Viral Hemorrhagic fever:
description
Transcript of 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.
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.
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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.
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.
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.
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.
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.
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.
Crimean-Congo -Hemorrhagic fever caused by Nairovirus: N
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.
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.
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.
Pathogenesis of Flaviviruses:N