Chikungunya

Introduction

• Chikungunya virus (CHIKV): An arthropod-borne alphavirus in the family Togaviridae.
• Transmission: By Aedes mosquitoes, primarily Aedes aegypti and Aedes albopictus.
• Disease: Causes Chikungunya fever, characterized by acute febrile illness, rash, and severe arthralgia.
• Chronic Symptoms: May lead to debilitating arthritis lasting months to years.
• Discovery: Isolated in the Makonde Plateau, Tanzania, in 1952.
• Etymology: “Chikungunya” means “that which bends up” in the Makonde language, referring to the stooped posture of sufferers.
• Notable Outbreak: Reunion Island (2005-2006), affecting 35% of the population.
• Global Spread: Reached the Americas in 2013 via St. Martin in the Caribbean.
• Current Status: Widespread and a global public health concern.

Etiology

• Primary Vectors: Aedes aegypti and Aedes albopictus (Asian Tiger mosquito).
• Vector Characteristics:
  • Invasiveness: Preference for human blood and ability to establish outside native range.
  • Vector Competence: Ability to ingest the virus with a blood meal and infect salivary glands.
  • Vector Capacity: Influenced by mosquito density, feeding frequency, survivability, and extrinsic incubation period.
• Vector Adaptation: Mutation in E1 membrane protein during the 2005-06 Indian Ocean outbreak improved fitness in Ae. albopictus.
• Global Spread: Facilitated by human and vector travel, especially in tropical and subtropical regions.

Epidemiology

• Discovery: First identified in Tanzania in 1952.
• Spread: Reached the Americas in 2013, spreading to Florida by July 2014.
• Endemic Regions: Parts of West Africa; global distribution aided by travel.
• Transmission: Primarily via mosquito bites; also maternal-fetal and blood product transmission during outbreaks.
• Coinfection: Vectors also transmit Dengue and Zika, complicating diagnosis and treatment.

Pathophysiology

• Transmission Cycles:
  • Urban: Human-mosquito-human (main source of Western Hemisphere epidemic).
  • Sylvatic: Animal-mosquito-human (found in Africa).
• Infection Route:
  • Inoculation into epithelial and endothelial cells, fibroblasts, and macrophages.
  • Initial immune response followed by viremia through lymphatic and circulatory systems.
  • Target organs: Muscles, joints, liver, brain.
  • Acute symptoms: Inflammatory reaction mediated by CD8+ and CD4+ T lymphocytes, pro-inflammatory cytokines.
  • Chronic symptoms: Persistent infected monocytes in joints causing chronic joint disease.

Histopathology

• Virus Classification:
  • Arthropod-borne alphavirus in the Togaviridae family.
  • Three genotypes: Asian, West African, East Central South African.
• Virus Structure: Positive-sense, single-stranded RNA virus, sensitive to temperatures >58°C.

History and Physical

• Symptoms:
  • High-grade fever and myalgia following a 3-7 day incubation period, lasting 3-5 days.
  • Bilateral symmetrical polyarthralgia 2-5 days post-fever onset, affecting distal joints (hands, knees, ankles).
  • Maculopapular rash 3 days after fever onset, often starting on extremities.
  • Other symptoms: Abdominal pain, diarrhea, vomiting, generalized lymphadenopathy, red eyes, conjunctivitis, anterior uveitis.
  • Rare manifestations: Vesiculobullous and mucocutaneous lesions, encephalitis (especially in newborns from maternal-fetal transmission), sepsis, renal issues.
  • Ocular issues: Red eyes, conjunctivitis, anterior uveitis, retinitis.

Evaluation

• Clinical Findings: Fever and polyarthralgia in a person recently returning from an affected region.
• Differentiation from Dengue: CHIKV more likely to cause severe arthralgia, arthritis, rash, lymphopenia; DENV more likely to cause neutropenia, thrombocytopenia, hemorrhage, shock, death.
• Diagnostic Methods:
  • RT-PCR: Best during acute infection (first five days).
  • Serology (ELISA, IFA): Detection of anti-chikungunya antibodies (IgM and IgG).
• CDC and WHO Recommendations: Gather serology for CHIKV, DENV, and Zika virus for all patients with suspicious symptoms.

Treatment / Management

• Symptomatic Relief: Hydration, rest, pain/fever relief with acetaminophen.
• Initial Care: Avoid aspirin and NSAIDs during the first 48 hours to prevent platelet dysfunction, especially with possible DENV coinfection.
• Chronic Symptoms: May respond to hydroxychloroquine with corticosteroids or other DMARDs.
• Research: Promising results for specific antivirals, but none approved for human use.
• Prevention:
  • Avoidance of mosquito bites with repellents (DEET), protective clothing, bed nets, reduction of water puddles.
  • Use of insecticides, though resistance is a growing concern.
• Vaccines: Under research, none approved for use.

Differential Diagnosis

• Acute Manifestations:
  • Malaria
  • Yellow fever
  • Leptospirosis
  • Measles
  • Mononucleosis
  • African tick bite fever
• Chronic Arthralgia:
  • Seronegative rheumatoid arthritis
  • Reiter arthritis
  • Rheumatoid arthritis
  • Hepatitis C
  • Systemic lupus erythematosus

Prognosis

• Low Case Fatality Ratio: Significant chronic polyarthralgia, defined as joint pains lasting longer than 6 weeks.
• Post-Chikungunya Arthritis: Reported in 26-40% of cases, causing substantial morbidity.

Complications

• Chronic Arthritis: Most common and severe complication.
• Ocular Manifestations: Conjunctivitis, optic neuritis, iridocyclitis, episcleritis, retinitis, uveitis, typically benign and self-limited.

Consultations

• Rheumatologists: For chronic arthritis due to swelling, recurrent pain, treatment challenges, and similarity to rheumatic arthritis.

Deterrence and Patient Education

• Awareness: Understanding mosquito transmission, symptoms, and prevention.
• Preventive Measures: DEET, protective clothing, mosquito nets, eliminating breeding sites.
• Seeking Medical Care: For symptoms post-travel to affected areas.

Pearls and Other Issues

• Global Impact: CHIKV endemic in Asia, transmitted by Aedes mosquitoes.
• Co-infection: Possible with Dengue and Zika.
• Clinical Manifestations: High fever, polyarthralgia, maculopapular rash, headache, myalgia.
• Chronic Arthritis: Requires rheumatologic care.
• Diagnosis: Based on clinical findings, travel history, RT-PCR, and serology.
• Treatment: Supportive care, avoiding aspirin/NSAIDs initially.
• Prevention: Mosquito bite avoidance, DEET, protective clothing, mosquito nets, insecticides.
• Reportable Disease

Enhancing Healthcare Team Outcomes

• Vector Control: Main form of prevention due to lack of specific treatments.
• Public Health Campaigns: Effective insecticide use, though resistance is a concern.
• Personal Protection: Use of DEET, bed nets, protective clothing, reduction of water reservoirs.
• Proper Diagnosis and Management: Key to avoiding poor prognosis, particularly in cases of CHIKV and DENV co-infection.