Ticks in Arizona

There are two families of ticks in the order Parasitiformes: Ixodidae, hard ticks or ixodids, and Argasidae, soft ticks or argasids. Soft ticks have oval bodies sporting two round discs. Their mouth parts are not visible and they feed on blood in a matter of hours. Hard ticks, unlike soft, have a shield on their backs called a scutum. Bottom edges of the scutum have festoons, or indentations. Mouths of hard ticks are visible in the head area, called the capitulum. Hard ticks feed on a host over a matter of days. Both types of ticks have hypostomes, harpoon-like structures to break the host's skin and to anchor the tick while feeding.

The brown dog tick (Rhipicephalus sanguineus), an ixodid, is found in Arizona and throughout the United States. While this tick usually parasitizes dogs, humans are becoming blood meals, too. Unlike other ticks, the brown dog tick can complete a life-cycle indoors. Consequently, these ticks can travel on hosts to a variety of places, even cold climates. The reddish-brown color of the tick is a key to identification. Dogs get two types of diseases from this tick: canine ehrlichiosis (Ehrlichia canis) and canine babesia (Babesia canis). Humans contract Rocky Mountain spotted fever.

The Dermacentor andersoni, or Rocky Mountain wood tick, is an ixodid found in the arid brushy areas of northern Arizona. They are temperature sensitive, preferring lower elevations at higher temperatures (1,600 to 2,200 meters) and higher elevations at lower temperatures (2,350 to 2,500 meters). Dermacentor andersoni is also reddish-brown in color. These ticks differ from the reddish-brown dog tick in that female Rocky Mountain wood ticks have gray on the upper part on the scutum and males are streaked with gray. These ticks also transmit Rocky Mountain spotted fever to humans.

Ixodes Pacificus, the western black-legged tick, is endemic along the West Coast of the United States. However, these ixodids have been found in Arizona in the Hualapai Mountain Park, Mohave County. White-tailed deer are an important host for these ticks. Male bodies are long and slender; females are rounder. The reddish-brown markings on the scutum are offset by black; on the female, the upper part of the shield is black. Males have black mottling. These ticks transmit Lyme disease to humans.