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A new potential route of tick-transmitted bacterial diseasesto man and animals?To the Editor:Ticks are obligate hematophagous arthropods ofconsiderable medical and veterinary importancebecause they harm the host through their feedingaction and vector many pathogens.1 The role ofRipicephalus sanguineus, the brown dog tick, in thetransmission of disease to man was first establishedin the 1930s.2 Because Ripicephalus sanguineus isbecoming more antropophilic and the species ismutating to be more adapted to humans,3 tick-borne diseases constitute an emerging infectionthreat to humans.1

They transmit bacteria when their feeding sites arecontaminated with salivary secretions, regurgitatedmidgut contents, and feces.

A scanning electron microscopic study was com-pleted of brown dog ticks recovered from free-roam-

ing dogs in Uberlândia, State of Minas Gerais, Brazil.The parasites were fixed in 4% formalin, dehydrat-ed in ascending concentrations of ethanol, gluedonto aluminum stubs, sputter-coated with gold, andexamined in a Zeiss EM940A scanning electronmicroscope at 10 kV. A large number of bacteriagrew as microcolonies, and an adherent biofilm wasfound on the parasite body surface often obscuringits structural details (Fig 1). This image suggests adirect route of transmission of pathogens carried onthe parasite body surface directly to men and ani-mals during feeding. Additional studies evaluatingthis new potential route, including the survey of bac-terial pathogens in the biofilm by molecular meth-ods, are needed.

Rogério O. RossiMarcos A. Rossi, MD, PhDUberlândia, Minas Gerais andRibeirão Preto, São Paulo, Brazil

References1. Parola P,Raoult D.Ticks and tick-borne bacterial diseases in humans:

an emerging infectious threat. Clin Infect Dis 2001;32:897-928.2. Brumpt E. Longevité du virus de la fièvre botounneuse

(Rickettsia coronii, n. sp.) chez la tique Ripicephalus sanguineus.C R Soc Biol 1932;110:1197-9.

3. Goodard J. Focus of human parasitism by the brown dog tick,Ripicephalus sanguineus (Acari: Ixodidae). J Med Entomol 1989;26:628-9.

doi:10.1067/mic.2003.53

Copyright © 2003 by the Association for Professionals in InfectionControl and Epidemiology, Inc.

0196-6553/2003/$30.00 + 0

Fig 1. Scanning electron micrograph of the anterior part of the body (dorsal aspect) of a female Ripicephalus san-guineus.An adherent biofilm on the parasite surface, sometimes obscuring its details, can be seen (A). Higher magni-fications (B and C) show the presence of bacilli and cocci (B and C). A, Bar = 400 µm; B, bar = 10 µm; C, bar = 3 µm.

A

B

C

lettersto the Editor

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