Arboviruses arthropod borne viruses transmitted by arthropods (mosquitoes,

ticks, sandflies, or other biting arthropods )

Arboviruses are a group of infectious agents that are transmitted by bloodsucking or wild animals from one vertebrate(spinal column) host to another.

Life cycle of Arbovirus

Classification worldwide distributed 530 species 150 species are pathogenic to humanInclude 3 families BunyaviridaeBunyaviridae

FlaviviridaeFlaviviridae

TogaviridaeTogaviridae

.Common properties

1.+ssRNA, icosahedral, enveloped, hemagglutinin.2.Sensitive to heat, lipo-solvents, acid.3.Intra-cytoplasmic multiplication, newborn mice

are susceptible.4.Reproduce in arthropods, arthropods are

vector and reservoir host.5.Epidemics with marked geographical and

seasonal distribution..

.Diseases caused by arboviruses

1.Encephalitis: e.g. B encephalitis.2.Systemic infection: e.g. Dengue fever3.Hemorrhagic fever: e.g. Dengue hemorrhagic

fever.4.Hepatitis associated infection: e.g. yellow fever. 5. acute polyarthropathy

Japanese encephalitis virus (JEV)---epidemic type B encephalitis virus

Biological properties:40-50nm , roughly spherical, +ssRNA, icosahedral

capsid, enveloped;1 serotype, antigenicity is stable.

Epidemic:*Culicine mosquito is vector and reservoir host.*Young pig is major infectous source and reservoir host.

Pathogenesis:Virus(mosquito bite) multiply in vascularendothelium and local lymphonodesviremiamultiply in mononuclear phagocyte system blood-brain barrier CNS

Control:*Inactivated vaccine*attenuated live vaccine: not widely use

Hemorrhagic fever viruses

Are a group of viruses that can cause viral hemorrhagic fever (VHF)--------hyperpyrexia, hemorrhage, hypotension

In China, Hantavirus CrimeanCrimean--Congo hemorrhagic fever Congo hemorrhagic fever

virus, CCHFVvirus, CCHFV Dengue virusDengue virus

Hantaviruses1.cause haemorrhagic fever with renal syndrome

(HFRS) or, hantavirus pulmonary syndrome (HPS).

2 . Genome consists of 3 stranded segments; L, M, S.

3. At least 6 serotypes are known4 . The virus is found in the lungs, spleen and

kidneys for long periods in the rodent, perhaps for life. Saliva appears to play an important role in the horizontal transmission of the virus between rodents.

Chronically infected Chronically infected rodentrodent

Virus is present in Virus is present in aerosolized excreta, aerosolized excreta,

particularly urineparticularly urine

Horizontal transmission of Horizontal transmission of infection by infection by intraspecificintraspecific

aggressive behavioraggressive behaviorVirus also present in Virus also present in

throat swab and fecesthroat swab and feces

Secondary aerosols, mucous Secondary aerosols, mucous membrane contact, and skin membrane contact, and skin breaches are also sources of breaches are also sources of

infectioninfection

Transmission of HantavirusesTransmission of Hantaviruses

5. Transmission: transmitted by excretas from rodents---(1)through the respiratory route( via aerosols of virus particles excreted by rodents in their lungs, saliva, urine and faeces). (2) through degestive route.(3) bites by rodents.

6. multisystem pathology: damage to capillaries and small vessel walls,

resulting in vasodilation and congestion with hemorrhages.

Mechanisms: immunopathological mechanisms, viral cellular destruction.

Arboviruses Life cycle of ArbovirusClassification .Common properties.Diseases caused by arbovirusesJapanese encephalitis virus (JEV) ---epidemic type B encephalitis virusHemorrhagic fever viruses Hantaviruses