Tick-Borne Viruses in a Changing Climate: The Expanding Threat in Africa and Beyond

Abstract

Tick-borne viruses (TBVs), notably Orthonairovirus haemorrhagiae (Crimean-Congo hemorrhagic fever virus, CCHFV), are emerging global health threats intensified by climate change. Rising temperatures and altered precipitation patterns are expanding the habitats of key tick vectors, increasing their survival and reproductive success. The African continent is characterized by many different climatic zones, and climatic shifts have increased or changed CCHFV transmission patterns, becoming greater risk to humans and livestock. Beyond Africa, CCHFV spread in Europe, the Middle East, and Asia and has been facilitated by factors such as livestock movement, deforestation, and migratory birds. Climate-driven shifts in tick seasonality, behavior, and vector competence may further enhance viral transmission. Addressing these challenges requires integrated responses, including enhanced surveillance, predictive modeling, and climate-adaptive vector control strategies. A One Health approach-linking environmental, animal, and human health domains-is essential. Innovative strategies such as anti-tick vaccines and sustainable vector control methods offer promise in reducing the burden of these diseases. Proactive, collaborative efforts at regional and international levels are crucial in tackling this growing public health challenge.

Keywords: Africa; Crimean–Congo hemorrhagic fever virus; climate change; tick-borne viruses.

Figure 1

Geographic distribution of the most relevant tick species in Africa of importance for human and animal health. Shown are the known distribution ranges across Africa, Europe, and Asia, based on published occurrence data [49,73,74,75,76].

Figure 2

Conceptual diagram illustrating the pathways through which climate change, microbiome dynamics, and microbial interactions influence tick vector competence and pathogen transmission. Climate-driven environmental changes affect tick microbiome composition and virome diversity, which in turn modulate tick behavior, host-seeking activity, and vector competence. Intrinsic factors (tick species, life stage) and extrinsic factors (temperature, humidity, feeding system) shape microbial diversity. Key endosymbionts such as Francisella-like endosymbionts (FLEs) and Candidatus Midichloria mitochondrii (CMM) play central roles in modulating pathogen colonization, tick physiology, and immune responses. Interactions among microbial taxa—competitive (e.g., Coxiella vs. Rickettsia) or synergistic (e.g., Francisella + Rickettsia)—further influence pathogen persistence. Antibiotic exposure and artificial feeding systems perturb the microbiome, potentially altering vector competence. These multifactorial interactions ultimately shape the efficiency of pathogen transmission and present opportunities for microbiome-based tick control strategies.