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Arboviruses and other zoonotic viruses Arbovirus: Arthropod-borne Viruses maintained in nature principally, or to an important extent, through biological.

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Presentation on theme: "Arboviruses and other zoonotic viruses Arbovirus: Arthropod-borne Viruses maintained in nature principally, or to an important extent, through biological."— 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 FAMILYENVELOPE yes no SYMMETRY icosahedral helical icosahedral GENOME ssRNA (+ve) ssRNA (-ve) segmented dsRNA, segmented

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 - man –e.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.

4 Man-Arthropod-Man Cycle

5 Animal-Arthropod-Man Cycle


7 Arthropod Vectors Mosquitoes Japanese encephalitis, dengue, yellow fever, St. Louis encephalitis, EEE, WEE, VEE etc. Ticks Crimean-Congo haemorrhagic fever, various tick-borne encephalitides etc. Sandflies Sicilian sandfly fever, Rift valley fever.



10 Examples of Arthropod Vectors Aedes Aegyti Assorted Ticks Phlebotmine Sandfly Culex Mosquito

11 ARTHROPOD  Habitat  Diurnal activity  Preferred host  Annual activity  Overwintering ability  Transovarial transmission VERTEBRATE  Migratory activity  Persistence of viremia  Clinical consequences  Reservoir ?  Dead end host?

12 Prevention  Surveillance - of disease and vector populations  Control of vector - pesticides, elimination of breeding grounds  Personal protection - screening of houses, bed nets, insect repellants  Vaccination - available for a number of arboviral infections e.g. Yellow fever, Japanese encephalitis, Russian tick-borne encephalitis



15 ARBOVIRAL DISEASE  INITIAL VIRAL REPLICATION –All are cytolytic –endothelial cells –macrophages/monocyte lineage  INTERFERON (RNA VIRUSES) –headache, fever, myalgia (flulike)  VIREMIA –spread to target tissues, depending on tropism of virus  Role of innate immunity in disease progression  Non-neutralizing Ab  may enhance flavivirus infection via Fc receptors on macrophages


17 Flaviviruses  Spherical, nm  Positive sense, 11 kb ssRNA  3 structural proteins  Replication 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 mosquito  Some 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 Fever  After 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 serology  There is no specific antiviral treatment  An effective live attenuated vaccine is available against yellow fever and is used for persons living in or traveling to endemic areas.

22 Yellow Fever  50% of patients with frank YF  fatal disease with severe haemorrhagic manifestations, oliguria and hypotension   Diagnosis is usually made by serology, molecular detection  There is no specific antiviral treatment  Live 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 signs –Optic neuritis –Seizures –Weakness –Change in mental status –Myelitis –Polyradiculitis –A 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.



29 Dengue Fever  Vector: Aedes ; epidemic (> 100 countries)  Incubation period: 3-14 days (usually 4-7d)  4 serotypes called DENV-1, -2, -3, and -4  Three clinical presentation –Undifferentiated Fever; –Dengue Fever with or without hemorrhage; or –Dengue Hemorrhagic Fever or Dengue Shock Syndrome.








37 Bunyavirideae Bunyavirideae BunyavirusHantavirus Nairovirus Phlebovirus Tospovirus Ortho Bunyavirus HantavirusNairovirus Tospovirus Phlebovirus 7 serogroups; CCHF Grubu: -CCHFv* -Dugbe* -Nairobi koyun hastalığı virusu* -Hazara (Patojen değil)

38  Segmented ss RNA virus  L, S and M segments

39 Tick vectors –Hyalomma truncatum –Hyalomma marginatum –Hyalomma impeltatum –Hyalomma impressum –Amblyomma variegatum –Boophilus decolaratus




43 CCHF: transmission  Tick bite  Crushing of ticks  Contact with viremic animal’s carcasses  Nosocomial –Patient contact –Tissue & body fluids contact –Laboratory

44 Incubation: - Following tick bite 1-3 d; max. 9 days, - Following exposure to infected blood, tissue or body fluids 5-6 days: max. 13 days

45 Clinical course  Human –Flu like signs –Haemorrhagies + DIC… –Death (10-80%)  Animals –No disease –Temparate fever… –Viremia max. 10 days

46 Fatigue 86 (94) Fever 84 (91) Myalgia 83 (90) Head ache 74 (80) Sore throat 18 (20) Gastrointestinal Naussea 69 (75) Vomiting 63 (68) Diarrhea 36 (39) n (%) Symptoms

47 PLTs Incubation 3-7 days Prehemorrhagic period 1-7 days Hemorrhagic period 2-3 days Convelescence Bleeding from various sites (hematemesis, melena, etc.) somnolence AST ALT WBCs Fatality happens Polymerase Chain Reaction: The first 9 days Myalgia, Fever, Nausea-vomiting Diarrhea 7 d10 d days DIC IgM (7 days-4 months) and IgG (7 days-5 years) viremia Ergonul O. Lancet ID 2006; 6:



50 :150 cases; 4.5% fatality 2004: 249 cases; 5.2% fatality 2005: 266 cases; 5% fatality 2006: 224 cases..... The largest epidemic in the World


52 Hantavirus  Distinct 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 failure  Genralised hemorrhagia and shock  CFR is 5-15 %  Hantaan and Dobrova viruses in Asia and in Balkans  In Euroasia a mild form  nephropathia epidemica  caused by Puumala virus (Scandinavia)





58 HAntavirus Pulmonary Syndrome (HPS)  First described in 1993 in North America  Sin Nombre virus  Mortality 30 %

59 Sandfly Fever  Phlebovirus  Vector  Phlebotomus papatasii Naples virusNaples virus, Sicilian virus, Cyprus and Toscana virusSicilian virusToscana virus


61 Arenaviruses  Segmented RNA; two ss RNA molecules  Old and new world arenaviruses  Establish chronic infections among rodents  Lassa fever: Africa, most common seqelae is deafness


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