Dermatology MCQ - Viral Infections - Mayaro virus infection

A 32-year-old ecologist presents with abrupt onset of high fever, severe polyarthralgia, and a maculopapular rash after returning from a research trip in the Amazon rainforest. She reports intense joint pain in her wrists, ankles, and fingers, and notable lethargy. Physical examination confirms joint swelling and a generalized rash. Laboratory studies show leukopenia and elevated transaminases. Which of the following is the most likely causative agent and its primary vector?

A) Mayaro virus; Haemagogus mosquito
B) Dengue virus; Aedes aegypti mosquito
C) Oropouche virus; Culicoides midge
D) Yellow fever virus; Haemagogus mosquito
E) Chikungunya virus; Aedes aegypti mosquito

Correct Answer: A) Mayaro virus; Haemagogus mosquito

Explanation

This presentation is classic for Mayaro virus (MAYV) infection, an emerging arboviral disease in South America that closely resembles chikungunya.

Key Clinical Features of Mayaro Virus Infection:

• Acute Phase:

  • Abrupt high fever (often >39°C).

  • Severe polyarthralgia: Intense, debilitating joint pain, typically affecting wrists, ankles, fingers, and knees. Joint swelling and tenderness are common.

  • Maculopapular rash: Generalized, often pruritic, lasting 3-5 days.

  • Constitutional symptoms: Profound lethargy, myalgia, headache.

• Chronic Phase:

  • Persistent arthralgia may last for months (similar to chikungunya).

• Laboratory Findings: Leukopenia, thrombocytopenia, and elevated transaminases (AST/ALT).

Virologic and Transmission Features:

• Causative Agent: Mayaro virus (an alphavirus in the Togaviridae family).

• Vector: Primarily transmitted by canopy-dwelling Haemagogus mosquitoes (same genus that transmits yellow fever in sylvatic cycles).

• Reservoir: Primates (e.g., monkeys) and possibly birds serve as amplifying hosts.

• Geographic Distribution: Tropical forests of South America (e.g., Amazon Basin, Brazil, Peru, Bolivia).

Why Not the Other Options?

• (B) Dengue virus: Causes fever, rash, and arthralgia but arthralgia is typically less severe and not chronic. Transmitted by Aedes aegypti.

• (C) Oropouche virus: Causes Oropouche fever (fever, headache, myalgia) but locks significant polyarthralgia. Transmitted by Culicoides midges.

• (D) Yellow fever virus: Causes hemorrhagic fever with jaundice and high mortality, not polyarthralgia or prominent rash. Transmitted by Haemagogus mosquitoes in sylvatic cycles.

• (E) Chikungunya virus: Causes nearly identical symptoms (fever, polyarthralgia, rash) but is transmitted by Aedes aegypti and Ae. albopictus. The travel history to the Amazon rainforest and vector (Haemagogus) point to Mayaro virus.

Management:

• Supportive care: NSAIDs for pain and inflammation (avoid aspirin due to bleeding risk).

• No specific antiviral treatment or vaccine is available.

• Prevention: Mosquito avoidance (repellents, protective clothing) in endemic areas.

Prognosis:
Self-limiting acute illness, but chronic arthralgia can persist for months, impacting quality of life.

Note: Mayaro virus is often misdiagnosed as dengue or chikungunya due to overlapping symptoms. The key clues are exposure in the Amazon basin and the potential for chronic arthritis. Always consider MAYV in travelers with chikungunya-like symptoms returning from South American rainforests.