Rocky Mountain wood tick

The Rocky Mountain wood tick may be found throughout western North America. This tiny, spider-like creature lives on vegetation and waits for passing animals so it can suck their blood. This tick transfers diseases like Rocky Mountain spotted fever, Colorado tick fever, and tularaemia in people and certain animals.

Kingdom: Animalia

Phylum: Arthropoda

Class: Arachnida

Order: Ixodida

Family: Ixodidae

Genus: Dermacentor

Species: Andersoni

The small Rocky Mountain wood tick is a pest throughout North, Central, and South America. This tiny animal is only a few millimeters long but carries disease organisms to people and animals as it sucks their blood.

The Rocky Mountain wood tick has a rounded body with eight legs like spiders and other arachnids. Its body has two sections. The first is the cephalothorax. This section is also called the prosoma. The cephalothorax contains the head, biting mouthparts, and the thorax, or middle area of the body. The eight legs attach to this section also. They are for walking as well as sensing surroundings and detecting approaching animals or people on which to feed. Before feeding, the ticks measure 1/8 of an inch (3 1/5 millimeters) long, and after eating, they are 5/8 of an inch (16 1/2 millimeters) long.

Behind the cephalothorax is the abdomen, or the section sometimes called the opisthosoma. This is the section which contains all the organs. It is also the section that swells from being flat to looking like a glob when it is filled with blood. Covering the dorsal, or back, side of the tick is a scutum. This is a hard shield or plate and is the reason this species is called a hard tick. Other species do not have scuta and are called soft ticks.

Because it feeds on the blood of other animals and people, the Rocky Mountain wood tick is called a parasite. In general, a parasite is an animal or plant which lives and feeds on or inside another plant or animal. With its sharp jaws, this tick species attaches itself to an animal or person, called a host, pierces the skin, and sucks the blood. This may take several days. As it sucks the blood, it also releases its saliva with chemicals to prevent the blood from coagulating, or clotting. Common victims of adult Rocky Mountain wood tick are horses, cattle, sheep, other large animals, and people.

After feeding, the Rocky Mountain wood tick drops to the ground. Males feed for short times. Females mate shortly before or after such a meal. They feed for 4 to 17 days and lay up to 6,000 eggs before dying. The eggs hatch after two to five days. The larvae, or young, have six legs. They quickly find a host, feed, and then drop to the ground. The larvae molt, or shed, their skins and become nymphs. The nymphs find a second host and repeat the process. The next stage is adulthood and feeding on a third host. This species is called a three-host species. Hosts of larvae and nymphs are small animals like rabbits, squirrels, and chipmunks. The Rocky Mountain wood tick can survive for 600 days without feeding. Its life span may be up to 10 years.

The Rocky Mountain wood tick is well-known as the transmitter, or carrier, of certain diseases. These diseases are caused by other organisms, but ticks pass them on to their hosts. One disease is tularaemia, which affects rabbits and so is commonly called rabbit fever. Two diseases are Colorado tick fever virus (CTFV) and Rocky Mountain spotted fever (RMSF) caused by rickettsia (Rickettsia rickettsii). These result in rashes, itching, chills, fevers, and severe pain in muscles and joints. Treatment for tularaemia and Rocky Mountain spotted fever is antibiotic drugs.

The American dog tick, Dermacentor variabilis, also carries Rocky Mountain spotted fever.

Bibliography

Munyarubuga, Jean-Claude. "Dermacentor Andersoni." Animal Diversity Web, animaldiversity.org/accounts/Dermacentor‗andersoni. Accessed 15 Apr. 2024.

"Rocky Mountain Wood Ticks." Pest World, www.pestworld.org/pest-guide/ticks/rocky-mountain-wood-ticks. Accessed 15 Apr. 2024.