The term Occult Filariasis is commonly used to designate filarial infections in which mf are not found in the periphral blood although they may be seen in tissues. However, it has now been shown that in some cases with occult filariasis, mf may actually be found after more careful blood examination despite their low density. Occult filariasis is believed to result from a hypersensitivity reaction to filarial antigens derived from microfilariae.Only a very small proportion of individuals in a community where filariasis is endemic develop occult forms of the disease.

Glomerulonephritis is associated with lymphatic filariasis. Filarial antibodies have been detected in 2 of 5 children with filariasis and acute glomerulonephritis. Renal biopsy showed diffuse messangial proliferative glomerulonephritis with C₃ deposition on the basement membrane. The condition responds well to DEC therapy.

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Endomyocardial fibrosis is a rare diseasee seen in the equatorial belts.

The incrimination of filarial infection in its causation is based largely on circumstantial evidence. The geographic distribution of the disease in areas endemic for filariasis, the detection of antibodies to Loa loa in patients with EMF, certain clinical features resembling fialrial infection and the occurance of eosiniphilia and EMF with Loeffler's syndrome have led to the hypothesis of EMF being filarial in origin. Further, Filarial antibodies have been detected in patients with EMF supporting the theory that EMF may be of fialrial origin.

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This is a form of arthritis which usually affects the knee joints and is fairly common in filarial endemic areas.
Two types of filarial arthritis have been desbribed clinically

1.Oligoarticular filarial arthritis
2.Filarial pseudo-rheumatism

Oligoarticular filarial arthritis:
Typically affects just one large joint, most commonly a knee. Synovial fluid from the afffected joint does not contain microfilariae, adult worms or pyogenic organisms. Monoarticular inflammation may reflect a tissue reaction to a filarial worm in the vicinity of the joint. Rarely, lymphatic fistulation into the synovial sac causes chylous arthritis.

Filarial pseudo-rheumatism:
Less common in lymphatic filariasis than in onchocerciasis. Its pathogenesis involves intra-articular deposition of immune complexes. Intact microfilariae have been detected intra-articularly in some patients with filarial polyarthritis and the local release of proteases by the worms may directly damage synovial tissue.

Majority of patients with filarial arthritis do not have fever but a painless swelling of one or more joints (usually the knee).

Sometimes the affected joint may be painful, warm and tender with restriction of movement. The symptoms may recur, often in the same joint but occasionally in some other joint and may be mistaken for rhematoid arthritis.
It is found that 90% of the patients with filarial arthritis tested are positive for filarial antibodies when tested with mf of W.bancrofti in a fluorescent antibody test
These patients show normal or moderately elevated eosiniphil counts and erythtocyte sedimentation rates; X-rays of the involved joints show soft tissue swelling but no bony abnormalities. The antistreptolysin O titre is generally normal.

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This manifestaion is particularly prevalent in India and Srilanka where W.bancrofti is the predominant species. It has not been reported from areas endemic for Brugian filariasis. Filarial granulomas present as hard breast lumps attached to the overlying skin and are at times difficult to distinguish from malignant tumours. A histological examination can confirm the diagnosis by the finding of an eosinophilic granulomatous reation around the filarial parasites which are in varying stages of degeneration. Both adult worms and mf have been found in the granulomas. Filarial antibodies have been demonstrated in these patients and the condition responds to DEC therapy which, in many instances, can lead to complete disappearance of the lump.


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