The vectorial capacity encompasses the vector competence, which is defined as the ability of an arthropod to acquire, sustain replication and dissemination of a pathogen, and then successfully transmit it to new susceptible hosts ( Monath, 1988). Taken together, all these parameters contribute to the vectorial capacity, which is related to the efficiency of a vector population to transmit a pathogen under natural conditions. To be efficient, the vectorial system requires high densities of competent vectors, a high vector survival rate, and frequent contacts between vectors and susceptible vertebrate hosts. These changes imply that endemic pathogens can be transmitted by imported vectors, or newly introduced pathogens can be transmitted by local vector populations. In recent decades, growing trade and increased international tourism, have highly contributed to the expansion of vectors colonizing new territories and thus threatening new regions with new pathogens ( Esser et al., 2019). Vector-borne diseases (VBDs) represent almost one-fourth of annual deaths attributed to infectious diseases ( Jones et al., 2008). This review will demonstrate the dynamic nature and complexity of virus–vector interactions to help in designing appropriate practices in surveillance and prevention to reduce VBD threats.
Here, we review the factors that might limit pathogen transmission: internal (vector genetics, immune responses, microbiome including insect-specific viruses, and coinfections) and external, either biotic (adult and larvae nutrition) or abiotic (temperature, chemicals, and altitude). Despite the large distribution of arthropods (mosquitoes and ticks) and arboviruses, only a few pairings of arthropods (family, genus, and population) and viruses (family, genus, and genotype) successfully transmit. However, all tick or mosquito species are not able to transmit all viruses, suggesting important molecular mechanisms regulating viral infection, dissemination, and transmission by vectors. Mosquitoes and ticks are the main vectors of arboviruses including flaviviruses, which greatly affect humans. These diseases, caused by pathogens shared between animals and humans, are a growing threat to global health with more than 2.5 million annual deaths. More than 25% of human infectious diseases are vector-borne diseases (VBDs). Unit of Arboviruses and Insect Vectors, Institut Pasteur, Sorbonne Université, Paris, France.Marine Viglietta, Rachel Bellone, Adrien Albert Blisnick *† and Anna-Bella Failloux *†
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