Arboviruses
Arthropod-borne viruses (arboviruses) are transmitted by biting arthropod vectors. The viruses are genetically diverse and are from several different virus families, including Bunyaviridae, Togaviridae and Flaviviridae. The arthropod vectors are also varied, predominantly mosquitoes and ticks, but also include sandflies, lice, mites and bedbugs. Several emerging and re-emerging neglected diseases and zoonoses (infections that can pass between animals and humans) are caused by arboviruses, with vaccines available for only a few of these infections.
Disease incidence has grown dramatically around the world in recent decades, Dengue fever being the most common and responsible for 96 million cases worldwide every year. Arboviruses occur globally, although the range of each species is restricted by the distribution of the vector. During the viraemic stage of disease, when viruses enter the bloodstream, transmission can also occur by blood product transfusions or in healthcare associated settings. Human behaviours such as travel and trade can have environmental impacts that expand the geographical ranges for the vectors and the viruses. Many arboviruses have RNA genomes, which means that they have a predisposition to gain mutations more rapidly, allowing them to evade intervention strategies, acquire new vectors and alter pathogenesis1,2. Authenticated viruses from NCPV are used for developing:
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Investigating virus infection cycles, transmission and pathogenesis studies
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Developing antivirals, therapeutics and vaccines
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Validating virus inactivation methods
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Establishing animal models to assist research and development
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Whole genome sequencing analysis
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Validating diagnostic and sero-surveillance methods
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Vector competency studies to test viral transmission to help predict regions at risk of becoming endemic
Togaviridae is a family of enveloped viruses with linear non-segmented, single-stranded, positive-sense RNA genomes. Humans, mammals, birds, and mosquitoes serve as natural hosts. All arboviruses within this family lie within the Alphavirus genus.
Flaviviridae is a family of small enveloped viruses with RNA genomes of 9000–13000 bases. Most infect mammals and birds. Many flaviviruses are host-specific and pathogenic. The majority of known members in the genus Flavivirus are arthropod borne, and many are important human and veterinary pathogens3.
Bunyaviridae - in 2017 the International Committee on Taxonomy of Viruses reclassified the Bunyaviridae family, creating a new order Bunyavirales. This contains 9 families and 13 genera. Enveloped virions contain segmented negative-sense RNA genomes. Many viruses within this order cause severe illnesses.
Rhabdoviridae is a family of virus in the order Mononegavirales. Vertebrates, invertebrates and plants serve as natural hosts.
References
1. Liang G, Gao X and Gould EA (2015). Factors responsible for the emergence of arboviruses; strategies, challenges and limitations for their control. Emerging Microbes & Infections 4(3):e18.
2. World Health Organization. www.who.int/mediacentre/factsheets/fs117/en/
3. Simmonds et al (2017). ICTV Virus Taxonomy Profile: Flaviviridae. J Gen Virol 98:2-3.