Transmission dynamics and control of Rickettsia rickettsii in populations of Hydrochoerus hydrochaeris and Amblyomma sculptum

Author(s)

Polo, Gina ; Acosta, Carlos Mera ; Labruna, Marcelo B. ; Ferreira, Fernando

• Document type: Journal article
• Source: PLoS Neglected Tropical Diseases; v. 11, n. 6 JUN 2017.
• Web of Science Citations: 9

Abstract

Background Brazilian Spotted Fever (BSF), caused by the bacterium Rickettsia rickettsii, is the tickborne disease that generates the largest number of human deaths in the world. In Brazil, the current increase of BSF human cases has been associated with the presence and expansion of capybaras Hydrochoerus hydrochaeris, which act as primary hosts for the tick Amblyomma sculptum, vector of the R. rickettsii in this area. Methods We proposed a semi-discrete-time stochastic model to evaluate the role of capybaras in the transmission dynamics of R. rickettsii. Through a sensitivity analysis, we identified the parameters with significant influence on the R. rickettsii establishment. Afterward, we implemented the Gillespie's algorithm to simulate the impact of potential public health interventions to prevent BSF human cases. Results The introduction of a single infected capybara with at least one infected attached tick is enough to trigger the disease in a non-endemic area. We found that to avoid the formation of new BSF-endemic areas, it is crucial to impede the emigration of capybaras from endemic areas by reducing their birth rate by more than 58%. Model results were corroborated by exsitu data generated from field studies, and this supports our proposal to prevent BSF human cases by implementing control strategies focused on capybaras. Conclusion The proposed stochastic model illustrates how strategies for the control and prevention of vector-borne infectious diseases can be focused on amplifier hosts management practices. This work provides a basis for future prevention strategies for other neglected vector-borne diseases. (AU)

• FAPESP's process: 14/12213-1 - Modelling and stochastic simulation to study the dynamics of Rickettsia rickettsii in populations of Hydrochoerus hydrochaeris and Amblyomma cajennense in the State of São Paulo, Brazil
• Grantee: Gina Paola Polo Infante
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 13/18046-7 - Capybaras, ticks, and spotted fever
• Grantee: Marcelo Bahia Labruna
• Support Opportunities: Research Projects - Thematic Grants