Amblyomma americanum and a New Disease

By Karis Tutuska

2006 Dr. Amanda Loftis, Dr. William Nicholson, Dr. Will Reeves This photograph depicts a female “lone star tick” Amblyomma americanum. An Ixodes or “hard” tick, A. americanum is found through the southeast and south-central states, and has been shown to transmit the spirochete, Borrelia lonestari, the pathogen responsible for causing a Lyme disease-like rash known as “Southern tick-associated associated rash illness” (STARI). Representatives from all three of its life stages aggressively bite people in the southern U.S.  Research indicates that live spirochetes are observed in only 1-3% of specimens. The small chitinous scutum on the tick’s dorsal abdomen identified this as a female of the species. The reduced scutal size enables the abdomen to expand to enormous proportions when ingesting a blood meal the tick extracts from its host food source, as seen in PHIL# 8677.  In the male, the scutum covers almost the entire dorsal abdomen.  Also, note the four pairs of jointed legs, placing ticks in the Phylum Arthropoda, and the Class Arachnida.

2006
Dr. Amanda Loftis, Dr. William Nicholson, Dr. Will Reeves
This photograph depicts a female “lone star tick” Amblyomma americanum. An Ixodes or “hard” tick, A. americanum is found through the southeast and south-central states, and has been shown to transmit the spirochete, Borrelia lonestari, the pathogen responsible for causing a Lyme disease-like rash known as “Southern tick-associated associated rash illness” (STARI). Representatives from all three of its life stages aggressively bite people in the southern U.S. Research indicates that live spirochetes are observed in only 1-3% of specimens.
The small chitinous scutum on the tick’s dorsal abdomen identified this as a female of the species. The reduced scutal size enables the abdomen to expand to enormous proportions when ingesting a blood meal the tick extracts from its host food source, as seen in PHIL# 8677. In the male, the scutum covers almost the entire dorsal abdomen. Also, note the four pairs of jointed legs, placing ticks in the Phylum Arthropoda, and the Class Arachnida.

As bloodsuckers and disease-carriers, ticks are many people’s worst nightmares. However, a recent study conducted by the American Society of Tropical Medicine and Hygiene has shown that the rapid spreading of an aggressively-biting, disease-carrying tick species may be a blessing in disguise.

Rocky Mountain spotted fever is an often-deadly disease carried by American dog ticks. Since 2012, the number of reported cases has increased by a factor of eight, but the number of hospitalizations has halved. This phenomenon was found to correlate with the spread of a different tick species, Amblyomma americanum.

Incidents of Rocky Mountain spotted fever have surged, and related deaths have plummeted in areas infected by Amblyomma americanum.

                After much head scratching, the researches discovered that Amblyomma americanum carries the bacterium Rickettsia amblyommii, a genetic relative to the Rocky Mountain spotted fever bacterium that is not deadly to humans. These aggressive ticks vaccinate their victims against Rocky Mountain spotted fever. Who would have thought there would be a silver lining to a tick bite?

Source:

R.Bitchell. The lone star tick may be spreading a new disease across America. Health News from NPR. (2015).

 

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