Screening of tick-borne pathogens in Caribbean ticks using High-throughput qPCR (DOMOTICK Project)

Among hematophagous arthropods, ticks transmit the greater variety of pathogens of public health and veterinary importance. Due to socio-economic and environmental factors, such as human practices, increased travel, global market, global warming, and environmental changes, the incidence of tick-borne diseases in both humans and animals is increasing worldwide, leading to a need for extended surveillance tools. Recently, in Europe a large scale epidemiological study was conducted on 19,474 Ixodes ricinus nymphs collected from five European countries using a powerful new high-throughput approach to screen tick-borne pathogens (Michelet et al., 2014). The technology used in this study is a microfluidic high-throughput Taqman realtime PCR (BioMarkTM dynamic arrays, Fluidigm Corporation), allowing the simultaneous detection of 25 bacterial, 12 parasitic and 22 viral species across 94 samples of ticks. They successfully determined the prevalence of expected tick-borne pathogens (Borrelia burgdorferi sensu lato, Babesia divergens, Tick-Borne Encephalitis virus, etc.), unexpected (Borrelia miyamotoi, Nairo-like virus) or rare (Bartonella henselae, Eyach virus) tick-borne pathogens. This surveillance method represents a major improvement in epidemiological studies, able to facilitate comprehensive testing of tick-borne pathogens in various samples, and which can also be customized for the survey of emerging diseases in different areas of the world. Caribbean, are a risk area for the (re)-emergence of vector-borne diseases. Population in Caribbean is in expansion, leading to a growing food demand. Maintaining a healthy livestock industry is crucial but often difficult to manage because of tick-borne diseases such as anaplasmosis, ehrlichiosis, or babesiosis. The Caribbean is also a world interface, with numerous air and maritime networks (tourism, and animals trade) leading to a serious risk of dispersion of tick and their tick-borne pathogens in this area. Moreover, few reports are available on tick-borne diseases in the Caribbean and are only focusing on livestock pathogens such as Ehrlichia ruminantium, Babesia (bovis and bigemina) and Anaplasma marginale. In this context, the DOMOTICK project was designed to apply the high-throughput realtime-PCR technology for a large scale screening of tick-borne pathogens in the Caribbean. Methods included a comprehensive analysis of the literature on tick-borne pathogens, as well as pathogen detection by RNA-sequencing on nucleic acids extracted from ticks collected in Guadeloupe and Martinique to determine which pathogens need to be included in this new high-throughput technology. Preliminary results obtained from NGS analysis suggest that these ticks may harbor more pathogenic microorganisms than the currently known in the Caribbean, such as Rickettsia and Borrelia species of public health importance. Up to now, 40 bacterial species have been listed, including the genera Anaplasma, Ehrlichia, Bartonella, Borrelia, Rickettsia, Mycoplasma, Francisella, Coxiella, Aegyptianella, Mycoplasma ; 14 parasites species, belonging to the genera Babesia, Theleria, Hepatozoon, Leishmania, Rangelia vitalii, Cytauxzoon felis ; and 25 arboviruses belonging to viral families of Orthobunyavirus, Phlebovirus, Nairovirus, Asfivivirus, Thogotovirus, Flavivirus, Coltivirus and Orbivirus. The detection tool will be validated with tick samples collected on various vertebrate hosts through the Caribbean islands thanks to the CaribVet network, and to local veterinarians. Results obtained will be used to do an exploratory epidemiological study on the tick-borne pathogens circulating in the Caribbean. (Résumé d'auteur