Dengue, Japanese encephalitis, West Nile fever, chikungunya fever, hemorrhagic fevers, Kyasanur forest disease, are some of the arboviral infections prevalent in India.

1. ARBOVIRUSES
ARTHROPOD BORNE VIRUS
Dr. C. Vishwajeeth
Associate Professor
Comm. Med
M.A.M.S. Bachupally-HYD.

2. ARBOVIRUSES
2
⚫Transmitted by insect vectors.
⚫Cause infections in animals & birds.
⚫Transmitted to man by bite of infected
mosquitoes, ticks & sand flies.
⚫Worldwide, more in tropical areas than
temperate.
Transmission Cycles-
⚫Man –Arthropod – Man
⚫Animal –Arthropod - Man
4/5/2022 arboviral diseases

3. Man-Arthropod-Man Cycle
Reservoir may be either man or
arthropod vector (mosquitoes).
E.g.- dengue, yellow fever.
3
4/5/2022 arboviral diseases

4. Animal-Arthropod-Man Cycle
⚫The reservoir is an animal.
⚫The virus is maintained in nature in a transmission cycle
involving the mosquitoes and animals. Man becomes infected
accidently.
⚫e.g. Japanese encephalitis, yellow fever (by both cycles)
4
4/5/2022 arboviral diseases

5. Animal Reservoirs
• In many cases, the actual reservoir is unknown.
• The following animals are recognized reservoirs.
Birds -
Pigs -
Monkeys -
Rodents -
Japanese encephalitis, St Louis encephalitis.
Japanese encephalitis
Yellow Fever
Russian Spring-Summer encephalitis
5
4/5/2022 arboviral diseases

6. Arboviral Diseases
Mainly divide into two groups- A and B
• Chikungunya fever- A virus (alpha virus)Aedes aeg.
• Yellow fever-B virus-(flavivirus fibricus) Aedes aeg.
• Japanese encephalitis- B grp virus- culex M
• Kyasanur forest disease-B grp virus-Ticks
• West nile fever-B grp virus- culex M
• Sandfly fever- B grp - Sandfly
4/5/2022 arboviral diseases

7. Antigenic Structure:
9
⚫Three antigens are important in serological studies
namely:
a. Haemagglutinins
b. Complement fixing antigen
c. Neutralizing antigen
⚫ Cross reactions occur among arboviruses.
Pathogenesis
⚫Virus enters the body through bite of the vector.
⚫Virus multiplies in reticuloendothelial system and leads
to viraemia.
⚫Virus transported to target organs such as CNS –
encephalitis;
4/5/2022 arboviral diseases

8. Diseases Caused
⚫Febrile illness - This is usually a non-specific illness resembling a number
of other viral illnesses such as influenza, and enterovirus infections. The
patients may go on to develop encephalitis or haemorrhagic fever.
E.g. Chikungunya, Dengue.
⚫Encephalitis – Inflammation of brain.
E.g. St Louis encephalitis, Japanese encephalitis.
⚫Hemorrhagic fever – Bleeding disorder with high fever.
E.g. yellow fever, dengue hemorrhagic fever.
0
4/5/2022 arboviral diseases

9. Viruses causing Febrile illnesses:
1. Chikungunya virus:
15
The virus was first isolated from patients and mosquitoes during an epidemic
in Tanzania in 1952-53. The virus occurs widely in sub-Saharan Africa, India
and in many areas in Asia.
• A prominent symptom, seen especially in adult patients is arthropathy,
from which the disease gets its name.
• The arthropathy is manifested by pain, swelling and stiffness,
especially of the metacarpophalangeal, wrist, elbow, shoulder, knee,
ankle and metatarsal joints.
• It appears between 3rd and 5th day after the onset of clinical symptoms,
and it can persist for many months and even years.
• No deaths have been attributed to chikungunya fever.
4/5/2022 arboviral diseases

10. History- Chikungunya
• In 2006 the outbreak was first noticed in Andhra Pradesh, and it
subsequently spread to Tamil Nadu.
• Thereafter, Kerala and Karnataka were affected and then northwards as far
as Delhi.
• The other states involved were Maharashtra, Madhya Pradesh, Gujarat,
Rajasthan, Pondicherry, Goa, Orissa, West Bengal, Uttar Pradesh, Andaman
and Nicobar Islands.
• During 2013, 18,639 cases were reported by the Government of India.
Aedes aegypti
4/5/2022 arboviral diseases

11. Vaccine-Chikungunya
Not yet developed
arboviral diseases
4/5/2022

12. 2.Yellow fever
45 countries in Africa and America, are at risk of yellow fever.
In Africa, people living in 32 countries are at risk.
The remaining are in 13 countries of Latin America, with Bolivia, Brazil,
Colombia, Ecuador and Peru at greatest risk .
There are an estimated 200,000 cases and 30,000 deaths worldwide each year.
Small number of imported cases occur in countries free of yellow fever.
Although disease has never been reported in Asia, the region is at risk
because the conditions required for transmission are present there
4/5/2022 arboviral diseases

13. Yellow fever VACCINE:
⚫Effective vaccine available for Yellow fever .
⚫It is a live attenuated vaccine known as 17 – D strain .
⚫The vaccine is administered subcutaneously in one dose , with a
booster dose every 10 years .
⚫Recommended to travelers to endemic areas.
4/5/2022 arboviral diseases

14. 14
• Japanese Encephalitis is a Public health importance,
because of its epidemic potential, high case fatality rate,
permanent sequelae, no treatment and it is preventable.
• J.E. is primarily a disease of rural and semi urban having
agricultural areas where mosquitoes proliferate in close
association with pigs and other animal reservoirs.
• Approximately 70,000 cases of JE occur globally each year
with 20,000 deaths .
3.Japanese Encephalitis
4/5/2022 arboviral diseases

15. Japanese encephalitis:
Worldwide distribution
⚫ Korea, Japan, S/EAsia,
⚫Virus first isolated in Japan in 1935.
⚫1955 in India.
18
⚫Mortality- up to 50%. Residual neurological damage.
4/5/2022 arboviral diseases

16. JE ENDEMIC AREAS IN INDIA
JE affected areas
• Andhra Pradesh
• Assam
• Bihar
• Haryana
• Kerala
• Karnataka
• Maharashtra
• Manipur
• Tamil Nadu
• Uttar Pradesh
• West Bengal
4/5/2022 arboviral diseases

17. AREA OF HIGH OCCURRENCE
• The 04 southern states of Telangana, Tamil Nadu ,
Andhra Pradesh, Karnataka report higher
incidence.
• JE is emerging as a public health problem in
Kerala.
4/5/2022 arboviral diseases

18. Natural host and Reservior
• Chief reservior-Animals(pigs and cattle) and water birds.
• Pigs are called as ‘Amplifier host’ because infected pigs do
not manifest any symptoms, but they help only in
multiplication of virus.
• Man get infected due to mosquitoes which bites both
animals and man.
• Cattle –neither suffer nor act as amplifier host.
• Horse-the only animal which develop manifestation of
encephalitis.
• Birds – birds are natural reservoirs and amplifying host
for JEV.,(pond-herons and poultry ducks)
4/5/2022 arboviral diseases

19. Human Reservior
• Even the cases do not act as
source of infection because of
short period of viraemia and
low level of circulating viruses.
(That is why Man called as
dead-end hosts.)
• They are the only active clinical
cases and subclinical cases.
4/5/2022 arboviral diseases

20. Environmental conditions
 Atmospheric temperature of about 20 deg.C and relative
humidity 70 percent are favourable.
 Rice cultivation
 Pig rearing.
 Duck rearing.
 Availability of ponds and lakes.
 Movement of migratory birds.
4/5/2022 arboviral diseases

21. Clinical features
Incubation period-5 to 15 days
 Prodromal Stage
 Acute encephalitic Stage and
 Late stage
4/5/2022 arboviral diseases

22. Prodromal Stage : is characterised by
 Sudden onset of Fever
 Rigors
 Headache
 Nausea and
 Vomiting
The duration of this stage usually lasts
for 1 to 3 days.
4/5/2022 arboviral diseases

23. Acute Encephalitic Stage:
Begins by the 3rd day.
symptoms include:
 High grade fever(38-40.7 deg.C)
 Neck rigidity
 Convulsion
 Altered sensorium
 Disorientation
 Progressing in many cases to coma and
 death
4/5/2022 arboviral diseases

24. Late stage and sequelae
More than 50 percent of them develop neurological and
psychological defecits
Characterized by:
 Amnesia
 Abnormal movements,ataxia
 Personality changes
 Emotional disability
 Paralysis
The average period between onset of illness and death is
about 9 days
4/5/2022 arboviral diseases

25. Vaccines
03 types of vaccines-
1. Mouse brain derived, purified & inactive JE vaccine
2. Cell culture derived, inactivated JE vaccine
3. Cell culture derived, live attenuated SA 14-14-2 JE
vaccine
arboviral diseases
4/5/2022

26. 4.Kyasanur Forest disease
26
⚫Disease first recognized in Kyasanur forest in Karnataka in 1957.
⚫Severe prostrating illness.
⚫Reservoirs - Birds & animals. Tick may act as the reservoir.
⚫Transmission – by bite of Tick.
Clinical features:
⚫Incubation period: 3 – 7days
⚫Patient develops fever of sudden onset.
⚫Headache, vomiting, conjunctivitis, myalgia and sever prostration.
⚫Massive hemorrhages in alimentary canal, chest cavity and epistaxis may
occur.
⚫Case fatality – 5%.
⚫Vaccine – killed KFD vaccine is used
4/5/2022 arboviral diseases

27. 5.West nile fever
• An acute febrile illness caused by a group B arbovirus.
• The disease is endemic in Africa, the Middle East, South-West Asia and India,
and transmitted by certain species of Culex mosquitoes.
• Clinically, it is manifested by a sudden onset of fever, severe headache and
malaise lasting several days.
• In children, a maculopapular rash of short duration may appear. In the aged,
a fatal meningo-encephalitis may be produced.
4/5/2022 arboviral diseases

28. 6.Sandfly fever
• Sandfly fever is known to occur in the arid regions of West
Pakistan and Middle East.
• Its occurrence in India was thought to be doubtful.
• However, in 1967, the sandfly fever virus was isolated in
Aurangabad
• (Maharashtra) from febrile cases.
• The virus was also isolated from sandflies.
• The control of sandfly fever is based on the control of insect vector.
4/5/2022 arboviral diseases

29. Lab diagnosis of Arbovirus diseases
⚫Specimen: Blood, CSF, Brain may be used for virus isolation.
⚫Virus isolation:
1. Intra cerebral inoculation in suckling mice. Most sensitive. Develops fetal
encephalitis.
2. Yolk sac of chick embryo
3. Tissue culture
4. Xenodiagnosis (a method of animal inoculation using laboratory-breed bugs and
animals)
29
Serology:
⚫ELISA– Used for detection of serotype specific IgM antibody.
⚫Complement fixation test.
⚫Haemagglutination or neutralisation test.
4/5/2022 arboviral diseases