Send to

Choose Destination
Am J Trop Med Hyg. 2019 May 13. doi: 10.4269/ajtmh.18-0878. [Epub ahead of print]

Unbiased Assessment of Abundance of Rhipicephalus sanguineus sensu lato Ticks, Canine Exposure to Spotted Fever Group Rickettsia, and Risk Factors in Mexicali, México.

Author information

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California.
Laboratorio de Salud Pública Veterinaria, Instituto de Investigaciones en Ciencias Veterinarias, Universidad Autónoma de Baja California, Mexicali, México.
Facultad de Medicina, Universidad Autónoma de Baja California, Mexicali, México.
Public Health Department, Imperial County, California.
Rickettsial Zoonoses Branch, Centers for Disease Control and Prevention, Atlanta, Georgia.
Dirección de Enseñanza y Vinculación, Instituto de Servicios de Salud Pública del Estado de Baja California, Mexicali, México.


An epidemic of Rocky Mountain spotted fever (RMSF) is ongoing in Mexicali, México. We visited 100 neighborhoods with diagnosed human cases and 100 control neighborhoods to evaluate knowledge of the epidemic; obtain data on the spatial distribution of dogs, canine seroprevalence and active infection, tick infestations, and presence of rickettsial DNA in ticks; and evaluate risk factors for human cases, seropositivity, and tick infestation within an unbiased study design. The majority (80%) of residents had heard of RMSF, but only 48% used acaricides in the home or on dogs. Case neighborhoods and those with high canine seroprevalence tended to be on the city periphery or in the agricultural valley. No dogs were polymerase chain reaction (PCR) positive for Rickettsia rickettsii, and the overall seroprevalence was 65% (titers from 64 to 1,024). PCR prevalence in ticks was 0.70%, confirmed by DNA sequencing as R. rickettsii; neighborhood prevalence ranged from 0.7% to 6.1%. Twelve percent of dogs had high tick burdens, and all ticks were Rhipicephalus sanguineus. Epidemiologically significant risk factors were ground covering for a neighborhood having a human case; dogs having poor body condition and weighing < 10 kg for canine seropositivity; dogs living at the home for the number of ticks in the environment; and being near canals, having trash on the patio, and a dog being thin for tick burdens on dogs. A One Health approach is crucial to understanding RMSF and brown dog ticks.


Supplemental Content

Full text links

Icon for Ingenta plc
Loading ...
Support Center