ARBOVIRUS DISEASE----DENGUE,KFD,JE,YELLOW FEVER

Shilpa.KMicrobiolgy TutorAIMSRC

DengueDengue viruses transmitted to humans by the

bite of an infected mosquito, most commonly Aedes aegypti.

Classic dengue fever Sudden onset of high fever, severe myalgias,

headache, retroorbital pain, nausea and vomiting, rash

In rare cases, a subsequent infection with a different serotype of dengue virus leads to:

Dengue hemorrhagic fever (DHF) Dengue shock syndrome (DSS) Dengue fever used to be called "break-bone

fever" because it can entail excruciating joint and muscle pain.

Dengue

Dengue infection may range from asymptomatic to severe hemorrhagic fever to fatal shock (dengue shock syndrome).

Dengue fever is usually a nonspecific, self-limited biphasic febrile illness.

More than half of infected children are asymptomatic.

The illness is more severe and begins more suddenly in adults

Risk FactorsRisk factors for dengue feverResidence in or travel to an endemic area Risk factors for DHF/DSS include: Presence of enhancing and nonneutralizing

antibodies from prior dengue virus infection Age < 12 years ,Female sex Good nutritional status (malnutrition is protective) Sequence of infection For example, serotype 1 followed by serotype 2

seems to be more dangerous than serotype 4 followed by serotype 2.

Infecting serotype Dengue 2 is the most dangerous serotype.

Symptoms & SignsUndifferentiated fever: May be the most common

manifestation of dengue. Uncomplicated (classic) dengue Incubation period of 2–7 days Fever, often with sudden onset,

typically lasting 5–7 days Severe headache with retroorbital pain Back pain Severe ("break-bone") myalgias

Symptoms & Signs…….DHF High fever (up to 40–41°C) Hemorrhagic manifestations (e.g., spontaneous

GI bleeding without preexisting lesions) Increased vascular permeability Ascites, pleural effusions,

hemoconcentration Usually occurs 3–7 days after onset of

illness Hepatomegaly Restlessness, lethargy In moderate DHF cases, all signs and

symptoms subside after fever subsides.

Symptoms & Signs…….Hemorrhagic manifestations (may occur in dengue fever or DHF/DSS)Epistaxis Scattered petechiae, positive

tourniquet test Gastrointestinal (GI) bleeding

In dengue fever: from preexisting GI lesions In DHF/DSS: without preexisting lesions

Symptoms & Signs…….DSS Features of DHF Sudden collapse or prostration Cool, clammy extremities Hypotension with rapid, weak pulse

and narrowing of pulse pressure Circumoral cyanosis Lasts 1–2 days, usually responding

promptly to supportive therapy

Laboratory Tests……..Nonspecific laboratory findingsLeukopenia Thrombocytopenia Hemoconcentration (may be noted

on serial hematocrit measurements)

AST, ALTModest to marked elevation of

aminotransferase levels

Specific diagnosisDengue virus detection Culture (from blood) Performed using mosquito cell cultures or mosquito

inoculation Most useful in the first 5 days after onset of illness

(during febrile period)

Serology: most commonly used diagnostic method IgM ELISA (blood drawn 6–21 days after onset of

symptoms) Paired serology (acute- and convalescent-phase

samples collected at least 10–14 days apart) showing 4-fold rise in IgG titer

DHF Hemoconcentration

Low serum protein and albumin levels

Elevated serum aminotransferase levels Prolonged partial thromboplastin time

Hematuria

Specific TreatmentBed rest Avoidance of invasive procedures when

possible Fluids and electrolyte replacement For patients with shock Rapid infusion of initial bolus of 5% dextrose in

normal saline or Ringer’s lactate (10–20 mL/kg)

Antipyretics :Acetaminophen Avoidance of aspirin and NSAIDs because of

their anticoagulant properties Blood product support (red cells, platelets) for

active bleeding with severe thrombocytopenia

Kyasanur Forest Disease(KFD)Kyasanur Forest Disease (KFD,monkey

fever) is an infectious bleeding disease in monkey and human caused by a highly pathogenic virus called KFD virus (KFDV).

KFDV is of zoonotic origin , is transmitted primarily by infective tick, Haemaphysalis spinigera.

Rodents, shrews, monkeys and birds upon tick bite become reservoir for this virus.

Kyasanur Forest Disease(KFD)…..H. spinigera tick is widely distributed in

tropical forests of peninsular India and Sri Lanka.

Deforestation, subsequent cattle grazing in those areas and the low susceptibility of cattle for KFDV lead to conclude cattle being large mammal reservoir for vector maintenance and propagation.

However, KFD is not directly transmitted by human-human contact.

Kyasanur Forest Disease(KFD)….. symptoms at onset in human are

sudden chills, high fever, frontal headache, heightened sensitivity to light,

followed by continuous fever for 12 days or longer often associated with diarrhea, vomiting, cough,

severe pain in the neck, low back and extremities, accompanied by severe prostration.

Kyasanur Forest Disease(KFD)…Papulo-vesicular eruption on the

soft palate (blisters on the upper, inner mouth) is an important diagnostic sign in some patients.

Bleeding signs such as in the gum, nose , hemoptysis, gastrointestinal bleeding resulting in dark feces (melena), fresh blood in the stools are common

Kyasanur Forest Disease(KFD)…The convalescent phase constituting

the recovery is generally prolonged, maybe up to 4 weeks.

Relapse of the symptoms, often observed after 1 to 2 weeks of the first febrile period, last for 2 to12 days.

The relapse phase displays same symptoms as the first phase and in addition symptoms such as mental disturbance, giddiness.

Prevention and treatment

by vaccination, as well as preventive measures like protective clothing, tick control, and mosquito control are advised.

An attenuated live vaccineis now available.

Specific treatments are not available.

Japanese Encephalitisis a disease caused by the mosquito

borne Japanese encephalitis virus from the familyFlaviviridae.

Domestic pigs and wild birds are reservoirs of the virus; transmission to humans may cause severe symptoms.

the most important vectors of this disease are the mosquitoes Culex tritaeniorhynchus and Culex vishnui.

This disease is most prevalent in Southeast Asia and the Far East.

Signs and symptomsincubation period of 5 to 15 days and the

majority of infections are asymptomatic. Fever, headache and malaise are other non-

specific which may last for a period of between 1 and 6 days.

during the acute encephalitic stage --include neck rigidity, cachexia, hemiparesis, convulsions and a temperature between 38 and 41 degrees Celsius and coma are seen.

Mortality of this disease varies but is generally much higher in children.

Lifelong neurological defects such as deafness, emotional lability and hemiparesis may occur in those who have had central nervous system involvement.

Diagnosis…….Japanese Encephalitis is

diagnosed by detection of antibodies in serum and CSF (cerebrospinal fluid) by IgM capture ELISA.

Viral antigen can also be shown in tissues by indirect fluorescent antibody staining.

Treatment is symptomatic.

Treatment…….Supportive and symptomatic.

Yellow Fever……Yellow fever is a zoonotic flavivirus infection transmitted by Aedes and jungle mosquitoes.

It occurs in an urban and jungle cycle in Africa and in a jungle cycle in South America

Epidemics have extended far into the temperate zone during warm seasons.

Yellow Fever……The mosquito transmits the infection

by first biting an individual having the disease and then biting a susceptible individual after the virus has multiplied within the mosquito's body.

The incubation period in humans is 3–6 days.

Adults and children are equally susceptible, though attack rates are highest among adult males.

Between 5% and 50% of infections are asymptomatic

Symptoms and Signs

In Mild form of the disease………. malaise, headache, fever, retroorbital pain, nausea, vomiting, photophobia. Relative bradycardia, conjunctival

injection, and facial flushing may be present.

Severe form……… develops in about 15%. Initial symptoms are similar to the

mild form, but a brief fever remission lasting hours to a few days

it is followed by a "period of intoxication" manifested by fever and relative bradycardia (Faget sign),

hypotension, jaundice, hemorrhage (gastrointestinal, nasal,

oral), and delirium that may progress to coma

Diagnosis…….A direct confirmation can be obtained by

RT-PCR where the genome of the virus is amplified.

Another direct approach is the isolation of the virus and its growth in cell culture using blood plasma; this can take one to four weeks.

Serologically during the acute phase of the disease IgM Elisa against yellow fever) can confirm yellow fever.

Together with clinical symptoms, the detection of IgM or a fourfold increase in IgG-titer is considered sufficient indication for yellow fever.

Treatment……No specific antiviral therapy is available.

symptomatic relief and management of complications.

If not in an endemic area, the patient should be isolated from mosquitoes to prevent transmission, since blood in the acute phase is potentially infectious.

Prognosis……..The mortality rate of the severe form is 20–50%,

with death occurring most commonly between the sixth and the tenth days.

In survivors, the temperature returns to normal by the seventh or eighth day.

The prognosis in any individual case is guarded at the onset.

Intractable hiccups, copious black vomitus, melena, anuria, jaundice, and elevated AST are bad signs.

Convalescence is prolonged, including 1–2 weeks of asthenia.

Infection confers lifelong immunity to those who recover.

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