NEW YORK — Prevention and treatment of diseases transmitted through ticks — such as Lyme disease and Colorado tick fever virus — require adequate knowledge about the vectors, according to a presentation at the Infectious Diseases in Children Symposium.
Meg Fisher, MD, medical director at The Unterberg Children’s Hospital at Monmouth Medical Center, Long Branch, New Jersey, described the tick as an obligate, blood-sucking, ectoparasitic arthropod that has a specific distribution based on its species. Of the 878 species of tick, approximately 33 will feed on humans. Only 28 of these species harbor and transmit pathogens. In North America, they are the most commonly encountered vector.
“These arthropods actually have a preference for what kind of blood they want to drink,” Fisher said in her presentation. “Some will only drink the blood of birds or deer, and some are not as particular.”
The tick has no head, so to detect potential feeding sources, the arthropod uses chemoreceptors to sense carbon dioxide in the environment, she said.
The tick infects a host not through the bite but through its feeding process, specifically when ingesting blood. The feeding process of the tick can last from 2.5 to 8 days for tick larvae and from 5 to 12 days for adult ticks.
“During the time that they are attached [to a blood source], the ticks are salivating, defecating and regurgitating,” Fisher said. “Organisms in their gut are then getting mixed with the person’s blood. That is how ticks transmit diseases.”
The disease transmitted by the tick depends on which species of tick a person was bit by and their geographical location. According to Fisher, the Lone Star tick resides from Texas to the East Coast and can transmit Ehrlichia chaffeensis, Borrelia lonstari and Francisella tularensis. The Gulf Coast tick is most commonly found in the southern U.S. and transmits Rickettsia parkeri.
Other species that may transmit infections in humans include the Rocky Mountain Wood tick, which can spread R. rickettsii, Colorado tick fever virus and F. tularensis. The American Dog tick, which can be found in nearly all areas of the U.S., can transmit R. rickettsi and F. tularensis.
Although additional species can transmit Lyme disease, such as the Western Blacklegged tick, Ixodes scapularis — also known as the deer tick — are the most common vectors for the infection. These ticks are found in multiple locations within the U.S., but are predominantly located in the Northeast.
“This is a disease of the Northeast, but there are a whole bunch of cases in the Midwest area, with very little out on the West Coast,” Fisher said. “There are scattered areas [of Lyme] in the South, but those cases are likely due to travelers rather than local ticks.”
To avoid tick bites, Fisher suggests several steps, including staying out of the woods, staying on hiking trails, staying clear of grass in which you cannot see your feet, wearing long sleeves and tucking pants in socks or shoes. She also promotes the use of a tick repellant, such as DEET or permethrin and performing tick checks on families and household pets.
If a family member or pet has been bitten by a tick, it is frowned upon to remove them with alcohol, cigarettes, matches, nail polish or petroleum jelly. Instead, Fisher recommends grasping the tick close to the mouth parts with either forceps or covered fingers, then, pulling up and out. If mouth parts are left in the bitten area, do not remove these.
“These ticks feed for a long time,” Fisher said. “You want to get them off before they have had time to [infect you].” –by Katherine Bortz
Fisher M. Ticks, fleas and mosquitos: Small vectors, big problems. Presented at: IDC NY. Nov. 18-19; New York.
Disclosure: Fisher reports no relevant financial disclosures.