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, 20 (9), 1504-10

Feeding Period Required by Amblyomma Aureolatum Ticks for Transmission of Rickettsia Rickettsii to Vertebrate Hosts

Feeding Period Required by Amblyomma Aureolatum Ticks for Transmission of Rickettsia Rickettsii to Vertebrate Hosts

Danilo G Saraiva et al. Emerg Infect Dis.


Rocky Mountain spotted fever is endemic to the São Paulo metropolitan area, Brazil, where the etiologic agent, Rickettsia rickettsii, is transmitted to humans by adult Amblyomma aureolatum ticks. We determined the minimal feeding period required by A. aureolatum nymphs and adults to transmit R. rickettsii to guinea pigs. Unfed nymphs and unfed adult ticks had to be attached to the host for >10 hours to transmit R. rickettsii. In contrast, fed ticks needed a minimum of 10 minutes of attachment to transmit R. rickettsii to hosts. Most confirmed infections of Rocky Mountain spotted fever in humans in the São Paulo metropolitan area have been associated with contact with domestic dogs, the main host of A. aureolatum adult ticks. The typical expectation that transmission of tickborne bacteria to humans as well as to dogs requires ≥2 hours of tick attachment may discourage persons from immediately removing them and result in transmission of this lethal bacterium.


Figure 1
Figure 1
An adult male Amblyomma aureolatum tick attached to the hand of a person who became infested while in direct contact with a naturally infested dog in the metropolitan area of São Paulo, Brazil.
Figure 2
Figure 2
A typical area where infection with the Rickettsia rickettsii bacterium occurs, manifested as Rocky Mountain spotted fever, in the metropolitan area of São Paulo, Brazil. Humans have constructed their homes in the Atlantic rainforest fragment (habitat of the Amblyomma aureolatum tick, a vector of R. rickettsii), where many dogs are unrestrained. Dogs frequently enter the forest, become infested by adult A.aureolatum ticks, and bring them into homes, allowing the direct transfer of feeding ticks from dogs to humans.

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