Chikungunya is a viral  disease  that  spread by the bite of infected mosquitoes. It is a  debilitating  but usually nonfatal disease.   Chikungunya  virus belongs to  the family of  Togaviridae and genus alpha virus .  The disease was first reported from Tanzania in 1952. Chikungunya  is  a  Makonde  word in Tanzania  meaning “to walk bent over”  that which bends up. Previously  several chikungunya  epidemic  had  occured in  Africa, India ,  South east Asia and America .It was found  that the disease was  primarily occurred among   peoples residing in urban and  periurban areas  of those countries.

Spread  and  clinical manifestation:  Typically the spread is ---   Man –-Mosquito--Man  , although  mother to fetus transmission  have been reported .It spread by the bite of  mosquito  aedes aegypti  . Human are thought  to  be the major source or reservoir of  chikongunya  virus.  The mosquito  usually  transmits the disease by biting an infected person and then biting someother  else. An infected person can not  spread  the infection directly to other persons. Aedes aegypti mosquitoes bites usually during the day time .  Following an incubation  period of usually 2-7 days   it causes acute symptomatic illness fever, skin rashes and often incapacitating  arthralgia.  While less common manifestation of the illness like gastrointestinal disorder , neurologic complication such as  meningoencephalitis and seizure, hemorrhagic  manifestation may also occur.  In most cases symptom  will resolve in 2 weeks .  However  as many as 88% of patient can have arthalgia lasting for  1 month and ,but   in approximately 12% cases(   as  current literature reports  )  arthralgia  can progress to  a severe chronic  and  disabiling  rheumatic and musculoskeletal disorder   that can last months to  many years.

When arthalgia is   marked as chronic inflammatory  rheumatism ( cir) : Any  polyarticular  inflammatory  features  persisting more than 3  months after  chikungunaya viral  infection must suggest  the potential for  diagnosis of  post chikungunaya  chronic  inflammatory rheumatism.   Morning  stiffness  probably has a lower diagnostic value due to its high  prevalence in   post chikungunya  illness, whereas  synovitis  and tenosynovitis  are highly indicative of  CIR.  

Pathogenesis of such  arthalgia : The causal relationship  of  development of chronic arthralgia  following Chikungunya  infection   has not yet been established. But potential causes of chikungunya virus  induced   musculoskeletal disorder has been postulated  which includes

*Persistence  of  virus  in and around joints

*Induction  of  autoimmune disease process by viremia.

*Exacerbation of preexisting  joint disease.

The spectrum  of rheumatic  and musculoskeletal disorder are wide and  includes  multiple tendinitis and  tenosynovitis , plantar fasciitis, mechanical  disbalance in succeptible  joints , tunnel syndromes, oedematous  polyarthalgia , rheumatoid arthritis  and psoriatic arthritis. The musculoskeletal disorder in some cases may even be   diffuse  in  nature .A small group  of such patient  develop   (around 5%)  rheumatoid arthritis . The Chikungunya  virus strain  descending  from  the East/ Central/ south Africa(ECSA) lineage that has spread  in the Indian Ocean region after2004 has been  reported to cause  long lasting  musculoskeletal  and rheumatic disorder in Chikungunya virus infected patient.

These arthritogenic   Chikungunya viral infection   become an increasingly  medical  and economic burden  in the affected areas as it can  often  result a long term disabilities.  There is growing  concept   regarding the  aetiology  of chronic rheumatism and musculoskeletal disorder is that chikongunya virus has  tissue tropism   having primary target  with fibroblast  which  might explain  the  frequent involvement of musculoskeletal system by this disease. While any joint can   be affected, the most commonly reported are the distal  joints of  extremities such as wrist ,  metacarpal and  intephalangeal  joints   as well as ankle and  metatarsophalangeal  joints.  In some patient  knee  joints are also  commonly  involved. .  The  chikungunya virus also seems to suppress  the host immune responses, thereby contributing  to chronicity of the disease. There are reports regarding   finding   of  persistent  destructive  bone and joint   lesion  with persistent  specific  IgM , even  few years following  initial  infection.

 Management  

The post chikungunaya   rheumatic and musculoskeletal  disorder is a  spectrum of disease  involving few  or multiple  joints , tendons , ligaments with varying severity. Some are transient  and  responds to usual treatment and  others become  persistent  with destroying  and    debilitating  musculoskeletal disorder .  To date physicians are still facing difficulties with the nosological  approach  to chronic patient .  

 There is yet  no standarized  treatment recommendation  for these chronic  manifestations.   The treatment of  these disorder are still best done by evidence based management.    Specific and individualized approach to treatment   may recognize such  patient  those might progress prolonged  disability and  can  be managed specifically  to prevent worst functional prognosis.  

These chronic symptom  respond  only partially to   nonsteroidal  anti-inflammatory drugs and not relief  diffuse pain , stiffness and swelling , although  naproxen, ibuprofen and other  NSAID can be used  but  aspirin    should not  be  used  as  there is  risk of  bleeding in small number of patient.  Patient with persistent  or chronic phase   of arthritis  who fail to  respond to NSAIDS   may show some response to  chloroquine  phosphate , but clinical studies  revealed that its use is  of no real  long  time benefit. In the destructive  type   of chronic  inflammatory rheumatism  that   affect only a minority of patient  early use  of methotraxate  have been validitated  and  long term  cortico steroid therapy should also  be evaluated for these small group of patient to  limit  progress  of such destructive  condition.

 Because of similarities  between chronic chikungunya  associated arthralgia  and rheumatoid  arthritis  some disease modifying  antirheumatic drugs (DMARDS)   have  been utilized  (such as methotraxate , sulfasalazine , hydroxychloroquine) despite  of its  post infectious origin  but the efficacies of these drugs  are yet unclear.

So, post chikungunya   musculoskeletal  disorder  should be  treated  with   optimized  pain killer  keeping the adverse  effect  in mind  with addition graduated physiotherapy  and  local infiltration  as appropriate.  Initial vigorous physiotherapy  might be detrimental  but graduated  therapy  often  helpful.    NSAID  or short course  corticosteroid  may be added as validated.   

Asthenia , psychological  and daily life burden must also be taken  into account  to avoid perpetuation of symptoms and to help with disease acceptance and recovery.  

 A  musculoskeletal   disorder  that has tendency to persist for  months  and  if refractory to other agent may occasionally respond to   short  term corticosteroid .

It has to be use with caution  and has to be the last  resort in a clinical decision. Managing  persistent  musculo skeletal pain  prolonged use of   anti inflammatory therapy may be needed .   

Movement and  mild exercise tends to improve  morning stiffness and pain but intense exercise may exacerbate symptoms. Neuropathic pain must be  identified and  treated specifically .  It is  clear that diagnosis and treatment  should be individualized and that aside from pain killer and NSAID   no specific treatment can  be universally recommended for all patient  at the chronic  post infectious stage.

Infection  by some strain of  chikungunya virus have the potential  to generate  a   chronic  rheumatism  & musculoskeletal   disorder  which causes  prolonged disabilty  with  loss of productivity  and  needs  careful  management to limit such  problem .