RNA viruses - Enveloped, +ssRNA viruses - Arboviruses

Question 1

Transmission of +RNA Arboviruses

Answer 1

1- Mosquitoes and ticks transmit arboviruses among animal hosts: small rodents and birds
2- Zoonoses:
+ animal diseases that spread to humans
3- Arthropod vectors remain infected and present viremia
+ are a continual source of new infections through saliva
4- Humans are dead-end hosts for these viruses, since viremia is not persistent. Blood transfusion and organ transplant can be cause of transmission among humans.
5- Endocytosis of viruses. Abs increase endocytosis via FcRs
6- Most infections result in mild, flulike symptoms (interferons)

Question 2

What are the second stage infections of Arboviruses?

Answer 2

Arboviruses can occasionally result in second-stage infections:
Brain, skin, liver, blood vessels, monocytes, macrophages, DC
+ froms of ENCEPHALITIS, DUNGUE FEVER and YELLOW FEVER

Question 3

Talk about Encephalitis

Answer 3

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Question 4

What is the cause of ENCEPHALITIS?

Answer 4

1- Different Togaviruses (genus Alhavirus) causes Encephalitis in Horses and Humans
- Eastern Equine Encephalitis (EEE)
- Western Equine Encephalitis
- Venezuelan Equine Encephalitis (VEE)
Normal host is either sa bird (the 3 forms) or a rodent (VEE)
* EEE causes most severe disease in humans
2- West Nile Virus
- Flavivirus endemic in Africa
Severe cases may cause encephalitis and death

Question 5

Host and transmission of viruses of equine encephalitis and West Nile encephalitis

Answer 5

1- Mosquitoes are vectors of WEE, EEE, VEE and west nile viruses
2- Wild birds are the primary reservoir
3- Mammanls are normally dead end hosts
4- Horses are rarely other domestic mammals are hosts for equine viruses

Question 6

What is the virus in italy called

Answer 6

Chikungunya virus (Flaviviridae, Alphavirus)

Question 7

What arethe diseases of Flaviviridae?

Answer 7

1) Dengue Fever
2) Yellow Fever
3) Chikungunya

Question 8

Talk about Dengue fever

Answer 8

1- Flavivirus transmitted by Aedes mosquitoes
2- Endemic in Asia, South America and Mexico: 100 million people
3- Disease occurs in 2phases
+ Initially causes fever, weakness, edema, and severe pain in head, back, muscles (break bone fever) for one week.
+ Second phase causes brigthrash and return of the fever for7 days. Self limiting
4- Dengue hemorrhagic fever can occur following reinfection
+ causes internal bleeding, shock, and possibly death
5- No treatment is available

Question 9

Talk about Yellow fever

Answer 9

1- Caused by a Flavivirus
2- Disease involving degeneration of the liver, kidneys. and heart, massive hemorrhaging
+ Black vomit: hemorrhaging in the intestine
+ Jaundice
3- Mortality can approach 20%
4- Eradicated in several countries through vaccination and mosquito control
5- Still remains a significant cause of death worldwide, 200 000 infected, 30 000 death

Question 10

Diagnosis of Arboviruses

Answer 10

1- Serological Tests used fro diagnosis of arbovirus infections: ELISA, agglutination

Question 11

Treatment of Arboviruses

Answer 11

Supportive care is the ONLY treatment

Question 12

Prevention of Arboviruses

Answer 12

Involves the control of the vectors, insect repellents, netting

Vaccines exists for some arboviruses

• recommended for travelling to endemic areas
• Yellow fever, Japanese encephalitis, Russian spring-summer encephalityis. Dengue us under development.