This article was authored by Buyung Hadi, former SDSU Extension Pesticide Applicator Training & Urban Entomology Specialist.
After a long winter, it is understandable for South Dakotans to want to spend as much time outdoors as possible. Unfortunately, the warmer weather also signals the onset of tick activity.
Hard Ticks & Soft Ticks
Generally, there are two families of ticks: hard ticks (Ixodidae) and soft ticks (Argasidae). The ‘hard’ and ‘soft’ parts of the family names refer to a shield-like structure at the back of the hard ticks’ bodies; the soft ticks lack this structure. Both families are present in South Dakota.
Male and female hard ticks are typically different in appearance. Female hard ticks are capable of enormous expansion upon engorgement. The mouthparts of hard ticks extend forward and are visible from above (Figure 1a). Soft ticks are leathery and the males and females generally look similar. The mouthparts of soft ticks are attached below the body and are not readily visible from above (Figure 1b). The habitats for the two tick families are quite different. Hard ticks are commonly found in wooded or weedy areas containing a good number of hosts such as deer, cattle, dogs and small mammals. Soft ticks, encountered infrequently by human, are generally found in animal burrows or dens, dilapidated human dwellings and animal shelters. Many soft ticks are parasites on birds and bats.
Figure 1. Specimens of (a) hard tick and (b) soft tick collected in South Dakota.
Photo: Buyung Hadi, SDSU
American Dog Tick & Rocky Mountain Wood Tick
Two of the most critical species of hard ticks found outdoors in South Dakota are the American dog tick (Dermacentor variabilis) and the Rocky mountain wood tick (Dermacentor andersoni). While American dog ticks are probably widely distributed across the state, the presence of Rocky mountain wood tick is more limited to the western side of the state.
Figure 2. Engorged female American dog tick.
Photo: Buyung Hadi, SDSU
American dog ticks are reddish brown in color. The adult unfed females measured to about 0.18 inch long, slightly larger than adult males which measure about 0.14 inch long. When engorged, female American dog ticks measure about 0.59 inch long (Figure 2). Both female and male American dog ticks have a marbled or silvery dorsal shield on their back. The females’ shields are relatively short and do not cover the whole body while the males’ shield cover the whole length of their bodies (Figure 3).
Figure 3. Female (left) and male (right) American dog ticks collected in South Dakota.
Photo: Buyung Hadi, SDSU
The immature American dog ticks feed on small mammals and are active in winter and spring. The adults are abundant in late spring and early summer and feed on dogs and bigger mammals including humans.
Rocky mountain wood ticks are dark brown in color with a silver-grey dorsal shield. Like the American dog tick, the female ticks have a short dorsal shield while the male ticks’ shields extend over the length of the body. The size of unfed female and male Rocky mountain wood tick are roughly similar, about 0.2 inches long (Figure 4). Engorged female Rocky mountain wood ticks can measure about 0.64 inches long.
Figure 4. Male (left) and female (right) Rocky Mountain wood ticks.
Photo: Mat Pound, USDA Agricultural Research Service, Bugwood.org
Immature Rocky mountain wood ticks are most abundant in summer, feeding on small mammals. In fact, the primary reports of Rocky mountain wood ticks in South Dakota came from the burrows of black-tailed prairie dogs in the western half of the state (Kietzman 1987). The nymph and adult ticks are active in late spring and early summer and they feed on medium- and large-sized mammals.
Tick bites by themselves can pose a risk of causing tick paralysis due to a toxin in the tick’s saliva. On humans, tick paralysis is more likely to be seen on children. This effect is reversible if the tick is removed at the onset of the paralysis. Ticks also vector some human diseases. Diseases that can potentially be transmitted by American dog tick and Rocky mountain wood tick are listed in Table 1.
Table 1. Representation of tick-borne diseases associated with two common hard ticks in South Dakota
|Tick species||Human diseases|
|American dog tick (Dermacentor variabilis)||Tularemia, Rocky Mountain spotted fever, Powassan encephalitis|
|Rocky mountain wood tick (Dermacentor andersoni)||Tularemia, Rocky Mountain spotted fever, Colorado tick fever|
Black-Legged or Deer Tick
Black-legged tick, the vector of Lyme disease, was not found during the 2011 tick survey in South Dakota. However, a black-legged tick was collected from Roberts County in the fall of 2012. This was not the first time that black-legged tick was recorded in South Dakota. In 1969 and 1991 Burrus McDaniel, then an entomologist with SDSU, reported black-legged tick collection in the state.
Black-legged tick (Ixodes scapularis) is generally smaller than the American dog tick (Figure 5). The adult male black-legged tick is about 0.04 inch in length while the female tick is about 0.08 inches long. The female body is reddish with a brown dorsal shield while the male’s dorsal shield is dark brown and extends across its body length.
Figure 5. Male American dog tick (left) and black legged tick (right) collected in South Dakota.
Photo: Buyung Hadi, SDSU
Reporting Black-Legged Ticks
It is important to confirm the presence of black-legged ticks in the state. To determine whether this species is becoming established in South Dakota, anyone finding ticks matching the description above are encouraged to send the specimen for identification to Dr. Hadi at the address below.
Pesticide Education and Urban Entomology Coordinator
South Dakota State University
224 Berg Agricultural Hall (SAG), Box 2207A
Brookings, SD 57007
Phone: (605) 688 6784; Cell: (605) 690 4289
Tick samples should be sent in a small bottle sealed with tape. Please DO NOT crush the sample or put the tick on tape. Include your name, date and phone number with the bottle. If sending the sample via post, pack the vial in padded envelope or cardboard container. Ticks will be identified, but not tested for Lyme disease.
Tick Bite Prevention
Take preventative measures when spending extended time outdoors. When entering locations with known tick presence or with tall grasses, wear light colored clothing, long pants, socks and shoes. Tuck the pant legs into the socks to decrease potential skin exposure to ticks. Make it a habit to examine one’s body for ticks after spending time in locations with known or potential tick presence. The light colored clothing makes ticks easy to spot before they can bite.
Early removal of an attached tick is critical to avoid contracting tick-borne diseases. Using a pair of tweezers, grasp the tick on the mouthparts close to the skin surface and pull with slow, steady force until the tick is released. Twisting the tick using tweezers is not recommended since it may break the mouthparts and leave them embedded in the skin.
Tick repellents can be applied to both skin and clothing. The majority of commercially available tick repellents contain DEET. If the smell and skin-feel of DEET is bothersome for you, try products containing IR3535. Tick repellents containing permethrin should only be used to treat clothing material and NOT used on one’s skin. Please read and follow carefully the instructions listed on the product’s label.