How does Ross River fever affect toe joints?

Ross River Virus Effects on Toe Joints

Ross River virus commonly affects toe joints through polyarthralgia or arthritis, causing pain, swelling, and inflammation that typically resolves within 3-6 months without long-term joint damage. 1, 2

Clinical Presentation in Toe Joints

• Ross River virus (RRV) causes polyarthritis/arthralgia that can affect multiple joints, including the metatarsophalangeal joints of the toes 1
• While RRV arthritis more commonly affects larger joints (knees, ankles, wrists), the small joints of the feet including toe joints can be involved, though less frequently 3
• The arthritis in toe joints presents as:
  • Joint pain and swelling 2
  • Morning stiffness that is typically mild and brief 3
  • Symptoms that may migrate from one joint to another in a pattern similar to migratory polyarthritis 3

Pathophysiology of Joint Involvement

• RRV arthritis likely results from inflammation associated with productive viral infections in synovial macrophages within the joint 1
• The virus can persist in joint tissues despite neutralizing antibodies and antiviral cytokine responses 1
• Viral persistence may be facilitated by:
  • Downregulation of cytokine responses by virus-antibody complexes binding to Fc receptors 1
  • Induction of interleukin-10, which has immunomodulatory effects 1
  • Possible evasion of neutralizing antibodies through phagocytosis of apoptotic virus-infected cells 1

Disease Course and Prognosis

• Arthralgia is the most common presenting symptom and is usually associated with rash, fever, and lethargy 2
• The arthritis in toe joints, like other affected joints, typically follows a self-limited course 1, 2
• While RRV disease can be severe at onset, it progressively resolves over 3-6 months in most cases 1
• Some patients may experience symptoms lasting more than 12 months, but studies have shown this is often due to other unrelated rheumatic conditions 1
• Unlike some inflammatory arthritides, RRV does not cause long-term joint deformity or permanent damage to the toe joints 3, 1

Diagnosis

• Diagnosis of RRV affecting toe joints is based on:
  • Clinical presentation of joint pain and swelling 2
  • History of exposure to mosquitoes in endemic areas (Australia, Papua New Guinea, Pacific Islands) 2, 4
  • Serological tests showing rising titers of IgG antibodies 5
• Differential diagnosis should include other causes of toe joint pain such as:
  • Other inflammatory arthritides (rheumatoid arthritis, psoriatic arthritis) 3
  • Crystal arthropathies (gout, pseudogout) 3
  • Septic arthritis (requires urgent exclusion) 3

Treatment

• No specific antiviral treatment alters the course of RRV infection in toe joints 2
• Management is primarily symptomatic:
  • Simple analgesics or nonsteroidal anti-inflammatory drugs (NSAIDs) are the mainstay of treatment 1, 2
  • NSAIDs appear largely effective in controlling symptoms 1
  • Rest and elevation of affected joints may provide symptomatic relief 2
• There is no evidence of long-term sequelae or relapse after resolution 1

Prevention

• Prevention focuses on avoiding mosquito bites in endemic areas 2
• Personal protective measures include:
  • Using insect repellents containing DEET or picaridin 2
  • Wearing long-sleeved shirts and long pants 2
  • Avoiding outdoor activities during peak mosquito activity times 2

Key Differences from Other Viral Arthritides

• RRV causes more prominent arthritis compared to Barmah Forest virus (another Australian alphavirus) 5
• Unlike rheumatic fever, RRV does not lead to cardiac involvement or long-term joint damage 3, 1
• RRV arthritis in toe joints does not show the same predilection for metatarsophalangeal joints as seen in conditions like rheumatoid arthritis 3