Ticks transmit Rocky Mountain spotted fever, tularemia, Lyme disease, equine encephalitis, several forms of ehrlichiosis, and other diseases. Tick-borne diseases of livestock (e.g., babesiosis, anaplasmosis) are of great economic significance. Each species needs three different hosts to complete its life cycle. Typically the larval stage will feed on small reptiles, birds, or mammals; the nymph stage will parasitize larger vertebrates; and adults will parasitize large herbivores and livestock. The adult of the ixodid species Ixodes scapularis, the vector of Lyme disease and babesiosis in the E United States and Canada, usually chooses deer as its host (I. scapularis of all stages will feed on humans). The closely related I. pacificus, which transmits Lyme disease and Rocky Mountain spotted fever in the western states, prefers livestock in the adult stage. Ticks can sometimes harbor more than one disease organism at a time. Rapidly multiplying Asian long-horned ticks, Haemaphysalis longicornis, can also kill a young animal when the growing offspring consume a large quantity of its blood.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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