A compilation of ticks and tick-borne pathogen distributions in seven countries within North and West Africa from 1901 to 2022: a systematic literature review.

Abstract

<h4>Background</h4>Ticks continue to represent a significant threat to human and animal health worldwide. In the absence of comprehensive databases that compile the current published records of tick diversity and distributions, the information from hundreds of articles remains in isolation, incapable of being easily incorporated into surveillance gap analyses and tick-borne pathogen risk modeling. Here, our group systematically reviews and extracts data from published studies that detail ticks collected within seven target countries in North and West Africa.<h4>Methods</h4>We conducted a systematic literature review of documented tick distribution and tick-borne pathogen associations published from Algeria, Morocco, Nigeria, Niger, Senegal, Sierra Leone, and Tunisia between 1901 and 2022. Three databases were screened, and after a priori exclusion criteria, 372 articles were deemed eligible for review and underwent data extraction. Relevant information pertaining to ticks and tick-borne pathogens was collected and compiled into a dataset allowing for the articles to be georeferenced.<h4>Results</h4>The articles included within the final dataset reported 74 hard tick species and 30 soft tick species throughout the seven target countries. Species of the genus Rhipicephalus dominated (n = 24 species), followed by Hyalomma (n = 14), Ornithodoros (n = 14), and Haemaphysalis (n = 13). Almost 80% of collection events involved ticks removed from nonhuman vertebrates. Approximately 12% of collection events included evidence of an associated microbial species, including 17 bacterial genera, 3 eukaryotic genera, and 16 viruses. Through mapping of the collection events, we begin to characterize surveillance gaps within each country.<h4>Conclusions</h4>This systematic review highlights notable surveillance gaps that vary by country and region. While Morocco, Nigeria, and Senegal report numerous studies concerning tick diversity, certain regions appear oversampled, while reports from other regions are largely absent. Information on the ticks of Sierra Leone and Niger remains largely uncharacterized. Across all target countries, reports are heavily biased toward sampling and testing ticks collected from domestic animals. Future tick surveillance efforts need to include sampling and testing of ticks collected from the environment and wildlife species to obtain a more complete assessment of tick distribution and tick-borne pathogen ecology.