Dermatology MCQ - Viral Infections - Vesicular stomatitis virus infection

A 45-year-old horse breeder presents with fever, malaise, and painful vesicles on the lips, oral mucosa, and hands. He reports that several of his horses have similar lesions on their muzzles and hooves. Which of the following is the most likely causative agent and its primary mode of transmission?

A) Vesicular stomatitis virus; direct contact with infected animals or insect vectors
B) Herpes simplex virus type 1; direct contact with infected saliva
C) Coxsackievirus A16; fecal-oral route
D) Foot-and-mouth disease virus; aerosol transmission
E) Orf virus; direct contact with infected sheep or goats

Correct Answer: A) Vesicular stomatitis virus; direct contact with infected animals or insect vectors

Explanation

This presentation is classic for vesicular stomatitis virus (VSV) infection, a zoonotic disease that affects horses, cattle, and occasionally humans.

Key Clinical Features of Vesicular Stomatitis in Humans:

• Influenza-like illness: Fever, malaise, myalgia, headache.

• Vesicular lesions: Painful vesicles on the lips, oral mucosa, and hands (similar to herpes simplex or hand, foot, and mouth disease).

• Occupational exposure: Common in farmers, veterinarians, and animal handlers.

• Animal involvement: Concurrent illness in livestock (horses, cattle) with vesicles on muzzles, tongues, and hooves.

Virologic and Transmission Features:

• Causative Agent: Vesicular stomatitis virus (a rhabdovirus, genus Vesiculovirus).

• Transmission:

  • Direct contact with infected animals (saliva, vesicle fluid).

  • Insect vectors (e.g., sandflies, blackflies) are biological vectors.

  • Aerosol transmission is possible but less common.

• Geographic Distribution: Americas (e.g., United States, Mexico, Central and South America).

Why Not the Other Options?

• (B) Herpes simplex virus type 1: Causes herpetic gingivostomatitis but is not associated with livestock illness.

• (C) Coxsackievirus A16: Causes hand, foot, and mouth disease in humans, but not in animals.

• (D) Foot-and-mouth disease virus: Causes severe vesicular disease in cloven-hoofed animals (e.g., cattle, pigs) but very rarely infects humans (and not horses). Transmission is via aerosol or contact.

• (E) Orf virus: Causes contagious ecthyma in sheep/goats, with nodular lesions in humans, not vesicles.

Management:

• Supportive care: Analgesics, wound care to prevent secondary infection.

• Infection control: Avoid contact with infected animals; use PPE.

• Reportable disease: Must be reported to animal health authorities (mimics foot-and-mouth disease).

Prognosis:
Self-limiting in humans; resolves within 7-10 days. Animals may require supportive care.

Note: VSV is important because it is clinically indistinguishable from foot-and-mouth disease in animals, which is a high-consequence foreign animal disease. Always report suspected cases to regulatory authorities.