Examville.com Quick Review Of Arboviruses

Arboviruses Arthropod borne viruses Previously classified as - Arbovirus group A, Arbo V. group B but now they are kept under 3 families l. Togaviridae 2. Flaviviridae 3. Bunyaviridae These families contain both; Arboviruses and non-arboviruses Family l. Toga Viridae

2. Flavi Viridae

3. Bunya Viridae

Arbo Virses I. Alpha Viruses (Group A Arbovirus) -Encephalitis viruses -Chikungunya virus -Sindbis fever virus I. Flavi Virus or group B Arbovirus -

Japanese encephalitis virus Yellow fever Dengue KFD West nile

Non Arbo Viruses I. Rubivirus - Rubella virus

l. Pesti Viruses 2. Heoatitis C virus 3. Heoatitis G virus

I. Bunya Viruses - La crosse - Oropouchhe 2. Phlebo virus - Rift valley fever - Sand fly fever

I. Hanta virus

3. Nairo virus - Crimean congo haemorrhagic fever They are ++ SsRNA, Enveloped, Icosahedral Nucleocapsid Toga Viridae: This family contains 1. Alpha Viruses 2. Rubi Viruses Alpha Viruses VIRUS Eastern equine (EEE) Western equine encephalitis (WEE) Venezulean equine encephalitis (VEE) Chickungunya

VERTEBRATE RESERVOIR

VECTOR MOSQUITOES

DISEASE

GEOGRAPHIC DISTRIBUTION North Central and South America, Caribbean

Wild birds

Culiseta, Coquilettidea, Culex

Encephalitis

Wild birds

Culex

-do-

North and South America

Horses

Aedes, Culex

-do-

South and Central America

Monkeys humans Aedes

Fever, arthralgia, Africa, India, myalgia, rash outheast Asia

O'nyong-nyong

Humans

Anopheles

-do-

Africa South and Central America

Mayaro

Monkeys

Haemogogus

-do-

Ross river Sindbis

Marsupials, rodents

Culex Aedes

-do-

Australia, Fiji

Sindbis

Wild birds

Culex, Culista, aedes

-do-

Africa, Europe, India, Malaysia

Alpha viruses were previously known as group A arbo Viruses. Pathogenesis: Viruses enters human skin by mosquito bite & Multiplies in vascular endothelium, blood monocytes, and Macrophages in lymph node, Bone marrow, spleen & liver Viremia, Spreads to brain, causes encephalitis. Clinical features Fever, arthritis, rash, hepatitis, nephritis, encephalitis Rash is produced due to vasculitis Haemorrhages produced due to thrombocytopenia Lab diagnosis: 1. Mice inoculation 2. Cell culture - Vero, BHK, C6/36 derived from mosquito Aedes albopictus 3. ELISA - IgM Ab Rubi virus - Non Arthropod borne Rubella • Infection by aerosol inhalation, Person to Person spread • Neonatal infection during 1st trimester of pregnancy • Earlier the infection occurs to fetus more severe is the damage • If infection occur after 4 months of pregnancy then little damage, only residual sensorineural deafness. • Congenital rubella syndrome is a triad of sensorineural deafness, Cataract – Blindness, and cardiac anomalies. Also seen are - Microcephaly, Micro-ophthalmia retinopathy & Glaucoma Vaccine - RA 27/3 liye attenuated vaccine in human fibroblast cell line. Woman should not be immunized during first trimester. And in non pregnant, when vaccinated, should be advised to avoid conception for the next 2 -3 months. However accidental immunisation during pregnancy is riot an indication for termination of pregnancy. Flavi Viridae In contains - 4 genera Flavivirus - Previously Known group B arbovirus Pestivirus - Animal virus contain Hepatitis C virus Hepatitis G virus Flavi Viruses SYSNDROME 1. Encephalitis

VECTOR VIRUS Mosquito Japanese encephalitis Murray Valley encephalitis St. louis encephalitis

GEOGRAPHICAL DISTRIBUTION Asia Australia, New Guinea Americas

Tick

2 Yellow fever 3 Dengue 4 Haemorrhagic fever

Rocio encephalitis Louping - ill Powassan Tick-borne encephalitis

Mosquito Yellow fever Mosquito Dengue 1,2,3,4 Mosquito Dengue 1,2,3,4

Brazil British Isles Canada, United States, Russia Russia, Eastern Europe, Scandinavia Tropical Attica and tropical Central and South America Entire tropical zone India, Philippines

Tick 5 Miscellaneous tropical fever

Kyasanur Forest disease Southwest India Omsk haemorrhagic fever Siberia Mosquito Ileus Caribbean, South America

Japanese encephalitis 1st case seen in Japan Seen in Korea, Japan, SE Asia, India Vector is Culex tritaeniorhyncus which breeds in rice fields Amplifier hosts - Pigs & herons (Water birds) Mosquito transmits virus from amplifier hosts to man Clinical Features: Fever and Encephalitis Vaccine - live Attenuated Inactivated Yellow fever Yellow as it causes jaundice Disease of tropical America and Africa Not reported from Asia Two forms in forest/sylate cycle – Runs between monkeys and mosquitoes Urban cycle – Man and Aedes aegypticus mosquito Clinical Features - Virus multiplies in kupfer cells, jaundice & decreased prothrombin formation, Hematemesis & malena, Renal failure & death Vaccine - Line Attenuated vaccine Known as -17 D vaccine. Protection for 10 years. Deneue 4 serotypes 1 -4 Infection with one serotype gives partial immunity to infection with other serotypes Vector – Aedes mossquito Reservoir - Man & Monkey C/F - Classic dengue: Saddle back fever, Break bone fever Complete recovery Effects older children & adults Dengue Haemorrhagic fever: When a person previously infected by one serotype is now infected by a different serotype, then enhanced infection causes haemorrhages Dengue shock svndrome- DHF/DSS in 2 age groups: 6-9months & 5 - 10 years Vaccine Under trial

West Nile fever Reservoir host - Birds Vector - Culex mosquito C/F - Denque like illness rarely encephalitis Kavasanur Forest Disease (KFD) Epidemic in karnataka in 1957 Epizootic in Monkeys - fatal disease Forest birds and small mammals are reservoirs Tick - Haemaphysalis spinigera is vector Monkeys are the amplifier hosts Accidental infection in humans Fever with massive haemorrhages in GIT & chest & nose Vaccine available is killed vaccine Lab diagnosis of Flavi viruses I. Mice inoculation 2. Cell culture 3. IgM ELISA Bunyaviridae Bunya virus, Phlebo virus and Nairo virus are Arboviruses Hanta virus is non arbovirus Enveloped viruses containing three helical nucleocapsid each containing one segment of SS RNA Sandflv fever - Phlebovirus Vector - Sandfly Reservoir - Man C/ F - Dengue like fever Hanta Virus Rodents are reservoir Inhalation of aerosolized rodent urine causes human infection Haemorrhagic fever & nephropathy.

Filo Viridae Filo = Filaments 800 - 1.000 nm in length Enveloped Helical nucleocapsid SSRNA of 19 Kb Primarily infect .primates like monkeys Human infection by aerosols or handling blood, body fluids organs or tissue culture. C/F: virus multiplies in liver Fever and multiple haemorrhages, Shock, Death. 4 types 1. Marburg 2. Ebola - S - Sudan 3. Ebola - Z - Zaire 4. Ebola reston Maximum mortality in Ebola - Z

Lab diagnosis -

Electron microscopy Culture on verocells (Monkey cells) Bio safety level 4 pathogens} Serology

Arena Viridae Arena = Sand Due to incorporation of host cell ribosomes in virions - sand like appearance enveloped containing 2 Nucleocapsids having 2 SSRNA Natural host are rodents Virus shedding in urine Through abraded skin / aerosols Human infection Examples: Lymphocytic choriomeningitis Lassa fever Junin Machupo Guanarito