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Home , Dermacentor albipictus, Ixodidae, Ornithodoros hermsi, Otobius, Relapsing fever

Colorado and -Borne Diseases Fact Sheet No. 5.593 Insect Series|Trees and Shrubs by W.S. Cranshaw, F.B. Peairs and B.C. Kondratieff* Ticks are blood-feeding parasites of Quick Facts found throughout Colorado. They are particularly common at higher elevations. • The most common tick that Problems related to blood loss do occur bites humans and dogs among wildlife and livestock, but they are in Colorado is the Rocky rare. Presently 27 species of ticks are known Mountain wood tick. to occur in Colorado and Table 1 lists the more common ones. Almost all human • Rocky Mountain wood tick is encounters with ticks in Colorado involve most active and does most the Rocky Mountain wood tick. Fortunately, biting in spring, becoming some of the most important tick species dormant with warm weather in present elsewhere in the United States are summer. Figure 1: Adult Rocky Mountain wood tick prior either rare (lone star tick) or completely to feeding. Rocky Mountain wood tick is the most • Colorado tick is by far absent from the state (blacklegged tick). common tick that is found on humans and pets in Ticks most affect humans by their ability Colorado. the most common tick- to transmit pathogens that produce several transmitted disease of the important diseases. Diseases spread by ticks region. Despite its name, in Colorado include , Rocky Mountain spotted fever Rocky Mountain spotted fever, and is quite rare here. . • Several repellents are recommended for ticks Life Cycle of Ticks including DEET, picaridin, Two families of ticks occur in Colorado, Figure 2: Adult female and male of the Rocky IR3535, and oil of lemon hard ticks ( family) and soft ticks Mountain wood tick. Photograph courtesy of the eucalyptus. CDC Photo Image Library. ( family). Hard ticks can be distinguished by the presence of a plate • To remove a tick, grasp it with (scutellum) on the back behind the head. The larva, nymph and adult ticks are tweezers, as close to the skin They also have mouthparts that are directed active and feed on blood. When fully as possible and pull it straight forward and are easily visible. The soft ticks engorged with blood their body becomes out. lack the plate, have a less regularly rounded greatly distended to the shape of a pea. body and have mouthparts that are directed With some species, the entire life cycle of a beneath the tick, so they are not visible from tick may be completed within a single year. above. The more commonly encountered ticks in Ticks go through four life stages as they Colorado usually require two or three years develop. Eggs are laid in large masses that to complete development. often total thousands of eggs. At hatch, there Hard Ticks. Most hard ticks are three is a tiny larva (“seed tick”) that is six legged. host ticks. With this life cycle pattern each After it has fed and developed it will molt to feeding stage occurs often on a different an eight-legged nymph. When this has fed . For example, the larva of the and developed it will molt to the final stage Rocky Mountain wood tick ( adult. Both male and female ticks occur, andersoni) feeds on small mammals, often © Colorado State University with males usually smaller than females. a . When it has completed feeding Extension. 5/00. Revised 2/19. it drops from the animal, later molts to a extension.colostate.edu *Whitney Cranshaw, Frank Peairs and Boris Kondratieff nymph stage and the nymph seeks a new are all professors of entomology in the Department of Bioagricultural Sciences and Pest Management at host. In the case of the Rocky Mountain Colorado State University. 5/00. Revised 2/19. wood tick, the nymph also feeds on small only develops only on dogs, reinfesting an animal at each stage in its development. Brown dog ticks are more abundant in warmer areas, and in Colorado are found where dogs are present continuously and are kept together in enclosed areas, such as kennels and homes. A different pattern occurs with the winter tick (), which is a one host tick, and the Figure 3: Life stages of a hard tick (Ixodidae). Image courtesy of the CDC Photo Image Library. only one-host tick in Colorado. All feeding stages of winter tick remain on their host – large mammals such as , , or horses. The engorged adults drop from the animal sometime in spring and lay their eggs, which hatch in late summer and early autumn. Figure 6: An adult female of the American dog tick before and after a blood meal. Photograph Soft Ticks. Soft ticks are more courtesy of David Shetlar, The Ohio State continuously associated with their host University. animal and feed more frequently than do hard ticks. Most, are usually live next to areas where their mammal host Figure 4: First stage larvae of the winter tick. (often ) will nest or rest for long Tick larvae are extremely small and have only 3 periods. Periodically the tick will move pairs of legs. Photograph courtesy of the Ken to feed on the host, usually at night, then Gray Collection, Oregon State University. return. Feeding times are brief and each mammals, including dogs, then drops to stage (larva, nymph adult) will feed several the ground later transforming to the adult. times as they develop. This is the habit Adults of the Rocky Mountain tick feed of hermsi, the tick that is on larger mammals such deer, including associated with tick-borne relapsing fever humans. During each stage the tick may in Colorado. Figure 8: Top and bottom view of a male brown The “ear ticks” (Otobius species) have dog tick. Photograph courtesy of Jim Kalisch, feed for days, sometimes weeks, before The University of Nebraska. it becomes completely engorged blood. a somewhat different habit. They develop TheAmerican dog tick (Dermacentor as a one host tick and remain on the host variabilis), which is a common tick in animal continuously, dropping off only Tick-borne Diseases that the eastern plains areas of the state, has a when the adult is ready to lay eggs. Two Occur in Colorado species of these ticks occur in Colorado, similar life history. By far, the most common disease that When seeking a host, hard ticks will one that develops on rabbits and jackrabbits (O. lagophilus) the other (O. megnini) on is spread by ticks in Colorado is Colorado climb onto vegetation. There the tick will tick fever. This is caused by a virus and in remain immobile until a passing mammal various hooved mammals, particularly pronghorn. most people produces symptoms similar signals its presence through vibrations, to flu: , fever/chills, and a feeling the warmth of the animal, and the carbon of fatigue. In about half the cases there dioxide it exhales. The tick will then will be a few days of symptoms, followed actively extend its front legs (questing) to by recovery and then a second round of latch onto the animal as it brushes against symptoms (biphasic fever). Normally it. recovery is complete, and symptoms Hard ticks can be very resistant to disappear within a few days or weeks. In starvation and nymphs and adults may rare cases, serious complications can occur survive a year without feeding. Survival when the virus infects the central nervous is shorter under warm, dry conditions system. The Rocky Mountain wood tick and many ticks will go dormant with high is the vector of Colorado tick fever and temperatures in late spring and summer. symptoms usually develop between three Most cases of ticks biting humans in Figure 5: Adult male of the Rocky Mountain and seven days after the tick bite. wood tick questing on a plant stem. This is a Colorado occur in spring and end in Rocky Mountain spotted fever summer. position the ticks take when a potential host is detected. Photograph courtesy of the Ken Gray ( rickettsii) is caused by a Some hard ticks have slightly Collection, Oregon State University. type of bacterium. It can be a serious different life cycles. Thebrown dog tick disease, potentially life threatening. Early ( sanguineous) is also three- symptoms include headaches and upset host tick, dropping from the host after stomach, and a rash often develops a each blood meal. However, brown dog tick few days after fever symptoms. Rocky rodents are present behind walls, from which the ticks may emerge at night to feed. also affect cattle, dogs and some other Cases of this disease in Colorado are rare, mammals. usually less than a couple per year, but can Fortunately, the most important tick- occur year-round. borne disease in North America, Lyme Tularemia (Francisella tularensis) is also disease, is not present in wild animal a bacterial disease. It can be widespread populations in Colorado (i.e., not endemic). among many wild mammals, notably There has never been a confirmed case of rabbits, prairie dogs, and muskrats. Cats originating from a tick-bite can also become infected. Human cases in Colorado. There are a small number most often result from contact with the of cases of Coloradoans that have been blood of an infected animal but can also diagnosed as having Lyme disease (seven Figure 8: Winter tick collected near Salida in recorded cases between 2007-2017) but March laying a mass of eggs. occur from bites of Rocky Mountain wood tick or American dog tick. In most years all of these are thought to have originated there are very few human cases of tularemia from exposure to infected ticks in states in Colorado, but in 2014-2016 there was a where this disease is present. spike in incidence with 52 cases in 2015. The main reason that Lyme disease Most cases of tularemia have occurred in is not transmitted by ticks in Colorado Boulder and Larimer counties. is that the ticks capable of transmitting A rare but potentially serious condition the pathogen ( burgdorferi) do from tick feeding is . This not occur in the state. In eastern North occurs when certain ticks (in Colorado America, Lyme disease is transmitted to the Rocky Mountain wood tick) remain humans primarily by the blacklegged attached for a long period and produce tick or deer tick ( scapularis). In Figure 9: A comparison between blacklegged an ascending paralysis. Early symptoms, the Pacific states, ranging into Utah, the tick (top), lone star tick (bottom left) and the such as difficulty walking, progress to western blacklegged tick () American dog tick. The lone star tick and occurs and can transmit the Lyme disease American dog tick occur rarely in Colorado, more generalized symptoms, such as limb usually when carried on an animal. The numbness and difficulty breathing. This pathogen. In addition to Colorado, states blacklegged tick, the main vector of the condition is completely reversible when that do not have either of these species organism producing Lyme disease, does not include New Mexico, Wyoming, Montana, occur in Colorado. Photograph courtesy of Jim the tick is removed. Tick paralysis can Kalisch, The University of Nebraska. and Idaho. Recommended Resources. Diagnosis of Lyme disease is notoriously difficult. Mountain spotted fever can be successfully Further complicating the situation is that treated by physician prescribed there are several newly described diseases and if symptoms are suspected one associated with ticks in North America. should promptly seek medical attention. The best source for information on the Despite the name of this disease, Rocky present situation with tick-borne disease is Mountain spotted fever cases are quite always the Centers for Disease Control. rare in Colorado, usually only a couple of Also recommended is the website of the cases/year at most(states that have much American Lyme Disease Foundation. higher incidence of this disease are North Carolina, Oklahoma, Arkansas, Tennessee, Steps to Prevent Tick Bites and Missouri.) Rocky Mountain wood tick Figure 10: An adult soft tick, laying a mass of Avoid Tick Habitat is the primary vector tick of this disease eggs. Soft ticks may lay several masses of in Colorado, but the pathogen can also eggs. Photograph courtesy of the CDC Photo Ticks are most active in spring and Image Library. be transmitted by American dog tick and early summer and concentrate where their brown dog tick. animal hosts most commonly travel. This Tick-borne relapsing fever is also a includes brushy areas along the edges of disease produced by a bacterium (Borrelia fields and woodlands or commonly traveled hermsii). Symptoms include high fever, paths through grassy areas and shrublands. , and muscle/joint aches. These During tick season these sites should be symptoms often follow a cyclical pattern, avoided when possible and when walking lasting about three days followed by a on paths remain in the center to avoid largely symptom-free period of 7 days, with brushing vegetation on which ticks perch. symptoms then reoccurring. The vector of tick-borne relapsing fever is the soft tick Wear Protective Clothing Ornithodorus hermsi, which is associated Figure 11: “Ear ticks” present in the ear of a Long pants, long-sleeved shirts and with nesting rodents. Humans are usually rabbit. Photograph courtesy of David Shetlar, other clothing can help exclude ticks or bitten when sleeping in rustic cabins where The Ohio State University. keep them from attaching to the skin. Ticks Table 1: Common ticks found in Colorado. Scientific name (common name) Hosts Dermacentor albipictus Deer, elk and large domestic animals, especially horses. (winter tick) D. andersoni Small rodents, porcupines, deer, horses, cattle and other larger animals. Most common species that (Rocky Mountain wood tick) bites people. D. parumapertus Primarily cottontail rabbits and jackrabbits. D. variabilis Small rodents, dogs, raccoons, and other animals. Occasionally feeds on people. Uncommon in Colo- (American dog tick) rado and usually associated movements of pets infested in areas of the eastern U.S. leporispalustris Cottontail rabbits, jackrabbits. (rabbit tick) I. kingi Prairie dogs, mice, ground squirrels and other associated animals. I. sculptus Burrowing rodents, such as ground squirrels, and their predators. I. spinipalpis Cottontail rabbits, wood rats, and Peromyscus mice. I. texanus Weasels, skunks, and martens. americanum (lone star tick) Wide host range including livestock, many kinds of wildlife, and dogs. Will readily bite humans. A very rare species in the state that may occur in some sites in extreme eastern/southeastern Colorado. Dogs. Infrequently feeds on people. Sometimes reproduces within the home. (brown dog tick) Chipmunks, rock squirrels, other rodents. Otobius lagophilus Primarily cottontail rabbits and jackrabbits Otobious megnini (ear tick) Large ungulate mammals, particularly pronghorn

Table 2: Tick-borne diseases in Colorado. Disease/causal organism Incidence in Colorado Symptoms Tick vectors Colorado tick fever/bipha- The most common disease transmit- Generally, flu-like, including aching, fever, chills Rocky Mountain wood tick, sic fever ted by ticks. About 200 cases per and fatigue. This typically lasts for 1 to 3 days. American dog tick (a virus) year are reported, but it is suspected Occasionally there will be a second cycle of that this disease is largely under- symptoms following a short recovery. Recovery reported. is normally complete, but in rare cases severe complications may develop. Lyme disease There has never been a confirmed Often a characteristic ring-like reddish rash Black-legged tick or deer tick (a bacterium, infection of a human that was traced develops at the feeding site. Aching, headache (). Ticks Borellia burgdorferi) to a tick bite in Colorado. A few and flu-like symptoms are typical early. Serious confirmed to transmit Lyme cases have been reported from the complications sometimes develop, including disease to humans do not occur state, but all are thought to have numbness and/or partial paralysis, severe head- in Colorado. originated from exposure to infected aches, fatigue, and effects on joints (arthritis), ticks outside Colorado. heart or nervous system. Relapsing fever/borreliosis Very rare. Rapidly developing fever 3 to ten days after ini- This pathogen is transmitted by (a bacterium, tial infection. Fever declines after about 4 days the soft tick Ornithodoros hermsi, ) but may recur in multiple cycles. which is associated with rodents (e.g., chipmunks, squirrels). Human infections typically occur when camping in rustic cabins inhabited by infected rodents. Rocky Mountain spotted Rare, much more common in some Initially, a general feeling of malaise and/or Rocky Mountain wood tick, fever areas along the Atlantic coast. About aches. A characteristic rash develops, starting American dog tick (a bacterium, three cases per year, on average, on the wrists and ankles and later spreading ) are reported in Colorado. Histori- to the rest of the body, including palms and cally, most cases have occurred in the soles of feet. High fever is associated with northwestern Colorado. infections. Tick paralysis (a reaction Rare. Occurs when certain ticks Early symptoms (e.g., difficulty walking) prog- Rocky Mountain wood tick to tick saliva) remain attached for a long period. ress to more generalized symptoms (e.g., limb numbness, difficulty breathing). This condi- tion is completely reversible when the tick is removed. Tularemia Very rare in people but can be wide- Sudden high fever, general weakness and swell- Rocky Mountain wood tick, (a bacterium, spread in wild animals, particularly ing/pain of the lymph nodes. American dog tick. Most human Francisella rabbits. infections occur from contact tularensis) with the blood of infected animals (e.g., while skinning rabbits). are usually acquired while brushing against How to Remove a Tick low vegetation, so pulling socks over the bottom of the pants leg also is useful. Light- Once a tick has become firmly attached colored clothing can make it easier to find to the skin, removal can be difficult and ticks that have been picked up. should be done with care. The mouthparts are barbed, so they may remain after Use Tick Repellents removal and allow infection. Fortunately, the Rocky Mountain wood tick, the most There are a several repellents that common species found in Colorado, are effective for ticks. Most commonly is relatively easy to remove because it available is DEET but three other active has relatively short mouthparts. The ingredients are also recommended: recommended procedure for removal of picaridan, IR3535, and oil of lemon ticks is: eucalyptus. These are applied either 1. Grasp the tick with fine tipped tweezers, directly to the skin or to clothing. as close to the skin as possible. If Repellents are most effective if applied to tweezers are not available and you must pants and other areas of the lower body use your fingers, cover them with tissue likely to come into contact with ticks. or thin plastic to avoid the possible When applying repellents directly to transmission of any disease organisms, the skin certain precautions should be such as tularemia, that the tick may considered: harbor. 1. On children, do not use high 2. Pull the tick slowly and steadily, straight concentration formulations (e.g., away from the skin. Try not to crush the DEET concentrations greater than 30 tick as you remove it. percent). 3. After the tick is removed, treat the 2. Apply the repellent to clothing, rather feeding site with a disinfectant. Wash than to skin; this can be particularly your hands when done. Never crush a effective for ticks that usually will tick with your fingers. Dispose of a live climb on clothing. tick by putting it in alcohol, placing it 3. Avoid applying repellents to hands or in a sealed bag/container, wrapping it other areas that may come into contact tightly in tape, or flushing it down the with the mouth. toilet. 4. Do not apply repellents to wounds or irritated skin. Many other methods have been 5. After use, wash or bathe treated areas, popularized to remove ticks, such as particularly on children. covering them with petroleum jelly or touching them with a hot match. These Permethrin is an alternative treatment methods are not always effective at that is applied to the exterior of clothing. removing the tick and are also slow to Clothing treated with permethrin can kill work. The goal of tick removal is to have it or repel or ticks for days or even weeks, done quickly, rather than to wait for the tick and often remains effective through a to detach on its own. few washings. Permethrin should not be If you develop a rash or fever within applied directly to the skin. several weeks of removing a tick, see your doctor. Be sure to tell the doctor about your Conduct Tick Checks recent tick bite, when the bite occurred, and Ticks take several hours to settle and where you most likely acquired the tick. begin feeding. This gives you ample time to detect and remove them. The Rocky Mountain wood tick typically takes 12 to 24 hours to start feeding. Therefore, a thorough “tick check” can be an effective alternative to repellents. After walking through areas where ticks might be present, carefully look for and remove any ticks you may have picked up. Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. 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