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American Dog Tick

Introduction

Dermacentor variabilis (Say), also known as the American dog tick or wood tick, is found predominantly in the United States, east of the Rocky Mountains, and as its name suggests, is most commonly found on dogs as an adult. The tick also occurs in certain areas of Canada, Mexico and the Pacific Northwest of the U.S. (Mcnemee et al. 2003). Dermacentor variabilis is a 3-host tick, targeting smaller mammals as a larva and nymph and larger mammals as an adult. Although it is normally found on dogs, this tick will readily attack larger animals, such as cattle, horses, and even humans. The 8-legged adult is a vector of the pathogens causing Rocky Mountain spotted fever (RMSF) and tularemia, and can cause canine tick paralysis. While the American dog tick can be managed without pesticides, when necessary a recommended acaricide is an effective way of eliminating an existing tick infestation near residences.

Distribution

The American dog tick is widely distributed in the United States east of a line drawn from Montana to South Texas. It is also found in Canada, east of Saskatchewan, and in California, west of the Cascade and the Sierra Nevada Mountain ranges. This species is most abundant in the eastern United States from Massachusetts south to Florida but is also common in more central areas of the U.S., including Iowa and Minnesota (Matheson 1950).

It was been suggested that adult ticks move to the edge of the roads and trails in an attempt to find a host, or “quest.” Some have hypothesized that because many animals typically follow trails, they leave an odor that attracts these ticks causing them to move toward and quest alongside trails in attempts to find a host (Mcnemee et al. 2003).

Description

The 8-legged adult male and female D. variabilis ticks are typically brown to reddish-brown in color with gray/silver markings on their scutum (dorsal “shield”). The female will vary in size depending on whether or not it has blood fed. Unfed females are typically 5 mm long and are slightly larger than males, which are about 3.6 mm long. Females can be distinguished by a short or small dorsal scutum, right behind the mouthparts while the male scutum covers the majority of its dorsal surface. Blood-fed (engorged) females can enlarge up to 15 mm long and 10 mm wide.

Removal

Ticks should not be removed by handpicking because infected tick secretions can be transferred from a person’s hands to his or her eyes, mucous membranes, mouth, etc. Therefore, forceps should be used when removing a tick (Smith and Whitman 1992). To properly remove a tick, grasp the mouthparts near the attachment site firmly with tweezers. Once the mouthparts are held, the tick should be pulled straight back slowly to ensure the entire mouthparts are removed from the body. It is important that the tick is removed slowly because the mouthparts are covered in sharp, backward directed barbs which assist the tick in holding onto its host (Parsons et al. 1989). Sometimes, by removing the tick, a piece of the hosts skin may break off, which should not be a great concern, but bears watching for infection or later reaction.

Management

The American dog tick occurs primarily in wooded, shrubby and long-grass areas. However, it is possible for residential areas to support populations of this tick. Shrubs, weeds, tall grass, clutter and debris on the property attracts the rodents that are hosts for immature ticks. By maintaining grass short, removing possible rodent harborages, and sealing cracks and crevices in and around the property one can directly reduce or prevent local tick populations. Keeping grass and weeds cut short decreases humidity, which helps kill ticks or makes an area undesirable for ticks and rodents. Additionally, it makes it difficult for ticks to climb on the vegetation and wait for its host. If pesticides are applied, cutting the vegetation short increases effectiveness and allows for better coverage. Removing rodent harborage areas may reduce an infestation.

Because dogs can easily pick up ticks while walking on infested grass or roaming through wooded areas, it is necessary to treat the pet properly. There are many products that can be applied to prevent or treat a tick infestation on an animal including topical treatments and sprays. Regularly grooming, washing bedding, and examining the dog are strongly recommended to prevent tick infestations.

UF/IFAS Insect Management Guide for ticks – http://edis.ifas.ufl.edu/IG088