1. ARBOVIRUSES By: Dr. Malak El Hazmi
Assistant Professor & Consultant Virologist College of Medicine & KKUH

2. Viral Zoonoses Arthropod-borne Vs Non arthropod-borne zoonoses
Mosquito-borne Vs
Yellow Fever V
Dengue V
Rabies V.
Ebola V.
Marburg V.
Lassa V .
Hantaviruses
Tick-borne Vs
Tick-borne encephalitis Vs
Colorado tick fever
Fly-borne Vs
Sandfly fever V.

3. Arboviruses: Def Etiology Epidemiology Diseases Dengue Yellow Fever
Rift Valley Fever
Dx. Rx
Prevention

4. Arthropod –borne Viruses
Arboviruses > 500 Vs
Classification
Togaviridae*
Flaviviridae*
Bunyaviridae*
Reoviridae
Orthomyxoviridae
Rhabdoviridae

5. Characteristic Properties of Arboviruses
Property
Toga
Flavi
Bunya
Rhabdo
Reo*
Ortho
Symmetry
Cubic
Helical
Bullet
Diameter (nm) 70
40-60
80-100
180 x 85
60-80
15-120
Nucleic acid
(+)ss
RNA
(-)ss
(-) ss ds
No. of Vs 29 68
318 63 77 2
*Non-enveloped

6. Epidemiology: Reservoir: Wild birds & Mammals
Vector: Mosquito, tick & Sandfly
Transmission: bite of infected vector
Natural Cycles
Human-mosquito cycle
Dengue + Urban yellow fever
Mosquito - bird cycle
West Nile Vs
Mosquito-mammal cycle
Venezuelan equine encephalitis

7. Life cycle of arboviruses

8. Epidemiology: Reservoir: Wild birds & Mammals
Vector: Mosquito, ticks& Sandfly
Transmission: bite of infected vector

9. Life cycle of arboviruses

10. Epidemiology: Natural cycles
1. Arthropod - bird cycle
West Nile Vs ,EEEV, WEEV

11. Epidemiology: Natural cycles
2. Arthropod -mammal cycle
Venezuelan equine encephalitis
Epidemiology: Natural cycles

12. Epidemiology: Natural cycles
3. Human- Arthropod cycle
Dengue & Urban yellow fever

13. Epidemiology: Natural cycles
1. Arthropod - bird cycle
2.Arthropod- mammal cycle
3. Human- arthropod cycle

14. Diseases Asymptomatic Infections* Diseases CNS disease ( encephalitis)
Fever, Rash & arthralgia
Hemorrhagic fever ± hepatitis

15. *ArboVs associated with CNS disease:
Virus
Vector
Reservoir
Distribution
Eastern equine
encephalitis EEEV
Mosquito
Birds
America
Western equine
encephalitis WEEV
Venezuelan equine
encephalitis VEEV
Rodent
Japanese encephalitis V
Birds Pigs
Orient
Murray Valley
encephalitis V
Australia
West Nile V
Europe, Africa
Middle East Asia, America

16. West Nile virus
Flaviviridae
Febrile illness encephalitis

17. Eastern equine encephalitis virus EEEV
Severe Encephalitis
Western equine encephalitis virus
WEEV
less severe
EEEV &WEEV
Togaviridae
Killed vaccine
for horses

18. Venezuelan equine encephalitis virus VEEV
Togaviridae
Febrile illness
encephalitis

19. *ArboVs associated with Hemorrhagic Fever
Virus
Vector
Reservoir
Distribution
Crimean Congo Virus
Tick
Mammals
Africa , Asia & Europe
Rift Valley fever virus
Mosquito
Sheep cattle
Africa
Yellow Fever virus
Monkeys Man
Africa & South America
Dengue Virus
Man
Entire tropical zone

20. *ArboVs associated with Fever-rash-arthralgia
Virus
Vector
Reservoir
Distribution
West Nile virus
Mosquito
Birds
Africa, Europe, America
Rift Valley Fever Virus
Sheep
Cattle
Africa
Dengue Virus
Man
Entire tropical zone
Sandfly fever Virus
Sandfly
Mediterranean

21. Yellow Fever Flaviviridae Asymptomatic to Jaundice + Fever ±
hemorrhage ± renal failure
Epidemiology
Tropical Africa
& South America
Jungle Yellow Fever
Urban Yellow Fever

22. It is a disease of humans
Jungle Yellow Fever:
Urban Yellow Fever:
Vector: mosquito
Reservoir: human
It is a disease of humans
Vector: mosquito
Reservoir: Monkeys
Accidental host: humans
It is a disease of Monkeys

23. Dengue Virus Vector : Mosquito Reservoir : human
Tropical parts of the world
Diseases
The classic dengue fever
Dengue Hemorrhagic Fever

24. Dengue Virus The classic dengue fever Dengue Hemorrhagic Fever
Fever – rash – arthralgia
Break bone fever
Self-limiting
Dengue Hemorrhagic Fever
Severe disease
Mortality rate 15%
C/F
- F-R-A
- Hemorrhage (GI, skin)

25. Rift Valley Fever Bunyaviridae Sheep, Cattle , etc Spread Mosquitoes
Infected animal
blood or tissue
Raw milk

26. Diseases Febrile disease* Retinitis
Fulminant disease with Hge + Jaundice + Hepatitis
Rarely: encephalitis

27. Dx. Rx. Reference Lab Lab. Methods :
Isolation (Good standard )
Samples: blood, CSF, Viscera .
Cell culture CPE
Identify by IF
B - IgM -AB* - EIEA, IF: (most used)
C - Arbovirus RNA by RT-PCR
Rx.
Ribavirin (some bunyavirus & Togavirus)

28. Prevention Vector Control: Vaccines: Elimination of
vector breading sites
using insecticides
Avoidance contact
with vectors
( repellants , net )
Vaccines:

29. 2- Vaccines: Yellow Fever vaccine Tick-borne encephalitis vaccine
(LAV, 17D strain, one dose /10 yrs)
Tick-borne encephalitis vaccine
(killed, 2 doses ,3rd doses after 1 yr.
booster every 3-5 yrs)
Japanese encephalitis
(killed,
LAV)