Parasitology and Virology Quiz: DNA Viruses

DNA Viruses

• DNA viruses can be classified into two categories: enveloped and non-enveloped viruses.
• Enveloped viruses include Herpes simplex virus (HSV), Varicella-Zoster virus (VZV), Epstein-Barr virus (EBV), Cytomegalovirus (CMV), Molluscum Contagiosum Virus (MCV), and Poxviruses.
• Non-enveloped viruses include Adenovirus.

Herpes Simplex Virus (HSV)

• HSV-1 and HSV-2 share many characteristics, including DNA homology, antigenic determinants, tropism, and symptoms.
• Recurrences occur despite high titers of circulating antibodies.
• Cell-mediated immunity plays a crucial role in protection.
• Diagnosis involves the Tzanck test, demonstrating multi-nucleated giant cells with internuclear inclusion bodies in scrapings from the lesion.
• Treatment includes acyclovir ointments for herpatic keratitis and intravenous acyclovir for encephalitis.
• Cortisone is contraindicated as it may lower the immune response.

Varicella-Zoster Virus (VZV)

• VZV causes varicella (chickenpox) and zoster (shingles).
• VZV is a highly communicable respiratory infection that usually occurs in epidemics during winter.
• The disease is mild in children and severe in neonates and adults.
• Infection usually develops long-life immunity.
• Symptoms include initial replication of the virus in the respiratory tract, followed by viremia, fever, and a skin vesicular rash.
• The rash starts on the trunk and spreads to the limbs and face, but rarely leaves scars.
• Zoster is a recurrent endogenous infection that occurs in cell-mediated immunosuppressed adults.
• Zoster starts with severe pain due to inflammation of sensory nerves and ganglia, followed by vesicles appearing in the enervated area.

Laboratory Diagnosis and Treatment

• Laboratory diagnosis involves the Tzanck test and tissue culture.
• Treatment for chickenpox includes calamine lotion or crystal violet, while treatment for shingles includes acyclovir.

Comparison between Chickenpox and Shingles

• Chickenpox is a primary infection, while shingles is a recurrent infection.
• Chickenpox is more common in childhood, while shingles is more common in adulthood.
• Protection against chickenpox is humoral, while protection against shingles is cellular.
• Vesicles in chickenpox are painless and scattered, while vesicles in shingles are very painful and appear in crops.

Epstein-Barr Virus (EBV)

• EBV is associated with African endemic Burkitt's lymphoma and infectious mononucleosis.
• African endemic Burkitt's lymphoma is a poorly differentiated B-cell lymphoma that is endemic to the children of malarial regions of Africa.
• The virus is enveloped with an inner membrane enclosing the core, which is linear dsDNA.
• The disease shows a very characteristic skin vesicular rash.

Smallpox (Variola)

• Smallpox is transmitted through inhalation of the variola virus, which invades the mucus membranes of the mouth, throat, and respiratory tract.
• The virus migrates to regional lymph nodes, begins to multiply, and eventually causes widespread lysis of infected cells.
• There are two variants of the disease: Variola major (25% mortality) and Variola minor (1% mortality).
• Smallpox is already eradicated since 1980, and eradication was successful due to the virus being an exclusive human pathogen, having a single serotype that protects against all infections, and other factors.