Poxvirus: History, Classification, Morphology, Pathogenesis, Laboratory Di

Poxvirus: History, Classification, Morphology, Pathogenesis, Laboratory Diagnosis, Treatment and Keynotes

History of Poxvirus

Poxvirus (Pox = pus-filled blister = Pocks)

Dr. John Buist (1887): demonstrated microscopically

Paschen (1906): developed a staining technique and demonstrated elementary bodies (Paschen bodies)from a lesion of smallpox.

Smallpox was an infectious disease and it was caused by one of two virus variants, Variola major and Variola minor.

Classification of Poxvirus

(unranked): Virus

Realm: Varidnaviria

Kingdom: Bamfordvirae

Phylum: Nucleocytoviricota

Class: Pokkesviricetes

Order: Chitovirales

Family: Poxviridae

Genus: orthopoxvirus and it contains smallpox virus (variola), vaccinia virus, cowpox virus, and monkeypox virus.

Properties of Poxvirus

Large and complex virus
Replicate in the cytoplasm of host cells from elementary bodies (Paschen bodies).

Morphology of Poxvirus

Double-stranded DNA Virus and brick-shaped
Size: 302 to 350 nm×244 to 270 nm
Have an irregular arrangement of tubules on the outer membrane on the outer membrane and does not show any symmetry hence called ‘Complex’.
During replication produces cytoplasmic inclusion bodies (Paschen bodies)

Pathogenesis of Poxvirus

Virus→inhalation or transmission
by scabs ( occasionally)→Multiplication in the upper respiratory tract→
lymphatics ( macrophage)→Lymph nodes ( spleen, bone marrow, additional organs lymph nodes)→blood ( primary viremia)→hemorrhage of small vessels of the dermis, leading to rash and pox→secondary viremia

Incubation period: around 12 days

Symptoms of smallpox

High fever
Head and body aches
Sometimes vomiting
Early rash
Pustular rash and scabs
Scabs fall of
No scabs

Laboratory Diagnosis of Smallpox

Specimen: Pustular fluid or scabs

Microscopy: Observation of brick-shaped virions by electron microscope

Histological Diagnosis: Skin biopsies stained with hematoxylin and eosin shows cytoplasmic inclusion bodies i.e. Paschen bodies.

Cultivation of poxvirus

Chorio Allantoic Membrane (CAM) of chick embryo
Tissue culture: Monkey kidney cell line, HeLa cell, Chick embryo cell time

Molecular test: PCR

Serological test: ELISA

Treatment of Smallpox

In the vast majority of people, vaccination against smallpox within three days of exposure can avoid or substantially decrease the incidence of symptoms of smallpox. Vaccination may provide some defense against disease four to seven days after vaccination or can alter the seriousness of the disease. Treatment of smallpox is mostly supportive, rather than vaccination, such as wound management and infection prevention, fluid therapy, and possible ventilator assistance. Drugs, cidofovir, and tecovirimat are used as therapeutic agents.

Keynotes on Poxvirus

On May 8, 1980; WHO officially declared global eradication of Small Pox.
Chickenpox, a similarly called disease, is not a true poxvirus and is primarily caused by the varicella-zoster herpesvirus.
In 1986, all virus samples were destroyed or transferred to two approved WHO reference laboratories: at the headquarters of the federal Centers for Disease Control and Prevention (the CDC) in Atlanta, Georgia (the USA) and at the Institute of Virus Preparations in Moscow.
The first smallpox vaccine was developed in 1796 by Edward Jenner.
Other historical names for smallpox include great pox, pox, speckled monster, and the red plague.

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