Found throughout eastern North America and parts of the Pacific coast, American dog ticks (Ixodida: Ixodidae: Dermacentor variabilis) are well-known parasites of mammals. After hatching these arachnids go through three life stages from larvae to nymphs to adults. At each stage they feed on the blood of progressively larger mammals. Larvae and nymphs commonly feed on small animals like mice and rats. Adults frequently attack dogs, but will also feed on other larger mammals, including humans.
American dog ticks are important vectors for two serious diseases. They can transmit Rickettsia rickettsii from rodents to dogs and humans. This bacterium causes Rocky Mountain spotted fever. They can also infect humans with Francisella tularensis, the bacterium that causes tularemia. If that wasn’t enough these arachnids can cause tick paralysis in both dogs and children. It’s thought that this illness is produced by a toxin in tick saliva. They do not, however, appear to transmit the bacterium that causes Lyme disease. That is vectored by blacklegged ticks of the genus Ixodes.
Tick-borne disease can be prevented in several ways. Avoid areas that may host ticks when possible. When entering such areas wear long clothing and repellent. After leaving, inspect yourself and remove any ticks you may find. Disease transmission can take several hours or more, so prompt removal can prevent infection. Repellents and removal on dogs can protect them as well, and prevent them from transporting ticks indoors.