Properties of dengue virus:
2. RNA, enveloped virus
3. Has 4 serotypes- DEN- 1,2,3,4
4. Replication is in cytoplasm
5. Females Aedes Aegypti mosquito transmit the disease
6. Viraemia is present at the time of fever
Dengue (disease):
Dengue is a mosquito born infection which is caused by
dengue virus
Common feature - fever and acute systemic illness
Incubation Period- 2-7 days
Endemic: in south-east asia, india, Africa, carribean and the Americas
Environmental aedes aegypti: It breeds in
·
Standing water
·
Collection of water in containers
·
Water-based air coolers
·
Tire dumps
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Clinical Features and Pathogenesis of Dengue |
Mode of transmission of dengue virus:
Female aedes aegypti mosquito transmits the disease
Reservoir: patients are the reservoir
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Transmission of Dengue Virus |
Clinical feature of dengue:
1. Prodrom:
2 days of malaise and headache
2. Acute onset: fever, backache, arthalgia, headache, G.pain (break-bone fever), pain on eye movement, larcimation, anorexia, nausea, vomiting, relative bradycardia, prostration, depression, lymphadenopathy, sclera injection
3. Fever: Continuous or “saddle back” with break on 4th or 5th days and then recrudescence usually last 7-8 days
4. Rash: initial flushing faint macular rash in 1st 1-2 days, maculopapular scarlet morbilliform rash from days 3-5 on trunk, spreading centrifugally and sparing the palms and soles. Onset is often with fever effervescence. May desquamate on resolution or give rise to petechiae on extensor surface
5. Convalescence: Slow
6. Complication: Minor bleeding from the mucosal sites, hepatitis, cerebral hemorrhage or oedema, rhabdomyolysis
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Symptoms of Dengue Fever |
Pathogenesis of classical dengue/ 1st exposure dengue/ breakbone fever:
1. Dengue
infection by dengue virus
3. Formation
of immune complex and activation of complement
Increased vascular permeability and thrombocytopenia
Pathogenesis of dengue haemorrhagic fever:
1. The
patient recovers from classic dengue caused by one of the 4 serotype and Ab
against that serotype already produced.
2. Patient gets infected with another serotype of dengue virus
3. An
anamnestic, heterotypic reaction occurs
4. Large
amount of cross reacting Ab to the 1st serotype are produced
5. There
are two hypotheses about what happens next:
A. Immune
complex composed of virus and Ab are formed and that activates compliments
causing increased vascular permeability and thrombocytopenia
B. The
Ab increases the entry of the virus into monocytes with the consequent
liberation of large amount of cytokines
6. Resulting in shock and haemorrhage
7. Dengue haemorrhagic fever
Lab Diagnosis of Dengue:
1 Specimen: Blood
2 Isolation of the virus by: Cell culture, Acute phase protein, plasma
3 Demonstration of a rising titer of a specific serum dengue antibodies: by ICT, ELISA, Haemagglutination inhibition test, CFT, Neutralization test
4 Demonstration of a specific viral Ag or RNA in serum or tissue by: PCR, Counter current immunoelectrophoresis, Immuno-chemical staining of peripheral blood mononuclear cells
5 Other tests: CBC, LFT, S. electrolytes, CXR-P/A/V, USG of W/A, S. protein, Blood grouping and Rh typing
That's all for today!
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Dengue is dangerous disease that may also lead to death.Therefore if a person is suspected of dengue an urgent treatment should be given.
ReplyDeleteEmergency care Houston