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Madeline Phillips, Carlton, Christopher E.
Dermacentor variabilis, the American dog tick (also called the wood tick), is typically east of the Rocky Mountains and California in the U.S. Unfed (nonengorged) American dog ticks average about 4 mm in length and vary in color, from uniform reddish-brown to reddish-brown with tan markings. The scutum forms a large oval at the front of the body and bears the mouthparts and four pairs of legs. Males have a cream-colored pattern that extends from the scutum onto the abdomen. Typically, this pattern forms two vertical zigzags down the entire length of the body. Females also have cream-colored patterns, but the pattern only forms a U-shape on the scutum. The scutum is relatively larger on male ticks. Engorged adults can reach 15 mm in length and are uniform gray or tan. Female ticks are slightly larger than males.
The minute eggs are deposited in clumps numbering thousands of eggs each. Hatchlings possess three pairs of legs and are referred to as larvae. Larval ticks of various species are called seed ticks colloquially. Second stage ticks (nymphs) are about 1 mm long and possess four pairs of legs. Engorged nymphs are larger and dark gray in color.
The American dog tick is one of five species in the genus Dermacentor in the U.S. and the only member of the genus found in Louisiana. The other species are more northern and/or western in distribution. The species are similar in appearance and a taxonomist or diagnostician should be consulted in cases where the identity is uncertain.
Adult male, left, and adult female (Mat Pound, Bugwood.org, Creative Commons 3.0).
American dog ticks go through a total of four life stages: egg, larva, nymph and adult. This life cycle normally lasts two years from egg to the adult stage. During the fall, adult females lay their eggs in leaf litter or other surface debris. The three-legged larvae hatch the same season and overwinter. When spring arrives, they seek their first host, which is typically a small mammal such as a rodent, but they can attach to humans at any stage, although this is uncommon for larvae and nymphs. Engorged larvae fall from the first host by summer and molt into the second, nymphal stage by fall of the first year. During the following spring, the nymphs seek a second host, typically another small mammal. Nymphs feed until fall of the second year, then drop from the second host and molt into adults. The following spring, these adults search for their third hosts which are generally larger mammals such as deer and other wild animals, dogs or humans. Adult ticks can survive many months without a blood meal. Males and females mate on the host while the female feeds. Several hosts can be used by a single tick, depending on availability. When mating and feeding are complete, the female drops and begins laying eggs.
American dog ticks are typical of open habitats such as grasslands and scrub. They also occur along trails and in forest edge habitats. Immature stages are most active during spring, and adults are active during summer.
The American dog tick is of great medical and veterinary importance. In humans, American dog ticks are major disease vectors of Rocky Mountain spotted fever (RMSF) and tularemia. In canines they can cause canine tick paralysis. RMSF is a serious disease that can be deadly when not treated. Early detection is crucial for effective treatment. Typically, RMSF begins with flu-like symptoms and later a large rash may spread across the body that can produce permanent scars and other complications. The disease is difficult to diagnose, but treatment is effective with early medical intervention. Recent presence in tick infested areas or known tick bites are important clues that may alert physicians of the possibility of RMSF. Tularemia is a bacterial disease of humans and other animals vectored by various ticks and blood feeding insects. As with RMSF, it can be effectively treated if diagnosed early.
Adult female Dermacentor variabilis (Gary Alpert, Bugwood.org, Creative Commons 3.0).
Monitoring and prevention. Surveying for ticks by specialists is usually done by flagging, which documents tick species and relative abundance. Flagging utilizes a piece of cloth attached to a handle that is waved through foliage or dragged along the ground. Ticks detect the movement, attach to the cloth and are then collected, identified, preserved and deposited into collections as vouchers. Collection efficiency can be enhanced using carbon dioxide in the form of dry ice as an attractant.
Individuals walking in tick infested habitats should frequently and thoroughly check their bodies for ticks. Larval ticks (seed ticks) can be difficult to detect initially and can rapidly inflict large numbers of bites on exposed skin. Removal of ticks within 24 hours of attachment can be effective in preventing disease transmission. Wearing long pants and high socks can minimize tick access to bare skin, and treating clothing with high percentage formulations of DEET or pyrethroid based insecticides appropriately labeled for clothing treatment is more effective in deterring ticks. Always follow label directions when applying repellents or clothing treatments of insecticides.
Natural control. In residential situations, especially in rural surroundings, tick populations can be managed by keeping lawns cut short, keeping shrubbery away from homes and buildings, and treating pets with appropriately labeled tick prophylactic formulations. Maintaining awareness of tick seasonal cycles of activity and species occurring in the vicinity can also contribute to avoiding bites.
Chemical control. Perimeter sprays using pyrethroid-based formulations labeled for ticks can reduce populations in small areas, but no effective control for large areas of tick habitat is available.
Contact Us: For advice about pest identification or diagnosis, contact the LSU AgCenter Department of Entomology. Reach the department through the Contact Us webpage.
P4015
9/15/2025
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