American Dog Ticks

Scientific name: 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. 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.

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. Blood-fed (engorged) females can enlarge up to 15 mm long and 10 mm wide. Dermacentor variabilis develops from the egg stage, to the 6-legged larva, to the 8-legged nymph, and finally to the adult. The cycle requires a blood meal before progression from larva to nymph, from nymph to adult and by the adult for egg production. This cycle also requires three different hosts and requires at least 54 days to complete, but can take up to two years depending on the host availability, host location and the temperature.

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. 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. Sometimes, by removing the tick, a piece of the hosts skin may fall off, which should not be a great concern for infection or later reaction.