Filariasis is a  mosquito borne disease.  The microfilariae sucked up by mosquito from infected man develop to infective larvae in 10-14 days. Mosquito harbouring infective  stage larvae  bite and infect a fresh host (man). Larvae migrate
Lymphatic filariasis is characterised by a wide spectrum of clinical manifestations

Asymptomatic microfilaraemia

     This stage is characterised by the presence of microfilariae in peripheral blood during night but without any overt clinical manifestations of filariasis.  It is possible that some of  these   have hidden lymphatic pathology in the form of dilatation at high risk of developing disease.

Acute manifestations

    These are characterised by recurrent attacks of fever associated with inflammation of the lymphnodes and lymphvessels - acute adenolymphangitis (ADL).  Various factors related to parasite like release of toxins, immune response in infected human host ,  trauma in the affected  area and secondary bacterial and / or fungal infections play a role in causing the ADL attacks.  The inflammed lymphatics of the male genitalia lead to funiculitis or epididymoorchitis.

Chronic manifestations

    Major chronic clinical manifestations are   hydrocele,  lymphoedema  and elephantiasis.  While hydrocele is the commonest genital manifestation in the male population, chronic epididymitis, funiculitis and  lymphomatous thickening of scrotal skin can be the other genital manifestations.Lymphoedema commonly affects the  lower limbs, some times the hands, and rarely the genitals and breast in females .   There may be repeated attacks of ADL.  Lymphoedema progresses from pitting oedema (reversible on elevation) and then non-pitting oedema  followed by increase  in oedema fluid volume, resulting in fibrous  tissue formation, followed by skin thickening, ulceration,  nodule formation and disfiguration (elephantiasis).  Chyluria  is  prevalent  in some endemic areas.

Occult manifestations

     Some filarial  patients do not have any classical clinical manifestations and do not show  microfilariae in peripheral blood, although the parasites may occur in internal organs or tissues.  The major  occult filarial manifestations include tropical  pulmonary eosinophilia (resulting from allergic reaction to parasite and characterised by nocturnal
paroxysmal cough and hypereosinophilia), glomerulopathies, endomyocardial fibrosis,  monoarthritis, tenosynovitis, acute abdomen, central  serous retinopathy (CSR), iridocyclitis, urticaria, haematuria etc. in adults.
         Pulmonary eosinophilia associated with cough, asthmatic bronchitis, arthritis, recurrent URI, pneumonitis, etc. were observed in children in filaria endemic areas  responding to DEC therapy.

Bilateral vaginal hydrocele  Grade I

Bilateral vaginal hydrocele
Grade II

Hydrocele Grade III

Lymphoedema Grade I

Lymphoedema Grade

Elephantiasis