variety of hosts, including humans, cats, and dogs. These ticks typically take two to three years to complete their life cycle.

 


Habitat & Range

Appropriately named, the Rocky Mountain wood tick is found predominantly in states with the Rocky Mountains, and is typically found around shrublands, lightly wooded areas, open grasslands, and along trails, mainly at lower elevations.