Persistent rheumatic musculoskeletal pain and disorders at one year post-chikungunya epidemic in south Maharashtra—a rural community based observational study with special focus on naïve persistent rheumatic musculoskeletal cases and selected cytokine expression

Abstract

The recent Chikungunya (CHIKV) epidemic (2006) unleashed an unrecognized spectrum of rheumatic musculoskeletal (RMSK) pain and disorders. The data on persistent RMSK is lacking. About 10% clinical acute cases are considered to suffer from chronic arthritis. We used an arthritis camp approach in a 9000 populated village Modnimb (district Sholapur) in December 2007 to identify naive cases of RMSK following symptomatic CHIKV outbreak in December 2006. A 10-day intensive publicity through public announcement and media pamphlet distribution program was carried out to attract villagers with persistent aches and pains and a past history of acute CHIKV illness to attend a 3 day free of cost evaluation arthritis camps. Blood samples were collected from consenting patients. Village volunteers and health workers participated in it. 1.4 percent (95% confidence interval 1.13, 1.60) village population was found to suffer from naive persistent RMSK pain and disorders at 1 year following acute CHIKV infection. Patients were generally >45 years age and females were predominant. Knee was the predominant pain site in 79% cases. Though 27% cases suffered from non-specific arthralgias (NSA), the diagnosis in 48% and 15% cases respectively was consistent with OA (often knee and spine) and undifferentiated inflammatory arthritis (0.2% crude prevalence). Overall, the clinical RMSK profile was benign and none reported any significant functional disability or mobility impairment. Seventy-three percent patients tested seropositive for anti-CHIKV IgG antibody; none for IgM antibody. None showed any abnormality on routine laboratory haematology and biochemistry testing; seropositive RF, ANA and anti-CCP was infrequent. Though CRP values were low, IL-6 was elevated and was not associated with any clinical phenotype. As compared to normal healthy population values assayed a year prior to the epidemic in a neighboring village, cases with persistent RMSK showed elevated IFN-γ, TNF-α and IL-13. Also, the clinical phenotype and cytokine expression did not seem to differ between the seropositive and seronegative groups for anti-CIKV IgG antibody. Conclusion In this rural community study, at least 1.4% population continued to suffer from some form of RMSK at 1 year following acute CHIKV epidemic. Though clinically unimpressive, a large number showed elevated pro-inflammatory cytokine expression. A longer follow-up may explain this disconnect.