Dengue a viral disease affecting millions worldwide is a vector borne disease.this ppt includes its etiology pathogenesis case management and epidemiology

1. BY : Dr. KUSHAL GRAKH(MVSc scholar)
LUVAS HISAR

2.  Dengue is a self limiting acute mosquito
transmitted viral disease characterized by
fever, headache, muscle, joint pains, rash,
nausea and vomiting.
 Some infections result in Dengue
Haemorrhagic Fever (DHF) and in its severe
form Dengue Shock Syndrome (DSS) can
threaten the patients life primarily through
increased vascular permeability and shock.

3.  The first evidence of occurrence of DF in the
country was reported during 1956 from Vellore
district in Tamil Nadu.
 The first DHF outbreak occurred in Calcutta (West
Bengal) in 1963 with 30% of cases showing
haemorrhagic manifestations.
 All the four serotypes i.e. Dengue 1,2,3 and 4
have been isolated in India.
 As Ae aegypti breeding is more common in
urban areas the disease was observed mostly
prevalent in urban areas.
 However, socio economic and man made
ecological changes, has resulted in invasion of
Ae. aegypti mosquitoes into rural areas, which
has increased the chances of spread of the
disease to rural areas.

5.  The dengue viruses - members of the genus
Flavivirus.
 These small (50nm) viruses contain single stranded
RNA.
 Four virus serotypes designated as DEN-1, DEN-2,
DEN-3 and DEN-4.
 All four serotypes are antigenically similar. Infection
with any one serotype confers lifelong immunity to
the virus serotype.
 Man and mosquito are reservoirs of infection.
Transovarian transmission has made the control
more complicated.
 At present DEN1 and DEN2 serotypes are
widespread in India.

6.  Dengue viruses are transmitted by the bite of
female Aedes (Ae) mosquitoes.
 Ae. aegypti - most potential vector.
 Other species such as Ae albopictus, Ae.
polynesiensis and Ae. niveus have also been
incriminated as secondary vectors.
 In India Ae. aegypti is the main vector in most
urban areas.
 However, Ae albopictus is also found as
vector in few areas of southern India.

10. Febrile phase :
 An acute febrile illness of 2-7 days duration with two or more of the
following manifestations: Headache, retro-orbital pain, myalgia,
arthralgia, rash, haemorrhagic manifestations.
Critical phase :
1.Dengue Haemorrhagic Fever :
 a). A probable or confirmed case of dengue
plus
 b). Haemorrhagic tendencies evidenced by one or more of the following
 1. Positive tourniquet test
 2. Petechiae, ecchymoses or purpura
 3. Bleeding from mucosa, gastrointestinal tract, injection sites or other
sites
 4. Haematemesis or malena
Plus
 c). Thrombocytopenia (<100,000 cells per cumm)
plus
 d). Evidence of plasma leakage due to increased vascular permeability,
manifested by one or more of the following :
 1. A rise in average haematocrit for age and sex > 20%
 2. A more than 20% drop in haematocrit following volume replacement
treatment compared to baseline
 3. Signs of plasma leakage (pleural effusion, ascitis, hypoproteinaemia.

11. 2.Dengue Shock Syndrome :
 All the above criteria for DHF plus
 evidence of circulatory failure manifested by
rapid and weak pulse and
 narrow pulse pressure (<20 mm Hg) or
hypotension for age, cold and clammy skin and
restlessness.
Recovery phase : the patient survives the 24–48
hour critical phase, a gradual reabsorption of
extravascular compartment fluid takes place in the
following 48–72 hours.
General well-being improves, appetite returns,
gastrointestinal symptoms abate, haemodynamic
status stabilizes and diuresis ensues.
Some may experience generalized pruritus.
Bradycardia and electrocardiographic changes are
common during this stage.

12.  Early symptoms of dengue fever mimic other diseases
often prevalent in areas where it is endemic, such as
chikungunya, malaria and leptospirosis.
 Hence for proper management rapid differential
diagnosis is very crucial.
 Laboratory diagnosis can be carried out by one or
more of the following tests:
 Isolation of Dengue virus from serum, plasma,
leucocytes or autopsy samples.
 Demonstaration of a fourfold or greater rise in
reciprocal IgG antibody titres to one or more dengue
virus antigen in paired sera samples.
 Demonstaration of dengue virus antigen in autopsy
tissue by immunohistochemistry or
immunofluorescence or in serum samples by EIA
 Detection of viral genomic sequences in autopsy
tissue, serum or CSF sample by PCR.

13. Serological tests:
 Haemagglutination-Inhibition (HI)
 Complement Fixation (CF)
 Neutralization test (NT)
 IgM capture enzyme-linked immunosorbent
assay (MAC-ELISA)
 Indirect IgG ELISA
 Rapid Diagnostic test kits

14. Management of Dengue Fever (DF)
 Management of Dengue fever is symptomatic
and supportive
 i. Bed rest is advisable during the acute
phase.
 ii. cold sponging to keep temp.below 39o C.
 iii. Antipyretics-to lower the body
temperature. Paracetamol is prefered.
 Iv.fluid therapy
 Aspirin/NSAID like Ibuprofen etc should be
avoided since it may cause gastritis,
vomiting, acidosis and platelet dysfunction.

15. Management of DHF and DSS:
 Management of DHF(grade I,II,III,IV) and DSS
require additional fluid therapy based on the
condition as internal bleeding occurs in these
cases .
 Treatment therefore include replacement of
fluid and whole blood infusion or platelet
transfusion to cope up progressive
thrombocytopenia and blood loss.
 Other symptomatic therapy is same as used
in dengue fever cases.

16.  Dengue fever vaccines are designed to
prevent the spread of denue virus.
 Dengvaxia –first dengue vaccine approved for
use in prevention of dengue (available in
Mexico and Brazil only).
 It is a live attenuated tetravalent chimeric
vaccine.
 Manufacturer recommended that vaccine can
only be used in people who have previously
had a dengue infection otherwise it may
worsen subsequent infection.

17.  Preventing or reducing dengue virus transmission
depends entirely on control of the mosquito
vectors or interruption of human–vector contact.
 Activities to control transmission should target
Ae. aegypti (the main vector) in the habitats of its
immature and adult stages in the household as
well as other settings where human–vector
contact occurs (e.g. schools, hospitals and
workplaces)
 Ae. aegypti proliferates in many purposely-filled
household containers:
 such as those used for domestic water storage
and for decorative plants,
 rain-filled habitats – including used tyres,
discarded food and beverage containers, blocked
gutters and buildings under construction.

18.  Typically, these mosquitoes do not fly far, the
majority remaining within 100 metres of where
they emerged.
 They feed almost entirely on humans, mainly
during daylight hours, and both indoors and
outdoors.
 The habitats are eliminated by preventing
access by mosquitoes to these containers or by
frequently emptying and cleaning them.
 By removing the developing stages using
insecticides or biological control agents, by
killing the adult mosquitoes using insecticides,
or by combinations of these methods

19.  Tourniquet test : The tourniquet test is
performed by inflating a blood pressure cuff
to a mid point between the systolic and
diastolic pressure for five minutes. The test is
considered positive when 10 or more
petechiae per 2.5 cm2 are observed.
 In DHF, the test usually gives a definite
positive test with 20 petechiae or more.
 The test may be negative or only mildly
positive during the phase of profound shock
(DSS).