Lymphatic filariasis most often consists of asymptomatic microfilaremia.
Some patients develop lymphatic dysfunction causing lymphedema and elephantiasis (frequently in the lower extremities) and, with
Wuchereria bancrofti, hydrocele and scrotal elephantiasis. Episodes of febrile lymphangitis and lymphadenitis may occur.
Persons who have newly arrived in disease-endemic areas can develop afebrile episodes of lymphangitis and lymphadenitis.
An additional manifestation of filarial infection, mostly in Asia, is pulmonary tropical eosinophilia syndrome, with nocturnal cough and wheezing, fever, and eosinophilia.
Onchocerciasis can cause pruritus, dermatitis, onchocercomata (subcutaneous nodules), and lymphadenopathies.
The most serious manifestation consists of ocular lesions that can progress to blindness.
Loiasis (Loa loa) is often asymptomatic. Episodic angioedema (Calabar swellings) and subconjunctival migration of an adult worm can occur.
Infections by Mansonella perstans, while often asymptomatic, can be associated with angioedema, pruritus, fever, headaches, arthralgias, and neurologic manifestations.
Mansonella streptocerca can cause skin manifestations including pruritus, papular eruptions and pigmentation changes.
Eosinophilia is often prominent in filarial infections. Mansonella ozzardi can cause symptoms that include arthralgias, headaches, fever, pulmonary symptoms, adenopathy, hepatomegaly, and pruritus.
Identification of microfilariae
by microscopic examination is the most practical diagnostic procedure.
Examination of blood samples will allow identification of microfilariae of Wuchereria
bancrofti, Brugia malayi, Brugia timori, Loa loa, Mansonella perstans, and M.
ozzardi. It is important to time the blood collection with the known periodicity of
the microfilariae. The blood sample can be a thick smear, stained with Giemsa or
hematoxylin and eosin. For increased sensitivity, concentration techniques can be used.
These include centrifugation of the blood sample lyzed in 2% formalin (Knott's technique),
or filtration through a Nucleopore®
Examination of skin snips will identify microfilariae of Onchocerca volvulus and Mansonella
streptocerca. Skin snips can be obtained using a corneal-scleral punch, or more simply
a scalpel and needle. The sample must be allowed to incubate for 30 minutes to 2 hours in
saline or culture medium, and then examined for microfilariae that would have migrated
from the tissue to the liquid phase of the specimen.
detection using an immunoassay for circulating filarial antigens
constitutes a useful diagnostic approach, because microfilaremia can
be low and variable. A rapid-format immunochromatographic test,
applicable to Wuchereria bancrofti antigens, has been recently
evaluated in the field.
diagnosis using polymerase chain reaction is available for W.
bancrofti and B. malayi.
of adult worms is possible from tissue samples collected during
nodulectomies (onchocerciasis), or during subcutaneous biopsies or worm
removal from the eye (loiasis).
detection is of limited value. Substantial antigenic cross
reactivity exists between filaria and other helminths, and a positive
serologic test does not distinguish between past and current infection.
Special Procedures for Detecting Microfilariae
aids for filariasis
are recommended for the treatment of filariasis depending on the specific