Pacific Coast Tick

There are two types of ticks – hard shelled and soft shelled. Hard ticks have a shield-like plate (scutum) covering part of their back while soft ticks lack a scutum. Ticks, like spiders, are classified as Arachnids and have 8 legs.

All ticks are dependent upon blood for survival. Their life cycle cannot be completed without finding hosts whose blood they can feed upon. Egg, larva, nymph and adult are the four stages of a tick’s life cycle.

The Pacific Coast tick (Dermacentor occidentalis) is a hard-shelled tick found in shrub lands, chaparral and along trails from Oregon through California to Baja and Mexico. The Pacific Coast tick’s body is relatively flat, non-segmented and pear-shaped. It is brown with the back mottled with grey, black and brown.

Many people fear tick bites, with good reason. All life stages of the Pacific Coast tick transmit Rocky Mountain spotted fever (Rikettsia rickettsii) to humans, cats and dogs. Adults and nymphs also transmit 364D rickettsiosis (Rickettsia phillipi) to humans, tularemia (Francisella tularensis) to human, cats and dogs, bovine anaplasmosis to cattle and tick bite paralysis to cattle, deer and ponies. Pacific Coast ticks are not supposed to transmit Lyme disease, however there is some recent research that indicates some possibility of Lyme disease transmission by D. occidentalis.

Adult Pacific Coast ticks feed on cattle, deer, horses, humans and other large mammals. Males attach and feed for a short time in order to initiate spermatogenesis then fall off. Females feed and engorge themselves with blood for 6 to 10 days before dropping off and laying several thousand eggs.

In about a month the Packfic Coast tick eggs hatch into larvae. The larvae feed on small rodents for about four days before detaching and falling to the ground. The larvae develop into nymphs after about two weeks.

Nymphs prefer to feed on small rodents, particularly squirrels, and other small mammals for about 6 days before detaching. It takes 15 to 25 days for Pacific Coast nymphs to develop into adults and begin the cycle again.

A few days ago I picked up this Pacific Coast tick while hiking along the Loop Trail at Baum Lake (Shasta County CA). Pacific Coast ticks are active throughout most of the year.




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