Abstract
Animal arboviruses replicate in their invertebrate vectors and vertebrate hosts. They use several strategies to ensure replication/transmission. Their high mutation rates and propensity to generate recombinants and/or genome segment reassortments help them adapt to new hosts/emerge in new geographical areas. Studying arbovirus genetic variability has been used to identify indicators which predict their potential to adapt to new hosts and/or emergence and in particular quasi-species. Multiple studies conducted with insect-borne viruses laid the foundations for the “trade-off” hypothesis (alternation of host transmission cycle constrains arbovirus evolution). It was extrapolated to tick-borne viruses, where too few studies have been conducted, even though humans faced emergence of numerous tick-borne virus during the last decades. There is a paucity of information regarding genetic variability of these viruses. In addition, insects and ticks do not have similar lifecycles/lifestyles. Indeed, tick-borne viruses are longer associated with their vectors due to tick lifespan. The objectives of this review are: (i) to describe the state of the art for all strategies developed to study genetic variability of insect-borne viruses both in vitro and in vivo and potential applications to tick-borne viruses; and (ii) to highlight the specificities of arboviruses and vectors as a complex and diverse system.
Highlights
Sandflies and ticks do not have the same lifecycle and lifestyle, tick-borne viruses are longer associated with their vectors than mosquito- or sandfly-borne viruses, due to vector life span
Crimean-Congo haemorrhagic fever virus (CCHFV) genome diversity was higher in ticks than in mice [31]. These results showed that tick vectors play a principal role in expanding the genetic variability of tick-borne viruses
Characteristics and molecular aspects of arboviruses were identified during multiple studies aiming to assess their genetic variability and in particular the insect-borne viruses (Table 3)
Summary
More than half of the world is at risk from vector-borne diseases. They are illnesses caused by pathogens in human and animal populations. Each year more than one billion humans are infected and more than one million die from vector-borne diseases. The most affected by these diseases are the poorest and least-developed countries [1]. In addition to the public health burden, vector-borne diseases negatively impact the economies of affected countries. Vector-borne diseases cause important economic losses in the breeding industry. The economic impact of BTV outbreaks can be substantial. In 2006, a BTV outbreak in Europe cost $1.4 billion and $85 million to France and the Netherlands, respectively [3]
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