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Arboviruses . Dr. M Mohammed Arif . Associate professor. Consultant virologist. Head of the virology unit . Arboviruses. Arboviruses = Arthropod born viruses . These viruses require the presence of vertebrate host and arthropod vector usually mosquitoes , ticks or sand flies .

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arboviruses

Arboviruses .

Dr. M Mohammed Arif .

Associate professor.

Consultant virologist.

Head of the virology unit .

arboviruses1
Arboviruses
  • Arboviruses = Arthropod born viruses .
  • These viruses require the presence of vertebrate host and arthropod vector usually mosquitoes , ticks or sand flies .
  • In the natural environment the virus is maintained in a cycle that involves the vertebrate host and the vector .
arboviruses2
Arboviruses
  • These viruses multiply inside the vertebrate host as well as the vector .
  • The vector transmits the disease to human and other mammals , through the bite .
  • Man generally plays no role in the natural history of arboviruses .
  • Humans are not the natural reservoir for the virus .
arboviruses3
Arboviruses
  • There are hundreds of arboviruses, many of which are not pathogens to human .
  • Human pathogens arboviruses are grouped into three viral families :
  • 1- Togaviridae .
  • 2- Bunyaviridae .
  • 3- Flaviviridae .
  • Arboviruses are enveloped, with ss-RNA genome .
transmission
Transmission
  • Humans are infected through the bite of infected vector , or when they come into contact with infected host .
  • Vector : Mosquitoes, ticks or sand flies .
  • Vertebrate host : Mammals and birds.
diseases associated with arboviruses
Diseases associated with arboviruses
  • 1- Hemorrhagic fever .
  • 2- Encephalitis .
  • 3- Fever with rash and arthralgia .
arboviruses associated with hemorrhagic fever
Arboviruses associated with hemorrhagic fever .

1- Dengue virus .

Family: Flaviviridae .

2- Yellow fever virus .

family : Flaviviridae .

3- Rift valley fever virus .

Family : Bunyaviridae .

4- Crimean congo hemorrhagic fever virus .

Family : Bunyaviridae .

family flaviviridae
Family: Flaviviridae .
  • Enveloped , icosahedral particle .
  • About 40 -60 nm in diameter .
  • The viral genome is ss-RNA , with positive polarity .
  • Flavi = Yellow .
family bunyaviridae
Family : Bunyaviridae .
  • Enveloped with helical symmetry
  • About 90 – 100 nm in diameter .
  • The viral genome consists of three segments of ss- RNA (large , medium and small ) , with negative polarity .
arboviruses associated with hemorrhagic fever1
Arboviruses associated with hemorrhagic fever
  • 1- Dengue fever ( break bone fever ) :
  • Geographical distribution : Asia, Middle east , Africa & South America .
  • Vector: Mosquitoes .
  • Vertebrate host : human .
  • Diseases :

1-Most cases are mild or asymptomatic .

2- Dengue hemorrhagic shock syndrome .

arboviruses with hemorrhagic fever
Arboviruses with hemorrhagic fever
  • 2- yellow fever :
  • Geographical distribution : Africa and South America .
  • Vector : Mosquitoes .
  • Vertebrate host : Human , monkeys.
  • Symptoms: Most cases are mild or asymptomatic .
  • The severe form of the disease is characterized by fever, myalgia, arthralgia, nausea, vomiting, jaundice, mucosal bleeding, bleeding under the skin, vomiting blood, seizures and coma .
yellow fever cycle
Yellow fever cycle .

1- Jungle yellow fever :

Involves transmission between mosquitoes and non-human primate, with human as accidental host.

2- Urban yellow fever :

Involves transmission between mosquitoes and human

arboviruses associated wit hemorrhagic fever
Arboviruses associated wit hemorrhagic fever
  • 3- Rift valley fever :
  • Geographical distribution : Africa and Asia .
  • Vector : Mosquitoes .
  • Vertebrate host :Sheep, goats and cattle , camels and human .
  • Diseases 1-Most cases are mild or asymptomatic .
  • 2- Hemorrhagic form : are characterized by fever, headache, myalgia, arthralgia, nausea, mucosal bleeding and bleeding under the skin .
rift valley fever
Rift valley fever .
  • 3- Meningoencephalitis : fever, severe headache, stiffness of neck, back pain, hallucination. Mental confusion, lack of coordination, convulsions and coma .
  • Transmission :By direct contact with infected animal blood or tissue .
  • Through the bite of mosquitoes.
  • Human to human transmission has not been documented..
arboviruses associated with hemorrhagic fever2
Arboviruses associated with hemorrhagic fever
  • 4- Crimean Congo H F :
  • Geog. Dist. : Africa, Asia and middle east .
  • Vector : Ticks .
  • Vertebrate host : Sheep, goats , cattle and human .

Symptoms : Most cases are mild or asymptomatic .

  • In severe cases, the symptoms are : fever, headache, myalgia, artheralgia, nausea, vomiting, mucosal bleeding and bleeding under the skin .
transmission of crimean congo hf
Transmission of Crimean Congo HF.
  • Through the bite of infected ticks .
  • By direct contact with infected animal blood.
  • Human to human transmission occurs through direct contact with infected blood or body fluids.
2 arboviruses associated with encephalitis
2- Arboviruses associated with encephalitis .
  • 1- West Nile Encephalitis (WNE ) .
  • Family : Flaviviridae .
  • 2- Eastern Equine Encephalitis ( EEE ) .
  • Family : Togaviridae .
  • 3-Westwrn Equine Encephalitis (WEE ). .
  • Family : Togaviridae .
  • 4-Venezuelan Equine Encephalitis (VEE ). .
  • Family : Togaviridae .
family togaviridae
Family : Togaviridae .
  • Enveloped , icosahedral particle .
  • About 75- nm in diameter .
  • The viral genome is ss-RNA , with positive polarity .
arboviruses associated with encephalitis
Arboviruses associated with encephalitis .
  • 1- West Nile Encephalitis .
  • Family: Flaviviridae.
  • Geog. Dist. : Africa, Asia. Middle East, North America .
  • Vector : Mosquitoes .
  • Vertebrate host : Birds, horses, dogs, cats and human .
  • Diseases :Most cases are mild or asymptomatic .

2- Encephalitis .

transmission1
Transmission:
  • Through the bite of infected mosquitoes.
  • Human to human transmission has not been documented .
  • Can be transmitted through blood transfusion and organ transplantation .
arboviruses associated with encephalitis1
Arboviruses associated with Encephalitis
  • 2- Eastern equine encephalitis :
  • Family : Togaviridae .
  • Geog. Dist ; America .
  • Vector : mosquitoes .
  • Vertebrate host : Birds, horses and human .
  • Diseases :

1- Most cases are mild or asymptomatic .

2- Encephalitis .

eastern equine encephalitis1
Eastern equine encephalitis .
  • Transmission : Through the bite of infected mosquitoes .
arboviruses associated with encephalitis2
Arboviruses associated with encephalitis .
  • 3- Western equine encephalitis :
  • Family: Togaviridae.
  • Geog dist : America .
  • Vector : Mosquitoes .
  • Vertebrate host : Birds, horses and human .
  • Diseases :

1-Most cases are mild or asymptomatic .

2- Encephalitis .

western equine encephalitis1
Western equine encephalitis .
  • Transmission : Through the bite of infected mosquitoes .
arboviruses associated with encephalitis3
arboviruses associated with encephalitis .
  • 4- Venezuelan equine encephalitis :
  • Family : Togaviridae .
  • Geog, dist : America .
  • Vector : Mosquitoes .
  • Vertebrate host : Rodents, horses and human .
  • Diseases :

1-Most cases are mild or asymptomatic .

2- Encephalitis .

venezuelan equine encephalitis
Venezuelan equine encephalitis .
  • Transmission : Through the bite of infected mosquitoes .
lab diagnosis of arboviruses
Lab. Diagnosis of arboviruses.
  • Restricted to reference laboratories , with facilities for high level containment .
  • The most commonly lab. Methods are :

1- Detection of the viral RNA in the patient specimen, using PCR .

2- Isolation of the virus in tissue culture, followed by identification of the isolated virus .

3- Detection of IgM antibody .

vaccine
Vaccine .
  • The only vaccine available is for yellow fever .
  • It is a live attenuated vaccine .
  • The vaccine is known as 17 – D strain .
  • The vaccine is administered in one dose , with a booster dose every 10 years .
  • The vaccine is recommended to travelers to endemic areas.
  • Should not be given to children less than 9-months.
prevention measures
Prevention measures ,
  • Elimination of vector breading sites .
  • Elimination of vectors using suitable insecticides.
  • Avoidance contact with mosquitoes and ticks .