Parasitology and Virology: HSV-1 and HSV-2 Infections

Herpes Simplex Virus (HSV)

• HSV-1 infections are prevalent in the upper part of the body (head, throat, and chest) and are transmitted mainly by contact (kissing, sharing glass).
• HSV-2 infections are prevalent in the lower part of the body (genitals) and are transmitted by sexual contact.
• Both viruses initially infect and replicate in mucoepithelial cells and then establish latent infection in the enervating neurons (Trigeminal ganglia for HSV-1 and Sacral ganglia for HSV-2).

HSV-1 Symptoms

• Primary infection appears as painful ulcers but usually appears as gingivostomatitis.
• Recurrent infection occurs at the lips borders as herpes labialis (cold sores).
• Infection of fingers (whitlow), or eye infection (keratoconjunctivitis) which may lead to blindness, herpatic eczema, and encephalitis might occur.

HSV-2 Symptoms

• Primary infection appears as painful ulcers on the external genitals of both male and female, associated with fever and lymphadenopathy.
• Recurrent infection usually occurs at the same primary site and is induced by fever, local trauma, sun light, emotional stress, or menstruation.

Herpes Family

• Herpes simplex virus (HSV)
• Varicella-Zoster virus (VZV)
• Epstein-Barr virus (EBV)
• Cytomegalovirus (CMV)

Molluscum Contagiosum Virus (MCV)

• Causes small, pink, papular, benign tumors of the skin or mucous membranes.
• Transmitted by close personal contact, including sexually.
• Lesions are self-limited.
• Diagnosis - clinically (shape and location).
• Treatment - removal of the lesions by curettage or with liquid nitrogen.

Smallpox (Variola)

• The virus is large, brick-shaped, enveloped, with a linear dsDNA genome.
• Replicates in the cytoplasm, forming Guarnieri's inclusion bodies.
• The disease shows a very characteristic skin vesicular rash.
• Two variants of the disease exist: Variola major (25% mortality) and Variola minor (1% mortality).
• The disease is already eradicated since 1980.

Smallpox Vaccination

• Calf lymph vaccine: prepared by inoculation of vaccinia virus on shaved skin of calves and collection of vesicle fluid in 40% glycerol and 0.5% phenol.
• Lyophilized vaccine: prepared from vaccinia virus in embryonated eggs.
• Both vaccines are applied intradermally by scratching.

Comparison between Smallpox and Chickenpox

• Smallpox: Pox family, complex shape, replication in cytoplasm, Gaurnieri's inclusion bodies, fever 2-4 days before rash, slow development of rash, rash on palms and soles, severe course, high mortality, calf lymph vaccine and lyophilized vaccine.
• Chickenpox: Herpes family, icosahedral shape, replication in nucleus, no inclusion bodies, fever at onset of rash, rapid development of rash, no rash on palms and soles, mild course, uncommon mortality, live attenuated vaccine.