Rickettsia parkeriinDermacentor parumapertusTicks, Mexico

During a study to identify zoonotic pathogens in northwestern Mexico, we detected the presence of a rickettsial agent in Dermacentor parumapertus ticks from black-tailed jackrabbits (Lepus californicus).Comparison of 4 gene sequences (gltA, htrA, ompA, and ompB) of this agent showed 99%-100% identity with sequences of Rickettsia parkeri.R ickettsia parkeri is an emerging pathogen that causes a spotted fever group rickettsiosis, transmitted to humans primarily by several species of ticks of the genus Amblyomma, including A. maculatum, A. triste, A. tigrinum, and A. ovale.However, R. parkeri has also been detected in other hard ticks, including A. americanum, A. aureolatum, A. dubitatum, A. longirostre, A. nodosum, A. parkeri, Ixodes scapularis, Rhipicephalus sanguineus, Dermacentor parumapertus, and D. variabilis, in 8 countries in North (United States), Central (Belize), and South (Colombia, Peru, Brazil, Bolivia, Uruguay, Argentina) America (1,2) (Figure 1, panel A).Recently, a distinct strain of Rickettsia parkeri, designated R. parkeri Black Gap, was isolated and characterized from the tick Dermacentor parumapertus collected from black-tailed jackrabbits in Texas, USA (3).This isolate is phylogenetically related to Rickettsia sp.strain Atlantic rainforest, a well-known pathogenic lineage of R. parkeri associated with a mild rickettsiosis of humans in Brazil (4).In addition, the presence of R. parkeri in A. triste and A. maculatum ticks has been confirmed in several locations in Arizona (5,6).Although R. parkeri-infected ticks have now been identified in several US states that border Mexico, no studies have demonstrated the presence of R. parkeri in ticks in Mexico. The StudyWe conducted a study to identify zoonotic pathogens in northwestern Mexico; the study area comprised a region within the Janos Biosphere Reserve in Chihuahua state (30°51′50″N, 108°30′09″W) and in the San Pedro River Basin in Sonora state (31°30′90″N, 110°10′70″W) (Figure 1, panel B).The area is in a transition zone between the Sonoran Desert, the Sierra Madre Occidental, and the Chihuahuan Desert and comprises a mosaic of grasslands, mesquite scrublands, and oak forests.During September 2013-September 2014, we sampled lagomorphs in 6 trapping locations (Chihuahuan locations: Casa de Janos, El Cuervo, Monte Verde, Pancho Villa, and Rancho El Uno; Sonoran location: Palmitas).Lagomorphs were livetrapped in box traps and leg-hold traps during a separate study to evaluate Bartonella genotypes in wild carnivores (7) under permission no.FAUT-0250 of the Secretaría de Medio Ambiente y Recursos Naturales.We identified captured animals as to species, sex, and age (juvenile or adult) using a standard field guide (8).We physically restrained the lagomorphs and visually examined them for ticks, removed the ticks manually, and deposited them in cryovials containing 96% ethanol.We then released the hosts in situ.We performed morphological identification of ticks with specialized taxonomic keys (9).We collected 29 ticks: 23 D. parumapertus adults from 21 black-tailed jackrabbits (Lepus californicus), 2 D. parumapertus adults from 3 white-sided jackrabbits (Lepus callotis), and 2 D. parumapertus adults and 2 Amblyomma sp.nymphs from 4 desert cottontails (Sylvilagus audubonii).We deposited 1 female and 2 male D. parumapertus ticks in the