Molecular detection of Rickettsia species in ticks collected in the Mexico-USA transboundary region

Authors: MERINO, JOSE - University Of Tamaulipas; DE LA CRUZ, NED - University Of Tamaulipas; MARTINEZ, JULIO - University Of Tamaulipas; Perez De Leon, Adalberto - Beto; ROMERO-SALAS, DORA - University Of Veracruzana; ESTEVE-GASSENT, MARIA - Texas A&M University; LAGUNES-QUINTANILLA, RODOLFO - Instituto Nacional De Investigaciones Forestales Y Agropecuarias (INIFAP)

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2020
Publication Date: 4/5/2020
Citation: Merino, J.O., De La Cruz, N.I., Martinez, J., Perez De Leon, A.A., Romero-Salas, D., Esteve-Gassent, M., Lagunes-Quintanilla, R. 2020. Molecular detection of Rickettsia species in ticks collected in the Mexico-USA transboundary region. Experimental and Applied Acarology. 80:559-567. https://doi.org/10.1007/s10493-020-00483-5.
DOI: https://doi.org/10.1007/s10493-020-00483-5

Interpretive Summary: Tick-borne diseases (TBD) are increasing and have become a worldwide public health issue due to the many disease-causing agents,or pathogens, that ticks pick up during blood-feeding on infected wildlife and domestic animals and then transmit through their bite to humans. Among TBD, rickettsioses are diseases caused by bacterial species in the genus Rickettsia that represent a very important group due to the emergent character of the illness in humans. In this study ticks were collected from dogs, cattle, horses, feral swine, and humans in parts of the state of Tamaulipas including portions encompassing the Mexico-USA transboundary region shared with south Texas. The ticks were identified and subjected to molecular analysis to detect Rickettsia species. The brown dog tick, Rhipicephalus sanguineus, was the most common tick collected. Four ticks infesting dogs, one infesting a cow, and one a human were found to harbor nucleic acid of Rickettsia species. Five of these positive ticks were Amblyomma mixtum, and one was R. sanguineus. The information presented here helps understand the epidemiology of Rickettsia species, which is necessary for adequate diagnosis and intervention to prevent rickettsioses in the state of Tamaulipas. Because A. mixtum positive for Rickettsia was found infesting dogs, a human, and a cow, this tick represents a risk for the transmission of rickettsial pathogens between domestic animals and humans. These findings highlight the need for research and extension on tick control to manage tick-borne diseases of veterinary and public health importance in this sector of the Mexico-USA transboundary region.

Technical Abstract: Zoonotic tick-borne diseases, including those caused by Rickettsia species, continue to have serious consequences for public health worldwide. One such disease that has emerged as a major problem in several countries of the American continent is the Rocky Mountain Spotted Fever (RMSF) caused by the bacterium Rickettsia rickettsii. Several tick species are capable of transmitting R. rickettsia, including Amblyomma cajennense, A. aureolatum, A. imitator, Rhipicephalus sanguineus, Dermacentor andersoni, D. variabilis and possibly A. americanum. Despite previous reports in Mexico linking new outbreaks of RMSF to the presence of these tick species, no robust measures have tackled transmission. In the present study, we amplified R. rickettsii from 109 test DNA samples extracted from ticks collected from several animals and humans of Tamaulipas, Mexico, between November 2015 and December 2017. Our analysis revealed the presence of R. rickettsii in six samples and these findings contribute to a spatial distribution map that is intended to minimize the risk of transmission to humans.