Rickettsia parkeri Infection in Domestic Dogs, Southern Louisiana, USA, 2011

Britton J. Grasperge, Wendy Wolfson, and Kevin R. Macaluso

Author affiliations: Louisiana State University, Baton Rouge, Louisiana, USA

Abstract

The association between companion animals and tick-borne rickettsial disease has long been recognized and can be essential to the emergence of rickettsioses. We tested whole blood from dogs in temporary shelters by using PCR for rickettsial infections. Of 93 dogs, 12 (13%) were positive for Rickettsia parkeri, an emerging tick-borne rickettsiosis.

Tick-borne spotted fever group (SFG) rickettsioses are maintained in tick populations through vertical transmission of the rickettsial agent and horizontal transmission among vectors by a vertebrate host. Companion animals, specifically dogs, can serve as vertebrate hosts for arthropod vectors and SFG rickettsia (1), as shown by a report of a Rickettsia parkeri–infected dog in South America (2). Likewise, cases of rickettsioses in humans have been associated with cases in companion animals (3). Because of a substantial increase in tick-borne rickettsial diseases in the past decade, much effort has been directed to identifying the rickettsial agents present in ticks (4). On the basis of findings from field surveys of rickettsial infections in ticks and characterization of rickettsioses in humans, most cases of what is considered Rocky Mountain spotted fever, a disease caused by R. rickettsii, are likely caused by infections with rickettsial species other than R. rickettsii (5).

One of the better documented emerging rickettsial pathogens is R. parkeri, an SFG tick-borne rickettsial disease associated with Gulf Coast ticks (Amblyomma maculatum) (6) and commonly identified in the coastal states of the southeastern United States. We investigated the potential role domestic dogs play in the ecology of R. parkeri transmission to better understand the epidemiologic landscape of this emerging rickettsiosis.