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ARBOVIRUSES (Arthropod-Borne viruses)

y  Originally defined as:

Viruses transmitted by arthropod (mainly insect) vectors

y  1985 W.H.O criteria:

Arboviruses: those maintained in nature through biological transmission between

susceptible vertebrate hosts by haematopahous arthropods. They multiply and produce

viraemia in vertebrate, multiply in the tissues of arthropods and are passed on to new

vertebrates when arthropod takes a subsequent blood meal after a period of extrinsic

incubation.

y  International Catalogue of arboviruses

-  The term arbovirus jas NO taxonomic significance

-  535 heterogenous groups of viruses

-  Under 7 taxonomic families

-  Many are zoonotic viruses that do not require an arthropod vector!

ARBOVIRUSES (This table is not complete!! I couldnt type it out in time! Sorry!!!!!)

Toga Alphavirus

Ungrouped

Flavi Flavivirus

Bunya Bunya

Phlebo

Nairo

Uukuu

Hantavirus

Orbovirus

UnassignedVesiculovirus

SOME IMPORTANT ARBOVIRUSES

Family: Togaviridae

Genus: Alphavirus

No. of members: 28 (mosquito-borne)

Some important members:-

y  Western equine encephalitis (WEE)

y  Eastern equine encephalitis (EEE)

y  Venezuelan equine encephalitis (VEE)

y  Chikugunya

y  Ross river

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Genus: Rubivirus, spp. Rubella virus (not ar-bo)

Family: Flaviviridae

Genus: Flavivirus

Amount of members: ~80 

Some important members:-

A.  Mosquito-borne

-  St. Louis encephalitis

-  Japanese B encephalitis

-  Murray Valley encephalitis

-  Yellow Fever

-  Dengue

-  Ilheus

-  West Nile

B.  Tick-borne

-  Louping ill

-  Powassan

-  Tick-borne encephalitis

-  Kyasanur-Forest

-  Omsk Haemorrhagic fever

Genus: Hepacivirus

Family: Bunyaviridae

Genus: Bunyavirus

Amount of members: 212

Some important members:

y  La Crosse

y  Snowshoe hare

y  Oropouche

Genus: Phlebovirus

y  Rift valley fever

y  Punta Toro

y  Sandfly fever

y  Tascana

Genus: Nairovirus

y  Crimeas-Congo haemorrhagic fever

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Genus: Hantavirus

y  Sin Nombre (not ar-bo)

Family: Rhabdoviridae

Genus: Lyssavirus

Species: rabies virus (not ar-bo), 1 serotype

Other spp: Lagosm Mokota, Duvenhage, Kotonkan, Obodhiang

Important diseases caused by Arboviruses:-

y  Yellow fever

y  Dengue / DHF

y  Japanese encephalitis

y  Rubella (not ar-bo)

y  Hepatitis C (not ar-bo), also Hep-Gy  Rabies (not ar-bo)

DENGUE & Dengue haemorrhagic gever & Dengue shock syndrome (DF, DHF, DSS)

History

y  1780: Breakbone fever outbreak in Philadelphia, USA

y  1800s: sporadic outbreaks

y  1934: Floridal 1945 New Orleans

y  1897: Australia Clinical description of dengue complicated by haemorrhages, shock and

death in outnreaksy  1928 Greece, 1931 Formosa

y  1903: Mosquito-borne transmission of infection by Aedes aegypti demonstrated.

y  1944: Sabin

-  Isolated virus

-  Failure of 2 viral strains to cross protect humans

= evidence of serotypes

y  1956: Hammond characterized 2 more

y  After WWII: Start of a PENDEMIC with intensidied transmission of multiple viral serotypes in

SEAsia -> Outbreaks of DHF DSS

y  In last 2 decades similar patterns of intensified transmission and DHF-DSS in:

-  SE Asia

-  Americas

-  Oceania

y  Due to:

-  Urbanization

-  Population growth

-  mobility

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