2. PART 1: DENGUE
Dengue is the most rapidly spreading mosquito-borne
viral disease in the world.
Approximately 2.5 billion people live under the threat of
dengue transmission
Like malaria, dengue fever exists throughout the
tropics, and seems particularly prevalent in Asia, the
Middle East and Latin America,
Dengue in Africa appears to be mainly concentrated in
the eastern half of the continent.
2
4. DENGUE
Dengue virus in many ways seems to be the obverse of
malaria.
While malaria transmission occurs most frequently in
rural areas, dengue is a city disease.
While the Anopheles vectors of malaria bite mainly at
night, the Aedes vectors of dengue bite mainly in the
daytime.
4
5. TRANSMISSION
Dengue is caused by several closely related viruses,
called dengue virus
Dengue virus (DEN) is a small single-stranded RNA virus
comprising four distinct serotypes
1. DEN-1
2. DEN-2
3. DEN-3
4. DEN-4
These closely related serotypes of the dengue virus
belong to the genus Flavivirus, family Flaviviridae.
5
6. The disease is transmitted from person to person mainly
by Aedes aegypti, but Aedes albopictus can also act as a
vector.
In rare cases dengue can be transmitted in organ
transplants or blood transfusions from infected
donors, and there is evidence of transmission from an
infected pregnant mother to her fetus.
But in the vast majority of infections, a mosquito bite is
responsible.
6
7. Two forms of the disease occur
- dengue fever
- dengue haemorrhagic fever.
7
8. DENGUE FEVER
Dengue fever occurs in explosive epidemics that mainly
affect adults, sometimes with tens of thousands of cases,
especially in urban areas.
It is an acute febrile disease that starts suddenly and lasts
for a week or more, causing intense headache, pain in
joints and muscles, and rash.
Infection rarely results in death.
It occurs in most tropical countries and in some
subtropical areas.
It can occur in rural and urban areas, if suitable vector
mosquitos are present.
8
9. DENGUE HAEMORRHAGIC FEVER
Dengue haemorrhagic fever is a severe illness that
occurs in south-east Asia and has appeared relatively
recently in the Americas and the South Pacific, mainly
affecting children.
Infection starts with high
fever, vomiting, headache, difficulty in breathing and pain
in the abdomen.
Signs of internal bleeding are common.
Dengue shock syndrome may develop as a result of loss
of blood and lowered blood pressure.
If treatment is not available, as many as 50% of patients
with shock may die, but overall mortality from dengue
haemorrhagic fever is usually in the range of 5–10%. 9
10. Rash, which shows up 3-4 days
after the start of the
symptoms, starting from the
trunk region and spreading to the
face, arms and legs.
10
11. DENGUE: TREATMENT
There is no specific medication for treatment of a dengue
infection, but patients with dengue shock syndrome can
be treated by rapid administration of fluid and plasma and
the monitoring of vital signs.
Bed rest
Paracetamol
Oral fluids and electrolyte therapy
Dengue vaccines in development are of four types: live
attenuated viruses, chimeric live attenuated
viruses, inactivated or sub-unit vaccines, and nucleic 11
acid-based vaccine
13. CONTROL OF DENGUE/ DHF
No drug/vaccine available
Control of Aedes aegypti only method of choice
Personal protection against daytime-biting
mosquitoes, including the use of protective
clothing, repellents and house screening.
13
14. The most effective preventive measures aim at reducing
the population density of the vector, Aedes aegypti.
- large-scale prevention of breeding, through removal or
filling of breeding habitats in man-made and natural
containers, the burning of organic waste, screening or
fitting mosquito-proof lids to drinking-water storage
containers, installing piped drinking-water supply, and, if
other methods are not feasible or practical, applying safe
and effective larvicides to breeding sites.
14
15. In epidemic situations the same measures should be taken, but
attempts should also be made to reduce populations of adult
mosquitoes rapidly by outdoor space spraying with insecticides.
Insecticidal sprays are usually applied to the parts of towns
where abundant breeding sites are available, supporting large
populations of Aedes.
Space sprays can be applied with knapsack or hand-carried
fogging machines and by truck- or aircraft-mounted machines.
Residual wall spraying against Aedes aegypti is generally
ineffective as this species normally rests indoors on surfaces
that are not suitable for spraying, such as curtains and other
fabrics.
Stocks of insecticides should be kept for emergencies.
15
18. WHAT IS JAPANESE ENCEPHALITIS?
A viral disease- Flavivirus
Transmitted by infective bites of female mosquitoes mainly
belonging to:
1. Culex tritaeniorhynchus
2. Culex vishnui
3. Culex pseudovishnui
JE virus is primarily zoonotic in its natural cycle and man is an
accidental host
JE virus is neurotropic and arbovirus and primarily affects
central nervous system 18
19. TRANSMISSION CYCLE
Culex- Vector
Pigs- Amplifier host
- a vertebrate that has high level of pathogen that a
feeding vector will likely become infectious.
Ardeid birds (Cattle egret, Pond heron)- Natural hosts
Man- Dead end host
- a vertebrate that harbors the pathogen and is severely
affected by it, yet the level of pathogen in its body is too
low for blood sucking vector to become infective after
feeding on the host.
- Mosquitoes do not get infection from JE patient 19
21. The virus also can be transmitted when an infected pig's
body fluids such as saliva, nasal discharge, blood, uterine
discharge, urine and faeces, had a direct contact with
human mucus.
For example, a worker handling pigs sometimes feeds
the pigs by hand without any protection gears such as
gloves or mask.
This could lead to pig's mucus secreted from its nostril to
have contact with worker's hand or palm.
Then, the worker does not take care of his own hygiene
by eating without washing hands properly.
This careless mistake mentioned above can lead to the
21
infection of JE virus.
22. The transmission all started when the JE virus multiplies
in the pig's body and if the female Culex mosquito sucks
the blood of the pig, she will picks up the JE virus.
After an incubation period of 14 days, the Culex mosquito
is able to transmit the virus to a new host, especially pigs.
JE can infect humans and animals.
Besides pigs as the host for the virus, other animals like
cows, buffaloes, goats, sheep, dogs and cats also have
shown positive reaction rates ranging from 6-66%.
22
23. The virus cannot be spread from human to human.
Eating pork too cannot transmit the disease.
Leading cause of viral encephalitis in Asia with 30-50,000
cases reported annually
Fewer than 1 case/year is reported in U.S. civilians and
military personnel traveling to and living in Asia
23
24. Countries which have had major epidemics in the
past, but which have controlled the disease primarily by
vaccination
China Korea
Japan Taiwan
Thailand
Countries that still have periodic epidemics
Vietnam Cambodia
Myanmar India
Nepal Malaysia
24
26. WHY JE IS CONCENTRATED IN ASIA?
JE occurred in most of the Asian countries because these
countries such as China, Malaysia, Taiwan and many
more are the main exporter of pork in Asia that is still
practising the traditional ways of rearing pigs.
The farmers that are still using the old ways, did not
vaccinated their pigs eventhough the farms are built in
areas of known JE activity.
The staff that works in these farms are lacking of
vaccination too.
26
27. As a result of using the traditional ways, the rivers are
clogged with pig waste because those farmers just "dump
everything" into the river.
The clogged river then becomes the perfect place for
Culex mosquito to breed.
To make the situation worse, those farmers and workers
does not wear any protection gear such as mask, apron
and gloves during their daily work in those pig
farm, making them an easy target for the Culex mosquito.
27
28. Majority of those farmers also stay near their pig farms.
This also contribute to the spread of the disease.
To summarize the whole scenario, the spread of this
disease is because of poor management and condition of
those pig farms.
28
29. SYMPTOMS
JE begins clinically as a flu-like illness with
headache, fever and often gastrointestinal symptoms.
At the early stage, confusion and disturbances in
behaviour may occur.
After 3-14 days of fever and headache, drowsiness and
disorientation would take place.
Later, the illness may progress to a serious infection of
the brain that can lead to coma within 24-48 hours.
A quarter of patients with symptoms die and the
remaining one third of survivor will suffer brain damage.
Seizures are common, especially among children 29
30. PREVENTION, TREATMENT AND CONTROL
A vaccine against JE is used to immunize children in
some of the Asian countries in which the disease is
endemic.
The drug Ribavirin is now being given to all JE patients or
those suspected to have been infected with the disease to
help improve their chance of recovery
30
31. Infections can be prevented by using protective
clothing, repellents, house screening, mosquito nets, coils
and mats, and by the avoidance of outdoor activities in the
evening.
The spraying of houses and animal shelters in rural areas
to control the Culex vectors of JE is generally ineffective
because of the outdoor biting and resting habits of the
vector species.
In some areas control is possible by measures that
31
prevent breeding in rice fields and irrigation systems.
32. Outdoor space spraying with insecticides can be carried
out where epidemics occur.
In endemic areas it is recommended that domestic
animals be housed away from human habitations.
This applies especially to pigs in areas where JE is
endemic.
32
34. INTRODUCTION
Yellow fever is an acute disease of short duration which
often causes death.
The disease starts with a high fever, headache, body
aches, vomiting and sometimes jaundice (which gives the
patient a yellow colour).
This is followed by internal haemorrhages (bleeding) and
vomiting.
Death may occur within three days after the onset of the
disease. 34
35. TRANSMISSION AND DISTRIBUTION
The yellow fever virus mainly occurs in populations of
monkeys in dense forests and gallery forests in Africa and
South and Central America.
It is transmitted from monkey to monkey by forest-dwelling
mosquitos (Aedes species in Africa, Haemagogus and
Sabethes in South and Central America;
These mosquitos occasionally bite humans when they enter
forests and may thus transmit the virus from the monkey
reservoir to the human population.
There is evidence in some areas of endemicity that the virus is
maintained in mosquito populations through transovarial
transmission in the absence of a vertebrate reservoir.
35
37. In Africa, monkeys sometimes leave the forest in search
of bananas in plantations and may then infect the local
mosquito species, which in turn infect humans living or
working on the plantations.
People infected in or near forests can carry the virus to
rural or urban areas where Aedes aegypti or related
mosquitos can pick it up and transmit it among the human
population.
Such situations can result in serious epidemics and many
37
deaths.
38. In the Americas, urban outbreaks used to be extremely
severe but have not occurred since 1954.
However, the risk remains and cases are reported each
year among people working in forests.
In Africa, urban or rural outbreaks are occasionally
reported from areas near forests and may cause
thousands of deaths.
People working in forests also become infected regularly.
Yellow fever has never been reported in Asia.
38
41. PREVENTION AND CONTROL
Yellow fever is best prevented by immunization, which is
recommended for all persons working in or visiting forests
where yellow fever occurs.
Immunization is also indicated for people in urban or rural
areas at risk.
Vaccination normally provides protection for at least 10
years and revaccination every 10 years is required by the
port or frontier health authorities in a number of tropical
countries.
41
42. Epidemics can be controlled by vaccinating all persons
living in affected areas; by space-spraying with
insecticides against adult mosquitos; and by appropriate
larval control measures.
Non-immunized people can reduce the risk of infection by
protecting themselves from mosquito bites with protective
clothing, repellents and screens to prevent daytime biting.
42
44. Chikungunya fever is a viral disease transmitted to
humans by the bite of infected mosquitoes.
Chikungunya virus is a member of the genus Alphavirus,
in the family Togaviridae.
Chikungunya virus was first isolated from the blood of a
febrile patient in Tanzania in 1953, and has since been
cited as the cause of numerous human epidemics in
many areas of Africa and Asia and most recently in
limited areas of Europe.
Chikungunya virus is not currently found in the United
States
44
46. Chikungunya virus is spread by the bite of an infected
mosquito.
The Aedes aegypti mosquito is the principle vector
responsible for transmitting the chikungunya virus to
humans.
Mosquitoes become infected when they feed on a person
infected with chikungunya virus.
Infected mosquitoes can then spread the virus to other
humans when they bite.
Monkeys, and possibly other wild animals, may also
serve as reservoirs of the virus.
46
47. SYMPTOMS
Chikungunya virus infection can cause a debilitating illness,
most often characterized by fever, headache, fatigue, nausea,
vomiting, muscle pain, rash, and joint pain.
The term ‘chikungunya’ means ‘that which bends up’ in the
Kimakonde language of Mozambique.
Acute chikungunya fever typically lasts a few days to a few
weeks, but as with dengue, West Nile fever and other arboviral
fevers, some patients have prolonged fatigue lasting several
weeks.
Additionally, some patients have reported incapacitating joint
pain, or arthritis which may last for weeks or months.
Fatalities related to chikungunya virus are rare.
47
48. TREATMENT, CONTROL AND PREVENTION
There is no vaccine or specific antiviral treatment currently
available for chikungunya fever.
Treatment is symptomatic and can include rest, fluids, and
medicines to relieve symptoms of fever and aching such
as ibuprofen, naproxen, acetaminophen, or paracetamol.
Aspirin should be avoided.
Infected persons should be protected from further
mosquito exposure (staying indoors in areas with screens
and/or under a mosquito net) during the first few days of
the illness so they can not contribute to the transmission
cycle.
48
49. Pregnant women can become infected with chikungunya virus
during all stages of pregnancy and have symptoms similar to
other individuals.
Most infections occurring during pregnancy will not result in the
virus being transmitted to the fetus.
The highest risk for infection of the fetus/child occurs when a
woman has virus in her blood (viremic) at the time of delivery.
There are also rare reports of first trimester abortions occurring
after chikungunya infection.
Pregnant women should take precautions to avoid mosquito
bites.
Products containing DEET can be used in pregnancy without
adverse effects.
Currently, there is no evidence that the virus is transmitted
through breast milk. 49
50. The best way to prevent chikungunya virus infection is to
avoid mosquito bites.
Prevention tips are similar to those for other viral diseases
transmitted by mosquitoes, such as dengue
Additionally, a person with chikungunya fever should limit
their exposure to mosquito bites to avoid further spreading
the infection.
The person should use repellents when outdoors exposed
to mosquito bites or stay indoors in areas with screens or
under a mosquito net.
50
