Modeling of Control Efforts against Rhipicephalus sanguineus, the Vector of Rocky Mountain Spotted Fever in Sonora Mexico

SIMPLE SUMMARY: Rocky Mountain spotted fever (RMSF) is among the most fatal of all bacterial diseases in the Americas. Humans become ill through the bite of ticks infected with the bacterium Rickettsia rickettsii. Several biological, environmental, and social determinants play a role in the occurrence of the disease, which has extended its presence throughout the region. To prevent this medical threat, innovative interventions has been implemented in some communities, although they still do not have a widespread application and have not been used in combination. In this study, we examined through mathematical models the potential benefit of combining insecticidal dog collars and long-lasting wall treatments to reduce the burden of ticks in a socially vulnerable Mexican community with a high burden of cases and deaths due to RMSF. Overall, we found that if enough coverage is given for either treatment, the other one can be omitted. Both interventions have the potential to lessen the burden of ticks and may help to lower the risk to be ill from RMSF in communities such as of our study. We recommend further research including some other factors (i.e., political, budgetary, socioeconomics) linked to the disease. ABSTRACT: Rocky Mountain spotted fever (RMSF) is a significant health problem in Sonora, Mexico. The tick vector, Rhipicephalus sanguineus, feeds almost exclusively on domestic dogs that, in this region, also serve as the reservoir for the tick-borne pathogen, Rickettsia rickettsii. A process-based mathematical model of the life cycle of R. sanguineus was developed to predict combinations of insecticidal dog collars and long-lasting insecticidal wall treatments resulting in suppression of indoor tick populations. Because of a high burden of RMSF in a rural community near the Sonora state capital of Hermosillo, a test area was treated with a combination of insecticidal dog collars and long-lasting insecticidal wall treatments from March 2018 to April 2019, with subsequent reduction in RMSF cases and deaths. An estimated 80% of the dogs in the area had collars applied and 15% of the houses were treated. Data on tick abundance on walls and dogs, collected during this intervention, were used to parameterize the model. Model results show a variety of treatment combinations likely to be as successful as the one carried out in the test community.