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Rocky Mountain Spotted Fever (RMSF)

About Ticks

The ticks that spread RMSF in the U.S are the American Dog tick, Dermacentor variabilis, found in the east of the Rocky Mountains and the Rocky Mountain wood tick, Dermacentor andersoni, which is found in the Rocky Mountain States. In Arizona, the tick that spreads RMSF is the Brown Dog tick, Rhipicephalus Sanguineus, which is the most widely distributed tick in the world. Unlike other ticks that spread RMSF, the Brown Dog tick can live indoor, outdoor, or near homes where dogs live.

How Ticks Survive

Most ticks go through four life stages: egg, six-legged larva, eight-legged nymph, and adult. After hatching from the eggs, ticks must eat blood at every stage to survive. Brown Dog tick, R. sanguineus, primarily feed on dogs in all life stages and humans may become incidental hosts.

How Ticks Find Their Hosts


R. sanguineus (brown dog tick) “questing” and ready to attach
  • Ticks find their hosts by detecting the breath and body odors of animals, or by sensing body heat, moisture, and vibrations
  • Some ticks can even identify a shadow
  • Ticks pick a good place to wait by finding well-used paths, resting on tips of grasses and shrubs
  • Ticks can't fly or jump, but they wait in a position known as “questing”

How Ticks Spread Disease

Ticks are the primary hosts of R. rickesttsii and are able to pass the bacteria to their babies.

Ticks also pass the bacteria that cause RMSF (disease) through the process of feeding:

  • Preparing to feed can take from 10 minutes to 2 hours. When the tick finds a feeding spot, it grasps the skin and cuts into the surface.
  • The tick inserts its feeding tube, which may or may not have barbs to help keep the tick in place. Some ticks secrete a cement-like substance that keeps them firmly attached during the meal.
  • Ticks secrete small amounts of saliva so that the animal or person can't feel that the tick has attached itself. If the tick is in a sheltered spot, it can easily go unnoticed.
  • If the host animal has a blood-borne infection, the tick will ingest the pathogens with the blood. If the tick contains a pathogen, the infection may be transmitted to the host animal through small amounts of saliva that enter during the feeding process.
  • After feeding, most ticks will drop off and prepare for the next life stage. At its next feeding, it can then transmit the disease to the new host.

How to Remove a Tick

For information on how to remove a tick, go to RMSF and Prevention page

How Ticks can be Controlled

The best way to control ticks is through an integrated tick management approach which uses products that are effective for killing ticks and are safest for people and animals:

  • Apply pesticides to areas where ticks are likely to be found in the yard (such as places where dogs sleep, under decks and porches and in cracks and crevices)
  • Apply pesticides often and in the right season (in Arizona climate reapply every 3-4 weeks in heavily infested areas beginning in early spring through late fall)
  • Remove tick habitats in the yard including: leaf litter, brush, and yard clutter (boards, mattresses, old furniture, etc.)
  • Apply appropriate pesticides for area being treated (use different products for indoor and outdoor use)
  • Use spot-on treatments, tick collars, sprays, or dips to control ticks on pets (follow the label and your veterinarian's instructions)

For more information on tick control, see Tick Management Handbook. (Courtesy of the Connecticut Agriculture Experiment Station)