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Pathology of Ebola Virus Disease 

Dr Sampurna Roy MD

 

                                                                                                                      

 

 

Visit: Ebola: The deadly virus strikes again!

Ebola virus causes acute hemorrhagic fever leading to up to 90% lethality.

The Ebolaviruses known to have five subtypes:  Ebola virus (Formerly known as Zaire virus), Sudan virus, Reston virus (non human), Tai Forest virus and Bundibugyo virus.

Of the five identified ebolavirus subtypes, four are capable of human-to-human transmission.  

Recent study implicates "Fruit bats" as reservoir hosts for ebolaviruses.

Increasingly frequent outbreaks and the placement of Ebola virus in the category A list of potential biothreat agents  have boosted interest in this virus. 

The disease closely resembles Marburg Virus Disease.

Ebola Virus Disease has a high mortality.

Development of new technologies (Example: reverse genetics systems) and extensive studies on Ebola haemorrhagic fever in animal models have substantially expanded the knowledge on the pathogenic mechanisms that underlie this disease.

Two major factors in Ebola virus pathogenesis are the  impairment of the immune response and vascular dysfunction.

The deadly disease which has killed hundreds across West Africa (Guinea, Liberia and Sierra Leone) has now been reported in Lagos - Nigeria. (July 2014)

39 new cases and 21 deaths have been reported in Guinea between May and June 2014. In Sierra Leone 13 new cases have been reported during this same period. In Liberia 11 cases have been suspected and are being followed up.

 

History of past outbreaks:

Ebola virus infection was first recognized during a human outbreak in 1976 with almost simultaneous outbreaks in both the Sudan and Zaire (now the Democratic Republic of the Congo). It was named after a river in the Democratic Republic of the Congo.

After an outbreak in 1979 in the Sudan, Ebola appeared relatively quiescent until it appeared among macaque monkeys imported from the Philippines and housed at a primate facility in Reston, Virginia.

In late 1994, a single case in a researcher who performed a necropsy on an ill chimpanzee led to the identification of a new subtype, Ebola-Ivory Coast.

In Gabon, Africa, outbreaks of Ebola virus infection occurred from 1994 to 1997.

Another appearance was in 2000-2001 with an Ebola outbreak in Uganda that resulted in 425 cases with 224 deaths by January 2001. In this outbreak, events and conditions associated with acquired disease were : funeral attendance for those who died with Ebola hemorrhagic fever, intrafamilial contact, and nosocomial infections. Schools were closed and a ban against funerals was enacted. In November, 2001, an Ebola outbreak again occurred in Gabon. and in the Democratic Republic of the Congo, and multiple outbreaks occurred in 2000-2004 in Gabon, the Congo, Sudan, and Uganda.

Outbreaks continued in the Congo in 2005. At the same time, it was noted that Ebola outbreaks occurred in large mammals, mainly chimpanzees, duikers (a type of antelope), and gorillas, and that human outbreaks tended to follow those observed in animals. Airborne transmission of the Ebola Zaire strain to monkeys by aerosol have been demonstrated.

 

Pathology :

Liver: The is necrosis of the hepatocytes, fatty change and presence of large intracytoplasmic eosinophilic inclusion bodies.

Adrenal glands: There is necrosis of adrenal cortical cells

Lymphnodes: Lymphnodes are enlarged. Necrosis of lymphoid follicles and medulla. There is infection of macrophages and dendritic cells causing depletion of host immune response.

Spleen : Necrosis of the red pulp.

 

The ebolaviruses appear to spread rapidly by close and prolonged contact with an infected person or by inoculation from contaminated syringes and needles.

Infected patients should be strictly isolated to prevent spread of ebolavirus infection.

Related post: Marburg Virus Disease ;  Filovirus

Further update on Ebola virus infection:

As long there is one case of Ebola virus disease anywhere in the world and people are allowed to travel, every country in the world remains at risk -  Nigeria's health minister, Onyebuchi Chukwu. September 8th 2014

The Nigeria's health minister was absolutely right when he said those wise words.

Thomas Eric Duncan was tested positive for the deadly Ebola virus in USA. According to official report he travelled from Liberia to USA with no symptoms of infection.

In USA he started showing symptoms of Ebola and was admitted to Texas Health Presbyterian Hospital. He died after 2 weeks.

Dallas hospital nurse Nina Pham who took care of Thomas Eric Duncan was tested positive for Ebola. According to report her neck was exposed while taking care of the patient. She was shifted from Texas Health Presbyterian Hospital to National Institutes of Health's state-of-the-art facility in Bethesda, Maryland. She is stable and doing well.

The second nurse Amber Vinson was infected with Ebola at the Texas Health Presbyterian Hospital in Dallas while treating Thomas Eric Duncan, was shifted to Emory University Hospital in Atlanta for further treatment in a specialized isolation unit.  

New cases of Ebola in West Africa could reach 10,000 per week by December.

October 17th 2014

 

Further reading:

Fruit bats as reservoirs of Ebola virus

Pathology of Ebola Virus infection by FA Murphy

Ebola virus vaccines: an overview of current approaches.

Phylogenetic Analysis of Guinea 2014 EBOV Ebolavirus

The 2014 Ebola virus disease outbreak in west Africa.

 

 

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)

 

 


 

 

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