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Dengue fever
 

Dengue fever

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    Dengue fever Dengue fever Presentation Transcript

    • DENGUE FEVER Dr. Anita Lamichhane Deptt. Of pediatrics Shaikh Zayed Hospital
    • Etiological Agent
    • Dengue virus
      • Single stranded RNA virus,Arbovirus belonging to flaviviridae family
      • 4 antigenically distinct serotypes-DEN 1, 2,3, 4.
      • DEN-1, DEN-2 were prevalent until 1980s
      • DEN-3 is predominant in recent outbreak
      • DEN-4 primarily detected in secondary dengue infections
      • Serotype provides specific life time immunity and short term cross immunity
    • Dengue virus transmission
      • Two general patterns
      • Epidemic Dengue – dengue virus is introduced into a region as an isolated event that involves a single viral strain(Asia,Africa,America)
      • Hyperendemic Dengue -continuous circulation of multiple viral serotypes in an area where a large pool of susceptible hosts & a competent vector are constantly present,predominant pattern of global transmission.
    •  
    • The vector-Aedes aegypti
      • Transmitted by the infected female Aedes aegypti
      • Can be identified by the white bands or scale patterns on its legs and thorax
      • Primarily a daytime feeder
      • Found in tropical & subtropical region
      • Lives around human habitation
      • Lays egg & produces larvae preferentially in artificial containers
    • Vector & its transmission
      • 0 5 8 12 16 20 24 28
      • DAYS
      • Illness Illness
      • Human #1 Human #2
      Mosquito feeds/acquires virus Mosquito refeeds/transmits virus Viremia Intrinsic incubation period Extrinsic incubation period Viremia
    • Replication & transmission of Dengue virus
      • Virus inoculated into a human being with mosquito saliva
      • The virus localizes and replicates in various target organs-local lymph nodes & liver  released  spreads through the blood  infect the WBCs & reticuloendothelial system(dendritic cells,hepatocytes,endothelial cells)
      • The mosquito ingests blood containing the viruses (on biting an infective person)
      • Virus replicates in the midgut,ovaries,nerve tissue, fat body of the mosquito
      • It then escapes into the body cavity and later on infects the salivary glands
      • In the salivary glands, the virus replicates
      • When the mosquito bites another human ,the life cycle continues
      • Humans are the primary reservoir of infection
    • Vector
      • Aedes aegypti/Aedes albopictus
      • The female mosquito feeds on blood ( they need the protein found in blood to produce eggs)
      • Male mosquitoes feed only on plant nectar.
      • The mosquito is attracted by the body odours, carbon dioxide and heat emitted from the animal or humans .
    • Aedes aegypti Mosquito life cycle
      • Eggs are laid on the walls of water-filled containers in the house and patio.
      • The eggs can survive for months and hatch when submerged in water.
      • Female mosquitoes lay dozens of eggs up to 5 times during their life time.
      • The mosquito life cycle, takes 8 days and occurs in water. Adult mosquitoes live for one month.
      • Adult mosquitoes “usually” rest indoors in dark areas (closets, under beds, behind curtains); only female mosquitoes bite humans.
      • The dengue mosquito can fly several hundred yards looking for water-filled containers to lay their eggs.
      • The dengue mosquito does not lay eggs in ditches, drainages, canals, wetlands, rivers or lakes
    • Aedes aegypti
    • Aedes albopictus
    • PATHOPHYSIOLOGY
      • Rapid activation of the complement system
      • Blood level of soluble TNF receptor, interferon-gamma,& IL-2 are
      • C1q,C3,C4,C5-8 & C3 proactivators are
      • These factors interact at the endothelial cell to produce vascular permeability through the nitric oxide final pathway
      • The blood clotting & fibrinolytic system are & levels of factor XII are
      • Capillary damage allows fluid, electrolytes & small proteins ,red cells to leak into extravascular spaces
      • This internal redistribution of fluid together with deficits caused by fasting, thirst,vomiting results in hemoconcentration,hypovolaemia, increase cardiac work, tissue hypoxia, metabolic acidosis & hyponatremia
    • CLINICAL MANIFESTATIONS
    • Four dengue clinical syndrome
      • Undifferentiated fever
      • Classic dengue fever
      • Dengue hemorrhagic fever(DHF)
      • Dengue Shock Syndrome (DSS)- a severe form of DHF
    • Undifferentiated fever
      • Most common presentation
      • Silent transmission
      • Incubation period of 3-14 days(average 4-7 days)
      • Sudden onset of fever, biphasic
      • Severe headache(retro-orbital)
      • Myalgias & arthalgias that may be severe
      • Nausea & vomiting
      • Rash may be present at the different stages of illness- maculpapular, petechial, erythematous
      • Hemorrhagic manifestations
    • DENGUE HEMORRHAGIC FEVER
    • Dengue Hemorrhagic Fever
      • Usually develops around 3 rd -7 th day of illness
      • There is rapid onset of plasma leakage, altered hemostasis, and damage to the liver, resulting in severe fluid losses and bleeding
      • Skin hemorrhage- petechiae, purpura, ecchymosis
      • Gingival & nasal bleeding,Hematuria
      • GI bleeding- haetamesis,melena,haematochezia
      • Plasma leakage is due to increased capillary permeability ;manifest as hemoconcentration, pleural effusion & ascites.
      • Bleeding due to capillary fragility & thrombocytopenia
      • Liver damage manifests as increases in levels liver enzymes, low albumin levels, and deranged coagulation parameters(PT,PTT)
    • 3 phases of DHF
      • Febrile phase : 2-7 days
        • Sudden onset fever
        • Severe headache
        • Epigastric discomfort,anorexia, vomiting
        • Arthralgia, myalgia
        • Flushing
        • Tender hepatomegaly, splenomegaly
        • Maculopapular rash
    • Leakage phase
        • 1 ST 24-48 HOURS
        • Pleural effusion
        • Ascities
        • Pericardial effusion
        • Haemorrhagic menifestation
        • Haematemesis,malena ,epistaxis & menorrhagia
    • Convalescent phase
        • Short & uneventful
        • Short & uneventful
        • Return of appetite
        • Bradycardia
        • Recovery rash
        • Severe itching on palms & soles
        • of appetite
        • Bradycardia
        • Recovery z
    • Criteria to label Dengue Hemorrhagic Fever
    • WHO case definition of DHF
      • Fever-sudden onset 2-7 days
      • Hemorrhagic manifestations with positive tourniquet test
      • Low platelet count(1,00,000/mm 3 or less)
      • Objective evidence of plasma leak syndrome
        • Hematocrit ≥ 20% above baseline
        • Low albumin
        • Pleural/pericardial effusions
    • Four grades of DHF
      • Grade I - Fever & non-specific constitutional symptoms
      • Positive tourniquet test is only hemorrhagic manifestations
      • Grade II- Grade I manifestations + spontaneous bleeding
      • Grade III -signs of circulatory failure
      • Grade IV- profound shock (undetectable pulse & BP)
    • Danger signs in Dengue Hemorrhagic Fever
      • Abdominal pain-intense & sustained
      • Persistent vomiting
      • Abrupt change from fever to hypothermia, with sweating
      • Change in mental status of the patient
    • Unusual presentation of Severe Dengue Fever
      • Encephalopathy
      • Liver failure or fulminant hepatitis
      • Demonstrated by Increase aminotransferas, increase bilirubin, incresae PT,APTT
      • Cardiomyopathy-conduction defects, myocarditis
      • Severe GI hemorrhage
    • Risk Factors
      • Age: all groups are affected
      • Pre-existing anti –dengue antibody,either caused by previous infection or to maternal antibodies passed to infants
      • Higher risk in secondary infections
      • Higher risk inlocations with two or more seroypes circulating simultaneously at high levels
    • TOURNIQUET TEST
      • Inflate BP cuff to a point midway between SBP & DBP for 5 minute
      • After deflating the cuff, wait for the skin to return to its normal colour ,then count the number of petechiae visible in one inch-square area on the ventral surface of the forearm
      • Positive test: 20 0r more petechiae per one inch 2
    • Positive Tourniquet Test
      • A typical positive result from a tourniquet test may look like. This patient
      • has more than 20 petechiae per square inches.
    • Dengue Shock Syndrome
    • Four criteria
      • Evidence of circulatory failure, manifested indirectly by all of the following
        • Rapid & weak pulse
        • Narrow pulse pressure (≤ 20 mm Hg or hypotension for age)
        • Cold, clammy skin & altered mental status
        • Frank shock
    • Laboratory tests in Dengue Fever
      • Complete blood count:
        • WBC-leucopenia,lymphocytosis
        • Platelets-thrombocytopenia
        • Hematocrit:≥20% of the baseline
      • Liver function tests:
        • serum aminotransferases:deranged
        • Serum bilirubin:increased
        • serum albumin:low
      • Coagulation studies –PT,APTT:prolongrd
      • Serum electrolytes:deranged
      • Blood gases:metabolic acidosis
      • Tourniquet test:positive
      • Complement levels:low
      • Blood urea:raised
      • Chest X-ray- for effusions
      • ECG- sinus bradycardia, prolonged PR interval
      • Serological diagnosis
        • ELISA
        • Anti dengue IgM & IgG Ab
        • Sensitivity 84-98%
        • Specificity 100%
        • Haemagglutination inhibition test
        • Complement fixation test
      • Virus isolation
      • Molecular detection - PCR
    • Treatment
      • Mainly Supportive
      • No hemorrhagic manifestations & well hydrated: patient sent home with instructions for “follow up”
      • If hemorrhagic manifestations/hydration status borderline-patient observed in hospitals
      • If warning signs are present even without evidence of shock or if DSS present-hospitalized
      • Intravenous fluids with Electrolyte balance
      • Antipyretics-acetaminophen(aspirin and NSAIDS should be avoided as they interfere with platelet function)
      • H2 blockers,antiemetics(Domperidone)
      • Platelet and FFP transfusion when needed
      • Monitoring of BP, urine output, platelet count and hematocrit
      • Soft,balanced nutritious diet
    • Mosquito barrier
      • Needed until fever subsides(to prevent Aedes aegypti mosquito from biting patients & acquiring virus)
      • Patients should be kept ideally in screened room or under mosquito net
    • Treatment of DHF & DSS
      • A medical emergency
      • Admit in ICU
      • Keep the patient in supine position
      • Immediate evaluation of vital signs & degrees of hemoconcentration, dehydration & electrolyte imbalance
      • Rapid I/v replacement with wide bore cannula –N/S ideal fluid of choice
      • Monitor CBC, LFTs, S/E, PT/APTT
      • When pulse pressure is ≤ 10 mmHg or when elevation of Hct persists after replacement of fluids; plasma or colloids are indicated
      • FFP & platelets for bleeding
      • No role of corticosteroids
      • Look for evidence of complications
      • Avoid hypervolaemia
    • Complications
      • Fluid & electrolyte losses
      • Myocarditis
      • Hepatic dysfunction
      • Febrile convulsions
      • Residual brain damage
      • Encephalopathy
      • Disseminated Intravascular coagulation
      • Dengue shock syndrome
    • Indications for hospital discharge
      • Absence of fever for 24 hours(without anti-fever therapy) & return of appetite
      • Visible improvement in clnical picture
      • Stable haematocrit
      • 3 das after recovery from shock
      • platelets ≥ 50,000/mm 3
      • No respiratory distress from pleural effusion/ascites
    • Return IMMEDIATELY to clinic or emergency department if
      • any of the following warning signs appear :
      •  Severe abdominal pain or persistent vomiting
      •  Red spots or patches on the skin
      •  Bleeding from nose or gums , Vomiting blood
      •  Black, tarry stools
      •  Drowsiness or irritability
      •  Pale, cold, or clammy skin
      •  Difficulty breathing
    • Dengue Vaccine
      • No licensed vaccine at present
      • Effective vaccine must be tetravalent
      • Field testing of an attenuated tetravalent vaccine currently underway
    • PREVENTION
    • Vector control
      • Chemical control-
        • Larvicides may be used to kill the immature aquatic stages
        • Ultra-low volume fumigation is effective against adult mosquitoes
        • Mosquitoes may have resistance to commercial aerosols spray
      • Biological control
      • - largely experimental
      • -Placing fish in containers to eat the larvae
      • Environmental control
        • Elimination of larval habitats
        • Most likely method to be effective in the long term
    • Prophylaxis
      • Avoiding mosquito bites
        • Use of insecticides
        • Repellents
        • Body covering with clothing
        • Screening of house
        • Destruction of the vector breeding sites
        • Using mosquito nets
      • If storage is mandatory, a tight fitting lid or a thin layer of oil may prevent egg laying or hatching
      • A larvicide (Abate) available as a 1% sand –granule formations may be added safely to drinking water
    • Why to control??/Purpose of control
      • Reduce female vector density to a level below which epidemic vector transmission will not occur
      • The minimum vector density to prevent epidemic transmission is unknown
    • Program to minimize the impact of epidemic
      • Teaching the medical community how to diagnose and mange DHF
      • Educating the general public to encourage & enable them to carry out vector control in their home and neighborhood
    • Common containers in which eggs develop into adult dengue mosquitoes:
    • Recent advances
      • Gene-modified mosquitos could stop dengue fever : genetically modified mosquitoes wee released last year at sites in Malaysia and the Cayman Islands.
    • Key Message
      • Dengue infection is preventable disease
      • No direct person to person transmission
      • Prevent Man – Mosquito contact to prevent the disease