Ticks and tick-borne diseases on southwestern Indian Ocean islands

BACKGROUND: Tick-borne diseases represent a growing global health concern, affecting both humans and animals, with an increasing number of disease outbreaks reported worldwide. On the southwestern Indian Ocean islands (SWIO)-including the Comoros, Madagascar, Mauritius, La Réunion, Rodrigues and the Seychelles-the diversity of tick species and the pathogens they transmit remain poorly understood, posing a considerable impediment to improving public and animal health. METHODS: Here, we present the first comprehensive summary of tick species diversity and tick-borne pathogens in the SWIO region. RESULTS: In this review, we list 42 tick species across seven genera with Haemaphysalis (13 species) and Ixodes (13 species) being the most species-rich. Although many species appear endemic to the SWIO region and, in numerous cases, to specific islands, the main vectors involved in pathogen transmission are cosmopolitan and introduced taxa. Tick-borne diseases such as babesiosis, borreliosis, and cowdriosis circulate on different islands in the SWIO region, particularly affecting cattle and small ruminants. Importantly, we highlight critical issues related to taxonomic identifications, molecular diagnostics, vector competence studies, and the integration of One Health approaches (i.e., an integrated and systemic approach that aims to sustainably balance and optimize the health of humans, animals, and ecosystems), which are further accentuated by the socio-economic and ecological contexts of each island. CONCLUSIONS: Addressing these gaps will be essential to strengthen surveillance, assess risks, and design effective preventive and control strategies. We conclude that the insular context creates favorable conditions for the implementation of regional One Health strategies aimed at improving early detection, preparedness, and response to tick-borne diseases.