viral hemorrhagic fever:

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Viral Hemorrhagic fever: The viral hemorrhagic fevers (VHFs) are a diverse group of animal and human illnesses that are caused by four different families of RNA viruses: 1- Arenaviridae. 2- Filoviridae. 3- Bunyaviridae. 4- Flaviviridae. All types of VHF are characterized by fever and bleeding disorders and all can progress to high fever, shock and death in many cases.

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Viral Hemorrhagic fever: . The viral hemorrhagic fevers ( VHFs ) are a diverse group of animal and human illnesses that are caused by four different families of RNA viruses: 1- Arenaviridae . 2- Filoviridae . 3- Bunyaviridae . 4- Flaviviridae . - PowerPoint PPT Presentation

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Page 1: Viral Hemorrhagic fever:

Viral Hemorrhagic fever:

The viral hemorrhagic fevers (VHFs) are a diverse group of

animal and human illnesses that are caused by four different

families of RNA viruses: 1- Arenaviridae.2- Filoviridae.3- Bunyaviridae. 4- Flaviviridae.

All types of VHF are characterized by fever and bleeding disorders

and all can progress to high fever, shock and death in many cases.

Page 2: Viral Hemorrhagic fever:

Arenaviridae :Lassa virus , Junin virus, and Machupo virus (MACV) are associated with hemorrhagic fever.

Epidemiology:Lassa virus: West Africa.Junin virus: Argentina.Machupo virus: Bolivia.

Virology:-These are round, pleomorphic, and enveloped with a diameter of 120 nm. - Nucleocapsid with two single-stranded RNA circular segments.

Page 3: Viral Hemorrhagic fever:

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Viral reservoir:

Some Arenaviruses are zoonotic pathogens and are generally

associated with rodents transmitted disease.

Transmission:

Humans could be infected through mucosal exposure to aerosols, or

by direct contact of broken skin with the infectious material, derived

from infected rodents.

Ingestion of contaminated food, person-to-person contact is

incriminated with transmission of the virus in some cases.

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Pathogenesis and clinical picture: Incubation period: 10-14 days.

The viruses infect macrophages, carried to blood vessels ;

endothelial cells infection, T-cell mediated response,

vascular damage.

- Visceral hemorrhage.

- Liver and spleen necrosis.

- hemorrhage shock and cardiac damage. - Death in 50% of cases.

Page 5: Viral Hemorrhagic fever:

Filoviridae: Marburg virus and Ebola virus : Epidemiology : Endemic in Africa.1-Marburg virus (Zimbabwe and Kenya).2-Ebola virus (Sudan and Zaire).Reservoir: African green Monkeys and Wild Monkeys.

Transmission: - Monkeys-Human contact, human-human contact, and unknown routes of transmission.-The first infection was first detected among Laboratory workers in Marburg, who had been exposed to tissue culture of cell line prepared from Monkeys.

Page 6: Viral Hemorrhagic fever:

Virology:- Filoviruses have a Single stranded RNA, which encodes seven proteins- Enveloped filamentous virus with Helical nucleocapsid measuring 800 to as long as 14000 nm.

Page 7: Viral Hemorrhagic fever:

Pathogenesis and clinical picture:-Eosinophilic cytoplasmic inclusions are seen in cells infected with the virus.

-These virus infection disseminated with blood stream to parenchymal cells of liver, spleen, lymph nodes, and lung.

-Widespread hemorrhage causes edema and hypovolemic shock.-Liver function tests: SGPT, and alkaline phosphatase elevated. - Spleen destruction and lymph node enlargements.

Page 8: Viral Hemorrhagic fever:

Bunyaviridae:-Super-group of at least 200 different viruses. -Most are Arboviruses.

Virology: - Enveloped, spherical virion with a diameter of 90-100 nm.- Single-stranded RNA nucleocapsids virus.

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Transmission: Vector-born infection1-Phlebovirus: Sandfly , genus : Phlebotomus.2-Nairovirus: Ticks. 3-Bunyavirus: Mosquito. Vertebrate host:1-Phlebovirus: Sheep, cattle, others2-Nairovirus: cattle, goats3-Bunyavirus: Rodents, small mammals, and birds.

Disease:1-Rift Valley fever ; hemorrhagic fever, encephalitis.2-Crimean-Congo -Hemorrhagic fever.3-California encephalitis.

Page 10: Viral Hemorrhagic fever:

Pathogenesis and clinical picture: -Primary viremia; flu-like symptoms, infection of vascular endothelium and Macrophage of Reticuloendothelial system ; secondary viremia.

1-Vascular endothelial damage; leakage of plasma and erythrocytes, hemorrhagic fever.

2- Cerebral edema and encephalitis.

3- Kidney hemorrhagic necrosis.

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Crimean-Congo -Hemorrhagic fever caused by Nairovirus: N

Page 12: Viral Hemorrhagic fever:

Flaviviridae:Flaviviruses are Arboviruses transmitted to man by vector (flavus (Latin term) means yellow).

Two types of Flaviviridae cause Hemorrhagic fever (H.F), and Yellow fever:1-Dengue virus: DHF: dengue H.F, and DSS: dengue shock syndrome. 2-Yellow fever virus: Yellow fever and Hepatitis. Vector: Mosquito of the genus Aedes.Host: Human and Monkeys.(Zoonosis).Distribution:Dengue fever: Worldwide, especially tropics.Yellow fever: Africa, and South America.

Page 13: Viral Hemorrhagic fever:

Virology:- Positive Single-stranded RNA viruses. - Enveloped, Icosahedral nucleocapsid.- Size: 40-65 nm.- Glycoprotein spikes (adhesion of virus to tissue).

-All Flaviviruses are serologically related: So Anti-Virus serotype antibodies could be used as prophylactic vaccine for others.

Page 14: Viral Hemorrhagic fever:

Pathogenesis and clinical picture:

- Biting of the host skin by vector ( Female Mosquito). , inoculation of small capillaries bloodstream by virus in Saliva.-The virus will be carried by dendritic cells throughout small capillaries to the target tissue.

-Target tissue: 1-The endothelial cells of Capillaries. 2-The blood Macrophage and monocytes.

-Blood phagocytes will transfer the microbe to the Reticuloendothelial system(RES).

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- This will initiate Primary Viremia (fever, chill, headaches, and flu-like symptoms within 3-7 days).

- Secondary Viremia is associated with efficient replication of virus in RES.

-This viremia can produce sufficient virus to infect: 1-Liver: Hepatitis, and Jaundice; yellow fever. 2-Brain: Encephalitis.

3-Vasculature and skin: Hemorrhage and shock.

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Pathogenesis of Flaviviruses:N