Common Ticks and Tick-Borne Diseases in Pennsylvania

Common Ticks and Tick-borne Diseases in Pennsylvania Tick identification, life history, and distribution; Blacklegged tick (Ixodes scapularis) tick-borne diseases; and prevention Background Information Distribution: Ixodes scapularis is found throughout the eastern United States and in parts of the northern mid-west in Ticks are parasitic arthropods that feed on the blood of wooded, brushy locations as well as grassy edge habitat vertebrates, particularly mammals (including humans) but also (Figure 2). While it was less widespread historically, the range birds, reptiles and amphibians. Many species of ticks can of this species has been expanding in recent years and it can transmit pathogens between animals and to humans, including now be found throughout Pennsylvania. various parasitic worms, viruses, and bacteria. The most important of these in Pennsylvania are the bacteria that cause Lyme disease and Rocky Mountain spotted fever. There are more than 900 species of ticks worldwide, at least 25 of which occur in Pennsylvania. Of these, two species account for more than 90 percent of identification requests submitted to Penn State: blacklegged tick ( Ixodes scapularis ) and American dog tick ( Dermacentor variablis ). Three other species that may be encountered are also covered herein: lone star tick ( Amblyomma americanum ), Asian longhorn tick ( Haemaphysalis longicornis ), and winter tick ( Dermacentor albipictus ). Hosts: Blacklegged tick larvae preferentially feed on small mammals such as mice and chipmunks and occasionally birds; nymphs also feed on small mammals and birds, as well as a range of medium- and large-mammals like raccoons, deer, and black bears. Adult blacklegged ticks feed on larger mammals with some preference for white-tailed deer. However, any stage is capable of feeding on humans, livestock, and companion animals. Activity period (Figure 3): Adult ticks are present in the fall, American dog tick (Dermacentor variabilis) throughout the winter, and in early spring. During the winter, adult ticks can be active and seek hosts any day when temperatures are above freezing. Larval ticks are typically present during the late summer and nymphs during the late spring and through the summer. Distribution: Dermacentor variabilis is found in the eastern two-thirds of the United States from Nova Scotia to the Gulf Coast, including all of Pennsylvania (Figure 5). They prefer open locations with little or no tree cover, such as grassy fields and scrublands. Diseases: Blacklegged ticks are best known as the vector of the pathogens that cause Lyme disease but have also been known to vector other pathogens including Anaplasma spp. and Babesia spp. which can cause anaplasmosis and babesiosis, respectively. While there is still some debate, blacklegged ticks typically need to feed for 24 hours before Borrelia burgdorferi, the causative agent of Lyme disease, is transmitted. However, another pathogen, Powassan virus, can be transmitted in as little as 15 minutes. Because ticks need to feed from a host infected with pathogens to be able to transmit those pathogens to humans or other animals, only nymphs and adult ticks spread the pathogen. In Pennsylvania, 20–40% of blacklegged ticks test positive for B. burgdorferi depending on location. Activity period: Larvae are most common during the spring Note s: This tick is often called the "deer tick". However, and fall while nymphs and adults are found throughout the because deer have been historically considered the preferred summer. However, unfed individuals of all life stages can host only during the adult stage, blacklegged tick is the survive for more than a year between hosts (larvae: 15 months; preferred common name. nymphs: 20 months; adults: 30 months), so all life stages may be encountered year-round. Hosts: Larvae and nymphs prefer to feed on small rodents. Adults are frequently found on dogs (hence the common name) but also feed on other medium and large mammals such squirrels, raccoons, rabbits, ground hogs, fox, deer, domestic livestock, and humans. They can be extremely aggressive biters. Diseases: American dog ticks are main vector of the pathogens that cause Rocky Mountain spotted fever in Pennsylvania, which is less common than Lyme disease but a potentially more serious illness. They have also been known to transmit Page 2 Common Ticks and Tick-borne Diseases in Pennsylvania tularemia and to cause canine tick paralysis. Dermacentor Groundhog (Woodchuck) tick (Ixodes variablis do not vector the causative agent of Lyme disease. cookei) Notes: American dog ticks are much larger than blacklegged ticks and engorged female ticks may be the size of a grape. Lone star tick (Amblyomma americanum) Distribution: Amblyomma americanum is widely distributed in the United States from Texas north to Missouri and eastward to the Atlantic coast (Figure 7). It is found most often Distribution: Ixodes cookei is found east of the Rockies from in the southern counties of Pennsylvania near urbanized areas. Texas to South Dakota and northeastwards through Maine. Groundhog ticks were the most commonly encountered tick species in Pennsylvania prior to 1990 but have since declined in prevalence compared to blacklegged ticks and American dog ticks. Hosts: Groundhog ticks are host-specific on groundhogs, but are occasionally found on birds, small animals or humans. Diseases: Groundhog ticks can vector Powassan virus, which causes Powassan virus encephalitis. They are not an important vector of the pathogen that causes Lyme disease because of their tendency to feed only on groundhogs, which do not harbor the pathogen. Asian longhorned tick (Haemaphysalis Activity period: Larval lone star ticks are active during the longicornis) late summer and fall while nymphs and adults are active during the spring and summer. Lone star tick larvae are often encountered in large numbers. Hosts: This tick has a broad host range. The larvae feed on a variety of small to medium-sized animals, while the nymphs feed on many medium and large animals. Adults prefer to feed on larger animals. All stages are aggressive biters that will readily feed on humans, livestock, and companion animals. Diseases: Lone star ticks can vector the causative agents of Rocky Mountain spotted fever, ehrlichiosis, tularemia and STARI (southern tick-associated rash illness), as well as Heartland virus and Bourbon virus. Amblyomma americanum bites are also associated with alpha-gal (red meat) allergy. Notes: Adult females are easily identified by the presence of a single white dot in the center of a reddish-brown body. Page 3 Common Ticks and Tick-borne Diseases in Pennsylvania Distribution: Haemaphysalis longicornis is an invasive tick occasionally encephalomyelitis occur alone or in native to East and Central Asia. It has spread throughout the combinations. Atrioventricular conduction problems may arise Oceania and was first reported publicly from New Jersey in which may lead to myocarditis. Additional symptoms of 2013, but it appears this tick may have been present in the arthralgia, myalgia, fibromyalgia, headache, fatigue, stiff United States as early as 2010. A large population was neck, palpitations, and bundle branch block may be associated, discovered on a New Jersey sheep farm in 2017 and it has but are not confirmative of Lyme disease. since been detected in eight states. As of May 2019, only three For more information, please see the CDC webpage about samples of Asian longhorned tick have been found in Lyme disease. Pennsylvania, although this number is expected to rise as the tick becomes established. Rocky Mountain Spotted Fever (RMSF) Hosts: Because Asian longhorned tick is new to North RMSF is caused by the bacteria Rickettsia rickettsii. The America, it is unknown what it's preferred hosts will be. In disease was first recognized in the United States during the other areas of the world, larvae and nymphs prefer small 1890s, but until the 1930s it was reported only in the Rocky mammals and birds while adults prefer large animals, such as Mountains. By 1963, over 90 percent of all cases were cattle, horses, deer, and sheep. A single report of H. reported east of the Rockies. Rickettsia rickettsia is vectored longicornis biting a person has been reported in the US thus by American dog ticks and lone star ticks in the eastern US, far. while it is vectored in the western US by Rocky Mountain Diseases: Asian longhorned tick is not known to vector any wood ticks ( Dermacentor andersoni ). pathogens in North America. However, in its native range it is Symptoms of RMSF include a fever and often a red, purple, or known to vector Anaplasma spp., Ehrlichia spp., and black rash, which develops on the wrists and ankles 2-4 days Powassan virus so the potential exists that it will vector those after the fever begins. Other early symptoms include pathogens in the US as well. headaches, and malaise, nausea, and vomiting, while later Notes: For more information, see this Penn State fact sheet symptoms can include abdominal and joint pain, about Asian longhorned ticks. conjunctivitis, and forgetfulness. Due to the inability of common serologic tests to distinguish Diseases RMSF from closely related diseases (e.g., Rickettsia parkeri rickettsiosis, Pacific Coast tick fever, and rickettsialpox), Lyme Disease RMSF is reported with other spotted fever-group rickettsias (SFR). The number of SFR cases in the US has risen sharply Lyme Disease or Lyme borreliosis is an infection caused by from less than 1 to more than 15 cases per million people the bacterial spirochete Borrelia burgdorferi, which is between 1920 and 2018. However, the fatality rate has transmitted by ixodid ticks. Humans, dogs, and horses seem to dropped from 10–15% to less than 0.5% due to the discovery be the most susceptible to the infection. It is a multisystem of tetracycline antibiotics in the 1940's, which are used to treat illness characterized initially by erythema migrans (bullseye RMSF and other SFR. rash) and a series of common nonspecific complaints and symptoms including headache, fever, sore throat, and nausea.

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