Missouri’s diverse geography, characterized by extensive forests, river systems, and tallgrass prairies, creates an ideal environment for ticks to thrive. The state’s warm, humid climate contributes to a long active season for these arachnids, often extending from early spring well into late fall. This combination of hospitable habitat and prolonged activity results in frequent tick encounters for humans and pets. Consequently, Missouri residents face an increased risk of exposure to various tick-borne pathogens, including those causing diseases like Rocky Mountain Spotted Fever and Ehrlichiosis. Understanding the most common tick species is the first line of defense against these potential health threats.
Identifying the American Dog Tick
The American Dog Tick, scientifically known as Dermacentor variabilis, is one of the most frequently encountered species across Missouri. Adults are relatively large, measuring between 3.6 to 5 millimeters before feeding, and they are sometimes referred to as wood ticks. A key identification feature is their reddish-brown body with distinct white or grayish markings, particularly a mottled pattern on the back shield of the males. The female swells considerably to a gray color when fully engorged with blood.
These ticks prefer habitats with little to no tree cover, such as grassy fields, scrubland, and along trails. They employ a questing strategy, climbing onto low vegetation to wait for a host to brush past. The American Dog Tick is the primary vector for transmitting the bacterium that causes Rocky Mountain Spotted Fever (RMSF) in Missouri. It also transmits Francisella tularensis, the agent responsible for tularemia. Prompt removal is important, though the RMSF pathogen is not typically transmitted during the tick’s initial hours of attachment.
Identifying the Lone Star Tick
The Lone Star Tick (Amblyomma americanum) is the most common and aggressive tick species found throughout the state, having been identified in every county. Females are easily recognized by the single, prominent silvery-white or iridescent spot, the “lone star,” located on their reddish-brown back. Males are also reddish-brown but lack this distinct spot, instead having subtle white markings along the edges of their bodies. They are known for their aggressive, host-seeking behavior, actively crawling toward potential hosts rather than passively waiting.
This species is primarily found in wooded areas with dense undergrowth and fields. The Lone Star Tick is a major vector for human ehrlichiosis, caused by the bacteria Ehrlichia chaffeensis and Ehrlichia ewingii. It also transmits the pathogens responsible for Southern Tick-Associated Rash Illness (STARI), Heartland virus, and Bourbon virus.
Alpha-gal Syndrome
A unique risk associated with its bite is Alpha-gal Syndrome (AGS), a delayed allergic reaction to red meat. The tick transmits a sugar molecule (alpha-gal) into the host’s bloodstream during feeding. This triggers an immune response that creates antibodies against alpha-gal in some individuals. Subsequent consumption of mammal-derived products, like beef or pork, can lead to allergic symptoms. These symptoms often include hives, gastrointestinal distress, and anaphylaxis, typically occurring three to six hours after eating.
Identifying the Blacklegged Tick and Other Species
The Blacklegged Tick (Ixodes scapularis), often called the Deer Tick, is associated with Lyme disease. This tick is much smaller than the American Dog Tick or Lone Star Tick; nymphs are particularly tiny, comparable in size to a poppy seed. Adults are characterized by their dark, black legs and a reddish-orange body on the female, while the male is solid dark brown or black. The small size of the nymph stage makes it difficult to spot and remove, leading to a higher risk of disease transmission.
They are found predominantly in heavily wooded and brushy areas, especially where white-tailed deer populations are high. The Blacklegged Tick is the primary carrier of Borrelia burgdorferi, the bacterium that causes Lyme disease, which typically requires the tick to be attached for 24 to 48 hours for transmission to occur. This species can also transmit pathogens responsible for anaplasmosis and the rare Powassan virus.
Other Species in Missouri
Other tick species are present in Missouri but are encountered less often by the average person. The Gulf Coast Tick is expanding its range northward, likely due to changing climate patterns, and carries Rickettsia parkeri, which causes a form of spotted fever. The Rabbit Tick primarily feeds on rabbits and ground-dwelling birds, making human encounters relatively rare. The Brown Dog Tick is unique as it can complete its entire life cycle indoors, preferring to feed exclusively on dogs, but it is also a known vector for Rocky Mountain Spotted Fever.