January 1, 2018

A Closer Look at the Different Types of Ticks

Ticks come in a lot of different varieties that not only look different but also live in different regions and environments and can transmit different types of diseases to both people and animals.

The purpose of this article is to provide some basic information about ticks, as well as key details about the various species that you are most likely to encounter in different regions of the United States. If you suspect that you or a loved one has been bitten by a tick of any kind, try to keep it as in-tact as possible and take it in a secure container to your healthcare provider, veterinarian, or local vector control for identification.


What Are Ticks?

Ticks are a type of insects called arthropods. Like spiders, they fall under the classification of arachnids—a specific type of arthropod with eight legs. Unlike spiders, however, ticks feed on blood from mammals—including people, pets and livestock—as well as birds, reptiles, and amphibians. They have been reported in rural and urban environments around the world, but are most often found in grassy or wooded areas and are typically most active from spring through fall.

In general, ticks can be divided into two main families: hard ticks (Ixodidae) and soft ticks (Argasidae).

 

HARD TICKS (IXODIDAE) Hard ticks all share the distinguishing trait of a hard outer shield or black plate, known as a scutum.

SOFT TICKS (ARGASIDAE) Soft ticks do not have a scutum but instead have more rounded bodies.

Both of these families of ticks have species that can transmit diseases to humans; however, the typical length of time required to do so differs just like their feeding habits. Certain hard ticks that carry Lyme disease, for example, typically must be attached for 36 to 48 hours to infect a host, according to the Centers for Disease Control (CDC). Certain soft ticks that transmit Tick-Borne Relapsing Fever (TBRF), however, feed very quickly and can cause disease in humans.


What is the Typical Lifecycle of a Tick?

Ticks generally have four stages of life: egg, larvae, nymph and adult. Eggs, which can number into the thousands are laid by the female tick. These eggs hatch into larvae, which are also known as “seed ticks.” The larvae typically attach to smaller animals, such as mice and birds. After several days of feeding, the larvae develop into nymphs, which can then attach to larger hosts and then ultimately turn into adult ticks. Ticks advance through each of these stages by molting, a process during which they shed their outer skin.

Image Source: Dr. Christopher Paddock https://phil.cdc.gov/Details.aspx?pid=10879

 

What Types of Ticks Transmit Diseases to Humans?

Of the nearly 900 species of ticks that exist in the world, only a select number bite and transmit disease to humans within the United States. The following descriptions provide key facts about each of these different types of ticks, including what each tick looks like at various stages of the lifecycle, some distinguishing characteristics, regions where they’re typically found, and the potential diseases they can transmit to both people and pets.


Distinguishing Characteristics:
Sometimes called wood ticks, American dog ticks are a type of hard tick that is most often found in tall grass, as well as low-lying brush and twigs. At both adult and nymph stages, these ticks can feed on a variety of mammals, but adult females are most likely to bite humans. The adult females are most easily identified by the large, off-white scutum that starkly contrasts with the rest of their dark-brown bodies.

Diseases They Can Transmit:
Both nymphs and adults can transmit Rickettsia rickettsia, which causes Rocky Mountain Spotted Fever, and the bacteria that causes Tularemia.

Where Found in the U.S.:
American dog ticks are primarily found east of the Rocky Mountains, although they can also be found in certain areas along the Pacific Coast.

Image Source: https://phil.cdc.gov/Details.aspx?pid=14473

Distinguishing Characteristics:
Unfed female Eastern blacklegged ticks, also known as deer ticks, are easily distinguished from other ticks by the orange-red body surrounding the black scutum. Males do not feed. A type of hard tick, deer tick populations tend to be higher in elevation, in wooded and grassy areas where the animals they feed on live and roam, particularly their reproductive host, the white-tailed deer.

Diseases They Can Transmit:
At both adult and nymph stages, deer ticks can transmit Lyme disease as well as Anaplasmosis, Ehrlichiosis, Babesiosis, Tick-Borne Relapsing Fever, and Powassan disease.

Where Found in the U.S.:
These ticks are primarily distributed in the Northeastern and Upper Midwestern regions of the United States.

Image Source: http://www.tickencounter.org/tick_identification/brown_dog_tick

Distinguishing Characteristics:
Brown dog ticks are a type of hard tick that is most often are found around human dwellings, particularly where dogs reside. They can cause high levels of infestation both on dogs and in homes and can spend their entire life cycle indoors.

Diseases They Can Transmit:
At multiple stages of its lifecycle, the brown tick can transmit Rocky Mountain Spotted Fever (Rickettsia rickettsii) to both humans and dogs. At both nymphal and adult stages, brown ticks can transmit canine Ehrlichiosis (Ehrlichia canis) and canine Babesiosis (Babesia canis vogeli and Babesia gibsoni-like parasites) to dogs.

Where Found in the U.S.:
Brown ticks are found throughout the United States, but particularly in Southern states.

Image Source: http://www.tickencounter.org/tick_identification/gulf_coast_tick

Distinguishing Characteristics: 
The Gulf Coast tick resembles both the American dog tick and the Rocky Mountain wood tick. A type of hard tick, it is typically found in grass prairies and coastal uplands.

Diseases They can Transmit:
Adult ticks can transmit Rickettsia parkeri rickettsiosi, a form of spotted fever caused by R. parkeri, to humans.

Where Found in the U.S.:
Gulf Coast ticks are primarily found in areas along the Atlantic Coast and the Gulf of Mexico, but reports of the tick have recently occurred further north, in states like Virginia, and west to Oklahoma and Kansas.

Image Source: http://www.tickencounter.org/tick_identification/lone_star_tick
Distinguishing Characteristics:
One of the most recognizable ticks, the adult female lone star tick has a very visible white dot (or lone star) in the center of her back. A type of hard tick, the lone star ticks are very aggressive and known to pursue a host over long distances.

Diseases They Can Transmit:
The nymph and adult females most frequently bite humans and transmit disease, which can include Ehrlichiosis, Tularemia, Heartland Virus, and STARI (Southern Tick-Associated Rash Illness).

Where Found in the U.S.:
Lone star ticks are widely distributed throughout the Southeastern, Eastern and South Central states.

Image Source: http://www.tickencounter.org/tick_identification/rocky_mountain_wood_tick

Distinguishing Characteristics:
The Rocky Mountain wood tick resembles both the American Dog tick and the Gulf Coast tick, but it is a bit huskier in build with a rounded, thicker body.

Diseases They Can Transmit:
Rocky Mountain Spotted Fever, Colorado Tick Fever, and Tularemia. The saliva from these ticks contains a neurotoxin that can sometimes cause tick paralysis in both humans and pets; however, the paralysis usually dissipates within 24 to 72 hours after tick removal.1http://www.tickencounter.org/tick_identification/rocky_mountain_wood_tick

Where Found in the U.S.:
The Rocky Mountain wood tick is found throughout the Rocky Mountain states in elevations ranging from 4,000 feet to 10,500 feet.

Image Source: http://www.tickencounter.org/tick_identification/westernblacklegged_tick

Distinguishing Characteristics:
The Western black-legged tick is similar in appearance to the Eastern black-legged tick, or deer tick, and is the only other known species of tick that can transmit Lyme disease. At the nymph stage, this hard tick feeds primarily on small animals but can also attach to and feed on larger hosts, including humans. Adults generally feed on large mammals, including humans.

Diseases They Can Transmit:
The nymph and adult females are most likely to bite humans and transmit disease, which can include Anaplasmosis, Lyme disease, and Tick-Borne Relapsing Fever (TBRF).

Where Found in the U.S.:
Western blacklegged ticks are located along the Pacific Coast, particularly in Northern California. But they have also been found inland to eastern Oregon, western Utah, and Arizona.

Image Source: https://phil.cdc.gov/Details.aspx?pid=5970

Distinguishing Characteristics:
Unlike hard ticks, soft ticks don’t wait for hosts to come by in grassy or wooded areas; instead, they tend to live in rodent burrows and feed on a host while the host sleeps. People usually come into contact with these ticks when sleeping in rodent-infested cabins. Because the bites are painless and the ticks feed quickly (usually in less than an hour), most people are unaware that they have been bitten.

Diseases They Can Transmit:
Certain soft ticks can transmit Tick-Borne Relapsing Fever (Borrelia hermsii, B. parkerii, or B. turicatae) to humans and pets. TBRF is spread by multiple soft-tick species. Ornithodoros hermsi is responsible for most cases in the United States. The two other U.S. tick species known to transmit the disease are Ornithodoros parkeri and O. turicata.

Where Found in the U.S.:
O. hermsi tends to be found in coniferous forests at higher altitudes, ranging from 1,500 to 8,000 feet. O. parkeri and O. turicata are generally found at lower altitudes in the Southwest, including in caves and the burrows of ground squirrels, prairie dogs, and burrowing owls.

Number of reported cases of TBRF in the United States from 1990 to 2011. One dot was placed randomly in the county of exposure where known, and shading indicates those states where TBRF was reportable. This map does not reflect recent reported cases of TBRF that are caused by B. myamotoi.2https://www.cdc.gov/ticks/tickbornediseases/soft-tick.html


Additional Resources

 

 

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