Presentation on theme: "Arboviruses and other zoonotic viruses"— Presentation transcript:
1 Arboviruses and other zoonotic viruses Arbovirus: Arthropod-borne Viruses maintained in nature principally, or to an important extent, through biological transmission beten susceptible vertebrate hosts by haematophagus arthropods or through transovarian and possibly venereal transmission in arthropods
2 ARBOVIRUSES FAMILY ENVELOPE yes no SYMMETRY icosahedral helical GENOME ssRNA (+ve)ssRNA (-ve)segmenteddsRNA,
3 Transmission Cycles Man - arthropod -man e.g. dengue, urban yellow fever.Reservoir may be in either man or arthropod vector.In the latter transovarial transmission may take place.Animal - arthropod vector - mane.g. Japanese encephalitis, EEE, WEE, jungle yellow fever.The reservoir is in an animal.The virus is maintained in nature in a transmission cycle involving the arthropod vector and animal. Man becomes infected incidentally.Both cycles may be seen with some arboviruses such as yellow fever.
7 Arthropod Vectors Mosquitoes Ticks Sandflies Japanese encephalitis, dengue, yellow fever, St. Louis encephalitis, EEE, WEE, VEE etc.TicksCrimean-Congo haemorrhagic fever, various tick-borne encephalitides etc.SandfliesSicilian sandfly fever, Rift valley fever.
10 Examples of Arthropod Vectors Aedes AegytiAssorted TicksPhlebotmine SandflyCulex Mosquito
11 Overwintering ability Transovarial transmission VERTEBRATE ARTHROPODHabitatDiurnal activityPreferred hostAnnual activityOverwintering abilityTransovarial transmissionVERTEBRATEMigratory activityPersistence of viremiaClinical consequencesReservoir ?Dead end host?At least 150 species mosquito in US alone.~3500 species worldwide
12 Prevention Surveillance - of disease and vector populations Control of vector - pesticides, elimination of breeding groundsPersonal protection - screening of houses, bed nets, insect repellantsVaccination - available for a number of arboviral infections e.g. Yellow fever, Japanese encephalitis, Russian tick-borne encephalitis
15 ARBOVIRAL DISEASE INITIAL VIRAL REPLICATION INTERFERON (RNA VIRUSES) All are cytolyticendothelial cellsmacrophages/monocyte lineageINTERFERON (RNA VIRUSES)headache, fever, myalgia (flulike)VIREMIAspread to target tissues, depending on tropism of virusRole of innate immunity in disease progressionNon-neutralizing Ab may enhance flavivirus infection via Fc receptors on macrophages
16 RECOVERY INTERFERON CELL-MEDIATED IMMUNITY ANTIBODY MAY PLAY A ROLE IN PREVENTING SPREAD DURING VIREMIC PHASE
17 Flaviviruses Spherical, 40-60 nm Positive sense, 11 kb ssRNA 3 structural proteinsReplication and essembly in cell cytoplasm
19 Yellow Fever West Africa and South America Jungle YF is the natural reservoir of the disease in a cycle involving nonhuman primates and forest mosquitoes. Man may become incidentally infected on venturing into jungle areas.The urban form is transmitted between humans by the Aedes aegypti mosquitoSome patients may experience an asymptomatic infection or a mild undifferentiated febrile illness.
20 Mild illness: Fever, headache, pink eye Severe illness (%15 of the infected): Fever, chills, naussea, vomiting (vomitus negra), severe mylagia, lower back pain,yellow colorination of the sklerae (due to hepatic involvement), hemoorhagia, anuria, death
21 Yellow FeverAfter a period of 3 to 4 days, the more severely ill patients with a classical YF course will develop bradycardia (Faget's sign), jaundice, and haemorrhagic manifestations.50% of patients with frank YF will develop fatal disease characterized by severe haemorrhagic manifestations, oliguria and hypotension.Diagnosis is usually made by serologyThere is no specific antiviral treatmentAn effective live attenuated vaccine is available against yellow fever and is used for persons living in or traveling to endemic areas.
22 Yellow Fever50% of patients with frank YF fatal disease with severe haemorrhagic manifestations, oliguria and hypotensionDiagnosis is usually made by serology, molecular detectionThere is no specific antiviral treatmentLive attenuated vaccine persons living in or traveling to endemic areas.
24 West Nile virus Japanese encephalitis virus antigenic complex (Japanese encephalitis, St. Louis encephalitis, Murray Valley encephalitis, and Kunjin)
25 80% asymptomatic In 20 % Fever Headache Fatigue Skin rash on the trunk of the body (occasionally)Swollen lymph glands (occasionally)Eye pain (occasionally)
26 In 1/150 cases Fever Gastrointestinal symptoms Ataxia and extrapyramidal signsOptic neuritisSeizuresWeaknessChange in mental statusMyelitisPolyradiculitisA minority of patients with severe disease develop a maculopapular or morbilliform rash involving the neck, trunk, arms, or legs.Flaccid paralysis is sometimes seen.Although not observed in recent outbreaks, myocarditis, pancreatitis, and fulminant hepatitis have been described.
47 Prehemorrhagic period PLTsIncubation3-7 daysPrehemorrhagic period1-7 daysHemorrhagic period2-3 daysConvelescenceBleeding from various sites(hematemesis, melena, etc.)somnolenceASTALTWBCsFatality happensPolymerase Chain Reaction: The first 9 daysMyalgia,Fever,Nausea-vomitingDiarrhea7 d10 ddaysDICIgM (7 days-4 months) and IgG (7 days-5 years)viremiaErgonul O. Lancet ID 2006; 6:
52 HantavirusDistinct hantaviruses are associated with specific rodent hosts.Cause hemorrhagic fever with renal syndrome (HFRS) or hantavirus pulmonary sundrome (HPS)Transmission via: Inhalation of aeresols of rodent excreta
53 hemorrhagic fever with renal syndrome (HFRS) Interstitiel nephritis acute renal failureGenralised hemorrhagia and shockCFR is 5-15 %Hantaan and Dobrova viruses in Asia and in BalkansIn Euroasia a mild form nephropathia epidemica caused by Puumala virus (Scandinavia)